c1381adae5
git-svn-id: http://picoc.googlecode.com/svn/trunk@307 21eae674-98b7-11dd-bd71-f92a316d2d60
3152 lines
91 KiB
C
3152 lines
91 KiB
C
/*
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* This is a modified version of FPLIBM for picoc.
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*
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* FDLIBM (Freely Distributable LIBM) is a C math library
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* for machines that support IEEE 754 floating-point arithmetic.
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* In this release, only double precision is supported.
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*
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* FDLIBM is intended to provide a reasonably portable (see
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* assumptions below), reference quality (below one ulp for
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* major functions like sin,cos,exp,log) math library
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* (libm.a). For a copy of FDLIBM, please see
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* http://www.netlib.org/fdlibm/
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* or
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* http://www.validlab.com/software/
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*/
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/*
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* ====================================================
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* Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
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*
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* Developed at SunSoft, a Sun Microsystems, Inc. business.
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* Permission to use, copy, modify, and distribute this
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* software is freely granted, provided that this notice
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* is preserved.
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* ====================================================
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*/
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#include "picoc.h"
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#ifdef NEED_MATH_LIBRARY
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/* Sometimes it's necessary to define BIG_ENDIAN explicitly */
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#ifndef BIG_ENDIAN
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#define __HI(x) *(1+(int*)&x)
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#define __LO(x) *(int*)&x
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#define __HIp(x) *(1+(int*)x)
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#define __LOp(x) *(int*)x
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#else
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#define __HI(x) *(int*)&x
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#define __LO(x) *(1+(int*)&x)
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#define __HIp(x) *(int*)x
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#define __LOp(x) *(1+(int*)x)
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#endif
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/* handy constants */
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static const double
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tiny= 1.00000000000000000000e-300,
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huge= 1.00000000000000000000e+300,
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shuge = 1.0e307,
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halF[2] = {0.5,-0.5,},
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zero= 0.0,
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one= 1.0, /* 0x3FF00000, 0x00000000 */
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two = 2.0,
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ln2 = 6.93147180559945286227e-01, /* 0x3FE62E42, 0xFEFA39EF */
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pi = 3.14159265358979311600e+00, /* 0x400921FB, 0x54442D18 */
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two24 = 1.67772160000000000000e+07, /* 0x41700000, 0x00000000 */
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twon24 = 5.96046447753906250000e-08, /* 0x3E700000, 0x00000000 */
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invpio2 = 6.36619772367581382433e-01, /* 0x3FE45F30, 0x6DC9C883 */
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pio2_1 = 1.57079632673412561417e+00, /* 0x3FF921FB, 0x54400000 */
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pio2_1t = 6.07710050650619224932e-11, /* 0x3DD0B461, 0x1A626331 */
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pio2_2 = 6.07710050630396597660e-11, /* 0x3DD0B461, 0x1A600000 */
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pio2_2t = 2.02226624879595063154e-21, /* 0x3BA3198A, 0x2E037073 */
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pio2_3 = 2.02226624871116645580e-21, /* 0x3BA3198A, 0x2E000000 */
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pio2_3t = 8.47842766036889956997e-32, /* 0x397B839A, 0x252049C1 */
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pio2_hi = 1.57079632679489655800e+00, /* 0x3FF921FB, 0x54442D18 */
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pio2_lo = 6.12323399573676603587e-17, /* 0x3C91A626, 0x33145C07 */
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pio4_hi = 7.85398163397448278999e-01, /* 0x3FE921FB, 0x54442D18 */
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pio4 = 7.85398163397448278999e-01, /* 3FE921FB, 54442D18 */
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pio4lo = 3.06161699786838301793e-17, /* 3C81A626, 33145C07 */
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pS0 = 1.66666666666666657415e-01, /* 0x3FC55555, 0x55555555 */
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pS1 = -3.25565818622400915405e-01, /* 0xBFD4D612, 0x03EB6F7D */
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pS2 = 2.01212532134862925881e-01, /* 0x3FC9C155, 0x0E884455 */
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pS3 = -4.00555345006794114027e-02, /* 0xBFA48228, 0xB5688F3B */
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pS4 = 7.91534994289814532176e-04, /* 0x3F49EFE0, 0x7501B288 */
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pS5 = 3.47933107596021167570e-05, /* 0x3F023DE1, 0x0DFDF709 */
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qS1 = -2.40339491173441421878e+00, /* 0xC0033A27, 0x1C8A2D4B */
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qS2 = 2.02094576023350569471e+00, /* 0x40002AE5, 0x9C598AC8 */
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qS3 = -6.88283971605453293030e-01, /* 0xBFE6066C, 0x1B8D0159 */
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qS4 = 7.70381505559019352791e-02, /* 0x3FB3B8C5, 0xB12E9282 */
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twom1000= 9.33263618503218878990e-302, /* 2**-1000=0x01700000,0*/
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o_threshold= 7.09782712893383973096e+02, /* 0x40862E42, 0xFEFA39EF */
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u_threshold= -7.45133219101941108420e+02, /* 0xc0874910, 0xD52D3051 */
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ln2HI[2] ={ 6.93147180369123816490e-01, /* 0x3fe62e42, 0xfee00000 */
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-6.93147180369123816490e-01,},/* 0xbfe62e42, 0xfee00000 */
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ln2LO[2] ={ 1.90821492927058770002e-10, /* 0x3dea39ef, 0x35793c76 */
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-1.90821492927058770002e-10,},/* 0xbdea39ef, 0x35793c76 */
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invln2 = 1.44269504088896338700e+00, /* 0x3ff71547, 0x652b82fe */
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P1 = 1.66666666666666019037e-01, /* 0x3FC55555, 0x5555553E */
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P2 = -2.77777777770155933842e-03, /* 0xBF66C16C, 0x16BEBD93 */
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P3 = 6.61375632143793436117e-05, /* 0x3F11566A, 0xAF25DE2C */
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P4 = -1.65339022054652515390e-06, /* 0xBEBBBD41, 0xC5D26BF1 */
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P5 = 4.13813679705723846039e-08, /* 0x3E663769, 0x72BEA4D0 */
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ln2_hi = 6.93147180369123816490e-01, /* 3fe62e42 fee00000 */
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ln2_lo = 1.90821492927058770002e-10, /* 3dea39ef 35793c76 */
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two54 = 1.80143985094819840000e+16, /* 43500000 00000000 */
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Lg1 = 6.666666666666735130e-01, /* 3FE55555 55555593 */
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Lg2 = 3.999999999940941908e-01, /* 3FD99999 9997FA04 */
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Lg3 = 2.857142874366239149e-01, /* 3FD24924 94229359 */
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Lg4 = 2.222219843214978396e-01, /* 3FCC71C5 1D8E78AF */
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Lg5 = 1.818357216161805012e-01, /* 3FC74664 96CB03DE */
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Lg6 = 1.531383769920937332e-01, /* 3FC39A09 D078C69F */
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Lg7 = 1.479819860511658591e-01, /* 3FC2F112 DF3E5244 */
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ivln10 = 4.34294481903251816668e-01, /* 0x3FDBCB7B, 0x1526E50E */
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log10_2hi = 3.01029995663611771306e-01, /* 0x3FD34413, 0x509F6000 */
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log10_2lo = 3.69423907715893078616e-13, /* 0x3D59FEF3, 0x11F12B36 */
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bp[] = {1.0, 1.5,},
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dp_h[] = { 0.0, 5.84962487220764160156e-01,}, /* 0x3FE2B803, 0x40000000 */
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dp_l[] = { 0.0, 1.35003920212974897128e-08,}, /* 0x3E4CFDEB, 0x43CFD006 */
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two53 = 9007199254740992.0, /* 0x43400000, 0x00000000 */
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/* poly coefs for (3/2)*(log(x)-2s-2/3*s**3 */
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L1 = 5.99999999999994648725e-01, /* 0x3FE33333, 0x33333303 */
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L2 = 4.28571428578550184252e-01, /* 0x3FDB6DB6, 0xDB6FABFF */
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L3 = 3.33333329818377432918e-01, /* 0x3FD55555, 0x518F264D */
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L4 = 2.72728123808534006489e-01, /* 0x3FD17460, 0xA91D4101 */
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L5 = 2.30660745775561754067e-01, /* 0x3FCD864A, 0x93C9DB65 */
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L6 = 2.06975017800338417784e-01, /* 0x3FCA7E28, 0x4A454EEF */
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lg2 = 6.93147180559945286227e-01, /* 0x3FE62E42, 0xFEFA39EF */
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lg2_h = 6.93147182464599609375e-01, /* 0x3FE62E43, 0x00000000 */
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lg2_l = -1.90465429995776804525e-09, /* 0xBE205C61, 0x0CA86C39 */
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ovt = 8.0085662595372944372e-0017, /* -(1024-log2(ovfl+.5ulp)) */
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cp = 9.61796693925975554329e-01, /* 0x3FEEC709, 0xDC3A03FD =2/(3ln2) */
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cp_h = 9.61796700954437255859e-01, /* 0x3FEEC709, 0xE0000000 =(float)cp */
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cp_l = -7.02846165095275826516e-09, /* 0xBE3E2FE0, 0x145B01F5 =tail of cp_h*/
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ivln2 = 1.44269504088896338700e+00, /* 0x3FF71547, 0x652B82FE =1/ln2 */
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ivln2_h = 1.44269502162933349609e+00, /* 0x3FF71547, 0x60000000 =24b 1/ln2*/
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ivln2_l = 1.92596299112661746887e-08, /* 0x3E54AE0B, 0xF85DDF44 =1/ln2 tail*/
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half = 5.00000000000000000000e-01, /* 0x3FE00000, 0x00000000 */
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S1 = -1.66666666666666324348e-01, /* 0xBFC55555, 0x55555549 */
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S2 = 8.33333333332248946124e-03, /* 0x3F811111, 0x1110F8A6 */
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S3 = -1.98412698298579493134e-04, /* 0xBF2A01A0, 0x19C161D5 */
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S4 = 2.75573137070700676789e-06, /* 0x3EC71DE3, 0x57B1FE7D */
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S5 = -2.50507602534068634195e-08, /* 0xBE5AE5E6, 0x8A2B9CEB */
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S6 = 1.58969099521155010221e-10, /* 0x3DE5D93A, 0x5ACFD57C */
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C1 = 4.16666666666666019037e-02, /* 0x3FA55555, 0x5555554C */
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C2 = -1.38888888888741095749e-03, /* 0xBF56C16C, 0x16C15177 */
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C3 = 2.48015872894767294178e-05, /* 0x3EFA01A0, 0x19CB1590 */
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C4 = -2.75573143513906633035e-07, /* 0xBE927E4F, 0x809C52AD */
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C5 = 2.08757232129817482790e-09, /* 0x3E21EE9E, 0xBDB4B1C4 */
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C6 = -1.13596475577881948265e-11, /* 0xBDA8FAE9, 0xBE8838D4 */
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T[] = {
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3.33333333333334091986e-01, /* 3FD55555, 55555563 */
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1.33333333333201242699e-01, /* 3FC11111, 1110FE7A */
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5.39682539762260521377e-02, /* 3FABA1BA, 1BB341FE */
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2.18694882948595424599e-02, /* 3F9664F4, 8406D637 */
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8.86323982359930005737e-03, /* 3F8226E3, E96E8493 */
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3.59207910759131235356e-03, /* 3F6D6D22, C9560328 */
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1.45620945432529025516e-03, /* 3F57DBC8, FEE08315 */
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5.88041240820264096874e-04, /* 3F4344D8, F2F26501 */
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2.46463134818469906812e-04, /* 3F3026F7, 1A8D1068 */
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7.81794442939557092300e-05, /* 3F147E88, A03792A6 */
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7.14072491382608190305e-05, /* 3F12B80F, 32F0A7E9 */
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-1.85586374855275456654e-05, /* BEF375CB, DB605373 */
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2.59073051863633712884e-05, /* 3EFB2A70, 74BF7AD4 */
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},
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Q1 = -3.33333333333331316428e-02, /* BFA11111 111110F4 */
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Q2 = 1.58730158725481460165e-03, /* 3F5A01A0 19FE5585 */
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Q3 = -7.93650757867487942473e-05, /* BF14CE19 9EAADBB7 */
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Q4 = 4.00821782732936239552e-06, /* 3ED0CFCA 86E65239 */
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Q5 = -2.01099218183624371326e-07, /* BE8AFDB7 6E09C32D */
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Lp1 = 6.666666666666735130e-01, /* 3FE55555 55555593 */
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Lp2 = 3.999999999940941908e-01, /* 3FD99999 9997FA04 */
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Lp3 = 2.857142874366239149e-01, /* 3FD24924 94229359 */
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Lp4 = 2.222219843214978396e-01, /* 3FCC71C5 1D8E78AF */
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Lp5 = 1.818357216161805012e-01, /* 3FC74664 96CB03DE */
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Lp6 = 1.531383769920937332e-01, /* 3FC39A09 D078C69F */
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Lp7 = 1.479819860511658591e-01; /* 3FC2F112 DF3E5244 */
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/*
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* __kernel_rem_pio2(x,y,e0,nx,prec,ipio2)
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* double x[],y[]; int e0,nx,prec; int ipio2[];
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*
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* __kernel_rem_pio2 return the last three digits of N with
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* y = x - N*pi/2
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* so that |y| < pi/2.
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*
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* The method is to compute the integer (mod 8) and fraction parts of
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* (2/pi)*x without doing the full multiplication. In general we
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* skip the part of the product that are known to be a huge integer (
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* more accurately, = 0 mod 8 ). Thus the number of operations are
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* independent of the exponent of the input.
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*
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* (2/pi) is represented by an array of 24-bit integers in ipio2[].
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*
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* Input parameters:
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* x[] The input value (must be positive) is broken into nx
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* pieces of 24-bit integers in double precision format.
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* x[i] will be the i-th 24 bit of x. The scaled exponent
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* of x[0] is given in input parameter e0 (i.e., x[0]*2^e0
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* match x's up to 24 bits.
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*
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* Example of breaking a double positive z into x[0]+x[1]+x[2]:
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* e0 = ilogb(z)-23
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* z = scalbn(z,-e0)
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* for i = 0,1,2
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* x[i] = floor(z)
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* z = (z-x[i])*2**24
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*
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*
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* y[] ouput result in an array of double precision numbers.
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* The dimension of y[] is:
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* 24-bit precision 1
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* 53-bit precision 2
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* 64-bit precision 2
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* 113-bit precision 3
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* The actual value is the sum of them. Thus for 113-bit
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* precison, one may have to do something like:
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*
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* long double t,w,r_head, r_tail;
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* t = (long double)y[2] + (long double)y[1];
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* w = (long double)y[0];
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* r_head = t+w;
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* r_tail = w - (r_head - t);
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*
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* e0 The exponent of x[0]
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*
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* nx dimension of x[]
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*
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* prec an integer indicating the precision:
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* 0 24 bits (single)
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* 1 53 bits (double)
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* 2 64 bits (extended)
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* 3 113 bits (quad)
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*
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* ipio2[]
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* integer array, contains the (24*i)-th to (24*i+23)-th
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* bit of 2/pi after binary point. The corresponding
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* floating value is
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*
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* ipio2[i] * 2^(-24(i+1)).
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*
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* External function:
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* double scalbn(), floor();
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*
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*
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* Here is the description of some local variables:
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*
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* jk jk+1 is the initial number of terms of ipio2[] needed
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* in the computation. The recommended value is 2,3,4,
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* 6 for single, double, extended,and quad.
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*
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* jz local integer variable indicating the number of
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* terms of ipio2[] used.
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*
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* jx nx - 1
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*
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* jv index for pointing to the suitable ipio2[] for the
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* computation. In general, we want
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* ( 2^e0*x[0] * ipio2[jv-1]*2^(-24jv) )/8
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* is an integer. Thus
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* e0-3-24*jv >= 0 or (e0-3)/24 >= jv
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* Hence jv = max(0,(e0-3)/24).
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*
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* jp jp+1 is the number of terms in PIo2[] needed, jp = jk.
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*
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* q[] double array with integral value, representing the
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* 24-bits chunk of the product of x and 2/pi.
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*
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* q0 the corresponding exponent of q[0]. Note that the
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* exponent for q[i] would be q0-24*i.
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*
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* PIo2[] double precision array, obtained by cutting pi/2
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* into 24 bits chunks.
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*
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* f[] ipio2[] in floating point
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*
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* iq[] integer array by breaking up q[] in 24-bits chunk.
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*
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* fq[] final product of x*(2/pi) in fq[0],..,fq[jk]
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*
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* ih integer. If >0 it indicates q[] is >= 0.5, hence
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* it also indicates the *sign* of the result.
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*
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*/
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/*
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* Constants:
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* The hexadecimal values are the intended ones for the following
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* constants. The decimal values may be used, provided that the
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* compiler will convert from decimal to binary accurately enough
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* to produce the hexadecimal values shown.
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*/
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static const int init_jk[] = {2,3,4,6}; /* initial value for jk */
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static const double PIo2[] = {
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1.57079625129699707031e+00, /* 0x3FF921FB, 0x40000000 */
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7.54978941586159635335e-08, /* 0x3E74442D, 0x00000000 */
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5.39030252995776476554e-15, /* 0x3CF84698, 0x80000000 */
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3.28200341580791294123e-22, /* 0x3B78CC51, 0x60000000 */
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1.27065575308067607349e-29, /* 0x39F01B83, 0x80000000 */
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1.22933308981111328932e-36, /* 0x387A2520, 0x40000000 */
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2.73370053816464559624e-44, /* 0x36E38222, 0x80000000 */
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2.16741683877804819444e-51, /* 0x3569F31D, 0x00000000 */
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};
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int __kernel_rem_pio2(double *x, double *y, int e0, int nx, int prec, const int *ipio2)
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{
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int jz,jx,jv,jp,jk,carry,n,iq[20],i,j,k,m,q0,ih;
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double z,fw,f[20],fq[20],q[20];
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/* initialize jk*/
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jk = init_jk[prec];
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jp = jk;
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/* determine jx,jv,q0, note that 3>q0 */
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jx = nx-1;
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jv = (e0-3)/24; if(jv<0) jv=0;
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q0 = e0-24*(jv+1);
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/* set up f[0] to f[jx+jk] where f[jx+jk] = ipio2[jv+jk] */
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j = jv-jx; m = jx+jk;
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for(i=0;i<=m;i++,j++) f[i] = (j<0)? zero : (double) ipio2[j];
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|
|
/* compute q[0],q[1],...q[jk] */
|
|
for (i=0;i<=jk;i++) {
|
|
for(j=0,fw=0.0;j<=jx;j++) fw += x[j]*f[jx+i-j]; q[i] = fw;
|
|
}
|
|
|
|
jz = jk;
|
|
recompute:
|
|
/* distill q[] into iq[] reversingly */
|
|
for(i=0,j=jz,z=q[jz];j>0;i++,j--) {
|
|
fw = (double)((int)(twon24* z));
|
|
iq[i] = (int)(z-two24*fw);
|
|
z = q[j-1]+fw;
|
|
}
|
|
|
|
/* compute n */
|
|
z = scalbn(z,q0); /* actual value of z */
|
|
z -= 8.0*math_floor(z*0.125); /* trim off integer >= 8 */
|
|
n = (int) z;
|
|
z -= (double)n;
|
|
ih = 0;
|
|
if(q0>0) { /* need iq[jz-1] to determine n */
|
|
i = (iq[jz-1]>>(24-q0)); n += i;
|
|
iq[jz-1] -= i<<(24-q0);
|
|
ih = iq[jz-1]>>(23-q0);
|
|
}
|
|
else if(q0==0) ih = iq[jz-1]>>23;
|
|
else if(z>=0.5) ih=2;
|
|
|
|
if(ih>0) { /* q > 0.5 */
|
|
n += 1; carry = 0;
|
|
for(i=0;i<jz ;i++) { /* compute 1-q */
|
|
j = iq[i];
|
|
if(carry==0) {
|
|
if(j!=0) {
|
|
carry = 1; iq[i] = 0x1000000- j;
|
|
}
|
|
} else iq[i] = 0xffffff - j;
|
|
}
|
|
if(q0>0) { /* rare case: chance is 1 in 12 */
|
|
switch(q0) {
|
|
case 1:
|
|
iq[jz-1] &= 0x7fffff; break;
|
|
case 2:
|
|
iq[jz-1] &= 0x3fffff; break;
|
|
}
|
|
}
|
|
if(ih==2) {
|
|
z = one - z;
|
|
if(carry!=0) z -= scalbn(one,q0);
|
|
}
|
|
}
|
|
|
|
/* check if recomputation is needed */
|
|
if(z==zero) {
|
|
j = 0;
|
|
for (i=jz-1;i>=jk;i--) j |= iq[i];
|
|
if(j==0) { /* need recomputation */
|
|
for(k=1;iq[jk-k]==0;k++); /* k = no. of terms needed */
|
|
|
|
for(i=jz+1;i<=jz+k;i++) { /* add q[jz+1] to q[jz+k] */
|
|
f[jx+i] = (double) ipio2[jv+i];
|
|
for(j=0,fw=0.0;j<=jx;j++) fw += x[j]*f[jx+i-j];
|
|
q[i] = fw;
|
|
}
|
|
jz += k;
|
|
goto recompute;
|
|
}
|
|
}
|
|
|
|
/* chop off zero terms */
|
|
if(z==0.0) {
|
|
jz -= 1; q0 -= 24;
|
|
while(iq[jz]==0) { jz--; q0-=24;}
|
|
} else { /* break z into 24-bit if necessary */
|
|
z = scalbn(z,-q0);
|
|
if(z>=two24) {
|
|
fw = (double)((int)(twon24*z));
|
|
iq[jz] = (int)(z-two24*fw);
|
|
jz += 1; q0 += 24;
|
|
iq[jz] = (int) fw;
|
|
} else iq[jz] = (int) z ;
|
|
}
|
|
|
|
/* convert integer "bit" chunk to floating-point value */
|
|
fw = scalbn(one,q0);
|
|
for(i=jz;i>=0;i--) {
|
|
q[i] = fw*(double)iq[i]; fw*=twon24;
|
|
}
|
|
|
|
/* compute PIo2[0,...,jp]*q[jz,...,0] */
|
|
for(i=jz;i>=0;i--) {
|
|
for(fw=0.0,k=0;k<=jp&&k<=jz-i;k++) fw += PIo2[k]*q[i+k];
|
|
fq[jz-i] = fw;
|
|
}
|
|
|
|
/* compress fq[] into y[] */
|
|
switch(prec) {
|
|
case 0:
|
|
fw = 0.0;
|
|
for (i=jz;i>=0;i--) fw += fq[i];
|
|
y[0] = (ih==0)? fw: -fw;
|
|
break;
|
|
case 1:
|
|
case 2:
|
|
fw = 0.0;
|
|
for (i=jz;i>=0;i--) fw += fq[i];
|
|
y[0] = (ih==0)? fw: -fw;
|
|
fw = fq[0]-fw;
|
|
for (i=1;i<=jz;i++) fw += fq[i];
|
|
y[1] = (ih==0)? fw: -fw;
|
|
break;
|
|
case 3: /* painful */
|
|
for (i=jz;i>0;i--) {
|
|
fw = fq[i-1]+fq[i];
|
|
fq[i] += fq[i-1]-fw;
|
|
fq[i-1] = fw;
|
|
}
|
|
for (i=jz;i>1;i--) {
|
|
fw = fq[i-1]+fq[i];
|
|
fq[i] += fq[i-1]-fw;
|
|
fq[i-1] = fw;
|
|
}
|
|
for (fw=0.0,i=jz;i>=2;i--) fw += fq[i];
|
|
if(ih==0) {
|
|
y[0] = fq[0]; y[1] = fq[1]; y[2] = fw;
|
|
} else {
|
|
y[0] = -fq[0]; y[1] = -fq[1]; y[2] = -fw;
|
|
}
|
|
}
|
|
return n&7;
|
|
}
|
|
|
|
|
|
/* __ieee754_rem_pio2(x,y)
|
|
*
|
|
* return the remainder of x rem pi/2 in y[0]+y[1]
|
|
* use __kernel_rem_pio2()
|
|
*/
|
|
|
|
/*
|
|
* Table of constants for 2/pi, 396 Hex digits (476 decimal) of 2/pi
|
|
*/
|
|
static const int two_over_pi[] = {
|
|
0xA2F983, 0x6E4E44, 0x1529FC, 0x2757D1, 0xF534DD, 0xC0DB62,
|
|
0x95993C, 0x439041, 0xFE5163, 0xABDEBB, 0xC561B7, 0x246E3A,
|
|
0x424DD2, 0xE00649, 0x2EEA09, 0xD1921C, 0xFE1DEB, 0x1CB129,
|
|
0xA73EE8, 0x8235F5, 0x2EBB44, 0x84E99C, 0x7026B4, 0x5F7E41,
|
|
0x3991D6, 0x398353, 0x39F49C, 0x845F8B, 0xBDF928, 0x3B1FF8,
|
|
0x97FFDE, 0x05980F, 0xEF2F11, 0x8B5A0A, 0x6D1F6D, 0x367ECF,
|
|
0x27CB09, 0xB74F46, 0x3F669E, 0x5FEA2D, 0x7527BA, 0xC7EBE5,
|
|
0xF17B3D, 0x0739F7, 0x8A5292, 0xEA6BFB, 0x5FB11F, 0x8D5D08,
|
|
0x560330, 0x46FC7B, 0x6BABF0, 0xCFBC20, 0x9AF436, 0x1DA9E3,
|
|
0x91615E, 0xE61B08, 0x659985, 0x5F14A0, 0x68408D, 0xFFD880,
|
|
0x4D7327, 0x310606, 0x1556CA, 0x73A8C9, 0x60E27B, 0xC08C6B,
|
|
};
|
|
|
|
static const int npio2_hw[] = {
|
|
0x3FF921FB, 0x400921FB, 0x4012D97C, 0x401921FB, 0x401F6A7A, 0x4022D97C,
|
|
0x4025FDBB, 0x402921FB, 0x402C463A, 0x402F6A7A, 0x4031475C, 0x4032D97C,
|
|
0x40346B9C, 0x4035FDBB, 0x40378FDB, 0x403921FB, 0x403AB41B, 0x403C463A,
|
|
0x403DD85A, 0x403F6A7A, 0x40407E4C, 0x4041475C, 0x4042106C, 0x4042D97C,
|
|
0x4043A28C, 0x40446B9C, 0x404534AC, 0x4045FDBB, 0x4046C6CB, 0x40478FDB,
|
|
0x404858EB, 0x404921FB,
|
|
};
|
|
|
|
/*
|
|
* invpio2: 53 bits of 2/pi
|
|
* pio2_1: first 33 bit of pi/2
|
|
* pio2_1t: pi/2 - pio2_1
|
|
* pio2_2: second 33 bit of pi/2
|
|
* pio2_2t: pi/2 - (pio2_1+pio2_2)
|
|
* pio2_3: third 33 bit of pi/2
|
|
* pio2_3t: pi/2 - (pio2_1+pio2_2+pio2_3)
|
|
*/
|
|
|
|
int __ieee754_rem_pio2(double x, double *y)
|
|
{
|
|
double z,w,t,r,fn;
|
|
double tx[3];
|
|
int e0,i,j,nx,n,ix,hx;
|
|
|
|
hx = __HI(x); /* high word of x */
|
|
ix = hx&0x7fffffff;
|
|
if(ix<=0x3fe921fb) /* |x| ~<= pi/4 , no need for reduction */
|
|
{y[0] = x; y[1] = 0; return 0;}
|
|
if(ix<0x4002d97c) { /* |x| < 3pi/4, special case with n=+-1 */
|
|
if(hx>0) {
|
|
z = x - pio2_1;
|
|
if(ix!=0x3ff921fb) { /* 33+53 bit pi is good enough */
|
|
y[0] = z - pio2_1t;
|
|
y[1] = (z-y[0])-pio2_1t;
|
|
} else { /* near pi/2, use 33+33+53 bit pi */
|
|
z -= pio2_2;
|
|
y[0] = z - pio2_2t;
|
|
y[1] = (z-y[0])-pio2_2t;
|
|
}
|
|
return 1;
|
|
} else { /* negative x */
|
|
z = x + pio2_1;
|
|
if(ix!=0x3ff921fb) { /* 33+53 bit pi is good enough */
|
|
y[0] = z + pio2_1t;
|
|
y[1] = (z-y[0])+pio2_1t;
|
|
} else { /* near pi/2, use 33+33+53 bit pi */
|
|
z += pio2_2;
|
|
y[0] = z + pio2_2t;
|
|
y[1] = (z-y[0])+pio2_2t;
|
|
}
|
|
return -1;
|
|
}
|
|
}
|
|
if(ix<=0x413921fb) { /* |x| ~<= 2^19*(pi/2), medium size */
|
|
t = fabs(x);
|
|
n = (int) (t*invpio2+half);
|
|
fn = (double)n;
|
|
r = t-fn*pio2_1;
|
|
w = fn*pio2_1t; /* 1st round good to 85 bit */
|
|
if(n<32&&ix!=npio2_hw[n-1]) {
|
|
y[0] = r-w; /* quick check no cancellation */
|
|
} else {
|
|
j = ix>>20;
|
|
y[0] = r-w;
|
|
i = j-(((__HI(y[0]))>>20)&0x7ff);
|
|
if(i>16) { /* 2nd iteration needed, good to 118 */
|
|
t = r;
|
|
w = fn*pio2_2;
|
|
r = t-w;
|
|
w = fn*pio2_2t-((t-r)-w);
|
|
y[0] = r-w;
|
|
i = j-(((__HI(y[0]))>>20)&0x7ff);
|
|
if(i>49) { /* 3rd iteration need, 151 bits acc */
|
|
t = r; /* will cover all possible cases */
|
|
w = fn*pio2_3;
|
|
r = t-w;
|
|
w = fn*pio2_3t-((t-r)-w);
|
|
y[0] = r-w;
|
|
}
|
|
}
|
|
}
|
|
y[1] = (r-y[0])-w;
|
|
if(hx<0) {y[0] = -y[0]; y[1] = -y[1]; return -n;}
|
|
else return n;
|
|
}
|
|
/*
|
|
* all other (large) arguments
|
|
*/
|
|
if(ix>=0x7ff00000) { /* x is inf or NaN */
|
|
y[0]=y[1]=x-x; return 0;
|
|
}
|
|
/* set z = scalbn(|x|,ilogb(x)-23) */
|
|
__LO(z) = __LO(x);
|
|
e0 = (ix>>20)-1046; /* e0 = ilogb(z)-23; */
|
|
__HI(z) = ix - (e0<<20);
|
|
for(i=0;i<2;i++) {
|
|
tx[i] = (double)((int)(z));
|
|
z = (z-tx[i])*two24;
|
|
}
|
|
tx[2] = z;
|
|
nx = 3;
|
|
while(tx[nx-1]==zero) nx--; /* skip zero term */
|
|
n = __kernel_rem_pio2(tx,y,e0,nx,2,two_over_pi);
|
|
if(hx<0) {y[0] = -y[0]; y[1] = -y[1]; return -n;}
|
|
return n;
|
|
}
|
|
|
|
|
|
/* __ieee754_exp(x)
|
|
* Returns the exponential of x.
|
|
*
|
|
* Method
|
|
* 1. Argument reduction:
|
|
* Reduce x to an r so that |r| <= 0.5*ln2 ~ 0.34658.
|
|
* Given x, find r and integer k such that
|
|
*
|
|
* x = k*ln2 + r, |r| <= 0.5*ln2.
|
|
*
|
|
* Here r will be represented as r = hi-lo for better
|
|
* accuracy.
|
|
*
|
|
* 2. Approximation of exp(r) by a special rational function on
|
|
* the interval [0,0.34658]:
|
|
* Write
|
|
* R(r**2) = r*(exp(r)+1)/(exp(r)-1) = 2 + r*r/6 - r**4/360 + ...
|
|
* We use a special Remes algorithm on [0,0.34658] to generate
|
|
* a polynomial of degree 5 to approximate R. The maximum error
|
|
* of this polynomial approximation is bounded by 2**-59. In
|
|
* other words,
|
|
* R(z) ~ 2.0 + P1*z + P2*z**2 + P3*z**3 + P4*z**4 + P5*z**5
|
|
* (where z=r*r, and the values of P1 to P5 are listed below)
|
|
* and
|
|
* | 5 | -59
|
|
* | 2.0+P1*z+...+P5*z - R(z) | <= 2
|
|
* | |
|
|
* The computation of exp(r) thus becomes
|
|
* 2*r
|
|
* exp(r) = 1 + -------
|
|
* R - r
|
|
* r*R1(r)
|
|
* = 1 + r + ----------- (for better accuracy)
|
|
* 2 - R1(r)
|
|
* where
|
|
* 2 4 10
|
|
* R1(r) = r - (P1*r + P2*r + ... + P5*r ).
|
|
*
|
|
* 3. Scale back to obtain exp(x):
|
|
* From step 1, we have
|
|
* exp(x) = 2^k * exp(r)
|
|
*
|
|
* Special cases:
|
|
* exp(INF) is INF, exp(NaN) is NaN;
|
|
* exp(-INF) is 0, and
|
|
* for finite argument, only exp(0)=1 is exact.
|
|
*
|
|
* Accuracy:
|
|
* according to an error analysis, the error is always less than
|
|
* 1 ulp (unit in the last place).
|
|
*
|
|
* Misc. info.
|
|
* For IEEE double
|
|
* if x > 7.09782712893383973096e+02 then exp(x) overflow
|
|
* if x < -7.45133219101941108420e+02 then exp(x) underflow
|
|
*
|
|
* Constants:
|
|
* The hexadecimal values are the intended ones for the following
|
|
* constants. The decimal values may be used, provided that the
|
|
* compiler will convert from decimal to binary accurately enough
|
|
* to produce the hexadecimal values shown.
|
|
*/
|
|
|
|
double __ieee754_exp(double x) /* default IEEE double exp */
|
|
{
|
|
double y,hi,lo,c,t;
|
|
int k,xsb;
|
|
unsigned hx;
|
|
|
|
hx = __HI(x); /* high word of x */
|
|
xsb = (hx>>31)&1; /* sign bit of x */
|
|
hx &= 0x7fffffff; /* high word of |x| */
|
|
|
|
/* filter out non-finite argument */
|
|
if(hx >= 0x40862E42) { /* if |x|>=709.78... */
|
|
if(hx>=0x7ff00000) {
|
|
if(((hx&0xfffff)|__LO(x))!=0)
|
|
return x+x; /* NaN */
|
|
else return (xsb==0)? x:0.0; /* exp(+-inf)={inf,0} */
|
|
}
|
|
if(x > o_threshold) return huge*huge; /* overflow */
|
|
if(x < u_threshold) return twom1000*twom1000; /* underflow */
|
|
}
|
|
|
|
/* argument reduction */
|
|
if(hx > 0x3fd62e42) { /* if |x| > 0.5 ln2 */
|
|
if(hx < 0x3FF0A2B2) { /* and |x| < 1.5 ln2 */
|
|
hi = x-ln2HI[xsb]; lo=ln2LO[xsb]; k = 1-xsb-xsb;
|
|
} else {
|
|
k = (int)(invln2*x+halF[xsb]);
|
|
t = k;
|
|
hi = x - t*ln2HI[0]; /* t*ln2HI is exact here */
|
|
lo = t*ln2LO[0];
|
|
}
|
|
x = hi - lo;
|
|
}
|
|
else if(hx < 0x3e300000) { /* when |x|<2**-28 */
|
|
if(huge+x>one) return one+x;/* trigger inexact */
|
|
}
|
|
else k = 0;
|
|
|
|
/* x is now in primary range */
|
|
t = x*x;
|
|
c = x - t*(P1+t*(P2+t*(P3+t*(P4+t*P5))));
|
|
if(k==0) return one-((x*c)/(c-2.0)-x);
|
|
else y = one-((lo-(x*c)/(2.0-c))-hi);
|
|
if(k >= -1021) {
|
|
__HI(y) += (k<<20); /* add k to y's exponent */
|
|
return y;
|
|
} else {
|
|
__HI(y) += ((k+1000)<<20);/* add k to y's exponent */
|
|
return y*twom1000;
|
|
}
|
|
}
|
|
|
|
|
|
/* __ieee754_log(x)
|
|
* Return the logrithm of x
|
|
*
|
|
* Method :
|
|
* 1. Argument Reduction: find k and f such that
|
|
* x = 2^k * (1+f),
|
|
* where sqrt(2)/2 < 1+f < sqrt(2) .
|
|
*
|
|
* 2. Approximation of log(1+f).
|
|
* Let s = f/(2+f) ; based on log(1+f) = log(1+s) - log(1-s)
|
|
* = 2s + 2/3 s**3 + 2/5 s**5 + .....,
|
|
* = 2s + s*R
|
|
* We use a special Reme algorithm on [0,0.1716] to generate
|
|
* a polynomial of degree 14 to approximate R The maximum error
|
|
* of this polynomial approximation is bounded by 2**-58.45. In
|
|
* other words,
|
|
* 2 4 6 8 10 12 14
|
|
* R(z) ~ Lg1*s +Lg2*s +Lg3*s +Lg4*s +Lg5*s +Lg6*s +Lg7*s
|
|
* (the values of Lg1 to Lg7 are listed in the program)
|
|
* and
|
|
* | 2 14 | -58.45
|
|
* | Lg1*s +...+Lg7*s - R(z) | <= 2
|
|
* | |
|
|
* Note that 2s = f - s*f = f - hfsq + s*hfsq, where hfsq = f*f/2.
|
|
* In order to guarantee error in log below 1ulp, we compute log
|
|
* by
|
|
* log(1+f) = f - s*(f - R) (if f is not too large)
|
|
* log(1+f) = f - (hfsq - s*(hfsq+R)). (better accuracy)
|
|
*
|
|
* 3. Finally, log(x) = k*ln2 + log(1+f).
|
|
* = k*ln2_hi+(f-(hfsq-(s*(hfsq+R)+k*ln2_lo)))
|
|
* Here ln2 is split into two floating point number:
|
|
* ln2_hi + ln2_lo,
|
|
* where n*ln2_hi is always exact for |n| < 2000.
|
|
*
|
|
* Special cases:
|
|
* log(x) is NaN with signal if x < 0 (including -INF) ;
|
|
* log(+INF) is +INF; log(0) is -INF with signal;
|
|
* log(NaN) is that NaN with no signal.
|
|
*
|
|
* Accuracy:
|
|
* according to an error analysis, the error is always less than
|
|
* 1 ulp (unit in the last place).
|
|
*
|
|
* Constants:
|
|
* The hexadecimal values are the intended ones for the following
|
|
* constants. The decimal values may be used, provided that the
|
|
* compiler will convert from decimal to binary accurately enough
|
|
* to produce the hexadecimal values shown.
|
|
*/
|
|
|
|
double __ieee754_log(double x)
|
|
{
|
|
double hfsq,f,s,z,R,w,t1,t2,dk;
|
|
int k,hx,i,j;
|
|
unsigned lx;
|
|
|
|
hx = __HI(x); /* high word of x */
|
|
lx = __LO(x); /* low word of x */
|
|
|
|
k=0;
|
|
if (hx < 0x00100000) { /* x < 2**-1022 */
|
|
if (((hx&0x7fffffff)|lx)==0)
|
|
return -two54/zero; /* log(+-0)=-inf */
|
|
if (hx<0) return (x-x)/zero; /* log(-#) = NaN */
|
|
k -= 54; x *= two54; /* subnormal number, scale up x */
|
|
hx = __HI(x); /* high word of x */
|
|
}
|
|
if (hx >= 0x7ff00000) return x+x;
|
|
k += (hx>>20)-1023;
|
|
hx &= 0x000fffff;
|
|
i = (hx+0x95f64)&0x100000;
|
|
__HI(x) = hx|(i^0x3ff00000); /* normalize x or x/2 */
|
|
k += (i>>20);
|
|
f = x-1.0;
|
|
if((0x000fffff&(2+hx))<3) { /* |f| < 2**-20 */
|
|
if(f==zero) { if(k==0) return zero; else {dk=(double)k;
|
|
return dk*ln2_hi+dk*ln2_lo;} }
|
|
R = f*f*(0.5-0.33333333333333333*f);
|
|
if(k==0) return f-R; else {dk=(double)k;
|
|
return dk*ln2_hi-((R-dk*ln2_lo)-f);}
|
|
}
|
|
s = f/(2.0+f);
|
|
dk = (double)k;
|
|
z = s*s;
|
|
i = hx-0x6147a;
|
|
w = z*z;
|
|
j = 0x6b851-hx;
|
|
t1= w*(Lg2+w*(Lg4+w*Lg6));
|
|
t2= z*(Lg1+w*(Lg3+w*(Lg5+w*Lg7)));
|
|
i |= j;
|
|
R = t2+t1;
|
|
if(i>0) {
|
|
hfsq=0.5*f*f;
|
|
if(k==0) return f-(hfsq-s*(hfsq+R)); else
|
|
return dk*ln2_hi-((hfsq-(s*(hfsq+R)+dk*ln2_lo))-f);
|
|
} else {
|
|
if(k==0) return f-s*(f-R); else
|
|
return dk*ln2_hi-((s*(f-R)-dk*ln2_lo)-f);
|
|
}
|
|
}
|
|
|
|
|
|
/* __kernel_sin( x, y, iy)
|
|
* kernel sin function on [-pi/4, pi/4], pi/4 ~ 0.7854
|
|
* Input x is assumed to be bounded by ~pi/4 in magnitude.
|
|
* Input y is the tail of x.
|
|
* Input iy indicates whether y is 0. (if iy=0, y assume to be 0).
|
|
*
|
|
* Algorithm
|
|
* 1. Since sin(-x) = -sin(x), we need only to consider positive x.
|
|
* 2. if x < 2^-27 (hx<0x3e400000 0), return x with inexact if x!=0.
|
|
* 3. sin(x) is approximated by a polynomial of degree 13 on
|
|
* [0,pi/4]
|
|
* 3 13
|
|
* sin(x) ~ x + S1*x + ... + S6*x
|
|
* where
|
|
*
|
|
* |sin(x) 2 4 6 8 10 12 | -58
|
|
* |----- - (1+S1*x +S2*x +S3*x +S4*x +S5*x +S6*x )| <= 2
|
|
* | x |
|
|
*
|
|
* 4. sin(x+y) = sin(x) + sin'(x')*y
|
|
* ~ sin(x) + (1-x*x/2)*y
|
|
* For better accuracy, let
|
|
* 3 2 2 2 2
|
|
* r = x *(S2+x *(S3+x *(S4+x *(S5+x *S6))))
|
|
* then 3 2
|
|
* sin(x) = x + (S1*x + (x *(r-y/2)+y))
|
|
*/
|
|
|
|
double __kernel_sin(double x, double y, int iy)
|
|
{
|
|
double z,r,v;
|
|
int ix;
|
|
ix = __HI(x)&0x7fffffff; /* high word of x */
|
|
if(ix<0x3e400000) /* |x| < 2**-27 */
|
|
{if((int)x==0) return x;} /* generate inexact */
|
|
z = x*x;
|
|
v = z*x;
|
|
r = S2+z*(S3+z*(S4+z*(S5+z*S6)));
|
|
if(iy==0) return x+v*(S1+z*r);
|
|
else return x-((z*(half*y-v*r)-y)-v*S1);
|
|
}
|
|
|
|
|
|
/*
|
|
* __kernel_cos( x, y )
|
|
* kernel cos function on [-pi/4, pi/4], pi/4 ~ 0.785398164
|
|
* Input x is assumed to be bounded by ~pi/4 in magnitude.
|
|
* Input y is the tail of x.
|
|
*
|
|
* Algorithm
|
|
* 1. Since cos(-x) = cos(x), we need only to consider positive x.
|
|
* 2. if x < 2^-27 (hx<0x3e400000 0), return 1 with inexact if x!=0.
|
|
* 3. cos(x) is approximated by a polynomial of degree 14 on
|
|
* [0,pi/4]
|
|
* 4 14
|
|
* cos(x) ~ 1 - x*x/2 + C1*x + ... + C6*x
|
|
* where the remez error is
|
|
*
|
|
* | 2 4 6 8 10 12 14 | -58
|
|
* |cos(x)-(1-.5*x +C1*x +C2*x +C3*x +C4*x +C5*x +C6*x )| <= 2
|
|
* | |
|
|
*
|
|
* 4 6 8 10 12 14
|
|
* 4. let r = C1*x +C2*x +C3*x +C4*x +C5*x +C6*x , then
|
|
* cos(x) = 1 - x*x/2 + r
|
|
* since cos(x+y) ~ cos(x) - sin(x)*y
|
|
* ~ cos(x) - x*y,
|
|
* a correction term is necessary in cos(x) and hence
|
|
* cos(x+y) = 1 - (x*x/2 - (r - x*y))
|
|
* For better accuracy when x > 0.3, let qx = |x|/4 with
|
|
* the last 32 bits mask off, and if x > 0.78125, let qx = 0.28125.
|
|
* Then
|
|
* cos(x+y) = (1-qx) - ((x*x/2-qx) - (r-x*y)).
|
|
* Note that 1-qx and (x*x/2-qx) is EXACT here, and the
|
|
* magnitude of the latter is at least a quarter of x*x/2,
|
|
* thus, reducing the rounding error in the subtraction.
|
|
*/
|
|
|
|
|
|
double __kernel_cos(double x, double y)
|
|
{
|
|
double a,hz,z,r,qx;
|
|
int ix;
|
|
ix = __HI(x)&0x7fffffff; /* ix = |x|'s high word*/
|
|
if(ix<0x3e400000) { /* if x < 2**27 */
|
|
if(((int)x)==0) return one; /* generate inexact */
|
|
}
|
|
z = x*x;
|
|
r = z*(C1+z*(C2+z*(C3+z*(C4+z*(C5+z*C6)))));
|
|
if(ix < 0x3FD33333) /* if |x| < 0.3 */
|
|
return one - (0.5*z - (z*r - x*y));
|
|
else {
|
|
if(ix > 0x3fe90000) { /* x > 0.78125 */
|
|
qx = 0.28125;
|
|
} else {
|
|
__HI(qx) = ix-0x00200000; /* x/4 */
|
|
__LO(qx) = 0;
|
|
}
|
|
hz = 0.5*z-qx;
|
|
a = one-qx;
|
|
return a - (hz - (z*r-x*y));
|
|
}
|
|
}
|
|
|
|
|
|
/* __kernel_tan( x, y, k )
|
|
* kernel tan function on [-pi/4, pi/4], pi/4 ~ 0.7854
|
|
* Input x is assumed to be bounded by ~pi/4 in magnitude.
|
|
* Input y is the tail of x.
|
|
* Input k indicates whether tan (if k = 1) or -1/tan (if k = -1) is returned.
|
|
*
|
|
* Algorithm
|
|
* 1. Since tan(-x) = -tan(x), we need only to consider positive x.
|
|
* 2. if x < 2^-28 (hx<0x3e300000 0), return x with inexact if x!=0.
|
|
* 3. tan(x) is approximated by a odd polynomial of degree 27 on
|
|
* [0,0.67434]
|
|
* 3 27
|
|
* tan(x) ~ x + T1*x + ... + T13*x
|
|
* where
|
|
*
|
|
* |tan(x) 2 4 26 | -59.2
|
|
* |----- - (1+T1*x +T2*x +.... +T13*x )| <= 2
|
|
* | x |
|
|
*
|
|
* Note: tan(x+y) = tan(x) + tan'(x)*y
|
|
* ~ tan(x) + (1+x*x)*y
|
|
* Therefore, for better accuracy in computing tan(x+y), let
|
|
* 3 2 2 2 2
|
|
* r = x *(T2+x *(T3+x *(...+x *(T12+x *T13))))
|
|
* then
|
|
* 3 2
|
|
* tan(x+y) = x + (T1*x + (x *(r+y)+y))
|
|
*
|
|
* 4. For x in [0.67434,pi/4], let y = pi/4 - x, then
|
|
* tan(x) = tan(pi/4-y) = (1-tan(y))/(1+tan(y))
|
|
* = 1 - 2*(tan(y) - (tan(y)^2)/(1+tan(y)))
|
|
*/
|
|
|
|
double __kernel_tan(double x, double y, int iy)
|
|
{
|
|
double z, r, v, w, s;
|
|
int ix, hx;
|
|
|
|
hx = __HI(x); /* high word of x */
|
|
ix = hx & 0x7fffffff; /* high word of |x| */
|
|
if (ix < 0x3e300000) { /* x < 2**-28 */
|
|
if ((int) x == 0) { /* generate inexact */
|
|
if (((ix | __LO(x)) | (iy + 1)) == 0)
|
|
return one / fabs(x);
|
|
else {
|
|
if (iy == 1)
|
|
return x;
|
|
else { /* compute -1 / (x+y) carefully */
|
|
double a, t;
|
|
|
|
z = w = x + y;
|
|
__LO(z) = 0;
|
|
v = y - (z - x);
|
|
t = a = -one / w;
|
|
__LO(t) = 0;
|
|
s = one + t * z;
|
|
return t + a * (s + t * v);
|
|
}
|
|
}
|
|
}
|
|
}
|
|
if (ix >= 0x3FE59428) { /* |x| >= 0.6744 */
|
|
if (hx < 0) {
|
|
x = -x;
|
|
y = -y;
|
|
}
|
|
z = pio4 - x;
|
|
w = pio4lo - y;
|
|
x = z + w;
|
|
y = 0.0;
|
|
}
|
|
z = x * x;
|
|
w = z * z;
|
|
/*
|
|
* Break x^5*(T[1]+x^2*T[2]+...) into
|
|
* x^5(T[1]+x^4*T[3]+...+x^20*T[11]) +
|
|
* x^5(x^2*(T[2]+x^4*T[4]+...+x^22*[T12]))
|
|
*/
|
|
r = T[1] + w * (T[3] + w * (T[5] + w * (T[7] + w * (T[9] +
|
|
w * T[11]))));
|
|
v = z * (T[2] + w * (T[4] + w * (T[6] + w * (T[8] + w * (T[10] +
|
|
w * T[12])))));
|
|
s = z * x;
|
|
r = y + z * (s * (r + v) + y);
|
|
r += T[0] * s;
|
|
w = x + r;
|
|
if (ix >= 0x3FE59428) {
|
|
v = (double) iy;
|
|
return (double) (1 - ((hx >> 30) & 2)) *
|
|
(v - 2.0 * (x - (w * w / (w + v) - r)));
|
|
}
|
|
if (iy == 1)
|
|
return w;
|
|
else {
|
|
/*
|
|
* if allow error up to 2 ulp, simply return
|
|
* -1.0 / (x+r) here
|
|
*/
|
|
/* compute -1.0 / (x+r) accurately */
|
|
double a, t;
|
|
z = w;
|
|
__LO(z) = 0;
|
|
v = r - (z - x); /* z+v = r+x */
|
|
t = a = -1.0 / w; /* a = -1.0/w */
|
|
__LO(t) = 0;
|
|
s = 1.0 + t * z;
|
|
return t + a * (s + t * v);
|
|
}
|
|
}
|
|
|
|
|
|
/* sin(x)
|
|
* Return sine function of x.
|
|
*
|
|
* kernel function:
|
|
* __kernel_sin ... sine function on [-pi/4,pi/4]
|
|
* __kernel_cos ... cose function on [-pi/4,pi/4]
|
|
* __ieee754_rem_pio2 ... argument reduction routine
|
|
*
|
|
* Method.
|
|
* Let S,C and T denote the sin, cos and tan respectively on
|
|
* [-PI/4, +PI/4]. Reduce the argument x to y1+y2 = x-k*pi/2
|
|
* in [-pi/4 , +pi/4], and let n = k mod 4.
|
|
* We have
|
|
*
|
|
* n sin(x) cos(x) tan(x)
|
|
* ----------------------------------------------------------
|
|
* 0 S C T
|
|
* 1 C -S -1/T
|
|
* 2 -S -C T
|
|
* 3 -C S -1/T
|
|
* ----------------------------------------------------------
|
|
*
|
|
* Special cases:
|
|
* Let trig be any of sin, cos, or tan.
|
|
* trig(+-INF) is NaN, with signals;
|
|
* trig(NaN) is that NaN;
|
|
*
|
|
* Accuracy:
|
|
* TRIG(x) returns trig(x) nearly rounded
|
|
*/
|
|
|
|
double math_sin(double x)
|
|
{
|
|
double y[2],z=0.0;
|
|
int n, ix;
|
|
|
|
/* High word of x. */
|
|
ix = __HI(x);
|
|
|
|
/* |x| ~< pi/4 */
|
|
ix &= 0x7fffffff;
|
|
if(ix <= 0x3fe921fb) return __kernel_sin(x,z,0);
|
|
|
|
/* sin(Inf or NaN) is NaN */
|
|
else if (ix>=0x7ff00000) return x-x;
|
|
|
|
/* argument reduction needed */
|
|
else {
|
|
n = __ieee754_rem_pio2(x,y);
|
|
switch(n&3) {
|
|
case 0: return __kernel_sin(y[0],y[1],1);
|
|
case 1: return __kernel_cos(y[0],y[1]);
|
|
case 2: return -__kernel_sin(y[0],y[1],1);
|
|
default:
|
|
return -__kernel_cos(y[0],y[1]);
|
|
}
|
|
}
|
|
}
|
|
|
|
|
|
/* cos(x)
|
|
* Return cosine function of x.
|
|
*
|
|
* kernel function:
|
|
* __kernel_sin ... sine function on [-pi/4,pi/4]
|
|
* __kernel_cos ... cosine function on [-pi/4,pi/4]
|
|
* __ieee754_rem_pio2 ... argument reduction routine
|
|
*
|
|
* Method.
|
|
* Let S,C and T denote the sin, cos and tan respectively on
|
|
* [-PI/4, +PI/4]. Reduce the argument x to y1+y2 = x-k*pi/2
|
|
* in [-pi/4 , +pi/4], and let n = k mod 4.
|
|
* We have
|
|
*
|
|
* n sin(x) cos(x) tan(x)
|
|
* ----------------------------------------------------------
|
|
* 0 S C T
|
|
* 1 C -S -1/T
|
|
* 2 -S -C T
|
|
* 3 -C S -1/T
|
|
* ----------------------------------------------------------
|
|
*
|
|
* Special cases:
|
|
* Let trig be any of sin, cos, or tan.
|
|
* trig(+-INF) is NaN, with signals;
|
|
* trig(NaN) is that NaN;
|
|
*
|
|
* Accuracy:
|
|
* TRIG(x) returns trig(x) nearly rounded
|
|
*/
|
|
|
|
double math_cos(double x)
|
|
{
|
|
double y[2],z=0.0;
|
|
int n, ix;
|
|
|
|
/* High word of x. */
|
|
ix = __HI(x);
|
|
|
|
/* |x| ~< pi/4 */
|
|
ix &= 0x7fffffff;
|
|
if(ix <= 0x3fe921fb) return __kernel_cos(x,z);
|
|
|
|
/* cos(Inf or NaN) is NaN */
|
|
else if (ix>=0x7ff00000) return x-x;
|
|
|
|
/* argument reduction needed */
|
|
else {
|
|
n = __ieee754_rem_pio2(x,y);
|
|
switch(n&3) {
|
|
case 0: return __kernel_cos(y[0],y[1]);
|
|
case 1: return -__kernel_sin(y[0],y[1],1);
|
|
case 2: return -__kernel_cos(y[0],y[1]);
|
|
default:
|
|
return __kernel_sin(y[0],y[1],1);
|
|
}
|
|
}
|
|
}
|
|
|
|
|
|
/* tan(x)
|
|
* Return tangent function of x.
|
|
*
|
|
* kernel function:
|
|
* __kernel_tan ... tangent function on [-pi/4,pi/4]
|
|
* __ieee754_rem_pio2 ... argument reduction routine
|
|
*
|
|
* Method.
|
|
* Let S,C and T denote the sin, cos and tan respectively on
|
|
* [-PI/4, +PI/4]. Reduce the argument x to y1+y2 = x-k*pi/2
|
|
* in [-pi/4 , +pi/4], and let n = k mod 4.
|
|
* We have
|
|
*
|
|
* n sin(x) cos(x) tan(x)
|
|
* ----------------------------------------------------------
|
|
* 0 S C T
|
|
* 1 C -S -1/T
|
|
* 2 -S -C T
|
|
* 3 -C S -1/T
|
|
* ----------------------------------------------------------
|
|
*
|
|
* Special cases:
|
|
* Let trig be any of sin, cos, or tan.
|
|
* trig(+-INF) is NaN, with signals;
|
|
* trig(NaN) is that NaN;
|
|
*
|
|
* Accuracy:
|
|
* TRIG(x) returns trig(x) nearly rounded
|
|
*/
|
|
|
|
double math_tan(double x)
|
|
{
|
|
double y[2],z=0.0;
|
|
int n, ix;
|
|
|
|
/* High word of x. */
|
|
ix = __HI(x);
|
|
|
|
/* |x| ~< pi/4 */
|
|
ix &= 0x7fffffff;
|
|
if(ix <= 0x3fe921fb) return __kernel_tan(x,z,1);
|
|
|
|
/* tan(Inf or NaN) is NaN */
|
|
else if (ix>=0x7ff00000) return x-x; /* NaN */
|
|
|
|
/* argument reduction needed */
|
|
else {
|
|
n = __ieee754_rem_pio2(x,y);
|
|
return __kernel_tan(y[0],y[1],1-((n&1)<<1)); /* 1 -- n even
|
|
-1 -- n odd */
|
|
}
|
|
}
|
|
|
|
|
|
/* __ieee754_asin(x)
|
|
* Method :
|
|
* Since asin(x) = x + x^3/6 + x^5*3/40 + x^7*15/336 + ...
|
|
* we approximate asin(x) on [0,0.5] by
|
|
* asin(x) = x + x*x^2*R(x^2)
|
|
* where
|
|
* R(x^2) is a rational approximation of (asin(x)-x)/x^3
|
|
* and its remez error is bounded by
|
|
* |(asin(x)-x)/x^3 - R(x^2)| < 2^(-58.75)
|
|
*
|
|
* For x in [0.5,1]
|
|
* asin(x) = pi/2-2*asin(sqrt((1-x)/2))
|
|
* Let y = (1-x), z = y/2, s := sqrt(z), and pio2_hi+pio2_lo=pi/2;
|
|
* then for x>0.98
|
|
* asin(x) = pi/2 - 2*(s+s*z*R(z))
|
|
* = pio2_hi - (2*(s+s*z*R(z)) - pio2_lo)
|
|
* For x<=0.98, let pio4_hi = pio2_hi/2, then
|
|
* f = hi part of s;
|
|
* c = sqrt(z) - f = (z-f*f)/(s+f) ...f+c=sqrt(z)
|
|
* and
|
|
* asin(x) = pi/2 - 2*(s+s*z*R(z))
|
|
* = pio4_hi+(pio4-2s)-(2s*z*R(z)-pio2_lo)
|
|
* = pio4_hi+(pio4-2f)-(2s*z*R(z)-(pio2_lo+2c))
|
|
*
|
|
* Special cases:
|
|
* if x is NaN, return x itself;
|
|
* if |x|>1, return NaN with invalid signal.
|
|
*
|
|
*/
|
|
|
|
double __ieee754_asin(double x)
|
|
{
|
|
double t,w,p,q,c,r,s;
|
|
int hx,ix;
|
|
hx = __HI(x);
|
|
ix = hx&0x7fffffff;
|
|
if(ix>= 0x3ff00000) { /* |x|>= 1 */
|
|
if(((ix-0x3ff00000)|__LO(x))==0)
|
|
/* asin(1)=+-pi/2 with inexact */
|
|
return x*pio2_hi+x*pio2_lo;
|
|
return (x-x)/(x-x); /* asin(|x|>1) is NaN */
|
|
} else if (ix<0x3fe00000) { /* |x|<0.5 */
|
|
if(ix<0x3e400000) { /* if |x| < 2**-27 */
|
|
if(huge+x>one) return x;/* return x with inexact if x!=0*/
|
|
} else
|
|
t = x*x;
|
|
p = t*(pS0+t*(pS1+t*(pS2+t*(pS3+t*(pS4+t*pS5)))));
|
|
q = one+t*(qS1+t*(qS2+t*(qS3+t*qS4)));
|
|
w = p/q;
|
|
return x+x*w;
|
|
}
|
|
/* 1> |x|>= 0.5 */
|
|
w = one-fabs(x);
|
|
t = w*0.5;
|
|
p = t*(pS0+t*(pS1+t*(pS2+t*(pS3+t*(pS4+t*pS5)))));
|
|
q = one+t*(qS1+t*(qS2+t*(qS3+t*qS4)));
|
|
s = math_sqrt(t);
|
|
if(ix>=0x3FEF3333) { /* if |x| > 0.975 */
|
|
w = p/q;
|
|
t = pio2_hi-(2.0*(s+s*w)-pio2_lo);
|
|
} else {
|
|
w = s;
|
|
__LO(w) = 0;
|
|
c = (t-w*w)/(s+w);
|
|
r = p/q;
|
|
p = 2.0*s*r-(pio2_lo-2.0*c);
|
|
q = pio4_hi-2.0*w;
|
|
t = pio4_hi-(p-q);
|
|
}
|
|
if(hx>0) return t; else return -t;
|
|
}
|
|
|
|
|
|
/*
|
|
* wrapper asin(x)
|
|
*/
|
|
|
|
double math_asin(double x) /* wrapper asin */
|
|
{
|
|
#ifdef _IEEE_LIBM
|
|
return __ieee754_asin(x);
|
|
#else
|
|
double z;
|
|
z = __ieee754_asin(x);
|
|
if(_LIB_VERSION == _IEEE_ || isnan(x)) return z;
|
|
if(fabs(x)>1.0) {
|
|
return __kernel_standard(x,x,2); /* asin(|x|>1) */
|
|
} else
|
|
return z;
|
|
#endif
|
|
}
|
|
|
|
/* __ieee754_acos(x)
|
|
* Method :
|
|
* acos(x) = pi/2 - asin(x)
|
|
* acos(-x) = pi/2 + asin(x)
|
|
* For |x|<=0.5
|
|
* acos(x) = pi/2 - (x + x*x^2*R(x^2)) (see asin.c)
|
|
* For x>0.5
|
|
* acos(x) = pi/2 - (pi/2 - 2asin(math_sqrt((1-x)/2)))
|
|
* = 2asin(math_sqrt((1-x)/2))
|
|
* = 2s + 2s*z*R(z) ...z=(1-x)/2, s=math_sqrt(z)
|
|
* = 2f + (2c + 2s*z*R(z))
|
|
* where f=hi part of s, and c = (z-f*f)/(s+f) is the correction term
|
|
* for f so that f+c ~ sqrt(z).
|
|
* For x<-0.5
|
|
* acos(x) = pi - 2asin(sqrt((1-|x|)/2))
|
|
* = pi - 0.5*(s+s*z*R(z)), where z=(1-|x|)/2,s=sqrt(z)
|
|
*
|
|
* Special cases:
|
|
* if x is NaN, return x itself;
|
|
* if |x|>1, return NaN with invalid signal.
|
|
*
|
|
* Function needed: sqrt
|
|
*/
|
|
|
|
double __ieee754_acos(double x)
|
|
{
|
|
double z,p,q,r,w,s,c,df;
|
|
int hx,ix;
|
|
hx = __HI(x);
|
|
ix = hx&0x7fffffff;
|
|
if(ix>=0x3ff00000) { /* |x| >= 1 */
|
|
if(((ix-0x3ff00000)|__LO(x))==0) { /* |x|==1 */
|
|
if(hx>0) return 0.0; /* acos(1) = 0 */
|
|
else return pi+2.0*pio2_lo; /* acos(-1)= pi */
|
|
}
|
|
return (x-x)/(x-x); /* acos(|x|>1) is NaN */
|
|
}
|
|
if(ix<0x3fe00000) { /* |x| < 0.5 */
|
|
if(ix<=0x3c600000) return pio2_hi+pio2_lo;/*if|x|<2**-57*/
|
|
z = x*x;
|
|
p = z*(pS0+z*(pS1+z*(pS2+z*(pS3+z*(pS4+z*pS5)))));
|
|
q = one+z*(qS1+z*(qS2+z*(qS3+z*qS4)));
|
|
r = p/q;
|
|
return pio2_hi - (x - (pio2_lo-x*r));
|
|
} else if (hx<0) { /* x < -0.5 */
|
|
z = (one+x)*0.5;
|
|
p = z*(pS0+z*(pS1+z*(pS2+z*(pS3+z*(pS4+z*pS5)))));
|
|
q = one+z*(qS1+z*(qS2+z*(qS3+z*qS4)));
|
|
s = math_sqrt(z);
|
|
r = p/q;
|
|
w = r*s-pio2_lo;
|
|
return pi - 2.0*(s+w);
|
|
} else { /* x > 0.5 */
|
|
z = (one-x)*0.5;
|
|
s = math_sqrt(z);
|
|
df = s;
|
|
__LO(df) = 0;
|
|
c = (z-df*df)/(s+df);
|
|
p = z*(pS0+z*(pS1+z*(pS2+z*(pS3+z*(pS4+z*pS5)))));
|
|
q = one+z*(qS1+z*(qS2+z*(qS3+z*qS4)));
|
|
r = p/q;
|
|
w = r*s+c;
|
|
return 2.0*(df+w);
|
|
}
|
|
}
|
|
|
|
|
|
/*
|
|
* wrap_acos(x)
|
|
*/
|
|
|
|
double math_acos(double x) /* wrapper acos */
|
|
{
|
|
#ifdef _IEEE_LIBM
|
|
return __ieee754_acos(x);
|
|
#else
|
|
double z;
|
|
z = __ieee754_acos(x);
|
|
if(_LIB_VERSION == _IEEE_ || isnan(x)) return z;
|
|
if(fabs(x)>1.0) {
|
|
return __kernel_standard(x,x,1); /* acos(|x|>1) */
|
|
} else
|
|
return z;
|
|
#endif
|
|
}
|
|
|
|
|
|
/* atan(x)
|
|
* Method
|
|
* 1. Reduce x to positive by atan(x) = -atan(-x).
|
|
* 2. According to the integer k=4t+0.25 chopped, t=x, the argument
|
|
* is further reduced to one of the following intervals and the
|
|
* arctangent of t is evaluated by the corresponding formula:
|
|
*
|
|
* [0,7/16] atan(x) = t-t^3*(a1+t^2*(a2+...(a10+t^2*a11)...)
|
|
* [7/16,11/16] atan(x) = atan(1/2) + atan( (t-0.5)/(1+t/2) )
|
|
* [11/16.19/16] atan(x) = atan( 1 ) + atan( (t-1)/(1+t) )
|
|
* [19/16,39/16] atan(x) = atan(3/2) + atan( (t-1.5)/(1+1.5t) )
|
|
* [39/16,INF] atan(x) = atan(INF) + atan( -1/t )
|
|
*
|
|
* Constants:
|
|
* The hexadecimal values are the intended ones for the following
|
|
* constants. The decimal values may be used, provided that the
|
|
* compiler will convert from decimal to binary accurately enough
|
|
* to produce the hexadecimal values shown.
|
|
*/
|
|
|
|
static const double atanhi[] = {
|
|
4.63647609000806093515e-01, /* atan(0.5)hi 0x3FDDAC67, 0x0561BB4F */
|
|
7.85398163397448278999e-01, /* atan(1.0)hi 0x3FE921FB, 0x54442D18 */
|
|
9.82793723247329054082e-01, /* atan(1.5)hi 0x3FEF730B, 0xD281F69B */
|
|
1.57079632679489655800e+00, /* atan(inf)hi 0x3FF921FB, 0x54442D18 */
|
|
};
|
|
|
|
static const double atanlo[] = {
|
|
2.26987774529616870924e-17, /* atan(0.5)lo 0x3C7A2B7F, 0x222F65E2 */
|
|
3.06161699786838301793e-17, /* atan(1.0)lo 0x3C81A626, 0x33145C07 */
|
|
1.39033110312309984516e-17, /* atan(1.5)lo 0x3C700788, 0x7AF0CBBD */
|
|
6.12323399573676603587e-17, /* atan(inf)lo 0x3C91A626, 0x33145C07 */
|
|
};
|
|
|
|
static const double aT[] = {
|
|
3.33333333333329318027e-01, /* 0x3FD55555, 0x5555550D */
|
|
-1.99999999998764832476e-01, /* 0xBFC99999, 0x9998EBC4 */
|
|
1.42857142725034663711e-01, /* 0x3FC24924, 0x920083FF */
|
|
-1.11111104054623557880e-01, /* 0xBFBC71C6, 0xFE231671 */
|
|
9.09088713343650656196e-02, /* 0x3FB745CD, 0xC54C206E */
|
|
-7.69187620504482999495e-02, /* 0xBFB3B0F2, 0xAF749A6D */
|
|
6.66107313738753120669e-02, /* 0x3FB10D66, 0xA0D03D51 */
|
|
-5.83357013379057348645e-02, /* 0xBFADDE2D, 0x52DEFD9A */
|
|
4.97687799461593236017e-02, /* 0x3FA97B4B, 0x24760DEB */
|
|
-3.65315727442169155270e-02, /* 0xBFA2B444, 0x2C6A6C2F */
|
|
1.62858201153657823623e-02, /* 0x3F90AD3A, 0xE322DA11 */
|
|
};
|
|
|
|
double math_atan(double x)
|
|
{
|
|
double w,s1,s2,z;
|
|
int ix,hx,id;
|
|
|
|
hx = __HI(x);
|
|
ix = hx&0x7fffffff;
|
|
if(ix>=0x44100000) { /* if |x| >= 2^66 */
|
|
if(ix>0x7ff00000||
|
|
(ix==0x7ff00000&&(__LO(x)!=0)))
|
|
return x+x; /* NaN */
|
|
if(hx>0) return atanhi[3]+atanlo[3];
|
|
else return -atanhi[3]-atanlo[3];
|
|
} if (ix < 0x3fdc0000) { /* |x| < 0.4375 */
|
|
if (ix < 0x3e200000) { /* |x| < 2^-29 */
|
|
if(huge+x>one) return x; /* raise inexact */
|
|
}
|
|
id = -1;
|
|
} else {
|
|
x = fabs(x);
|
|
if (ix < 0x3ff30000) { /* |x| < 1.1875 */
|
|
if (ix < 0x3fe60000) { /* 7/16 <=|x|<11/16 */
|
|
id = 0; x = (2.0*x-one)/(2.0+x);
|
|
} else { /* 11/16<=|x|< 19/16 */
|
|
id = 1; x = (x-one)/(x+one);
|
|
}
|
|
} else {
|
|
if (ix < 0x40038000) { /* |x| < 2.4375 */
|
|
id = 2; x = (x-1.5)/(one+1.5*x);
|
|
} else { /* 2.4375 <= |x| < 2^66 */
|
|
id = 3; x = -1.0/x;
|
|
}
|
|
}}
|
|
/* end of argument reduction */
|
|
z = x*x;
|
|
w = z*z;
|
|
/* break sum from i=0 to 10 aT[i]z**(i+1) into odd and even poly */
|
|
s1 = z*(aT[0]+w*(aT[2]+w*(aT[4]+w*(aT[6]+w*(aT[8]+w*aT[10])))));
|
|
s2 = w*(aT[1]+w*(aT[3]+w*(aT[5]+w*(aT[7]+w*aT[9]))));
|
|
if (id<0) return x - x*(s1+s2);
|
|
else {
|
|
z = atanhi[id] - ((x*(s1+s2) - atanlo[id]) - x);
|
|
return (hx<0)? -z:z;
|
|
}
|
|
}
|
|
|
|
|
|
/* expm1(x)
|
|
* Returns exp(x)-1, the exponential of x minus 1.
|
|
*
|
|
* Method
|
|
* 1. Argument reduction:
|
|
* Given x, find r and integer k such that
|
|
*
|
|
* x = k*ln2 + r, |r| <= 0.5*ln2 ~ 0.34658
|
|
*
|
|
* Here a correction term c will be computed to compensate
|
|
* the error in r when rounded to a floating-point number.
|
|
*
|
|
* 2. Approximating expm1(r) by a special rational function on
|
|
* the interval [0,0.34658]:
|
|
* Since
|
|
* r*(exp(r)+1)/(exp(r)-1) = 2+ r^2/6 - r^4/360 + ...
|
|
* we define R1(r*r) by
|
|
* r*(exp(r)+1)/(exp(r)-1) = 2+ r^2/6 * R1(r*r)
|
|
* That is,
|
|
* R1(r**2) = 6/r *((exp(r)+1)/(exp(r)-1) - 2/r)
|
|
* = 6/r * ( 1 + 2.0*(1/(exp(r)-1) - 1/r))
|
|
* = 1 - r^2/60 + r^4/2520 - r^6/100800 + ...
|
|
* We use a special Remes algorithm on [0,0.347] to generate
|
|
* a polynomial of degree 5 in r*r to approximate R1. The
|
|
* maximum error of this polynomial approximation is bounded
|
|
* by 2**-61. In other words,
|
|
* R1(z) ~ 1.0 + Q1*z + Q2*z**2 + Q3*z**3 + Q4*z**4 + Q5*z**5
|
|
* where Q1 = -1.6666666666666567384E-2,
|
|
* Q2 = 3.9682539681370365873E-4,
|
|
* Q3 = -9.9206344733435987357E-6,
|
|
* Q4 = 2.5051361420808517002E-7,
|
|
* Q5 = -6.2843505682382617102E-9;
|
|
* (where z=r*r, and the values of Q1 to Q5 are listed below)
|
|
* with error bounded by
|
|
* | 5 | -61
|
|
* | 1.0+Q1*z+...+Q5*z - R1(z) | <= 2
|
|
* | |
|
|
*
|
|
* expm1(r) = exp(r)-1 is then computed by the following
|
|
* specific way which minimize the accumulation rounding error:
|
|
* 2 3
|
|
* r r [ 3 - (R1 + R1*r/2) ]
|
|
* expm1(r) = r + --- + --- * [--------------------]
|
|
* 2 2 [ 6 - r*(3 - R1*r/2) ]
|
|
*
|
|
* To compensate the error in the argument reduction, we use
|
|
* expm1(r+c) = expm1(r) + c + expm1(r)*c
|
|
* ~ expm1(r) + c + r*c
|
|
* Thus c+r*c will be added in as the correction terms for
|
|
* expm1(r+c). Now rearrange the term to avoid optimization
|
|
* screw up:
|
|
* ( 2 2 )
|
|
* ({ ( r [ R1 - (3 - R1*r/2) ] ) } r )
|
|
* expm1(r+c)~r - ({r*(--- * [--------------------]-c)-c} - --- )
|
|
* ({ ( 2 [ 6 - r*(3 - R1*r/2) ] ) } 2 )
|
|
* ( )
|
|
*
|
|
* = r - E
|
|
* 3. Scale back to obtain expm1(x):
|
|
* From step 1, we have
|
|
* expm1(x) = either 2^k*[expm1(r)+1] - 1
|
|
* = or 2^k*[expm1(r) + (1-2^-k)]
|
|
* 4. Implementation notes:
|
|
* (A). To save one multiplication, we scale the coefficient Qi
|
|
* to Qi*2^i, and replace z by (x^2)/2.
|
|
* (B). To achieve maximum accuracy, we compute expm1(x) by
|
|
* (i) if x < -56*ln2, return -1.0, (raise inexact if x!=inf)
|
|
* (ii) if k=0, return r-E
|
|
* (iii) if k=-1, return 0.5*(r-E)-0.5
|
|
* (iv) if k=1 if r < -0.25, return 2*((r+0.5)- E)
|
|
* else return 1.0+2.0*(r-E);
|
|
* (v) if (k<-2||k>56) return 2^k(1-(E-r)) - 1 (or exp(x)-1)
|
|
* (vi) if k <= 20, return 2^k((1-2^-k)-(E-r)), else
|
|
* (vii) return 2^k(1-((E+2^-k)-r))
|
|
*
|
|
* Special cases:
|
|
* expm1(INF) is INF, expm1(NaN) is NaN;
|
|
* expm1(-INF) is -1, and
|
|
* for finite argument, only expm1(0)=0 is exact.
|
|
*
|
|
* Accuracy:
|
|
* according to an error analysis, the error is always less than
|
|
* 1 ulp (unit in the last place).
|
|
*
|
|
* Misc. info.
|
|
* For IEEE double
|
|
* if x > 7.09782712893383973096e+02 then expm1(x) overflow
|
|
*
|
|
* Constants:
|
|
* The hexadecimal values are the intended ones for the following
|
|
* constants. The decimal values may be used, provided that the
|
|
* compiler will convert from decimal to binary accurately enough
|
|
* to produce the hexadecimal values shown.
|
|
*/
|
|
|
|
double math_expm1(double x)
|
|
{
|
|
double y,hi,lo,c,t,e,hxs,hfx,r1;
|
|
int k,xsb;
|
|
unsigned hx;
|
|
|
|
hx = __HI(x); /* high word of x */
|
|
xsb = hx&0x80000000; /* sign bit of x */
|
|
if(xsb==0) y=x; else y= -x; /* y = |x| */
|
|
hx &= 0x7fffffff; /* high word of |x| */
|
|
|
|
/* filter out huge and non-finite argument */
|
|
if(hx >= 0x4043687A) { /* if |x|>=56*ln2 */
|
|
if(hx >= 0x40862E42) { /* if |x|>=709.78... */
|
|
if(hx>=0x7ff00000) {
|
|
if(((hx&0xfffff)|__LO(x))!=0)
|
|
return x+x; /* NaN */
|
|
else return (xsb==0)? x:-1.0;/* exp(+-inf)={inf,-1} */
|
|
}
|
|
if(x > o_threshold) return huge*huge; /* overflow */
|
|
}
|
|
if(xsb!=0) { /* x < -56*ln2, return -1.0 with inexact */
|
|
if(x+tiny<0.0) /* raise inexact */
|
|
return tiny-one; /* return -1 */
|
|
}
|
|
}
|
|
|
|
/* argument reduction */
|
|
if(hx > 0x3fd62e42) { /* if |x| > 0.5 ln2 */
|
|
if(hx < 0x3FF0A2B2) { /* and |x| < 1.5 ln2 */
|
|
if(xsb==0)
|
|
{hi = x - ln2_hi; lo = ln2_lo; k = 1;}
|
|
else
|
|
{hi = x + ln2_hi; lo = -ln2_lo; k = -1;}
|
|
} else {
|
|
k = invln2*x+((xsb==0)?0.5:-0.5);
|
|
t = k;
|
|
hi = x - t*ln2_hi; /* t*ln2_hi is exact here */
|
|
lo = t*ln2_lo;
|
|
}
|
|
x = hi - lo;
|
|
c = (hi-x)-lo;
|
|
}
|
|
else if(hx < 0x3c900000) { /* when |x|<2**-54, return x */
|
|
t = huge+x; /* return x with inexact flags when x!=0 */
|
|
return x - (t-(huge+x));
|
|
}
|
|
else k = 0;
|
|
|
|
/* x is now in primary range */
|
|
hfx = 0.5*x;
|
|
hxs = x*hfx;
|
|
r1 = one+hxs*(Q1+hxs*(Q2+hxs*(Q3+hxs*(Q4+hxs*Q5))));
|
|
t = 3.0-r1*hfx;
|
|
e = hxs*((r1-t)/(6.0 - x*t));
|
|
if(k==0) return x - (x*e-hxs); /* c is 0 */
|
|
else {
|
|
e = (x*(e-c)-c);
|
|
e -= hxs;
|
|
if(k== -1) return 0.5*(x-e)-0.5;
|
|
if(k==1) {
|
|
if(x < -0.25) return -2.0*(e-(x+0.5));
|
|
else return one+2.0*(x-e);
|
|
}
|
|
if (k <= -2 || k>56) { /* suffice to return exp(x)-1 */
|
|
y = one-(e-x);
|
|
__HI(y) += (k<<20); /* add k to y's exponent */
|
|
return y-one;
|
|
}
|
|
t = one;
|
|
if(k<20) {
|
|
__HI(t) = 0x3ff00000 - (0x200000>>k); /* t=1-2^-k */
|
|
y = t-(e-x);
|
|
__HI(y) += (k<<20); /* add k to y's exponent */
|
|
} else {
|
|
__HI(t) = ((0x3ff-k)<<20); /* 2^-k */
|
|
y = x-(e+t);
|
|
y += one;
|
|
__HI(y) += (k<<20); /* add k to y's exponent */
|
|
}
|
|
}
|
|
return y;
|
|
}
|
|
|
|
|
|
/* __ieee754_sinh(x)
|
|
* Method :
|
|
* mathematically sinh(x) if defined to be (exp(x)-exp(-x))/2
|
|
* 1. Replace x by |x| (sinh(-x) = -sinh(x)).
|
|
* 2.
|
|
* E + E/(E+1)
|
|
* 0 <= x <= 22 : sinh(x) := --------------, E=expm1(x)
|
|
* 2
|
|
*
|
|
* 22 <= x <= lnovft : sinh(x) := exp(x)/2
|
|
* lnovft <= x <= ln2ovft: sinh(x) := exp(x/2)/2 * exp(x/2)
|
|
* ln2ovft < x : sinh(x) := x*shuge (overflow)
|
|
*
|
|
* Special cases:
|
|
* sinh(x) is |x| if x is +INF, -INF, or NaN.
|
|
* only sinh(0)=0 is exact for finite x.
|
|
*/
|
|
|
|
double __ieee754_sinh(double x)
|
|
{
|
|
double t,w,h;
|
|
int ix,jx;
|
|
unsigned lx;
|
|
|
|
/* High word of |x|. */
|
|
jx = __HI(x);
|
|
ix = jx&0x7fffffff;
|
|
|
|
/* x is INF or NaN */
|
|
if(ix>=0x7ff00000) return x+x;
|
|
|
|
h = 0.5;
|
|
if (jx<0) h = -h;
|
|
/* |x| in [0,22], return sign(x)*0.5*(E+E/(E+1))) */
|
|
if (ix < 0x40360000) { /* |x|<22 */
|
|
if (ix<0x3e300000) /* |x|<2**-28 */
|
|
if(shuge+x>one) return x;/* sinh(tiny) = tiny with inexact */
|
|
t = math_expm1(fabs(x));
|
|
if(ix<0x3ff00000) return h*(2.0*t-t*t/(t+one));
|
|
return h*(t+t/(t+one));
|
|
}
|
|
|
|
/* |x| in [22, log(maxdouble)] return 0.5*exp(|x|) */
|
|
if (ix < 0x40862E42) return h*__ieee754_exp(fabs(x));
|
|
|
|
/* |x| in [log(maxdouble), overflowthresold] */
|
|
lx = *( (((*(unsigned*)&one)>>29)) + (unsigned*)&x);
|
|
if ( ix<0x408633CE || ((ix==0x408633ce) &&(lx<=(unsigned)0x8fb9f87d))) {
|
|
w = __ieee754_exp(0.5*fabs(x));
|
|
t = h*w;
|
|
return t*w;
|
|
}
|
|
|
|
/* |x| > overflowthresold, sinh(x) overflow */
|
|
return x*shuge;
|
|
}
|
|
|
|
|
|
/*
|
|
* wrapper sinh(x)
|
|
*/
|
|
|
|
double math_sinh(double x) /* wrapper sinh */
|
|
{
|
|
#ifdef _IEEE_LIBM
|
|
return __ieee754_sinh(x);
|
|
#else
|
|
double z;
|
|
z = __ieee754_sinh(x);
|
|
if(_LIB_VERSION == _IEEE_) return z;
|
|
if(!finite(z)&&finite(x)) {
|
|
return __kernel_standard(x,x,25); /* sinh overflow */
|
|
} else
|
|
return z;
|
|
#endif
|
|
}
|
|
|
|
|
|
/* __ieee754_cosh(x)
|
|
* Method :
|
|
* mathematically cosh(x) if defined to be (exp(x)+exp(-x))/2
|
|
* 1. Replace x by |x| (cosh(x) = cosh(-x)).
|
|
* 2.
|
|
* [ exp(x) - 1 ]^2
|
|
* 0 <= x <= ln2/2 : cosh(x) := 1 + -------------------
|
|
* 2*exp(x)
|
|
*
|
|
* exp(x) + 1/exp(x)
|
|
* ln2/2 <= x <= 22 : cosh(x) := -------------------
|
|
* 2
|
|
* 22 <= x <= lnovft : cosh(x) := exp(x)/2
|
|
* lnovft <= x <= ln2ovft: cosh(x) := exp(x/2)/2 * exp(x/2)
|
|
* ln2ovft < x : cosh(x) := huge*huge (overflow)
|
|
*
|
|
* Special cases:
|
|
* cosh(x) is |x| if x is +INF, -INF, or NaN.
|
|
* only cosh(0)=1 is exact for finite x.
|
|
*/
|
|
|
|
double __ieee754_cosh(double x)
|
|
{
|
|
double t,w;
|
|
int ix;
|
|
unsigned lx;
|
|
|
|
/* High word of |x|. */
|
|
ix = __HI(x);
|
|
ix &= 0x7fffffff;
|
|
|
|
/* x is INF or NaN */
|
|
if(ix>=0x7ff00000) return x*x;
|
|
|
|
/* |x| in [0,0.5*ln2], return 1+expm1(|x|)^2/(2*exp(|x|)) */
|
|
if(ix<0x3fd62e43) {
|
|
t = math_expm1(fabs(x));
|
|
w = one+t;
|
|
if (ix<0x3c800000) return w; /* cosh(tiny) = 1 */
|
|
return one+(t*t)/(w+w);
|
|
}
|
|
|
|
/* |x| in [0.5*ln2,22], return (exp(|x|)+1/exp(|x|)/2; */
|
|
if (ix < 0x40360000) {
|
|
t = __ieee754_exp(fabs(x));
|
|
return half*t+half/t;
|
|
}
|
|
|
|
/* |x| in [22, log(maxdouble)] return half*exp(|x|) */
|
|
if (ix < 0x40862E42) return half*__ieee754_exp(fabs(x));
|
|
|
|
/* |x| in [log(maxdouble), overflowthresold] */
|
|
lx = *( (((*(unsigned*)&one)>>29)) + (unsigned*)&x);
|
|
if (ix<0x408633CE ||
|
|
((ix==0x408633ce)&&(lx<=(unsigned)0x8fb9f87d))) {
|
|
w = __ieee754_exp(half*fabs(x));
|
|
t = half*w;
|
|
return t*w;
|
|
}
|
|
|
|
/* |x| > overflowthresold, cosh(x) overflow */
|
|
return huge*huge;
|
|
}
|
|
|
|
|
|
/*
|
|
* wrapper cosh(x)
|
|
*/
|
|
|
|
double math_cosh(double x) /* wrapper cosh */
|
|
{
|
|
#ifdef _IEEE_LIBM
|
|
return __ieee754_cosh(x);
|
|
#else
|
|
double z;
|
|
z = __ieee754_cosh(x);
|
|
if(_LIB_VERSION == _IEEE_ || isnan(x)) return z;
|
|
if(fabs(x)>7.10475860073943863426e+02) {
|
|
return __kernel_standard(x,x,5); /* cosh overflow */
|
|
} else
|
|
return z;
|
|
#endif
|
|
}
|
|
|
|
|
|
/* Tanh(x)
|
|
* Return the Hyperbolic Tangent of x
|
|
*
|
|
* Method :
|
|
* x -x
|
|
* e - e
|
|
* 0. tanh(x) is defined to be -----------
|
|
* x -x
|
|
* e + e
|
|
* 1. reduce x to non-negative by tanh(-x) = -tanh(x).
|
|
* 2. 0 <= x <= 2**-55 : tanh(x) := x*(one+x)
|
|
* -t
|
|
* 2**-55 < x <= 1 : tanh(x) := -----; t = expm1(-2x)
|
|
* t + 2
|
|
* 2
|
|
* 1 <= x <= 22.0 : tanh(x) := 1- ----- ; t=expm1(2x)
|
|
* t + 2
|
|
* 22.0 < x <= INF : tanh(x) := 1.
|
|
*
|
|
* Special cases:
|
|
* tanh(NaN) is NaN;
|
|
* only tanh(0)=0 is exact for finite argument.
|
|
*/
|
|
|
|
double math_tanh(double x)
|
|
{
|
|
double t,z;
|
|
int jx,ix;
|
|
|
|
/* High word of |x|. */
|
|
jx = __HI(x);
|
|
ix = jx&0x7fffffff;
|
|
|
|
/* x is INF or NaN */
|
|
if(ix>=0x7ff00000) {
|
|
if (jx>=0) return one/x+one; /* tanh(+-inf)=+-1 */
|
|
else return one/x-one; /* tanh(NaN) = NaN */
|
|
}
|
|
|
|
/* |x| < 22 */
|
|
if (ix < 0x40360000) { /* |x|<22 */
|
|
if (ix<0x3c800000) /* |x|<2**-55 */
|
|
return x*(one+x); /* tanh(small) = small */
|
|
if (ix>=0x3ff00000) { /* |x|>=1 */
|
|
t = math_expm1(two*fabs(x));
|
|
z = one - two/(t+two);
|
|
} else {
|
|
t = math_expm1(-two*fabs(x));
|
|
z= -t/(t+two);
|
|
}
|
|
/* |x| > 22, return +-1 */
|
|
} else {
|
|
z = one - tiny; /* raised inexact flag */
|
|
}
|
|
return (jx>=0)? z: -z;
|
|
}
|
|
|
|
|
|
/* double log1p(double x)
|
|
*
|
|
* Method :
|
|
* 1. Argument Reduction: find k and f such that
|
|
* 1+x = 2^k * (1+f),
|
|
* where sqrt(2)/2 < 1+f < sqrt(2) .
|
|
*
|
|
* Note. If k=0, then f=x is exact. However, if k!=0, then f
|
|
* may not be representable exactly. In that case, a correction
|
|
* term is need. Let u=1+x rounded. Let c = (1+x)-u, then
|
|
* log(1+x) - log(u) ~ c/u. Thus, we proceed to compute log(u),
|
|
* and add back the correction term c/u.
|
|
* (Note: when x > 2**53, one can simply return log(x))
|
|
*
|
|
* 2. Approximation of log1p(f).
|
|
* Let s = f/(2+f) ; based on log(1+f) = log(1+s) - log(1-s)
|
|
* = 2s + 2/3 s**3 + 2/5 s**5 + .....,
|
|
* = 2s + s*R
|
|
* We use a special Reme algorithm on [0,0.1716] to generate
|
|
* a polynomial of degree 14 to approximate R The maximum error
|
|
* of this polynomial approximation is bounded by 2**-58.45. In
|
|
* other words,
|
|
* 2 4 6 8 10 12 14
|
|
* R(z) ~ Lp1*s +Lp2*s +Lp3*s +Lp4*s +Lp5*s +Lp6*s +Lp7*s
|
|
* (the values of Lp1 to Lp7 are listed in the program)
|
|
* and
|
|
* | 2 14 | -58.45
|
|
* | Lp1*s +...+Lp7*s - R(z) | <= 2
|
|
* | |
|
|
* Note that 2s = f - s*f = f - hfsq + s*hfsq, where hfsq = f*f/2.
|
|
* In order to guarantee error in log below 1ulp, we compute log
|
|
* by
|
|
* log1p(f) = f - (hfsq - s*(hfsq+R)).
|
|
*
|
|
* 3. Finally, log1p(x) = k*ln2 + log1p(f).
|
|
* = k*ln2_hi+(f-(hfsq-(s*(hfsq+R)+k*ln2_lo)))
|
|
* Here ln2 is split into two floating point number:
|
|
* ln2_hi + ln2_lo,
|
|
* where n*ln2_hi is always exact for |n| < 2000.
|
|
*
|
|
* Special cases:
|
|
* log1p(x) is NaN with signal if x < -1 (including -INF) ;
|
|
* log1p(+INF) is +INF; log1p(-1) is -INF with signal;
|
|
* log1p(NaN) is that NaN with no signal.
|
|
*
|
|
* Accuracy:
|
|
* according to an error analysis, the error is always less than
|
|
* 1 ulp (unit in the last place).
|
|
*
|
|
* Constants:
|
|
* The hexadecimal values are the intended ones for the following
|
|
* constants. The decimal values may be used, provided that the
|
|
* compiler will convert from decimal to binary accurately enough
|
|
* to produce the hexadecimal values shown.
|
|
*
|
|
* Note: Assuming log() return accurate answer, the following
|
|
* algorithm can be used to compute log1p(x) to within a few ULP:
|
|
*
|
|
* u = 1+x;
|
|
* if(u==1.0) return x ; else
|
|
* return log(u)*(x/(u-1.0));
|
|
*
|
|
* See HP-15C Advanced Functions Handbook, p.193.
|
|
*/
|
|
|
|
double math_log1p(double x)
|
|
{
|
|
double hfsq,f,c,s,z,R,u;
|
|
int k,hx,hu,ax;
|
|
|
|
hx = __HI(x); /* high word of x */
|
|
ax = hx&0x7fffffff;
|
|
|
|
k = 1;
|
|
if (hx < 0x3FDA827A) { /* x < 0.41422 */
|
|
if(ax>=0x3ff00000) { /* x <= -1.0 */
|
|
if(x==-1.0) return -two54/zero; /* log1p(-1)=+inf */
|
|
else return (x-x)/(x-x); /* log1p(x<-1)=NaN */
|
|
}
|
|
if(ax<0x3e200000) { /* |x| < 2**-29 */
|
|
if(two54+x>zero /* raise inexact */
|
|
&&ax<0x3c900000) /* |x| < 2**-54 */
|
|
return x;
|
|
else
|
|
return x - x*x*0.5;
|
|
}
|
|
if(hx>0||hx<=((int)0xbfd2bec3)) {
|
|
k=0;f=x;hu=1;} /* -0.2929<x<0.41422 */
|
|
}
|
|
if (hx >= 0x7ff00000) return x+x;
|
|
if(k!=0) {
|
|
if(hx<0x43400000) {
|
|
u = 1.0+x;
|
|
hu = __HI(u); /* high word of u */
|
|
k = (hu>>20)-1023;
|
|
c = (k>0)? 1.0-(u-x):x-(u-1.0);/* correction term */
|
|
c /= u;
|
|
} else {
|
|
u = x;
|
|
hu = __HI(u); /* high word of u */
|
|
k = (hu>>20)-1023;
|
|
c = 0;
|
|
}
|
|
hu &= 0x000fffff;
|
|
if(hu<0x6a09e) {
|
|
__HI(u) = hu|0x3ff00000; /* normalize u */
|
|
} else {
|
|
k += 1;
|
|
__HI(u) = hu|0x3fe00000; /* normalize u/2 */
|
|
hu = (0x00100000-hu)>>2;
|
|
}
|
|
f = u-1.0;
|
|
}
|
|
hfsq=0.5*f*f;
|
|
if(hu==0) { /* |f| < 2**-20 */
|
|
if(f==zero) {
|
|
if(k==0) return zero;
|
|
else {c += k*ln2_lo; return k*ln2_hi+c;}
|
|
}
|
|
R = hfsq*(1.0-0.66666666666666666*f);
|
|
if(k==0) return f-R; else
|
|
return k*ln2_hi-((R-(k*ln2_lo+c))-f);
|
|
}
|
|
s = f/(2.0+f);
|
|
z = s*s;
|
|
R = z*(Lp1+z*(Lp2+z*(Lp3+z*(Lp4+z*(Lp5+z*(Lp6+z*Lp7))))));
|
|
if(k==0) return f-(hfsq-s*(hfsq+R)); else
|
|
return k*ln2_hi-((hfsq-(s*(hfsq+R)+(k*ln2_lo+c)))-f);
|
|
}
|
|
|
|
|
|
/* asinh(x)
|
|
* Method :
|
|
* Based on
|
|
* asinh(x) = sign(x) * log [ |x| + sqrt(x*x+1) ]
|
|
* we have
|
|
* asinh(x) := x if 1+x*x=1,
|
|
* := sign(x)*(log(x)+ln2)) for large |x|, else
|
|
* := sign(x)*log(2|x|+1/(|x|+sqrt(x*x+1))) if|x|>2, else
|
|
* := sign(x)*log1p(|x| + x^2/(1 + sqrt(1+x^2)))
|
|
*/
|
|
|
|
double math_asinh(double x)
|
|
{
|
|
double t,w;
|
|
int hx,ix;
|
|
hx = __HI(x);
|
|
ix = hx&0x7fffffff;
|
|
if(ix>=0x7ff00000) return x+x; /* x is inf or NaN */
|
|
if(ix< 0x3e300000) { /* |x|<2**-28 */
|
|
if(huge+x>one) return x; /* return x inexact except 0 */
|
|
}
|
|
if(ix>0x41b00000) { /* |x| > 2**28 */
|
|
w = __ieee754_log(fabs(x))+ln2;
|
|
} else if (ix>0x40000000) { /* 2**28 > |x| > 2.0 */
|
|
t = fabs(x);
|
|
w = __ieee754_log(2.0*t+one/(math_sqrt(x*x+one)+t));
|
|
} else { /* 2.0 > |x| > 2**-28 */
|
|
t = x*x;
|
|
w =math_log1p(fabs(x)+t/(one+math_sqrt(one+t)));
|
|
}
|
|
if(hx>0) return w; else return -w;
|
|
}
|
|
|
|
|
|
/* __ieee754_acosh(x)
|
|
* Method :
|
|
* Based on
|
|
* acosh(x) = log [ x + sqrt(x*x-1) ]
|
|
* we have
|
|
* acosh(x) := log(x)+ln2, if x is large; else
|
|
* acosh(x) := log(2x-1/(sqrt(x*x-1)+x)) if x>2; else
|
|
* acosh(x) := log1p(t+sqrt(2.0*t+t*t)); where t=x-1.
|
|
*
|
|
* Special cases:
|
|
* acosh(x) is NaN with signal if x<1.
|
|
* acosh(NaN) is NaN without signal.
|
|
*/
|
|
|
|
double __ieee754_acosh(double x)
|
|
{
|
|
double t;
|
|
int hx;
|
|
hx = __HI(x);
|
|
if(hx<0x3ff00000) { /* x < 1 */
|
|
return (x-x)/(x-x);
|
|
} else if(hx >=0x41b00000) { /* x > 2**28 */
|
|
if(hx >=0x7ff00000) { /* x is inf of NaN */
|
|
return x+x;
|
|
} else
|
|
return __ieee754_log(x)+ln2; /* acosh(huge)=log(2x) */
|
|
} else if(((hx-0x3ff00000)|__LO(x))==0) {
|
|
return 0.0; /* acosh(1) = 0 */
|
|
} else if (hx > 0x40000000) { /* 2**28 > x > 2 */
|
|
t=x*x;
|
|
return __ieee754_log(2.0*x-one/(x+math_sqrt(t-one)));
|
|
} else { /* 1<x<2 */
|
|
t = x-one;
|
|
return math_log1p(t+math_sqrt(2.0*t+t*t));
|
|
}
|
|
}
|
|
|
|
|
|
/*
|
|
* wrapper acosh(x)
|
|
*/
|
|
|
|
double math_acosh(double x) /* wrapper acosh */
|
|
{
|
|
#ifdef _IEEE_LIBM
|
|
return __ieee754_acosh(x);
|
|
#else
|
|
double z;
|
|
z = __ieee754_acosh(x);
|
|
if(_LIB_VERSION == _IEEE_ || isnan(x)) return z;
|
|
if(x<1.0) {
|
|
return __kernel_standard(x,x,29); /* acosh(x<1) */
|
|
} else
|
|
return z;
|
|
#endif
|
|
}
|
|
|
|
|
|
/* __ieee754_atanh(x)
|
|
* Method :
|
|
* 1.Reduced x to positive by atanh(-x) = -atanh(x)
|
|
* 2.For x>=0.5
|
|
* 1 2x x
|
|
* atanh(x) = --- * log(1 + -------) = 0.5 * log1p(2 * --------)
|
|
* 2 1 - x 1 - x
|
|
*
|
|
* For x<0.5
|
|
* atanh(x) = 0.5*log1p(2x+2x*x/(1-x))
|
|
*
|
|
* Special cases:
|
|
* atanh(x) is NaN if |x| > 1 with signal;
|
|
* atanh(NaN) is that NaN with no signal;
|
|
* atanh(+-1) is +-INF with signal.
|
|
*
|
|
*/
|
|
|
|
double __ieee754_atanh(double x)
|
|
{
|
|
double t;
|
|
int hx,ix;
|
|
unsigned lx;
|
|
hx = __HI(x); /* high word */
|
|
lx = __LO(x); /* low word */
|
|
ix = hx&0x7fffffff;
|
|
if ((ix|((lx|(-lx))>>31))>0x3ff00000) /* |x|>1 */
|
|
return (x-x)/(x-x);
|
|
if(ix==0x3ff00000)
|
|
return x/zero;
|
|
if(ix<0x3e300000&&(huge+x)>zero) return x; /* x<2**-28 */
|
|
__HI(x) = ix; /* x <- |x| */
|
|
if(ix<0x3fe00000) { /* x < 0.5 */
|
|
t = x+x;
|
|
t = 0.5*math_log1p(t+t*x/(one-x));
|
|
} else
|
|
t = 0.5*math_log1p((x+x)/(one-x));
|
|
if(hx>=0) return t; else return -t;
|
|
}
|
|
|
|
|
|
/*
|
|
* wrapper atanh(x)
|
|
*/
|
|
|
|
double math_atanh(double x) /* wrapper atanh */
|
|
{
|
|
#ifdef _IEEE_LIBM
|
|
return __ieee754_atanh(x);
|
|
#else
|
|
double z,y;
|
|
z = __ieee754_atanh(x);
|
|
if(_LIB_VERSION == _IEEE_ || isnan(x)) return z;
|
|
y = fabs(x);
|
|
if(y>=1.0) {
|
|
if(y>1.0)
|
|
return __kernel_standard(x,x,30); /* atanh(|x|>1) */
|
|
else
|
|
return __kernel_standard(x,x,31); /* atanh(|x|==1) */
|
|
} else
|
|
return z;
|
|
#endif
|
|
}
|
|
|
|
|
|
/*
|
|
* wrapper exp(x)
|
|
*/
|
|
|
|
double math_exp(double x) /* wrapper exp */
|
|
{
|
|
#ifdef _IEEE_LIBM
|
|
return __ieee754_exp(x);
|
|
#else
|
|
double z;
|
|
z = __ieee754_exp(x);
|
|
if(_LIB_VERSION == _IEEE_) return z;
|
|
if(finite(x)) {
|
|
if(x>o_threshold)
|
|
return __kernel_standard(x,x,6); /* exp overflow */
|
|
else if(x<u_threshold)
|
|
return __kernel_standard(x,x,7); /* exp underflow */
|
|
}
|
|
return z;
|
|
#endif
|
|
}
|
|
|
|
|
|
/*
|
|
* fabs(x) returns the absolute value of x.
|
|
*/
|
|
|
|
double fabs(double x)
|
|
{
|
|
__HI(x) &= 0x7fffffff;
|
|
return x;
|
|
}
|
|
|
|
|
|
/*
|
|
* wrapper log(x)
|
|
*/
|
|
|
|
double math_log(double x) /* wrapper log */
|
|
{
|
|
#ifdef _IEEE_LIBM
|
|
return __ieee754_log(x);
|
|
#else
|
|
double z;
|
|
z = __ieee754_log(x);
|
|
if(_LIB_VERSION == _IEEE_ || isnan(x) || x > 0.0) return z;
|
|
if(x==0.0)
|
|
return __kernel_standard(x,x,16); /* log(0) */
|
|
else
|
|
return __kernel_standard(x,x,17); /* log(x<0) */
|
|
#endif
|
|
}
|
|
|
|
|
|
/* __ieee754_log10(x)
|
|
* Return the base 10 logarithm of x
|
|
*
|
|
* Method :
|
|
* Let log10_2hi = leading 40 bits of log10(2) and
|
|
* log10_2lo = log10(2) - log10_2hi,
|
|
* ivln10 = 1/log(10) rounded.
|
|
* Then
|
|
* n = ilogb(x),
|
|
* if(n<0) n = n+1;
|
|
* x = scalbn(x,-n);
|
|
* log10(x) := n*log10_2hi + (n*log10_2lo + ivln10*log(x))
|
|
*
|
|
* Note 1:
|
|
* To guarantee log10(10**n)=n, where 10**n is normal, the rounding
|
|
* mode must set to Round-to-Nearest.
|
|
* Note 2:
|
|
* [1/log(10)] rounded to 53 bits has error .198 ulps;
|
|
* log10 is monotonic at all binary break points.
|
|
*
|
|
* Special cases:
|
|
* log10(x) is NaN with signal if x < 0;
|
|
* log10(+INF) is +INF with no signal; log10(0) is -INF with signal;
|
|
* log10(NaN) is that NaN with no signal;
|
|
* log10(10**N) = N for N=0,1,...,22.
|
|
*
|
|
* Constants:
|
|
* The hexadecimal values are the intended ones for the following constants.
|
|
* The decimal values may be used, provided that the compiler will convert
|
|
* from decimal to binary accurately enough to produce the hexadecimal values
|
|
* shown.
|
|
*/
|
|
|
|
double __ieee754_log10(double x)
|
|
{
|
|
double y,z;
|
|
int i,k,hx;
|
|
unsigned lx;
|
|
|
|
hx = __HI(x); /* high word of x */
|
|
lx = __LO(x); /* low word of x */
|
|
|
|
k=0;
|
|
if (hx < 0x00100000) { /* x < 2**-1022 */
|
|
if (((hx&0x7fffffff)|lx)==0)
|
|
return -two54/zero; /* log(+-0)=-inf */
|
|
if (hx<0) return (x-x)/zero; /* log(-#) = NaN */
|
|
k -= 54; x *= two54; /* subnormal number, scale up x */
|
|
hx = __HI(x); /* high word of x */
|
|
}
|
|
if (hx >= 0x7ff00000) return x+x;
|
|
k += (hx>>20)-1023;
|
|
i = ((unsigned)k&0x80000000)>>31;
|
|
hx = (hx&0x000fffff)|((0x3ff-i)<<20);
|
|
y = (double)(k+i);
|
|
__HI(x) = hx;
|
|
z = y*log10_2lo + ivln10*__ieee754_log(x);
|
|
return z+y*log10_2hi;
|
|
}
|
|
|
|
|
|
/*
|
|
* wrapper log10(X)
|
|
*/
|
|
|
|
double math_log10(double x) /* wrapper log10 */
|
|
{
|
|
#ifdef _IEEE_LIBM
|
|
return __ieee754_log10(x);
|
|
#else
|
|
double z;
|
|
z = __ieee754_log10(x);
|
|
if(_LIB_VERSION == _IEEE_ || isnan(x)) return z;
|
|
if(x<=0.0) {
|
|
if(x==0.0)
|
|
return __kernel_standard(x,x,18); /* log10(0) */
|
|
else
|
|
return __kernel_standard(x,x,19); /* log10(x<0) */
|
|
} else
|
|
return z;
|
|
#endif
|
|
}
|
|
|
|
|
|
/* __ieee754_pow(x,y) return x**y
|
|
*
|
|
* n
|
|
* Method: Let x = 2 * (1+f)
|
|
* 1. Compute and return log2(x) in two pieces:
|
|
* log2(x) = w1 + w2,
|
|
* where w1 has 53-24 = 29 bit trailing zeros.
|
|
* 2. Perform y*log2(x) = n+y' by simulating muti-precision
|
|
* arithmetic, where |y'|<=0.5.
|
|
* 3. Return x**y = 2**n*exp(y'*log2)
|
|
*
|
|
* Special cases:
|
|
* 1. (anything) ** 0 is 1
|
|
* 2. (anything) ** 1 is itself
|
|
* 3. (anything) ** NAN is NAN
|
|
* 4. NAN ** (anything except 0) is NAN
|
|
* 5. +-(|x| > 1) ** +INF is +INF
|
|
* 6. +-(|x| > 1) ** -INF is +0
|
|
* 7. +-(|x| < 1) ** +INF is +0
|
|
* 8. +-(|x| < 1) ** -INF is +INF
|
|
* 9. +-1 ** +-INF is NAN
|
|
* 10. +0 ** (+anything except 0, NAN) is +0
|
|
* 11. -0 ** (+anything except 0, NAN, odd integer) is +0
|
|
* 12. +0 ** (-anything except 0, NAN) is +INF
|
|
* 13. -0 ** (-anything except 0, NAN, odd integer) is +INF
|
|
* 14. -0 ** (odd integer) = -( +0 ** (odd integer) )
|
|
* 15. +INF ** (+anything except 0,NAN) is +INF
|
|
* 16. +INF ** (-anything except 0,NAN) is +0
|
|
* 17. -INF ** (anything) = -0 ** (-anything)
|
|
* 18. (-anything) ** (integer) is (-1)**(integer)*(+anything**integer)
|
|
* 19. (-anything except 0 and inf) ** (non-integer) is NAN
|
|
*
|
|
* Accuracy:
|
|
* pow(x,y) returns x**y nearly rounded. In particular
|
|
* pow(integer,integer)
|
|
* always returns the correct integer provided it is
|
|
* representable.
|
|
*
|
|
* Constants :
|
|
* The hexadecimal values are the intended ones for the following
|
|
* constants. The decimal values may be used, provided that the
|
|
* compiler will convert from decimal to binary accurately enough
|
|
* to produce the hexadecimal values shown.
|
|
*/
|
|
|
|
double __ieee754_pow(double x, double y)
|
|
{
|
|
double z,ax,z_h,z_l,p_h,p_l;
|
|
double y1,t1,t2,r,s,t,u,v,w;
|
|
int i0,i1,i,j,k,yisint,n;
|
|
int hx,hy,ix,iy;
|
|
unsigned lx,ly;
|
|
|
|
i0 = ((*(int*)&one)>>29)^1; i1=1-i0;
|
|
hx = __HI(x); lx = __LO(x);
|
|
hy = __HI(y); ly = __LO(y);
|
|
ix = hx&0x7fffffff; iy = hy&0x7fffffff;
|
|
|
|
/* y==zero: x**0 = 1 */
|
|
if((iy|ly)==0) return one;
|
|
|
|
/* +-NaN return x+y */
|
|
if(ix > 0x7ff00000 || ((ix==0x7ff00000)&&(lx!=0)) ||
|
|
iy > 0x7ff00000 || ((iy==0x7ff00000)&&(ly!=0)))
|
|
return x+y;
|
|
|
|
/* determine if y is an odd int when x < 0
|
|
* yisint = 0 ... y is not an integer
|
|
* yisint = 1 ... y is an odd int
|
|
* yisint = 2 ... y is an even int
|
|
*/
|
|
yisint = 0;
|
|
if(hx<0) {
|
|
if(iy>=0x43400000) yisint = 2; /* even integer y */
|
|
else if(iy>=0x3ff00000) {
|
|
k = (iy>>20)-0x3ff; /* exponent */
|
|
if(k>20) {
|
|
j = ly>>(52-k);
|
|
if((j<<(52-k))==ly) yisint = 2-(j&1);
|
|
} else if(ly==0) {
|
|
j = iy>>(20-k);
|
|
if((j<<(20-k))==iy) yisint = 2-(j&1);
|
|
}
|
|
}
|
|
}
|
|
|
|
/* special value of y */
|
|
if(ly==0) {
|
|
if (iy==0x7ff00000) { /* y is +-inf */
|
|
if(((ix-0x3ff00000)|lx)==0)
|
|
return y - y; /* inf**+-1 is NaN */
|
|
else if (ix >= 0x3ff00000)/* (|x|>1)**+-inf = inf,0 */
|
|
return (hy>=0)? y: zero;
|
|
else /* (|x|<1)**-,+inf = inf,0 */
|
|
return (hy<0)?-y: zero;
|
|
}
|
|
if(iy==0x3ff00000) { /* y is +-1 */
|
|
if(hy<0) return one/x; else return x;
|
|
}
|
|
if(hy==0x40000000) return x*x; /* y is 2 */
|
|
if(hy==0x3fe00000) { /* y is 0.5 */
|
|
if(hx>=0) /* x >= +0 */
|
|
return math_sqrt(x);
|
|
}
|
|
}
|
|
|
|
ax = fabs(x);
|
|
/* special value of x */
|
|
if(lx==0) {
|
|
if(ix==0x7ff00000||ix==0||ix==0x3ff00000){
|
|
z = ax; /*x is +-0,+-inf,+-1*/
|
|
if(hy<0) z = one/z; /* z = (1/|x|) */
|
|
if(hx<0) {
|
|
if(((ix-0x3ff00000)|yisint)==0) {
|
|
z = (z-z)/(z-z); /* (-1)**non-int is NaN */
|
|
} else if(yisint==1)
|
|
z = -z; /* (x<0)**odd = -(|x|**odd) */
|
|
}
|
|
return z;
|
|
}
|
|
}
|
|
|
|
n = (hx>>31)+1;
|
|
|
|
/* (x<0)**(non-int) is NaN */
|
|
if((n|yisint)==0) return (x-x)/(x-x);
|
|
|
|
s = one; /* s (sign of result -ve**odd) = -1 else = 1 */
|
|
if((n|(yisint-1))==0) s = -one;/* (-ve)**(odd int) */
|
|
|
|
/* |y| is huge */
|
|
if(iy>0x41e00000) { /* if |y| > 2**31 */
|
|
if(iy>0x43f00000){ /* if |y| > 2**64, must o/uflow */
|
|
if(ix<=0x3fefffff) return (hy<0)? huge*huge:tiny*tiny;
|
|
if(ix>=0x3ff00000) return (hy>0)? huge*huge:tiny*tiny;
|
|
}
|
|
/* over/underflow if x is not close to one */
|
|
if(ix<0x3fefffff) return (hy<0)? s*huge*huge:s*tiny*tiny;
|
|
if(ix>0x3ff00000) return (hy>0)? s*huge*huge:s*tiny*tiny;
|
|
/* now |1-x| is tiny <= 2**-20, suffice to compute
|
|
log(x) by x-x^2/2+x^3/3-x^4/4 */
|
|
t = ax-one; /* t has 20 trailing zeros */
|
|
w = (t*t)*(0.5-t*(0.3333333333333333333333-t*0.25));
|
|
u = ivln2_h*t; /* ivln2_h has 21 sig. bits */
|
|
v = t*ivln2_l-w*ivln2;
|
|
t1 = u+v;
|
|
__LO(t1) = 0;
|
|
t2 = v-(t1-u);
|
|
} else {
|
|
double ss,s2,s_h,s_l,t_h,t_l;
|
|
n = 0;
|
|
/* take care subnormal number */
|
|
if(ix<0x00100000)
|
|
{ax *= two53; n -= 53; ix = __HI(ax); }
|
|
n += ((ix)>>20)-0x3ff;
|
|
j = ix&0x000fffff;
|
|
/* determine interval */
|
|
ix = j|0x3ff00000; /* normalize ix */
|
|
if(j<=0x3988E) k=0; /* |x|<sqrt(3/2) */
|
|
else if(j<0xBB67A) k=1; /* |x|<sqrt(3) */
|
|
else {k=0;n+=1;ix -= 0x00100000;}
|
|
__HI(ax) = ix;
|
|
|
|
/* compute ss = s_h+s_l = (x-1)/(x+1) or (x-1.5)/(x+1.5) */
|
|
u = ax-bp[k]; /* bp[0]=1.0, bp[1]=1.5 */
|
|
v = one/(ax+bp[k]);
|
|
ss = u*v;
|
|
s_h = ss;
|
|
__LO(s_h) = 0;
|
|
/* t_h=ax+bp[k] High */
|
|
t_h = zero;
|
|
__HI(t_h)=((ix>>1)|0x20000000)+0x00080000+(k<<18);
|
|
t_l = ax - (t_h-bp[k]);
|
|
s_l = v*((u-s_h*t_h)-s_h*t_l);
|
|
/* compute log(ax) */
|
|
s2 = ss*ss;
|
|
r = s2*s2*(L1+s2*(L2+s2*(L3+s2*(L4+s2*(L5+s2*L6)))));
|
|
r += s_l*(s_h+ss);
|
|
s2 = s_h*s_h;
|
|
t_h = 3.0+s2+r;
|
|
__LO(t_h) = 0;
|
|
t_l = r-((t_h-3.0)-s2);
|
|
/* u+v = ss*(1+...) */
|
|
u = s_h*t_h;
|
|
v = s_l*t_h+t_l*ss;
|
|
/* 2/(3log2)*(ss+...) */
|
|
p_h = u+v;
|
|
__LO(p_h) = 0;
|
|
p_l = v-(p_h-u);
|
|
z_h = cp_h*p_h; /* cp_h+cp_l = 2/(3*log2) */
|
|
z_l = cp_l*p_h+p_l*cp+dp_l[k];
|
|
/* log2(ax) = (ss+..)*2/(3*log2) = n + dp_h + z_h + z_l */
|
|
t = (double)n;
|
|
t1 = (((z_h+z_l)+dp_h[k])+t);
|
|
__LO(t1) = 0;
|
|
t2 = z_l-(((t1-t)-dp_h[k])-z_h);
|
|
}
|
|
|
|
/* split up y into y1+y2 and compute (y1+y2)*(t1+t2) */
|
|
y1 = y;
|
|
__LO(y1) = 0;
|
|
p_l = (y-y1)*t1+y*t2;
|
|
p_h = y1*t1;
|
|
z = p_l+p_h;
|
|
j = __HI(z);
|
|
i = __LO(z);
|
|
if (j>=0x40900000) { /* z >= 1024 */
|
|
if(((j-0x40900000)|i)!=0) /* if z > 1024 */
|
|
return s*huge*huge; /* overflow */
|
|
else {
|
|
if(p_l+ovt>z-p_h) return s*huge*huge; /* overflow */
|
|
}
|
|
} else if((j&0x7fffffff)>=0x4090cc00 ) { /* z <= -1075 */
|
|
if(((j-0xc090cc00)|i)!=0) /* z < -1075 */
|
|
return s*tiny*tiny; /* underflow */
|
|
else {
|
|
if(p_l<=z-p_h) return s*tiny*tiny; /* underflow */
|
|
}
|
|
}
|
|
/*
|
|
* compute 2**(p_h+p_l)
|
|
*/
|
|
i = j&0x7fffffff;
|
|
k = (i>>20)-0x3ff;
|
|
n = 0;
|
|
if(i>0x3fe00000) { /* if |z| > 0.5, set n = [z+0.5] */
|
|
n = j+(0x00100000>>(k+1));
|
|
k = ((n&0x7fffffff)>>20)-0x3ff; /* new k for n */
|
|
t = zero;
|
|
__HI(t) = (n&~(0x000fffff>>k));
|
|
n = ((n&0x000fffff)|0x00100000)>>(20-k);
|
|
if(j<0) n = -n;
|
|
p_h -= t;
|
|
}
|
|
t = p_l+p_h;
|
|
__LO(t) = 0;
|
|
u = t*lg2_h;
|
|
v = (p_l-(t-p_h))*lg2+t*lg2_l;
|
|
z = u+v;
|
|
w = v-(z-u);
|
|
t = z*z;
|
|
t1 = z - t*(P1+t*(P2+t*(P3+t*(P4+t*P5))));
|
|
r = (z*t1)/(t1-two)-(w+z*w);
|
|
z = one-(r-z);
|
|
j = __HI(z);
|
|
j += (n<<20);
|
|
if((j>>20)<=0) z = scalbn(z,n); /* subnormal output */
|
|
else __HI(z) += (n<<20);
|
|
return s*z;
|
|
}
|
|
|
|
|
|
/*
|
|
* wrapper pow(x,y) return x**y
|
|
*/
|
|
|
|
double math_pow(double x, double y) /* wrapper pow */
|
|
{
|
|
#ifdef _IEEE_LIBM
|
|
return __ieee754_pow(x,y);
|
|
#else
|
|
double z;
|
|
z=__ieee754_pow(x,y);
|
|
if(_LIB_VERSION == _IEEE_|| isnan(y)) return z;
|
|
if(isnan(x)) {
|
|
if(y==0.0)
|
|
return __kernel_standard(x,y,42); /* pow(NaN,0.0) */
|
|
else
|
|
return z;
|
|
}
|
|
if(x==0.0){
|
|
if(y==0.0)
|
|
return __kernel_standard(x,y,20); /* pow(0.0,0.0) */
|
|
if(finite(y)&&y<0.0)
|
|
return __kernel_standard(x,y,23); /* pow(0.0,negative) */
|
|
return z;
|
|
}
|
|
if(!finite(z)) {
|
|
if(finite(x)&&finite(y)) {
|
|
if(isnan(z))
|
|
return __kernel_standard(x,y,24); /* pow neg**non-int */
|
|
else
|
|
return __kernel_standard(x,y,21); /* pow overflow */
|
|
}
|
|
}
|
|
if(z==0.0&&finite(x)&&finite(y))
|
|
return __kernel_standard(x,y,22); /* pow underflow */
|
|
return z;
|
|
#endif
|
|
}
|
|
|
|
|
|
/* __ieee754_sqrt(x)
|
|
* Return correctly rounded sqrt.
|
|
* ------------------------------------------
|
|
* | Use the hardware sqrt if you have one |
|
|
* ------------------------------------------
|
|
* Method:
|
|
* Bit by bit method using integer arithmetic. (Slow, but portable)
|
|
* 1. Normalization
|
|
* Scale x to y in [1,4) with even powers of 2:
|
|
* find an integer k such that 1 <= (y=x*2^(2k)) < 4, then
|
|
* sqrt(x) = 2^k * sqrt(y)
|
|
* 2. Bit by bit computation
|
|
* Let q = sqrt(y) truncated to i bit after binary point (q = 1),
|
|
* i 0
|
|
* i+1 2
|
|
* s = 2*q , and y = 2 * ( y - q ). (1)
|
|
* i i i i
|
|
*
|
|
* To compute q from q , one checks whether
|
|
* i+1 i
|
|
*
|
|
* -(i+1) 2
|
|
* (q + 2 ) <= y. (2)
|
|
* i
|
|
* -(i+1)
|
|
* If (2) is false, then q = q ; otherwise q = q + 2 .
|
|
* i+1 i i+1 i
|
|
*
|
|
* With some algebric manipulation, it is not difficult to see
|
|
* that (2) is equivalent to
|
|
* -(i+1)
|
|
* s + 2 <= y (3)
|
|
* i i
|
|
*
|
|
* The advantage of (3) is that s and y can be computed by
|
|
* i i
|
|
* the following recurrence formula:
|
|
* if (3) is false
|
|
*
|
|
* s = s , y = y ; (4)
|
|
* i+1 i i+1 i
|
|
*
|
|
* otherwise,
|
|
* -i -(i+1)
|
|
* s = s + 2 , y = y - s - 2 (5)
|
|
* i+1 i i+1 i i
|
|
*
|
|
* One may easily use induction to prove (4) and (5).
|
|
* Note. Since the left hand side of (3) contain only i+2 bits,
|
|
* it does not necessary to do a full (53-bit) comparison
|
|
* in (3).
|
|
* 3. Final rounding
|
|
* After generating the 53 bits result, we compute one more bit.
|
|
* Together with the remainder, we can decide whether the
|
|
* result is exact, bigger than 1/2ulp, or less than 1/2ulp
|
|
* (it will never equal to 1/2ulp).
|
|
* The rounding mode can be detected by checking whether
|
|
* huge + tiny is equal to huge, and whether huge - tiny is
|
|
* equal to huge for some floating point number "huge" and "tiny".
|
|
*
|
|
* Special cases:
|
|
* sqrt(+-0) = +-0 ... exact
|
|
* sqrt(inf) = inf
|
|
* sqrt(-ve) = NaN ... with invalid signal
|
|
* sqrt(NaN) = NaN ... with invalid signal for signaling NaN
|
|
*
|
|
* Other methods : see the appended file at the end of the program below.
|
|
*---------------
|
|
*/
|
|
|
|
double __ieee754_sqrt(double x)
|
|
{
|
|
double z;
|
|
int sign = (int)0x80000000;
|
|
unsigned r,t1,s1,ix1,q1;
|
|
int ix0,s0,q,m,t,i;
|
|
|
|
ix0 = __HI(x); /* high word of x */
|
|
ix1 = __LO(x); /* low word of x */
|
|
|
|
/* take care of Inf and NaN */
|
|
if((ix0&0x7ff00000)==0x7ff00000) {
|
|
return x*x+x; /* sqrt(NaN)=NaN, sqrt(+inf)=+inf
|
|
sqrt(-inf)=sNaN */
|
|
}
|
|
/* take care of zero */
|
|
if(ix0<=0) {
|
|
if(((ix0&(~sign))|ix1)==0) return x;/* sqrt(+-0) = +-0 */
|
|
else if(ix0<0)
|
|
return (x-x)/(x-x); /* sqrt(-ve) = sNaN */
|
|
}
|
|
/* normalize x */
|
|
m = (ix0>>20);
|
|
if(m==0) { /* subnormal x */
|
|
while(ix0==0) {
|
|
m -= 21;
|
|
ix0 |= (ix1>>11); ix1 <<= 21;
|
|
}
|
|
for(i=0;(ix0&0x00100000)==0;i++) ix0<<=1;
|
|
m -= i-1;
|
|
ix0 |= (ix1>>(32-i));
|
|
ix1 <<= i;
|
|
}
|
|
m -= 1023; /* unbias exponent */
|
|
ix0 = (ix0&0x000fffff)|0x00100000;
|
|
if(m&1){ /* odd m, double x to make it even */
|
|
ix0 += ix0 + ((ix1&sign)>>31);
|
|
ix1 += ix1;
|
|
}
|
|
m >>= 1; /* m = [m/2] */
|
|
|
|
/* generate sqrt(x) bit by bit */
|
|
ix0 += ix0 + ((ix1&sign)>>31);
|
|
ix1 += ix1;
|
|
q = q1 = s0 = s1 = 0; /* [q,q1] = sqrt(x) */
|
|
r = 0x00200000; /* r = moving bit from right to left */
|
|
|
|
while(r!=0) {
|
|
t = s0+r;
|
|
if(t<=ix0) {
|
|
s0 = t+r;
|
|
ix0 -= t;
|
|
q += r;
|
|
}
|
|
ix0 += ix0 + ((ix1&sign)>>31);
|
|
ix1 += ix1;
|
|
r>>=1;
|
|
}
|
|
|
|
r = sign;
|
|
while(r!=0) {
|
|
t1 = s1+r;
|
|
t = s0;
|
|
if((t<ix0)||((t==ix0)&&(t1<=ix1))) {
|
|
s1 = t1+r;
|
|
if(((t1&sign)==sign)&&(s1&sign)==0) s0 += 1;
|
|
ix0 -= t;
|
|
if (ix1 < t1) ix0 -= 1;
|
|
ix1 -= t1;
|
|
q1 += r;
|
|
}
|
|
ix0 += ix0 + ((ix1&sign)>>31);
|
|
ix1 += ix1;
|
|
r>>=1;
|
|
}
|
|
|
|
/* use floating add to find out rounding direction */
|
|
if((ix0|ix1)!=0) {
|
|
z = one-tiny; /* trigger inexact flag */
|
|
if (z>=one) {
|
|
z = one+tiny;
|
|
if (q1==(unsigned)0xffffffff) { q1=0; q += 1;}
|
|
else if (z>one) {
|
|
if (q1==(unsigned)0xfffffffe) q+=1;
|
|
q1+=2;
|
|
} else
|
|
q1 += (q1&1);
|
|
}
|
|
}
|
|
ix0 = (q>>1)+0x3fe00000;
|
|
ix1 = q1>>1;
|
|
if ((q&1)==1) ix1 |= sign;
|
|
ix0 += (m <<20);
|
|
__HI(z) = ix0;
|
|
__LO(z) = ix1;
|
|
return z;
|
|
}
|
|
|
|
/*
|
|
Other methods (use floating-point arithmetic)
|
|
-------------
|
|
(This is a copy of a drafted paper by Prof W. Kahan
|
|
and K.C. Ng, written in May, 1986)
|
|
|
|
Two algorithms are given here to implement sqrt(x)
|
|
(IEEE double precision arithmetic) in software.
|
|
Both supply sqrt(x) correctly rounded. The first algorithm (in
|
|
Section A) uses newton iterations and involves four divisions.
|
|
The second one uses reciproot iterations to avoid division, but
|
|
requires more multiplications. Both algorithms need the ability
|
|
to chop results of arithmetic operations instead of round them,
|
|
and the INEXACT flag to indicate when an arithmetic operation
|
|
is executed exactly with no roundoff error, all part of the
|
|
standard (IEEE 754-1985). The ability to perform shift, add,
|
|
subtract and logical AND operations upon 32-bit words is needed
|
|
too, though not part of the standard.
|
|
|
|
A. sqrt(x) by Newton Iteration
|
|
|
|
(1) Initial approximation
|
|
|
|
Let x0 and x1 be the leading and the trailing 32-bit words of
|
|
a floating point number x (in IEEE double format) respectively
|
|
|
|
1 11 52 ...widths
|
|
------------------------------------------------------
|
|
x: |s| e | f |
|
|
------------------------------------------------------
|
|
msb lsb msb lsb ...order
|
|
|
|
|
|
------------------------ ------------------------
|
|
x0: |s| e | f1 | x1: | f2 |
|
|
------------------------ ------------------------
|
|
|
|
By performing shifts and subtracts on x0 and x1 (both regarded
|
|
as integers), we obtain an 8-bit approximation of sqrt(x) as
|
|
follows.
|
|
|
|
k := (x0>>1) + 0x1ff80000;
|
|
y0 := k - T1[31&(k>>15)]. ... y ~ sqrt(x) to 8 bits
|
|
Here k is a 32-bit integer and T1[] is an integer array containing
|
|
correction terms. Now magically the floating value of y (y's
|
|
leading 32-bit word is y0, the value of its trailing word is 0)
|
|
approximates sqrt(x) to almost 8-bit.
|
|
|
|
Value of T1:
|
|
static int T1[32]= {
|
|
0, 1024, 3062, 5746, 9193, 13348, 18162, 23592,
|
|
29598, 36145, 43202, 50740, 58733, 67158, 75992, 85215,
|
|
83599, 71378, 60428, 50647, 41945, 34246, 27478, 21581,
|
|
16499, 12183, 8588, 5674, 3403, 1742, 661, 130,};
|
|
|
|
(2) Iterative refinement
|
|
|
|
Apply Heron's rule three times to y, we have y approximates
|
|
sqrt(x) to within 1 ulp (Unit in the Last Place):
|
|
|
|
y := (y+x/y)/2 ... almost 17 sig. bits
|
|
y := (y+x/y)/2 ... almost 35 sig. bits
|
|
y := y-(y-x/y)/2 ... within 1 ulp
|
|
|
|
|
|
Remark 1.
|
|
Another way to improve y to within 1 ulp is:
|
|
|
|
y := (y+x/y) ... almost 17 sig. bits to 2*sqrt(x)
|
|
y := y - 0x00100006 ... almost 18 sig. bits to sqrt(x)
|
|
|
|
2
|
|
(x-y )*y
|
|
y := y + 2* ---------- ...within 1 ulp
|
|
2
|
|
3y + x
|
|
|
|
|
|
This formula has one division fewer than the one above; however,
|
|
it requires more multiplications and additions. Also x must be
|
|
scaled in advance to avoid spurious overflow in evaluating the
|
|
expression 3y*y+x. Hence it is not recommended uless division
|
|
is slow. If division is very slow, then one should use the
|
|
reciproot algorithm given in section B.
|
|
|
|
(3) Final adjustment
|
|
|
|
By twiddling y's last bit it is possible to force y to be
|
|
correctly rounded according to the prevailing rounding mode
|
|
as follows. Let r and i be copies of the rounding mode and
|
|
inexact flag before entering the square root program. Also we
|
|
use the expression y+-ulp for the next representable floating
|
|
numbers (up and down) of y. Note that y+-ulp = either fixed
|
|
point y+-1, or multiply y by nextafter(1,+-inf) in chopped
|
|
mode.
|
|
|
|
I := FALSE; ... reset INEXACT flag I
|
|
R := RZ; ... set rounding mode to round-toward-zero
|
|
z := x/y; ... chopped quotient, possibly inexact
|
|
If(not I) then { ... if the quotient is exact
|
|
if(z=y) {
|
|
I := i; ... restore inexact flag
|
|
R := r; ... restore rounded mode
|
|
return sqrt(x):=y.
|
|
} else {
|
|
z := z - ulp; ... special rounding
|
|
}
|
|
}
|
|
i := TRUE; ... sqrt(x) is inexact
|
|
If (r=RN) then z=z+ulp ... rounded-to-nearest
|
|
If (r=RP) then { ... round-toward-+inf
|
|
y = y+ulp; z=z+ulp;
|
|
}
|
|
y := y+z; ... chopped sum
|
|
y0:=y0-0x00100000; ... y := y/2 is correctly rounded.
|
|
I := i; ... restore inexact flag
|
|
R := r; ... restore rounded mode
|
|
return sqrt(x):=y.
|
|
|
|
(4) Special cases
|
|
|
|
Square root of +inf, +-0, or NaN is itself;
|
|
Square root of a negative number is NaN with invalid signal.
|
|
|
|
|
|
B. sqrt(x) by Reciproot Iteration
|
|
|
|
(1) Initial approximation
|
|
|
|
Let x0 and x1 be the leading and the trailing 32-bit words of
|
|
a floating point number x (in IEEE double format) respectively
|
|
(see section A). By performing shifs and subtracts on x0 and y0,
|
|
we obtain a 7.8-bit approximation of 1/sqrt(x) as follows.
|
|
|
|
k := 0x5fe80000 - (x0>>1);
|
|
y0:= k - T2[63&(k>>14)]. ... y ~ 1/sqrt(x) to 7.8 bits
|
|
|
|
Here k is a 32-bit integer and T2[] is an integer array
|
|
containing correction terms. Now magically the floating
|
|
value of y (y's leading 32-bit word is y0, the value of
|
|
its trailing word y1 is set to zero) approximates 1/sqrt(x)
|
|
to almost 7.8-bit.
|
|
|
|
Value of T2:
|
|
static int T2[64]= {
|
|
0x1500, 0x2ef8, 0x4d67, 0x6b02, 0x87be, 0xa395, 0xbe7a, 0xd866,
|
|
0xf14a, 0x1091b,0x11fcd,0x13552,0x14999,0x15c98,0x16e34,0x17e5f,
|
|
0x18d03,0x19a01,0x1a545,0x1ae8a,0x1b5c4,0x1bb01,0x1bfde,0x1c28d,
|
|
0x1c2de,0x1c0db,0x1ba73,0x1b11c,0x1a4b5,0x1953d,0x18266,0x16be0,
|
|
0x1683e,0x179d8,0x18a4d,0x19992,0x1a789,0x1b445,0x1bf61,0x1c989,
|
|
0x1d16d,0x1d77b,0x1dddf,0x1e2ad,0x1e5bf,0x1e6e8,0x1e654,0x1e3cd,
|
|
0x1df2a,0x1d635,0x1cb16,0x1be2c,0x1ae4e,0x19bde,0x1868e,0x16e2e,
|
|
0x1527f,0x1334a,0x11051,0xe951, 0xbe01, 0x8e0d, 0x5924, 0x1edd,};
|
|
|
|
(2) Iterative refinement
|
|
|
|
Apply Reciproot iteration three times to y and multiply the
|
|
result by x to get an approximation z that matches sqrt(x)
|
|
to about 1 ulp. To be exact, we will have
|
|
-1ulp < sqrt(x)-z<1.0625ulp.
|
|
|
|
... set rounding mode to Round-to-nearest
|
|
y := y*(1.5-0.5*x*y*y) ... almost 15 sig. bits to 1/sqrt(x)
|
|
y := y*((1.5-2^-30)+0.5*x*y*y)... about 29 sig. bits to 1/sqrt(x)
|
|
... special arrangement for better accuracy
|
|
z := x*y ... 29 bits to sqrt(x), with z*y<1
|
|
z := z + 0.5*z*(1-z*y) ... about 1 ulp to sqrt(x)
|
|
|
|
Remark 2. The constant 1.5-2^-30 is chosen to bias the error so that
|
|
(a) the term z*y in the final iteration is always less than 1;
|
|
(b) the error in the final result is biased upward so that
|
|
-1 ulp < sqrt(x) - z < 1.0625 ulp
|
|
instead of |sqrt(x)-z|<1.03125ulp.
|
|
|
|
(3) Final adjustment
|
|
|
|
By twiddling y's last bit it is possible to force y to be
|
|
correctly rounded according to the prevailing rounding mode
|
|
as follows. Let r and i be copies of the rounding mode and
|
|
inexact flag before entering the square root program. Also we
|
|
use the expression y+-ulp for the next representable floating
|
|
numbers (up and down) of y. Note that y+-ulp = either fixed
|
|
point y+-1, or multiply y by nextafter(1,+-inf) in chopped
|
|
mode.
|
|
|
|
R := RZ; ... set rounding mode to round-toward-zero
|
|
switch(r) {
|
|
case RN: ... round-to-nearest
|
|
if(x<= z*(z-ulp)...chopped) z = z - ulp; else
|
|
if(x<= z*(z+ulp)...chopped) z = z; else z = z+ulp;
|
|
break;
|
|
case RZ:case RM: ... round-to-zero or round-to--inf
|
|
R:=RP; ... reset rounding mod to round-to-+inf
|
|
if(x<z*z ... rounded up) z = z - ulp; else
|
|
if(x>=(z+ulp)*(z+ulp) ...rounded up) z = z+ulp;
|
|
break;
|
|
case RP: ... round-to-+inf
|
|
if(x>(z+ulp)*(z+ulp)...chopped) z = z+2*ulp; else
|
|
if(x>z*z ...chopped) z = z+ulp;
|
|
break;
|
|
}
|
|
|
|
Remark 3. The above comparisons can be done in fixed point. For
|
|
example, to compare x and w=z*z chopped, it suffices to compare
|
|
x1 and w1 (the trailing parts of x and w), regarding them as
|
|
two's complement integers.
|
|
|
|
...Is z an exact square root?
|
|
To determine whether z is an exact square root of x, let z1 be the
|
|
trailing part of z, and also let x0 and x1 be the leading and
|
|
trailing parts of x.
|
|
|
|
If ((z1&0x03ffffff)!=0) ... not exact if trailing 26 bits of z!=0
|
|
I := 1; ... Raise Inexact flag: z is not exact
|
|
else {
|
|
j := 1 - [(x0>>20)&1] ... j = logb(x) mod 2
|
|
k := z1 >> 26; ... get z's 25-th and 26-th
|
|
fraction bits
|
|
I := i or (k&j) or ((k&(j+j+1))!=(x1&3));
|
|
}
|
|
R:= r ... restore rounded mode
|
|
return sqrt(x):=z.
|
|
|
|
If multiplication is cheaper then the foregoing red tape, the
|
|
Inexact flag can be evaluated by
|
|
|
|
I := i;
|
|
I := (z*z!=x) or I.
|
|
|
|
Note that z*z can overwrite I; this value must be sensed if it is
|
|
True.
|
|
|
|
Remark 4. If z*z = x exactly, then bit 25 to bit 0 of z1 must be
|
|
zero.
|
|
|
|
--------------------
|
|
z1: | f2 |
|
|
--------------------
|
|
bit 31 bit 0
|
|
|
|
Further more, bit 27 and 26 of z1, bit 0 and 1 of x1, and the odd
|
|
or even of logb(x) have the following relations:
|
|
|
|
-------------------------------------------------
|
|
bit 27,26 of z1 bit 1,0 of x1 logb(x)
|
|
-------------------------------------------------
|
|
00 00 odd and even
|
|
01 01 even
|
|
10 10 odd
|
|
10 00 even
|
|
11 01 even
|
|
-------------------------------------------------
|
|
|
|
(4) Special cases (see (4) of Section A).
|
|
|
|
*/
|
|
|
|
|
|
/*
|
|
* wrapper sqrt(x)
|
|
*/
|
|
|
|
double math_sqrt(double x) /* wrapper sqrt */
|
|
{
|
|
#ifdef _IEEE_LIBM
|
|
return __ieee754_sqrt(x);
|
|
#else
|
|
double z;
|
|
z = __ieee754_sqrt(x);
|
|
if(_LIB_VERSION == _IEEE_ || isnan(x)) return z;
|
|
if(x<0.0) {
|
|
return __kernel_standard(x,x,26); /* sqrt(negative) */
|
|
} else
|
|
return z;
|
|
#endif
|
|
}
|
|
|
|
|
|
/*
|
|
* ceil(x)
|
|
* Return x rounded toward -inf to integral value
|
|
* Method:
|
|
* Bit twiddling.
|
|
* Exception:
|
|
* Inexact flag raised if x not equal to ceil(x).
|
|
*/
|
|
|
|
double math_ceil(double x)
|
|
{
|
|
int i0,i1,j0;
|
|
unsigned i,j;
|
|
i0 = __HI(x);
|
|
i1 = __LO(x);
|
|
j0 = ((i0>>20)&0x7ff)-0x3ff;
|
|
if(j0<20) {
|
|
if(j0<0) { /* raise inexact if x != 0 */
|
|
if(huge+x>0.0) {/* return 0*sign(x) if |x|<1 */
|
|
if(i0<0) {i0=0x80000000;i1=0;}
|
|
else if((i0|i1)!=0) { i0=0x3ff00000;i1=0;}
|
|
}
|
|
} else {
|
|
i = (0x000fffff)>>j0;
|
|
if(((i0&i)|i1)==0) return x; /* x is integral */
|
|
if(huge+x>0.0) { /* raise inexact flag */
|
|
if(i0>0) i0 += (0x00100000)>>j0;
|
|
i0 &= (~i); i1=0;
|
|
}
|
|
}
|
|
} else if (j0>51) {
|
|
if(j0==0x400) return x+x; /* inf or NaN */
|
|
else return x; /* x is integral */
|
|
} else {
|
|
i = ((unsigned)(0xffffffff))>>(j0-20);
|
|
if((i1&i)==0) return x; /* x is integral */
|
|
if(huge+x>0.0) { /* raise inexact flag */
|
|
if(i0>0) {
|
|
if(j0==20) i0+=1;
|
|
else {
|
|
j = i1 + (1<<(52-j0));
|
|
if(j<i1) i0+=1; /* got a carry */
|
|
i1 = j;
|
|
}
|
|
}
|
|
i1 &= (~i);
|
|
}
|
|
}
|
|
__HI(x) = i0;
|
|
__LO(x) = i1;
|
|
return x;
|
|
}
|
|
|
|
|
|
/*
|
|
* floor(x)
|
|
* Return x rounded toward -inf to integral value
|
|
* Method:
|
|
* Bit twiddling.
|
|
* Exception:
|
|
* Inexact flag raised if x not equal to floor(x).
|
|
*/
|
|
|
|
double math_floor(double x)
|
|
{
|
|
int i0,i1,j0;
|
|
unsigned i,j;
|
|
i0 = __HI(x);
|
|
i1 = __LO(x);
|
|
j0 = ((i0>>20)&0x7ff)-0x3ff;
|
|
if(j0<20) {
|
|
if(j0<0) { /* raise inexact if x != 0 */
|
|
if(huge+x>0.0) {/* return 0*sign(x) if |x|<1 */
|
|
if(i0>=0) {i0=i1=0;}
|
|
else if(((i0&0x7fffffff)|i1)!=0)
|
|
{ i0=0xbff00000;i1=0;}
|
|
}
|
|
} else {
|
|
i = (0x000fffff)>>j0;
|
|
if(((i0&i)|i1)==0) return x; /* x is integral */
|
|
if(huge+x>0.0) { /* raise inexact flag */
|
|
if(i0<0) i0 += (0x00100000)>>j0;
|
|
i0 &= (~i); i1=0;
|
|
}
|
|
}
|
|
} else if (j0>51) {
|
|
if(j0==0x400) return x+x; /* inf or NaN */
|
|
else return x; /* x is integral */
|
|
} else {
|
|
i = ((unsigned)(0xffffffff))>>(j0-20);
|
|
if((i1&i)==0) return x; /* x is integral */
|
|
if(huge+x>0.0) { /* raise inexact flag */
|
|
if(i0<0) {
|
|
if(j0==20) i0+=1;
|
|
else {
|
|
j = i1+(1<<(52-j0));
|
|
if(j<i1) i0 +=1 ; /* got a carry */
|
|
i1=j;
|
|
}
|
|
}
|
|
i1 &= (~i);
|
|
}
|
|
}
|
|
__HI(x) = i0;
|
|
__LO(x) = i1;
|
|
return x;
|
|
}
|
|
|
|
|
|
/*
|
|
* fabs(x) returns the absolute value of x.
|
|
*/
|
|
|
|
double math_fabs(double x)
|
|
{
|
|
__HI(x) &= 0x7fffffff;
|
|
return x;
|
|
}
|
|
|
|
#endif /* NEED_MATH_LIBRARY */
|
|
|