From 3a27994091d6d5271d804a047101ff024b2684f1 Mon Sep 17 00:00:00 2001
From: gered <gered@blarg.ca>
Date: Wed, 26 Apr 2023 18:29:02 -0400
Subject: [PATCH] add simd f32x4 nearly_equal helper function

---
 ggdt/src/math/mod.rs | 35 +++++++++++++++++++++++++++++++++++
 1 file changed, 35 insertions(+)

diff --git a/ggdt/src/math/mod.rs b/ggdt/src/math/mod.rs
index 6e91b1b..717eb8c 100644
--- a/ggdt/src/math/mod.rs
+++ b/ggdt/src/math/mod.rs
@@ -1,4 +1,6 @@
 use std::ops::{Add, Div, Mul, Sub};
+use std::simd;
+use std::simd::{SimdFloat, SimdPartialOrd};
 
 mod circle;
 mod matrix3x3;
@@ -47,6 +49,11 @@ pub fn nearly_equal(a: f32, b: f32, epsilon: f32) -> bool {
 	a == b || (a - b).abs() <= epsilon
 }
 
+#[inline]
+pub fn nearly_equal_simd(a: simd::f32x4, b: simd::f32x4, epsilon: f32) -> simd::mask32x4 {
+	(a - b).abs().simd_le(simd::f32x4::splat(epsilon))
+}
+
 /// Linearly interpolates between two values.
 ///
 /// # Arguments
@@ -211,6 +218,34 @@ mod tests {
 		assert!(!nearly_equal(1.0001, 1.0005, 0.0001));
 	}
 
+	#[test]
+	pub fn test_nearly_equal_simd() {
+		assert_eq!(
+			simd::mask32x4::from_array([true, true, true, true]),
+			nearly_equal_simd(
+				simd::f32x4::from_array([1.0, 2.0, 3.0, 4.0]),
+				simd::f32x4::from_array([1.0, 2.0, 3.0, 4.0]),
+				0.1
+			)
+		);
+		assert_eq!(
+			simd::mask32x4::from_array([true, true, false, false]),
+			nearly_equal_simd(
+				simd::f32x4::from_array([1.0, 1.95, 3.2, 3.7]),
+				simd::f32x4::from_array([1.0, 2.0, 3.0, 4.0]),
+				0.1
+			)
+		);
+		assert_eq!(
+			simd::mask32x4::from_array([false, false, false, false]),
+			nearly_equal_simd(
+				simd::f32x4::from_array([1.0002, 2.0003, 2.9997, 4.00015]),
+				simd::f32x4::from_array([1.0, 2.0, 3.0, 4.0]),
+				0.0001
+			)
+		);
+	}
+
 	#[test]
 	pub fn test_lerp() {
 		assert!(nearly_equal(15.0, lerp(10.0, 20.0, 0.5), 0.0001));