From 25c79ada2c0fcc6c5ecb3e71ca073109adc1d7eb Mon Sep 17 00:00:00 2001
From: Sai Praveen Bangaru <31557731+saipraveenb25@users.noreply.github.com>
Date: Wed, 20 Sep 2023 15:22:51 -0400
Subject: Fix `atan2` stdlib derivative + add tests. (#3218)

* Fix atan2 stdlib derivative. Add tests for atan2

* Create dstdlib-atan2.slang.expected.txt

* Update tests
---
 source/slang/diff.meta.slang | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

(limited to 'source/slang')

diff --git a/source/slang/diff.meta.slang b/source/slang/diff.meta.slang
index 495b6b989..75c57018c 100644
--- a/source/slang/diff.meta.slang
+++ b/source/slang/diff.meta.slang
@@ -1259,7 +1259,7 @@ __generic<T : __BuiltinFloatingPointType>
 DifferentialPair<T> __d_atan2(DifferentialPair<T> dpy, DifferentialPair<T> dpx)
 {
     T.Differential dx = __mul_p_d(-dpy.p / (dpx.p * dpx.p + dpy.p * dpy.p), dpx.d);
-    T.Differential dy = __mul_p_d(-dpx.p / (dpx.p * dpx.p + dpy.p * dpy.p), dpy.d);
+    T.Differential dy = __mul_p_d(dpx.p / (dpx.p * dpx.p + dpy.p * dpy.p), dpy.d);
     return DifferentialPair<T>(
         atan2(dpy.p, dpx.p),
         T.dadd(dx, dy));
@@ -1271,8 +1271,8 @@ __generic<T : __BuiltinFloatingPointType>
 [BackwardDerivativeOf(atan2)]
 void __d_atan2(inout DifferentialPair<T> dpy, inout DifferentialPair<T> dpx, T.Differential dOut)
 {
-    dpx = diffPair(dpx.p, __mul_p_d(-dpy.p / (dpx.p * dpx.p + dpy.p * dpy.p), dpx.d));
-    dpy = diffPair(dpy.p, __mul_p_d(-dpx.p / (dpx.p * dpx.p + dpy.p * dpy.p), dpy.d));
+    dpx = diffPair(dpx.p, __mul_p_d(-dpy.p / (dpx.p * dpx.p + dpy.p * dpy.p), dOut));
+    dpy = diffPair(dpy.p, __mul_p_d(dpx.p / (dpx.p * dpx.p + dpy.p * dpy.p), dOut));
 }
 
 VECTOR_MATRIX_BINARY_DIFF_IMPL(atan2)
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