Make `DifferentialPair` able to nest. (#2477)

1 files changed, 23 insertions, 0 deletions

diff --git a/tests/autodiff/high-order-forward-diff.slang b/tests/autodiff/high-order-forward-diff.slang
new file mode 100644
index 000000000..fde659227
--- /dev/null
+++ b/tests/autodiff/high-order-forward-diff.slang
@@ -0,0 +1,23 @@
+//DTEST(compute):COMPARE_COMPUTE_EX:-slang -compute -shaderobj -output-using-type
+//DTEST(compute, vulkan):COMPARE_COMPUTE_EX:-vk -compute -shaderobj -output-using-type
+
+//TEST_INPUT:ubuffer(data=[0 0 0 0], stride=4):out,name=outputBuffer
+RWStructuredBuffer<float> outputBuffer;
+
+[ForwardDifferentiable]
+float f(float x)
+{
+    return x * x;
+}
+
+[ForwardDifferentiable]
+float df(float x)
+{
+    return __fwd_diff(f)(DifferentialPair<float>(x, 1.0)).d();
+}
+
+[numthreads(1, 1, 1)]
+void computeMain(uint3 dispatchThreadID : SV_DispatchThreadID)
+{
+    outputBuffer[0] = __fwd_diff(df)(DifferentialPair<float>(1.0, 1.0)).d(); // Expect: 2.0
+}