Add of GlobalMaxPool Gradient (#23502)

### Description
Added gradient computation support for the GlobalMaxPool node.



### Motivation and Context
Improve the training capabilities of ONNX Runtime.

Author: cocotdf

orttraining/orttraining/core/graph/gradient_builder.cc

@@ -2239,5 +2239,23 @@ IMPLEMENT_GRADIENT_BUILDER(GetAtanGradient) {
   return result;
 }
 
+IMPLEMENT_GRADIENT_BUILDER(GetGlobalMaxPoolGradient) {
+  // For GlobalMaxPool's gradient, a binary mask flags max elements.
+  // We multiply that mask by the incoming gradient, passing gradients only to maxima.
+  std::vector<NodeDef> result;
+  result.push_back(NodeDef("Shape", {I(0)}, {IA("X_shape")}));
+  result.push_back(NodeDef("Expand", {O(0), IA("X_shape")}, {IA("expanded_Y")}));
+  result.push_back(NodeDef("Equal", {I(0), IA("expanded_Y")}, {IA("mask")}));
+  result.push_back(NodeDef("Cast",
+                           {IA("mask")},
+                           {IA("mask_cast")},
+                           {MakeAttribute("to", static_cast<int64_t>(IElemType(0)))}));
+
+  result.push_back(NodeDef("Expand", {GO(0), IA("X_shape")}, {IA("expanded_dY")}));
+  result.push_back(NodeDef("Mul", {IA("mask_cast"), IA("expanded_dY")}, {GI(0)}));
+
+  return result;
+}
+
 }  // namespace training
 }  // namespace onnxruntime

orttraining/orttraining/core/graph/gradient_builder.h

@@ -94,6 +94,7 @@ DECLARE_GRADIENT_BUILDER(GetLeakyReluGradient)
 DECLARE_GRADIENT_BUILDER(GetConvTransposeGradient)
 DECLARE_GRADIENT_BUILDER(GetResizeGradient)
 DECLARE_GRADIENT_BUILDER(GetAtanGradient)
+DECLARE_GRADIENT_BUILDER(GetGlobalMaxPoolGradient)
 
 DECLARE_GRADIENT_BUILDER(GetExternalGradient)
 

orttraining/orttraining/core/graph/gradient_builder_registry.cc

@@ -126,6 +126,7 @@ void GradientBuilderRegistry::RegisterGradientBuilders() {
   REGISTER_GRADIENT_BUILDER("ConvTranspose", GetConvTransposeGradient);
   REGISTER_GRADIENT_BUILDER("Resize", GetResizeGradient);
   REGISTER_GRADIENT_BUILDER("Atan", GetAtanGradient);
+  REGISTER_GRADIENT_BUILDER("GlobalMaxPool", GetGlobalMaxPoolGradient);
 
   REGISTER_GRADIENT_BUILDER("ExternalGradient", GetExternalGradient);
 };

orttraining/orttraining/test/gradient/gradient_ops_test.cc

@@ -3356,6 +3356,29 @@ TEST(GradientCheckerTest, ResizeGrad) {
 
 TEST(GradientCheckerTest, AtanGrad) { UnaryOpGradientTest("Atan"); }
 
+TEST(GradientCheckerTest, GlobalMaxPoolGrad) {
+  float max_error;
+  GradientChecker<float, float, float> gradient_checker;
+  OpDef op_def{"GlobalMaxPool", kOnnxDomain, 11};
+  constexpr float error_tolerance = 1e-3f;
+
+  // globalmaxpool
+  {
+    ASSERT_STATUS_OK(gradient_checker.ComputeGradientError(op_def, {{2, 3, 5, 5}}, {{2, 3, 1, 1}}, &max_error, {},
+                                                           /*check_not_have_gradient*/ true,
+                                                           /*check_not_have_shape_inferencing*/ true));
+    EXPECT_IS_TINIER_THAN(max_error, error_tolerance);
+  }
+
+  // globalmaxpool_precomputed
+  {
+    ASSERT_STATUS_OK(gradient_checker.ComputeGradientError(op_def, {{2, 1, 3, 3}}, {{2, 1, 1, 1}}, &max_error, {},
+                                                           /*check_not_have_gradient*/ true,
+                                                           /*check_not_have_shape_inferencing*/ true));
+    EXPECT_IS_TINIER_THAN(max_error, error_tolerance);
+  }
+}
+
 }  // namespace test
 }  // namespace onnxruntime