Add max_pool2d_with_indices_backward

kernels/aten/functions.yaml

@@ -249,6 +249,8 @@
 
 - op: max_pool2d_with_indices.out
 
+- op: max_pool2d_with_indices_backward.grad_input
+
 - op: max.dim_max
 
 - op: max.unary_out

kernels/portable/cpu/op_max_pool2d_with_indices_backward.cpp

@@ -0,0 +1,180 @@
+/*
+ * Copyright (c) Meta Platforms, Inc. and affiliates.
+ * All rights reserved.
+ *
+ * This source code is licensed under the BSD-style license found in the
+ * LICENSE file in the root directory of this source tree.
+ */
+
+#include <executorch/kernels/portable/cpu/util/kernel_ops_util.h>
+#include <executorch/runtime/kernel/kernel_includes.h>
+
+namespace torch {
+namespace executor {
+namespace native {
+
+using Tensor = executorch::aten::Tensor;
+using ScalarType = executorch::aten::ScalarType;
+using IntArrayRef = executorch::aten::ArrayRef<int64_t>;
+
+namespace {
+
+bool check_max_pool2d_backward_args(
+    const Tensor& grad_output,
+    const Tensor& input,
+    IntArrayRef kernel_size,
+    IntArrayRef stride,
+    IntArrayRef padding,
+    IntArrayRef dilation,
+    bool ceil_mode,
+    const Tensor& indices,
+    const Tensor& grad_input) {
+  ET_LOG_AND_RETURN_IF_FALSE(tensors_have_same_dtype(grad_output, input));
+  ET_LOG_AND_RETURN_IF_FALSE(tensors_have_same_dtype(grad_input, input));
+
+  ET_CHECK_OR_RETURN_FALSE(
+      check_max_pool2d_with_indices_args(
+          input,
+          kernel_size,
+          stride,
+          padding,
+          dilation,
+          ceil_mode,
+          grad_output,
+          indices),
+      "Invalid max_pool_2d arguments");
+
+  size_t output_ndim = 0;
+  // @lint-ignore CLANGTIDY facebook-hte-CArray
+  executorch::aten::SizesType output_sizes[kTensorDimensionLimit];
+  get_max_pool2d_with_indices_out_target_size(
+      input,
+      kernel_size,
+      stride,
+      padding,
+      dilation,
+      ceil_mode,
+      output_sizes,
+      &output_ndim);
+
+  ET_LOG_AND_RETURN_IF_FALSE(
+      output_size_is_valid({output_sizes, output_ndim}, 2));
+
+  ET_CHECK_OR_RETURN_FALSE(
+      grad_output.dim() == input.dim(),
+      "grad_output should have same number of dimensions as input");
+
+  ET_LOG_AND_RETURN_IF_FALSE(
+      tensor_has_expected_size(grad_output, {output_sizes, output_ndim}));
+
+  return true;
+}
+
+template <typename CTYPE, bool is_3d>
+void max_pool_backward_impl(
+    const Tensor& grad_input,
+    const Tensor& grad_output,
+    const Tensor& indices) {
+  const CTYPE* grad_output_data = grad_output.const_data_ptr<CTYPE>();
+  const int64_t* indices_data = indices.const_data_ptr<int64_t>();
+  CTYPE* grad_input_data = grad_input.mutable_data_ptr<CTYPE>();
+
+  // treat batch size and channels as one dimension
+  //
+  // MaxPool2d:
+  //   ndim == 3: CHW
+  //   ndim == 4: NCHW
+  //
+  // MaxPool3d:
+  //   ndim == 4: CDHW
+  //   ndim == 5: NCDHW
+  int64_t ndim = grad_output.dim();
+  int64_t channels;
+  if (is_3d) {
+    channels = ndim == 4 ? grad_output.size(0)
+                         : grad_output.size(0) * grad_output.size(1);
+  } else {
+    channels = ndim == 3 ? grad_output.size(0)
+                         : grad_output.size(0) * grad_output.size(1);
+  }
+  int64_t input_depth = is_3d ? grad_input.size(-3) : 1;
+
+  int64_t input_height = grad_input.size(ndim - 2);
+  int64_t input_width = grad_input.size(ndim - 1);
+  int64_t output_depth = is_3d ? grad_output.size(ndim - 3) : 1;
+  int64_t output_height = grad_output.size(ndim - 2);
+  int64_t output_width = grad_output.size(ndim - 1);
+
+  for (int64_t c = 0; c < channels; ++c) {
+    CTYPE* grad_input_ptr =
+        grad_input_data + c * input_depth * input_height * input_width;
+    const CTYPE* grad_output_ptr =
+        grad_output_data + c * output_depth * output_height * output_width;
+    const int64_t* indices_ptr =
+        indices_data + c * output_depth * output_height * output_width;
+
+    for (int64_t od = 0; od < output_depth; od++) {
+      for (int64_t oh = 0; oh < output_height; oh++) {
+        for (int64_t ow = 0; ow < output_width; ow++) {
+          // retrieve position of max
+          int64_t index =
+              od * output_height * output_width + oh * output_width + ow;
+          int64_t maxindex = indices_ptr[index];
+          if (maxindex != -1) {
+            // update gradient
+            grad_input_ptr[maxindex] += grad_output_ptr[index];
+          }
+        }
+      }
+    }
+  }
+}
+
+} // namespace
+
+Tensor& max_pool2d_with_indices_backward_out(
+    KernelRuntimeContext& ctx,
+    const Tensor& grad_output,
+    const Tensor& input,
+    ET_UNUSED IntArrayRef kernel_size,
+    ET_UNUSED IntArrayRef stride,
+    ET_UNUSED IntArrayRef padding,
+    ET_UNUSED IntArrayRef dilation,
+    ET_UNUSED bool ceil_mode,
+    const Tensor& indices,
+    Tensor& grad_input) {
+  (void)ctx;
+
+  ET_KERNEL_CHECK(
+      ctx,
+      check_max_pool2d_backward_args(
+          grad_output,
+          input,
+          kernel_size,
+          stride,
+          padding,
+          dilation,
+          ceil_mode,
+          indices,
+          grad_input),
+      InvalidArgument,
+      grad_input);
+
+  ET_KERNEL_CHECK(
+      ctx,
+      resize_tensor(grad_input, input.sizes()) == Error::Ok,
+      InvalidArgument,
+      grad_input);
+
+  constexpr auto name = "max_pool2d_with_indices_backward.grad_input";
+
+  ET_SWITCH_FLOATHBF16_TYPES(input.scalar_type(), ctx, name, CTYPE, [&]() {
+    max_pool_backward_impl<CTYPE, false>(grad_input, grad_output, indices);
+  });
+
+  return grad_input;
+}
+
+} // namespace native
+} // namespace executor
+} // namespace torch

kernels/portable/cpu/util/kernel_ops_util.cpp

@@ -470,8 +470,8 @@ bool check_max_pool2d_with_indices_args(
     IntArrayRef padding,
     IntArrayRef dilation,
     bool ceil_mode,
-    Tensor& out,
-    Tensor& indices) {
+    const Tensor& out,
+    const Tensor& indices) {
   ET_LOG_AND_RETURN_IF_FALSE(tensors_have_same_dtype(in, out));
   ET_CHECK_OR_RETURN_FALSE(
       indices.scalar_type() == ScalarType::Long,

kernels/portable/cpu/util/kernel_ops_util.h

@@ -442,8 +442,8 @@ bool check_max_pool2d_with_indices_args(
     IntArrayRef padding,
     IntArrayRef dilation,
     bool ceil_mode,
-    Tensor& out,
-    Tensor& indices);
+    const Tensor& out,
+    const Tensor& indices);
 
 void get_max_pool2d_with_indices_out_target_size(
     const Tensor& in,

kernels/portable/functions.yaml

@@ -572,6 +572,11 @@
     - arg_meta: null
       kernel_name: torch::executor::max_pool2d_with_indices_out
 
+- op: max_pool2d_with_indices_backward.grad_input
+  kernels:
+    - arg_meta: null
+      kernel_name: torch::executor::max_pool2d_with_indices_backward_out
+
 - op: mean.out
   kernels:
     - arg_meta: null