chore: import upstream snapshot with attribution

paddle/phi/kernels/cpu/scatter_grad_kernel.cc

@@ -0,0 +1,83 @@
+// Copyright (c) 2022 PaddlePaddle Authors. All Rights Reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include "paddle/phi/kernels/scatter_grad_kernel.h"
+
+#include "paddle/phi/backends/cpu/cpu_context.h"
+#include "paddle/phi/core/kernel_registry.h"
+#include "paddle/phi/core/tensor_utils.h"
+#include "paddle/phi/kernels/full_kernel.h"
+#include "paddle/phi/kernels/funcs/gather.h"
+#include "paddle/phi/kernels/funcs/scatter.h"
+namespace phi {
+
+template <typename T, typename Context>
+void ScatterGradKernel(const Context &dev_ctx,
+                       const DenseTensor &index,
+                       const DenseTensor &updates UNUSED,
+                       const DenseTensor &out_grad,
+                       bool overwrite UNUSED,
+                       DenseTensor *x_grad,
+                       DenseTensor *updates_grad) {
+  if (out_grad.numel() == 0) {
+    if (x_grad) {
+      dev_ctx.template Alloc<T>(x_grad);
+    }
+    if (updates_grad) {
+      Full<T, Context>(dev_ctx, updates_grad->dims(), 0, updates_grad);
+    }
+    return;
+  }
+  const auto &index_type = index.dtype();
+  bool index_type_match =
+      index_type == DataType::INT32 || index_type == DataType::INT64;
+  PADDLE_ENFORCE_EQ(index_type_match,
+                    true,
+                    common::errors::InvalidArgument(
+                        "scatter_op index holds the wrong type, it holds [%s],"
+                        "but desires to be [%s] or [%s]",
+                        index_type,
+                        DataType::INT32,
+                        DataType::INT64));
+
+  if (x_grad) {
+    Copy(dev_ctx, out_grad, dev_ctx.GetPlace(), false, x_grad);
+    if (index_type == DataType::INT32) {
+      funcs::CPUScatterGradForX<T, int32_t>(dev_ctx, index, x_grad);
+    } else {
+      funcs::CPUScatterGradForX<T, int64_t>(dev_ctx, index, x_grad);
+    }
+  }
+
+  if (updates_grad) {
+    dev_ctx.template Alloc<T>(updates_grad);
+    // Gradient by Gather: dUpdates = dO[Ids]
+    if (index_type == DataType::INT32) {
+      funcs::CPUGather<T, int32_t>(dev_ctx, out_grad, index, updates_grad);
+    } else {
+      funcs::CPUGather<T, int64_t>(dev_ctx, out_grad, index, updates_grad);
+    }
+  }
+}
+
+}  // namespace phi
+
+PD_REGISTER_KERNEL(scatter_grad,
+                   CPU,
+                   ALL_LAYOUT,
+                   phi::ScatterGradKernel,
+                   float,
+                   double,
+                   int,
+                   int64_t) {}