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2026-07-13 12:40:42 +08:00

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// 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/prelu_grad_kernel.h"
#include "paddle/phi/backends/cpu/cpu_context.h"
#include "paddle/phi/core/kernel_registry.h"
#include "paddle/phi/kernels/full_kernel.h"
namespace phi {
template <typename T, typename Context>
void PReluGradKernel(const Context& dev_ctx,
const DenseTensor& x,
const DenseTensor& alpha,
const DenseTensor& out_grad,
const std::string& data_format,
const std::string& mode,
DenseTensor* x_grad,
DenseTensor* alpha_grad) {
if (x_grad->numel() == 0) {
dev_ctx.template Alloc<T>(x_grad);
if (alpha_grad) {
Full<T, Context>(dev_ctx, alpha_grad->dims(), 0, alpha_grad);
}
return;
}
const T* alpha_ptr = alpha.data<T>();
const T* x_ptr = x.data<T>();
const T* out_grad_ptr = out_grad.data<T>();
int numel = static_cast<int>(x.numel());
auto dim = x.dims();
int index = 0;
int i = 0;
if (x_grad) {
T* x_grad_ptr = dev_ctx.template Alloc<T>(x_grad);
if (mode == "channel") {
if (data_format == "NCHW") {
int temp = 1;
for (int j = 2; j < dim.size(); j++) {
temp *= static_cast<int>(dim[j]);
}
for (i = 0; i < numel; i++) {
index = static_cast<int>((i / temp) % dim[1]);
x_grad_ptr[i] = x_ptr[i] > 0 ? out_grad_ptr[i]
: alpha_ptr[index] * out_grad_ptr[i];
}
} else {
for (i = 0; i < numel; i++) {
index = static_cast<int>(i % dim[dim.size() - 1]);
x_grad_ptr[i] = x_ptr[i] > 0 ? out_grad_ptr[i]
: alpha_ptr[index] * out_grad_ptr[i];
}
}
} else if (mode == "element") {
int temp = 1;
for (int j = 1; j < dim.size(); j++) {
temp *= static_cast<int>(dim[j]);
}
for (i = 0; i < numel; i++) {
index = i % temp;
x_grad_ptr[i] =
x_ptr[i] > 0 ? out_grad_ptr[i] : alpha_ptr[index] * out_grad_ptr[i];
}
} else {
for (i = 0; i < numel; i++) {
x_grad_ptr[i] =
x_ptr[i] > 0 ? out_grad_ptr[i] : alpha_ptr[0] * out_grad_ptr[i];
}
}
}
index = 0;
if (alpha_grad) {
T* alpha_grad_ptr = dev_ctx.template Alloc<T>(alpha_grad);
memset(alpha_grad_ptr, 0, sizeof(T) * alpha_grad->numel());
if (mode == "channel") {
if (data_format == "NCHW") {
int temp = 1;
for (int j = 2; j < dim.size(); j++) {
temp *= static_cast<int>(dim[j]);
}
for (i = 0; i < numel; i++) {
index = static_cast<int>((i / temp) % dim[1]);
alpha_grad_ptr[index] +=
x_ptr[i] > 0 ? 0 : x_ptr[i] * out_grad_ptr[i];
}
} else {
for (i = 0; i < numel; i++) {
index = static_cast<int>(i % dim[dim.size() - 1]);
alpha_grad_ptr[index] +=
x_ptr[i] > 0 ? 0 : x_ptr[i] * out_grad_ptr[i];
}
}
} else if (mode == "element") {
int temp = 1;
for (int j = 1; j < dim.size(); j++) {
temp *= static_cast<int>(dim[j]);
}
for (i = 0; i < numel; i++) {
index = i % temp;
alpha_grad_ptr[index] += x_ptr[i] > 0 ? 0 : x_ptr[i] * out_grad_ptr[i];
}
} else {
for (i = 0; i < numel; i++) {
alpha_grad_ptr[0] += x_ptr[i] > 0 ? 0 : x_ptr[i] * out_grad_ptr[i];
}
}
}
}
} // namespace phi
PD_REGISTER_KERNEL(
prelu_grad, CPU, ALL_LAYOUT, phi::PReluGradKernel, float, double) {}