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paddlepaddle--paddle/paddle/phi/kernels/cpu/p_norm_grad_kernel.cc
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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/p_norm_grad_kernel.h"
#include "paddle/phi/backends/cpu/cpu_context.h"
#include "paddle/phi/core/kernel_registry.h"
#include "paddle/phi/kernels/funcs/eigen/common.h"
#include "paddle/phi/kernels/funcs/eigen/eigen_function.h"
#include "paddle/phi/kernels/funcs/math_function.h"
namespace phi {
inline void GetDims(
const DDim& dim, int axis, int* pre, int* n, int* post, bool asvector) {
*pre = 1;
*post = 1;
*n = static_cast<int>(dim[axis]);
if (asvector) {
*n = static_cast<int>(product(dim));
} else {
for (int i = 0; i < axis; ++i) {
(*pre) *= static_cast<int>(dim[i]);
}
for (int i = axis + 1; i < dim.size(); ++i) {
(*post) *= static_cast<int>(dim[i]);
}
}
}
template <typename T, typename Context>
void PNormGradKernel(const Context& dev_ctx,
const DenseTensor& x,
const DenseTensor& out,
const DenseTensor& out_grad,
double porder,
int axis,
float epsilon,
bool keepdim UNUSED,
bool asvector,
DenseTensor* x_grad) {
auto* in_x = &x;
auto* in_norm = &out;
auto* in_norm_dy = &out_grad;
auto* out_dx = x_grad;
dev_ctx.template Alloc<T>(out_dx);
if (out_dx->numel() == 0) {
return;
}
T eps = static_cast<T>(epsilon);
auto xdim = in_x->dims();
if (axis < 0) axis = xdim.size() + axis;
int pre, n, post;
GetDims(xdim, axis, &pre, &n, &post, asvector);
Eigen::DSizes<int64_t, 3> shape(pre, n, post);
Eigen::DSizes<int64_t, 3> rshape(pre, static_cast<int64_t>(1), post);
auto* place = dev_ctx.eigen_device();
auto x_e = EigenVector<T>::Flatten(*in_x);
auto dx_e = EigenVector<T>::Flatten(*out_dx);
auto norm_e = EigenVector<T>::Flatten(*in_norm);
auto norm_dy_e = EigenVector<T>::Flatten(*in_norm_dy);
auto xr = x_e.reshape(shape);
auto dx = dx_e.reshape(shape);
auto norm = norm_e.reshape(rshape);
auto norm_dy = norm_dy_e.reshape(rshape);
Eigen::DSizes<int, 1> rdim(1);
Eigen::DSizes<int, 3> bcast(1, n, 1);
if (porder == 0) {
funcs::SetConstant<Context, T> set_zero;
set_zero(dev_ctx, out_dx, static_cast<T>(0));
} else if (porder == INFINITY || porder == -INFINITY) {
dx.device(*place) = (xr.abs() == norm.broadcast(bcast)).template cast<T>() *
xr.sign() * norm_dy.broadcast(bcast);
} else {
dx.device(*place) =
(xr.abs()).pow(porder - 1.0) /
((norm.broadcast(bcast)).pow(porder - 1.0) + xr.constant(eps));
dx.device(*place) = dx * norm_dy.broadcast(bcast) * xr.sign();
}
}
} // namespace phi
PD_REGISTER_KERNEL(
p_norm_grad, CPU, ALL_LAYOUT, phi::PNormGradKernel, float, double) {}