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paddlepaddle--paddle/paddle/phi/kernels/cpu/temporal_shift_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/temporal_shift_grad_kernel.h"
#include "paddle/common/layout.h"
#include "paddle/phi/backends/cpu/cpu_context.h"
#include "paddle/phi/core/kernel_registry.h"
namespace phi {
template <typename T>
void TemporalShiftBwNCHW(const T* output_grad,
T* input_grad,
const int64_t ntchw,
const int64_t tchw,
const int64_t chw,
const int64_t hw,
const int t,
const int c1,
const int c2) {
int src_it = 0;
for (int64_t i = 0; i < ntchw; i++) {
int64_t it = (i % tchw) / chw;
int64_t ic = (i % chw) / hw;
if (ic < c1) {
src_it = it + 1;
} else if (ic < c2) {
src_it = it - 1;
} else {
src_it = it;
}
if (src_it >= 0 && src_it < t) {
input_grad[i] = output_grad[i + (src_it - it) * chw];
} else {
input_grad[i] = 0;
}
}
}
template <typename T>
void TemporalShiftBwNHWC(const T* output_grad,
T* input_grad,
const int64_t nthwc,
const int64_t thwc,
const int64_t hwc,
const int t,
const int c,
const int c1,
const int c2) {
int src_it = 0;
for (int64_t i = 0; i < nthwc; i++) {
int64_t it = (i % thwc) / hwc;
int64_t ic = i % c;
if (ic < c1) {
src_it = it + 1;
} else if (ic < c2) {
src_it = it - 1;
} else {
src_it = it;
}
if (src_it >= 0 && src_it < t) {
input_grad[i] = output_grad[i + (src_it - it) * hwc];
} else {
input_grad[i] = 0;
}
}
}
template <typename T, typename Context>
void TemporalShiftGradKernel(const Context& dev_ctx,
const DenseTensor& out_grad,
int seg_num,
float shift_ratio,
const std::string& data_format_str,
DenseTensor* x_grad) {
if (x_grad && x_grad->numel() == 0) {
dev_ctx.template Alloc<T>(x_grad);
return;
}
auto* input_grad = x_grad;
auto* output_grad = &out_grad;
int t = seg_num;
const DataLayout data_layout = StringToDataLayout(data_format_str);
const int nt = static_cast<int>(output_grad->dims()[0]);
const int c = static_cast<int>(data_layout == DataLayout::NCHW
? output_grad->dims()[1]
: output_grad->dims()[3]);
const int h = static_cast<int>(data_layout == DataLayout::NCHW
? output_grad->dims()[2]
: output_grad->dims()[1]);
const int w = static_cast<int>(data_layout == DataLayout::NCHW
? output_grad->dims()[3]
: output_grad->dims()[2]);
const int64_t hw = static_cast<int64_t>(h) * w;
const int64_t chw = static_cast<int64_t>(c) * hw;
const int64_t tchw = static_cast<int64_t>(t) * chw;
const int64_t ntchw = static_cast<int64_t>(nt) * chw;
const int c1 = static_cast<int>(static_cast<float>(c) * shift_ratio);
const int c2 = static_cast<int>(static_cast<float>(c) * 2.f * shift_ratio);
DDim in_grad_dims =
(data_layout == DataLayout::NCHW ? make_ddim({nt, c, h, w})
: make_ddim({nt, h, w, c}));
const T* output_grad_data = output_grad->data<T>();
input_grad->Resize(in_grad_dims);
T* input_grad_data = dev_ctx.template Alloc<T>(input_grad);
if (data_layout == DataLayout::NCHW) {
TemporalShiftBwNCHW<T>(
output_grad_data, input_grad_data, ntchw, tchw, chw, hw, t, c1, c2);
} else {
TemporalShiftBwNHWC<T>(
output_grad_data, input_grad_data, ntchw, tchw, chw, t, c, c1, c2);
}
}
} // namespace phi
PD_REGISTER_KERNEL(temporal_shift_grad,
CPU,
ALL_LAYOUT,
phi::TemporalShiftGradKernel,
float,
double) {}