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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/yolo_loss_kernel.h"
#include <algorithm>
#include <cstdint>
#include <vector>
#include "paddle/phi/backends/cpu/cpu_context.h"
#include "paddle/phi/core/kernel_registry.h"
#include "paddle/phi/kernels/cpu/yolo_loss_functor.h"
#include "paddle/phi/kernels/funcs/math_function.h"
namespace phi {
template <typename T>
static inline bool LessEqualZero(T x) {
return x < 1e-6;
}
template <typename T>
static T SigmoidCrossEntropy(T x, T label) {
return (x > 0 ? x : 0.0) - x * label + std::log(1.0 + std::exp(-std::abs(x)));
}
template <typename T>
static T L1Loss(T x, T y) {
return std::abs(y - x);
}
static int GetMaskIndex(std::vector<int> mask, int val) {
for (int i = 0; i < static_cast<int>(mask.size()); i++) {
if (mask[i] == val) {
return i;
}
}
return -1;
}
template <typename T>
static inline Box<T> GetYoloBox(const T* x,
std::vector<int> anchors,
int i,
int j,
int an_idx,
int grid_size,
int input_size,
int64_t index,
int64_t stride,
float scale,
float bias) {
Box<T> b = {};
b.x = (i + sigmoid<T>(x[index]) * scale + bias) / grid_size;
b.y = (j + sigmoid<T>(x[index + stride]) * scale + bias) / grid_size;
b.w = std::exp(x[index + 2 * stride]) * anchors[2 * an_idx] / input_size;
b.h = std::exp(x[index + 3 * stride]) * anchors[2 * an_idx + 1] / input_size;
return b;
}
template <typename T>
static inline T BoxOverlap(T c1, T w1, T c2, T w2) {
T l1 = c1 - w1 / 2.0;
T l2 = c2 - w2 / 2.0;
T left = l1 > l2 ? l1 : l2;
T r1 = c1 + w1 / 2.0;
T r2 = c2 + w2 / 2.0;
T right = r1 < r2 ? r1 : r2;
return right - left;
}
template <typename T>
static inline T CalcBoxIoU(Box<T> b1, Box<T> b2) {
T w = BoxOverlap(b1.x, b1.w, b2.x, b2.w);
T h = BoxOverlap(b1.y, b1.h, b2.y, b2.h);
T inter_area = (w < 0 || h < 0) ? 0.0 : w * h;
T union_area = b1.w * b1.h + b2.w * b2.h - inter_area;
return inter_area / union_area;
}
template <typename T>
static void CalcBoxLocationLoss(T* loss,
const T* input,
Box<T> gt,
std::vector<int> anchors,
int an_idx,
int64_t box_idx,
int gi,
int gj,
int grid_size,
int input_size,
int64_t stride,
T score) {
T tx = gt.x * grid_size - gi;
T ty = gt.y * grid_size - gj;
T tw = std::log(gt.w * input_size / anchors[2 * an_idx]);
T th = std::log(gt.h * input_size / anchors[2 * an_idx + 1]);
T scale = (2.0 - gt.w * gt.h) * score;
loss[0] += SigmoidCrossEntropy<T>(input[box_idx], tx) * scale;
loss[0] += SigmoidCrossEntropy<T>(input[box_idx + stride], ty) * scale;
loss[0] += L1Loss<T>(input[box_idx + 2 * stride], tw) * scale;
loss[0] += L1Loss<T>(input[box_idx + 3 * stride], th) * scale;
}
template <typename T>
static inline void CalcLabelLoss(T* loss,
const T* input,
const int64_t index,
const int label,
const int class_num,
const int64_t stride,
const T pos,
const T neg,
T score) {
for (int i = 0; i < class_num; i++) {
T pred = input[index + i * stride];
loss[0] += SigmoidCrossEntropy<T>(pred, (i == label) ? pos : neg) * score;
}
}
template <typename T>
static inline void CalcObjnessLoss(T* loss,
const T* input,
const T* objness,
const int n,
const int an_num,
const int h,
const int w,
const int64_t stride,
const int64_t an_stride) {
for (int i = 0; i < n; i++) {
for (int j = 0; j < an_num; j++) {
for (int k = 0; k < h; k++) {
for (int l = 0; l < w; l++) {
T obj = objness[k * w + l];
if (obj > 1e-5) {
// positive sample: obj = mixup score
loss[i] += SigmoidCrossEntropy<T>(input[k * w + l], 1.0) * obj;
} else if (obj > -0.5) {
// negative sample: obj = 0
loss[i] += SigmoidCrossEntropy<T>(input[k * w + l], 0.0);
}
}
}
objness += stride;
input += an_stride;
}
}
}
template <typename T>
static void inline GtValid(bool* valid,
const T* gtbox,
const int n,
const int b) {
for (int i = 0; i < n; i++) {
for (int j = 0; j < b; j++) {
if (LessEqualZero(gtbox[j * 4 + 2]) || LessEqualZero(gtbox[j * 4 + 3])) {
valid[j] = false;
} else {
valid[j] = true;
}
}
valid += b;
gtbox += b * 4;
}
}
template <typename T, typename Context>
void YoloLossKernel(const Context& dev_ctx,
const DenseTensor& x,
const DenseTensor& gt_box,
const DenseTensor& gt_label,
const optional<DenseTensor>& gt_score,
const std::vector<int>& anchors,
const std::vector<int>& anchor_mask,
int class_num,
float ignore_thresh,
int downsample_ratio,
bool use_label_smooth,
float scale_x_y,
DenseTensor* loss,
DenseTensor* objectness_mask,
DenseTensor* gt_match_mask) {
auto* input = &x;
auto objness_mask = objectness_mask;
float scale = scale_x_y;
float bias = -0.5f * (scale - 1.f);
const int n = static_cast<int>(input->dims()[0]);
const int h = static_cast<int>(input->dims()[2]);
const int w = static_cast<int>(input->dims()[3]);
const int an_num = static_cast<int>(anchors.size() / 2);
const int mask_num = static_cast<int>(anchor_mask.size());
const int b = static_cast<int>(gt_box.dims()[1]);
int input_size = downsample_ratio * h;
const int64_t stride = static_cast<int64_t>(h) * w;
const int64_t an_stride = static_cast<int64_t>(class_num + 5) * stride;
T label_pos = 1.0;
T label_neg = 0.0;
if (use_label_smooth) {
T smooth_weight = std::min(1.0 / static_cast<T>(class_num), 1.0 / 40);
label_pos = 1.0 - smooth_weight;
label_neg = smooth_weight;
}
const T* input_data = input->data<T>();
const T* gt_box_data = gt_box.data<T>();
const int* gt_label_data = gt_label.data<int>();
loss->Resize({n});
T* loss_data = dev_ctx.template Alloc<T>(loss);
memset(loss_data, 0, loss->numel() * sizeof(T));
objness_mask->Resize({n, mask_num, h, w});
T* obj_mask_data = dev_ctx.template Alloc<T>(objness_mask);
memset(obj_mask_data, 0, objness_mask->numel() * sizeof(T));
gt_match_mask->Resize({n, b});
int* gt_match_mask_data = dev_ctx.template Alloc<int>(gt_match_mask);
const T* gt_score_data = nullptr;
DenseTensor gtscore;
if (!(gt_score.is_initialized())) {
gtscore.Resize({n, b});
dev_ctx.template Alloc<T>(&gtscore);
funcs::SetConstant<Context, T>()(dev_ctx, &gtscore, static_cast<T>(1.0));
gt_score_data = gtscore.data<T>();
} else {
gt_score_data = gt_score.get_ptr()->data<T>();
}
// calc valid gt box mask, avoid calc duplicately in following code
DenseTensor gt_valid_mask;
gt_valid_mask.Resize({n, b});
bool* gt_valid_mask_data = dev_ctx.template Alloc<bool>(&gt_valid_mask);
GtValid<T>(gt_valid_mask_data, gt_box_data, n, b);
for (int i = 0; i < n; i++) {
for (int j = 0; j < mask_num; j++) {
for (int k = 0; k < h; k++) {
for (int l = 0; l < w; l++) {
// each predict box find a best match gt box, if overlap is bigger
// then ignore_thresh, ignore the objectness loss.
int64_t box_idx =
GetEntryIndex(i, j, k * w + l, mask_num, an_stride, stride, 0);
Box<T> pred = GetYoloBox(input_data,
anchors,
l,
k,
anchor_mask[j],
h,
input_size,
box_idx,
stride,
scale,
bias);
T best_iou = 0;
for (int t = 0; t < b; t++) {
if (!gt_valid_mask_data[i * b + t]) {
continue;
}
Box<T> gt = GetGtBox(gt_box_data, i, b, t);
T iou = CalcBoxIoU(pred, gt);
if (iou > best_iou) {
best_iou = iou;
}
}
// If best IoU is bigger then ignore_thresh,
// ignore the objectness loss.
if (best_iou > ignore_thresh) {
int64_t obj_idx = (i * mask_num + j) * stride + k * w + l;
obj_mask_data[obj_idx] = static_cast<T>(-1);
}
// all losses should be calculated if best IoU
// is bigger then truth thresh, but currently,
// truth thresh is an unreachable value as 1.0.
}
}
}
for (int t = 0; t < b; t++) {
if (!gt_valid_mask_data[i * b + t]) {
gt_match_mask_data[i * b + t] = -1;
continue;
}
Box<T> gt = GetGtBox(gt_box_data, i, b, t);
int gi = static_cast<int>(gt.x * w);
int gj = static_cast<int>(gt.y * h);
Box<T> gt_shift = gt;
gt_shift.x = 0.0;
gt_shift.y = 0.0;
T best_iou = 0.0;
int best_n = 0;
// each gt box find a best match anchor box as positive sample,
// for positive sample, all losses should be calculated, and for
// other samples, only objectness loss is required.
for (int an_idx = 0; an_idx < an_num; an_idx++) {
Box<T> an_box = {};
an_box.x = 0.0;
an_box.y = 0.0;
an_box.w = anchors[2 * an_idx] / static_cast<T>(input_size);
an_box.h = anchors[2 * an_idx + 1] / static_cast<T>(input_size);
float iou = CalcBoxIoU<T>(an_box, gt_shift);
if (iou > best_iou) {
best_iou = iou;
best_n = an_idx;
}
}
int mask_idx = GetMaskIndex(anchor_mask, best_n);
gt_match_mask_data[i * b + t] = mask_idx;
if (mask_idx >= 0) {
T score = gt_score_data[i * b + t];
int64_t box_idx = GetEntryIndex(
i, mask_idx, gj * w + gi, mask_num, an_stride, stride, 0);
CalcBoxLocationLoss<T>(loss_data + i,
input_data,
gt,
anchors,
best_n,
box_idx,
gi,
gj,
h,
input_size,
stride,
score);
int64_t obj_idx = (i * mask_num + mask_idx) * stride + gj * w + gi;
obj_mask_data[obj_idx] = score;
int label = gt_label_data[i * b + t];
int64_t label_idx = GetEntryIndex(
i, mask_idx, gj * w + gi, mask_num, an_stride, stride, 5);
CalcLabelLoss<T>(loss_data + i,
input_data,
label_idx,
label,
class_num,
stride,
label_pos,
label_neg,
score);
}
}
}
CalcObjnessLoss<T>(loss_data,
input_data + 4 * stride,
obj_mask_data,
n,
mask_num,
h,
w,
stride,
an_stride);
}
} // namespace phi
PD_REGISTER_KERNEL(
yolo_loss, CPU, ALL_LAYOUT, phi::YoloLossKernel, float, double) {
kernel->OutputAt(2).SetDataType(phi::DataType::INT32);
}