sxjscience commented on a change in pull request #14894: Accelerate ROIPooling
layer
URL: https://github.com/apache/incubator-mxnet/pull/14894#discussion_r303173424
##########
File path: src/operator/roi_pooling.cc
##########
@@ -137,91 +140,18 @@ template<typename Dtype>
inline void ROIPoolBackwardAcc(const Tensor<cpu, 4, Dtype> &in_grad,
const Tensor<cpu, 4, Dtype> &out_grad,
const Tensor<cpu, 2, Dtype> &bbox,
- const Tensor<cpu, 4, Dtype> &max_idx,
+ const Tensor<cpu, 4, index_t> &max_idx,
const float spatial_scale_) {
const Dtype *top_diff = out_grad.dptr_;
- const Dtype *bottom_rois = bbox.dptr_;
Dtype *bottom_diff = in_grad.dptr_;
- Dtype *argmax_data = max_idx.dptr_;
-
- const int batch_size_ = in_grad.size(0);
- const int channels_ = in_grad.size(1);
- const int height_ = in_grad.size(2);
- const int width_ = in_grad.size(3);
- const int pooled_height_ = out_grad.size(2);
- const int pooled_width_ = out_grad.size(3);
-
- const int num_rois = bbox.size(0);
-
- for (int b = 0; b < batch_size_; ++b) {
- for (int c = 0; c < channels_; ++c) {
- for (int h = 0; h < height_; ++h) {
- for (int w = 0; w < width_; ++w) {
- int offset_bottom_diff = (b * channels_ + c) * height_ * width_;
- offset_bottom_diff += h * width_ + w;
-
- Dtype gradient = 0;
- // Accumulate gradient over all ROIs that pooled this element
- for (int roi_n = 0; roi_n < num_rois; ++roi_n) {
- const Dtype* offset_bottom_rois = bottom_rois + roi_n * 5;
- int roi_batch_ind = offset_bottom_rois[0];
- assert(roi_batch_ind >= 0);
- assert(roi_batch_ind < batch_size_);
- if (b != roi_batch_ind) {
- continue;
- }
+ index_t *argmax_data = max_idx.dptr_;
- int roi_start_w = std::round(offset_bottom_rois[1] *
spatial_scale_);
- int roi_start_h = std::round(offset_bottom_rois[2] *
spatial_scale_);
- int roi_end_w = std::round(offset_bottom_rois[3] * spatial_scale_);
- int roi_end_h = std::round(offset_bottom_rois[4] * spatial_scale_);
+ const index_t count = out_grad.shape_.Size();
- bool in_roi = (w >= roi_start_w && w <= roi_end_w &&
- h >= roi_start_h && h <= roi_end_h);
- if (!in_roi) {
- continue;
- }
-
- // force malformed ROIs to be 1 * 1
- int roi_height = max(roi_end_h - roi_start_h + 1, 1);
- int roi_width = max(roi_end_w - roi_start_w + 1, 1);
- const Dtype bin_size_h = static_cast<Dtype>(roi_height)
- / static_cast<Dtype>(pooled_height_);
- const Dtype bin_size_w = static_cast<Dtype>(roi_width)
- / static_cast<Dtype>(pooled_width_);
-
- // compute pooled regions correspond to original (h, w) point
- int phstart = static_cast<int>(floor(static_cast<Dtype>(h -
roi_start_h)
- / bin_size_h));
- int pwstart = static_cast<int>(floor(static_cast<Dtype>(w -
roi_start_w)
- / bin_size_w));
- int phend = static_cast<int>(ceil(static_cast<Dtype>(h -
roi_start_h + 1)
- / bin_size_h));
- int pwend = static_cast<int>(ceil(static_cast<Dtype>(w -
roi_start_w + 1)
- / bin_size_w));
-
- // clip to boundaries of pooled region
- phstart = min(max(phstart, 0), pooled_height_);
- phend = min(max(phend, 0), pooled_height_);
- pwstart = min(max(pwstart, 0), pooled_width_);
- pwend = min(max(pwend, 0), pooled_width_);
-
- // accumulate over gradients in pooled regions
- int offset = (roi_n * channels_ + c) * pooled_height_ *
pooled_width_;
- const Dtype* offset_top_diff = top_diff + offset;
- const Dtype* offset_argmax_data = argmax_data + offset;
- for (int ph = phstart; ph < phend; ++ph) {
- for (int pw = pwstart; pw < pwend; ++pw) {
- const int pooled_index = ph * pooled_width_ + pw;
- if (static_cast<int>(offset_argmax_data[pooled_index]) == h *
width_ + w) {
- gradient += offset_top_diff[pooled_index];
- }
- }
- }
- }
- bottom_diff[offset_bottom_diff] += gradient;
- }
- }
+ for (int index = 0; index < count; ++index) {
+ index_t max_idx = argmax_data[index];
+ if (max_idx >= 0) {
+ bottom_diff[max_idx] += top_diff[index];
Review comment:
Is it possible that two threads are writing to the same max_idx?
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