[GitHub] [incubator-mxnet] Jerryzcn commented on a change in pull request #16619: add aligned roi introduced in Detectron2

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Jerryzcn commented on a change in pull request #16619: add aligned roi introduced in Detectron2
URL: https://github.com/apache/incubator-mxnet/pull/16619#discussion_r339256359
 
 

 ##########
 File path: src/operator/contrib/mrcnn_mask_target.cu
 ##########
 @@ -135,14 +136,21 @@ __device__ void RoIAlignForward(
 
     const T* offset_rois = rois + batch_idx * (4 * num_rois) + n * 4;
     // Do not using rounding; this implementation detail is critical
-    T roi_start_w = offset_rois[0];
-    T roi_start_h = offset_rois[1];
-    T roi_end_w = offset_rois[2];
-    T roi_end_h = offset_rois[3];
+    T roi_offset = continuous_coordinate ? static_cast<T>(0.5) : static_cast<T>(0);
+    T roi_start_w = offset_rois[0] - roi_offset;
+    T roi_start_h = offset_rois[1] - roi_offset;
+    T roi_end_w = offset_rois[2] - roi_offset;
+    T roi_end_h = offset_rois[3] - roi_offset;
+
+    T roi_width = roi_end_w - roi_start_w;
+    T roi_height = roi_end_h - roi_start_h;
 
     // Force malformed ROIs to be 1x1
-    T roi_width = max(roi_end_w - roi_start_w, (T)1.);
-    T roi_height = max(roi_end_h - roi_start_h, (T)1.);
+    if (!continuous_coordinate) {  // backward compatiblity
 
 Review comment:
   save computation

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