Fix wrong clamping in RoIAlign with aligned=True (#2438)

* Fix wrong clamping in RoIAlign with aligned=True

* Fix silly mistake

* Bugfix pointed out during code-review

torchvision/csrc/cpu/ROIAlign_cpu.cpp

@@ -141,9 +141,13 @@ void ROIAlignForward(
     T roi_end_w = offset_rois[3] * spatial_scale - offset;
     T roi_end_h = offset_rois[4] * spatial_scale - offset;
 
-    // Force malformed ROIs to be 1x1
-    T roi_width = std::max(roi_end_w - roi_start_w, (T)1.);
-    T roi_height = std::max(roi_end_h - roi_start_h, (T)1.);
+    T roi_width = roi_end_w - roi_start_w;
+    T roi_height = roi_end_h - roi_start_h;
+    if (!aligned) {
+      // Force malformed ROIs to be 1x1
+      roi_width = std::max(roi_width, (T)1.);
+      roi_height = std::max(roi_height, (T)1.);
+    }
 
     T bin_size_h = static_cast<T>(roi_height) / static_cast<T>(pooled_height);
     T bin_size_w = static_cast<T>(roi_width) / static_cast<T>(pooled_width);
@@ -309,9 +313,13 @@ void ROIAlignBackward(
     T roi_end_w = offset_rois[3] * spatial_scale - offset;
     T roi_end_h = offset_rois[4] * spatial_scale - offset;
 
-    // Force malformed ROIs to be 1x1
-    T roi_width = std::max(roi_end_w - roi_start_w, (T)1.);
-    T roi_height = std::max(roi_end_h - roi_start_h, (T)1.);
+    T roi_width = roi_end_w - roi_start_w;
+    T roi_height = roi_end_h - roi_start_h;
+    if (!aligned) {
+      // Force malformed ROIs to be 1x1
+      roi_width = std::max(roi_width, (T)1.);
+      roi_height = std::max(roi_height, (T)1.);
+    }
 
     T bin_size_h = static_cast<T>(roi_height) / static_cast<T>(pooled_height);
     T bin_size_w = static_cast<T>(roi_width) / static_cast<T>(pooled_width);

torchvision/csrc/cuda/ROIAlign_cuda.cu

@@ -91,9 +91,13 @@ __global__ void RoIAlignForward(
     T roi_end_w = offset_rois[3] * spatial_scale - offset;
     T roi_end_h = offset_rois[4] * spatial_scale - offset;
 
-    // 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.);
+    T roi_width = roi_end_w - roi_start_w;
+    T roi_height = roi_end_h - roi_start_h;
+    if (!aligned) {
+      // Force malformed ROIs to be 1x1
+      roi_width = max(roi_width, (T)1.);
+      roi_height = max(roi_height, (T)1.);
+    }
 
     T bin_size_h = static_cast<T>(roi_height) / static_cast<T>(pooled_height);
     T bin_size_w = static_cast<T>(roi_width) / static_cast<T>(pooled_width);
@@ -229,9 +233,13 @@ __global__ void RoIAlignBackward(
     T roi_end_w = offset_rois[3] * spatial_scale - offset;
     T roi_end_h = offset_rois[4] * spatial_scale - offset;
 
-    // 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.);
+    T roi_width = roi_end_w - roi_start_w;
+    T roi_height = roi_end_h - roi_start_h;
+    if (!aligned) {
+      // Force malformed ROIs to be 1x1
+      roi_width = max(roi_width, (T)1.);
+      roi_height = max(roi_height, (T)1.);
+    }
 
     T bin_size_h = static_cast<T>(roi_height) / static_cast<T>(pooled_height);
     T bin_size_w = static_cast<T>(roi_width) / static_cast<T>(pooled_width);