[GitHub] [incubator-tvm] kevinthesun commented on a change in pull request #5844: [Relay] symbolic max_output_size

[GitBox <gi...@apache.org>]

kevinthesun commented on a change in pull request #5844:
URL: https://github.com/apache/incubator-tvm/pull/5844#discussion_r442390568



##########
File path: topi/python/topi/vision/nms.py
##########
@@ -326,30 +329,40 @@ def hybrid_nms(data, sorted_index, valid_count, indices, batch_size, num_anchors
             # Apply nms
             box_start_idx = coord_start
             batch_idx = i
+            num_valid_boxes = 0
 
             for j in range(valid_count[i]):
-                if output[i, j, score_index] > 0 and (id_index < 0 or output[i, j, id_index] >= 0):
+                if num_valid_boxes == max_output_size:
+                    for k in range(box_data_length):
+                        output[i, j, k] = -one
+                    box_indices[i, j] = -1
+
+                elif output[i, j, score_index] > 0:
                     box_a_idx = j
-                    for k in parallel(valid_count[i]):
+                    is_valid_box = 1
+
+                    # a_l: left, a_t: top, a_r: right, a_b: bottom
+                    a_l = min(output[batch_idx, box_a_idx, box_start_idx],
+                              output[batch_idx, box_a_idx, box_start_idx + 2])
+                    a_t = min(output[batch_idx, box_a_idx, box_start_idx + 1],
+                              output[batch_idx, box_a_idx, box_start_idx + 3])
+                    a_r = max(output[batch_idx, box_a_idx, box_start_idx],
+                              output[batch_idx, box_a_idx, box_start_idx + 2])
+                    a_b = max(output[batch_idx, box_a_idx, box_start_idx + 1],
+                              output[batch_idx, box_a_idx, box_start_idx + 3])
+
+                    # check if current box j is valid by calculating iou with
+                    # all existing valid boxes
+                    for k in parallel(j):

Review comment:
       ```suggestion
                       for k in range(j):
   ```
   I found use serial loop here can actually improve performance a bit.




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