perf(head): faster computation to find overlapped anchor (Megvii-BaseDetection#1473)

Author: developer0hye

yolox/models/yolo_head.py

@@ -630,7 +630,7 @@ def dynamic_k_matching(self, cost, pair_wise_ious, gt_classes, num_gt, fg_mask):
         del topk_ious, dynamic_ks, pos_idx
 
         anchor_matching_gt = matching_matrix.sum(0)
-        if (anchor_matching_gt > 1).sum() > 0:
+        if anchor_matching_gt.max() > 1:
             _, cost_argmin = torch.min(cost[:, anchor_matching_gt > 1], dim=0)
             matching_matrix[:, anchor_matching_gt > 1] *= 0
             matching_matrix[cost_argmin, anchor_matching_gt > 1] = 1