Optimize the performance of NMSFast in the multiclass_nms3_kernel. (#…

…71479)

paddle/phi/kernels/cpu/multiclass_nms3_kernel.cc

@@ -302,37 +302,36 @@ void NMSFast(const DenseTensor& bbox,
   T adaptive_threshold = nms_threshold;
   const T* bbox_data = bbox.data<T>();
 
-  while (!sorted_indices.empty()) {
-    const int idx = sorted_indices.front().second;
+  size_t num_indices = sorted_indices.size();
+  selected_indices->reserve(num_indices);
+  for (size_t i = 0; i < num_indices; ++i) {
+    const int idx = sorted_indices[i].second;
     bool keep = true;
-    for (const auto kept_idx : *selected_indices) {
-      if (keep) {
-        T overlap = T(0.);
-        // 4: [xmin ymin xmax ymax]
-        if (box_size == 4) {
-          overlap = JaccardOverlap<T>(bbox_data + idx * box_size,
-                                      bbox_data + kept_idx * box_size,
-                                      normalized);
-        }
-        // 8: [x1 y1 x2 y2 x3 y3 x4 y4] or 16, 24, 32
-        if (box_size == 8 || box_size == 16 || box_size == 24 ||
-            box_size == 32) {
-          overlap = PolyIoU<T>(bbox_data + idx * box_size,
-                               bbox_data + kept_idx * box_size,
-                               box_size,
-                               normalized);
-        }
-        keep = overlap <= adaptive_threshold;
-      } else {
+    const T* current_bbox = bbox_data + idx * box_size;
+    size_t selected_size = selected_indices->size();
+
+    for (size_t j = 0; j < selected_size; ++j) {
+      const auto kept_idx = (*selected_indices)[j];
+      T overlap = T(0.);
+      const T* kept_bbox = bbox_data + kept_idx * box_size;
+      // 4: [xmin ymin xmax ymax]
+      if (box_size == 4) {
+        overlap = JaccardOverlap<T>(current_bbox, kept_bbox, normalized);
+      } else if (box_size == 8 || box_size == 16 || box_size == 24 ||
+                 box_size ==
+                     32) {  // 8: [x1 y1 x2 y2 x3 y3 x4 y4] or 16, 24, 32
+        overlap = PolyIoU<T>(current_bbox, kept_bbox, box_size, normalized);
+      }
+      keep = overlap <= adaptive_threshold;
+      if (!keep) {
         break;
       }
     }
     if (keep) {
       selected_indices->push_back(idx);
-    }
-    sorted_indices.erase(sorted_indices.begin());
-    if (keep && eta < 1 && adaptive_threshold > 0.5) {
-      adaptive_threshold *= eta;
+      if (eta < 1 && adaptive_threshold > 0.5) {
+        adaptive_threshold *= eta;
+      }
     }
   }
 }