add label smooth. test=develop

paddle/fluid/operators/yolov3_loss_op.h

@@ -159,7 +159,9 @@ static inline void CalcLabelLoss(T* loss, const T* input, const int index,
                                  const int label, const int class_num,
                                  const int stride) {
   for (int i = 0; i < class_num; i++) {
-    loss[0] += SCE<T>(input[index + i * stride], (i == label) ? 1.0 : 0.0);
+    T pred = input[index + i * stride] < -0.5 ? input[index + i * stride]
+                                              : 1.0 / class_num;
+    loss[0] += SCE<T>(pred, (i == label) ? 1.0 : 0.0);
   }
 }
 
@@ -169,8 +171,10 @@ static inline void CalcLabelLossGrad(T* input_grad, const T loss,
                                      const int label, const int class_num,
                                      const int stride) {
   for (int i = 0; i < class_num; i++) {
+    T pred = input[index + i * stride] < -0.5 ? input[index + i * stride]
+                                              : 1.0 / class_num;
     input_grad[index + i * stride] =
-        SCEGrad<T>(input[index + i * stride], (i == label) ? 1.0 : 0.0) * loss;
+        SCEGrad<T>(pred, (i == label) ? 1.0 : 0.0) * loss;
   }
 }
 
@@ -406,15 +410,12 @@ class Yolov3LossGradKernel : public framework::OpKernel<T> {
 
     for (int i = 0; i < n; i++) {
       for (int t = 0; t < b; t++) {
+        int mask_idx = gt_match_mask_data[i * b + t];
+        if (mask_idx >= 0) {
           Box<T> gt = GetGtBox(gt_box_data, i, b, t);
-        if (LessEqualZero<T>(gt.w) || LessEqualZero<T>(gt.h)) {
-          continue;
-        }
           int gi = static_cast<int>(gt.x * w);
           int gj = static_cast<int>(gt.y * h);
 
-        int mask_idx = gt_match_mask_data[i * b + t];
-        if (mask_idx >= 0) {
           int box_idx = GetEntryIndex(i, mask_idx, gj * w + gi, mask_num,
                                       an_stride, stride, 0);
           CalcBoxLocationLossGrad<T>(

python/paddle/fluid/tests/unittests/test_yolov3_loss_op.py

@@ -86,6 +86,10 @@ def YOLOv3Loss(x, gtbox, gtlabel, attrs):
     pred_box[:, :, :, :, 0] = (grid_x + sigmoid(pred_box[:, :, :, :, 0])) / w
     pred_box[:, :, :, :, 1] = (grid_y + sigmoid(pred_box[:, :, :, :, 1])) / h
 
+    x[:, :, :, :, 5:] = np.where(x[:, :, :, :, 5:] < -0.5, x[:, :, :, :, 5:],
+                                 np.ones_like(x[:, :, :, :, 5:]) * 1.0 /
+                                 class_num)
+
     mask_anchors = []
     for m in anchor_mask:
         mask_anchors.append((anchors[2 * m], anchors[2 * m + 1]))
@@ -207,7 +211,7 @@ class TestYolov3LossOp(OpTest):
         self.ignore_thresh = 0.7
         self.downsample = 32
         self.x_shape = (3, len(self.anchor_mask) * (5 + self.class_num), 5, 5)
-        self.gtbox_shape = (3, 10, 4)
+        self.gtbox_shape = (3, 5, 4)
 
 
 if __name__ == "__main__":