fix bpr loss; test=developp

paddle/fluid/operators/bpr_loss_op.cc

@@ -32,10 +32,14 @@ class BprLossOp : public framework::OperatorWithKernel {
     int rank = x_dims.size();
     PADDLE_ENFORCE_EQ(rank, label_dims.size(),
                       "Input(X) and Input(Label) shall have the same rank.");
-    PADDLE_ENFORCE_EQ(framework::slice_ddim(x_dims, 0, rank - 1),
-                      framework::slice_ddim(label_dims, 0, rank - 1),
-                      "Input(X) and Input(Label) shall have the same shape "
-                      "except the last dimension.");
+
+    if (ctx->IsRuntime() || (framework::product(x_dims) > 0 &&
+                             framework::product(label_dims) > 0)) {
+      PADDLE_ENFORCE_EQ(framework::slice_ddim(x_dims, 0, rank - 1),
+                        framework::slice_ddim(label_dims, 0, rank - 1),
+                        "Input(X) and Input(Label) shall have the same shape "
+                        "except the last dimension.");
+    }
 
     auto y_dims = x_dims;
     y_dims[rank - 1] = 1;