fix rowwise_add_grad_op

paddle/operators/rowwise_add_op.cc

@@ -63,7 +63,7 @@ class RowwiseAddGradOp : public framework::OperatorWithKernel {
                             "Input(Out@GRAD) should not be null");
     auto dims0 = ctx.Input<Tensor>("X")->dims();
     auto dims1 = ctx.Input<Tensor>("b")->dims();
-    PADDLE_ENFORCE_EQ(1, framework::product(dims1), "b dims should be 1")
+    PADDLE_ENFORCE_EQ(1, dims1.size(), "b dims should be 1")
     ctx.Output<Tensor>(framework::GradVarName("X"))->Resize(dims0);
     ctx.Output<Tensor>(framework::GradVarName("b"))->Resize(dims1);
   }