sum op handle empty input update selected_rows_functor.cu

paddle/fluid/operators/math/selected_rows_functor.cu

@@ -305,12 +305,29 @@ struct MergeAdd<platform::CUDADeviceContext, T> {
   void operator()(const platform::CUDADeviceContext& context,
                   const std::vector<const framework::SelectedRows*>& inputs,
                   framework::SelectedRows* output) {
-    PADDLE_ENFORCE_GT(inputs.size(), 0, "should have at least one input");
-    auto input_width = inputs[0]->value().dims()[1];
-    auto input_height = inputs[0]->height();
+    if (inputs.size() == 0) {
+      VLOG(3) << "no input! return";
+      return;
+    }
+    const framework::SelectedRows* has_value_input = nullptr;
+    for (auto* in : inputs) {
+      if (!in->rows().empty()) {
+        has_value_input = in;
+        break;
+      }
+    }
+    if (has_value_input == nullptr) {
+      VLOG(3) << "no input has value! just return" << std::endl;
+      return;
+    }
+    auto input_width = has_value_input->value().dims()[1];
+    auto input_height = has_value_input->height();
     framework::SelectedRows& out = *output;
     std::set<int64_t> merged_row_set;
     for (auto* input : inputs) {
+      if (input->rows().empty()) {
+        continue;
+      }
       PADDLE_ENFORCE_EQ(input_width, input->value().dims()[1],
                         "all input should have same "
                         "dimension except for the first one");
@@ -338,11 +355,11 @@ struct MergeAdd<platform::CUDADeviceContext, T> {
     dim3 threads(block_size, 1);
 
     for (auto* input : inputs) {
-      auto* input_data = input->value().data<T>();
-      auto& input_rows = input->rows();
-      if (input_rows.size() == 0) {
+      if (input->rows().empty()) {
         continue;
       }
+      auto* input_data = input->value().data<T>();
+      auto& input_rows = input->rows();
       dim3 grid1(input_rows.size(), 1);
 
       MergeAddKernel<T, 256><<<grid1, threads, 0, context.stream()>>>(