fix numel nce and prefetch

paddle/fluid/operators/distributed/parameter_prefetch.cc

@@ -114,9 +114,15 @@ static void MergeMultipleVarsIntoOneBySection(
     id_to_offset[ids_vector[i]].push_back(i);
   }
 
-  auto& id_tensor = scope.FindVar(id_name)->Get<framework::LoDTensor>();
+  auto& id_tensor = scope->FindVar(id_name)->Get<framework::LoDTensor>();
   auto* out_tensor =
-      scope.FindVar(out_name)->GetMutable<framework::LoDTensor>();
+      scope->FindVar(out_name)->GetMutable<framework::LoDTensor>();
+
+  PADDLE_ENFORCE_GT(
+      out_tensor->numel(), 0,
+      "When calling this method, the Tensor's numel must larger than zero. "
+      "Please check Tensor::Resize has been called first.");
+
   auto* out_tensor_data = out_tensor->mutable_data<float>(id_tensor.place());
 
   bool is_on_cpu_place = true;

paddle/fluid/operators/nce_op.h

@@ -166,11 +166,12 @@ class NCEKernel : public framework::OpKernel<T> {
       std::set<T> st(labels.begin(), labels.end());
       labels.assign(st.begin(), st.end());
 
-      auto &local_scope = context.scope().NewScope();
+      framework::Scope &local_scope = context.scope().NewScope();
+
       auto height_sections = context.Attr<std::vector<int>>("height_sections");
       auto table_names = context.Attr<std::vector<std::string>>("table_names");
 
-      auto *ids = local_scope.Var("Ids@Local");
+      auto *ids = local_scope.Var("Ids@Prefetch");
       auto *x_tensor = ids->GetMutable<framework::LoDTensor>();
       x_tensor->mutable_data<int64_t>(
           framework::make_ddim({static_cast<int64_t>(labels.size()), 1}),
@@ -179,12 +180,18 @@ class NCEKernel : public framework::OpKernel<T> {
       std::memcpy(x_tensor->data<int64_t>(), labels.data(),
                   labels.size() * sizeof(int64_t));
 
-      local_scope.Var("Weight@Local");
+      std::vector<int> w_dims = paddle::framework::vectorize2int(
+          context.Input<Tensor>("Weight")->dims());
+      w_dims[0] = static_cast<int>(labels.size());
+
+      auto *w_tensor = local_scope.Var("Weight@Prefetch")
+                           ->GetMutable<framework::LoDTensor>();
+      w_tensor->Resize(framework::make_ddim(w_dims));
 
 #ifdef PADDLE_WITH_DISTRIBUTE
-      operators::distributed::prefetch("Ids@Local", "Weight@Local", table_names,
-                                       epmap, height_sections, context,
-                                       &local_scope);
+      operators::distributed::prefetch("Ids@Prefetch", "Weight@Prefetch",
+                                       table_names, epmap, height_sections,
+                                       context, local_scope);
 #else
       PADDLE_THROW(
           "paddle is not compiled with distribute support, can not do "
@@ -192,7 +199,7 @@ class NCEKernel : public framework::OpKernel<T> {
 #endif
 
       auto weight_mat = EigenMatrix<T>::From(
-          (local_scope.Var("Weight@Local")->Get<framework::LoDTensor>()));
+          (local_scope.Var("Weight@Prefetch")->Get<framework::LoDTensor>()));
       for (int64_t i = 0; i < sample_labels->numel(); ++i) {
         std::vector<int64_t>::iterator it =
             std::find(labels.begin(), labels.end(), sample_labels_data[i]);