Merge pull request #15534 from JiabinYang/fix/multi_output_support_imperative

test=develop, fix/multi_output_support_imperative

Author: JiabinYang

paddle/fluid/framework/operator.cc

@@ -555,18 +555,17 @@ Tensor* ExecutionContext::LegacyOutput<Tensor>(const std::string& name) const {
 template <>
 std::vector<Tensor*> ExecutionContext::MultiOutput<Tensor>(
     const std::string& name) const {
-  auto names = op().Outputs(name);
+  auto it = ctx_.outputs.find(name);
+  if (it == ctx_.outputs.end()) {
+    return {};
+  }
+  const std::vector<Variable*>& vars = it->second;
   std::vector<Tensor*> res;
-  res.reserve(names.size());
-  std::transform(names.begin(), names.end(), std::back_inserter(res),
-                 [&](const std::string& sub_name) -> Tensor* {
-                   auto var = scope_.FindVar(sub_name);
-                   if (var == nullptr) return nullptr;
-                   PADDLE_ENFORCE(
-                       var->IsType<LoDTensor>(),
-                       "%s should be LoDTensor, but the received type is %s",
-                       sub_name, ToTypeName(var->Type()));
-                   return var->GetMutable<LoDTensor>();
+  res.reserve(vars.size());
+  std::transform(vars.begin(), vars.end(), std::back_inserter(res),
+                 [&](Variable* var) -> Tensor* {
+                   return var == nullptr ? nullptr
+                                         : var->GetMutable<LoDTensor>();
                  });
   return res;
 }