fix trt engine test error.

test=develop

paddle/fluid/operators/tensorrt/tensorrt_engine_op.h

@@ -82,7 +82,7 @@ class TensorRTEngineOp : public framework::OperatorBase {
       calibrator_.reset(new TRTInt8Calibrator(calibration_data_));
     }
 
-    if (!calibration_mode_) {
+    if (!calibration_mode_ && !engine_serialized_data_.empty()) {
       trt_engine_.reset(new inference::tensorrt::TensorRTEngine(
           max_batch_size_, workspace_size_, enable_int8_, calibrator_.get(),
           device_id_));
@@ -236,6 +236,9 @@ class TensorRTEngineOp : public framework::OperatorBase {
   TensorRTEngine *GetEngine(const framework::Scope &scope,
                             const platform::Place &dev_place) const {
     if (!trt_engine_) {
+      trt_engine_.reset(new inference::tensorrt::TensorRTEngine(
+          max_batch_size_, workspace_size_, enable_int8_, calibrator_.get(),
+          device_id_));
       PrepareTRTEngine(scope, trt_engine_.get());
     }
     return trt_engine_.get();

paddle/fluid/operators/tensorrt/tensorrt_engine_op_test.cc

@@ -108,6 +108,8 @@ TEST(TensorRTEngineOp, manual) {
                          std::vector<std::string>({"z0"}));
   engine_op_desc.SetAttr("subgraph", std::string(block_->SerializeAsString()));
   engine_op_desc.SetAttr("engine_serialized_data", std::string(""));
+  int device_id = 0;
+  engine_op_desc.SetAttr("gpu_id", device_id);
 
   LOG(INFO) << "create engine op";
   auto engine_op = framework::OpRegistry::CreateOp(engine_op_desc);
@@ -204,6 +206,8 @@ void Execute(int batch_size, int input_dim, int output_dim, int nlayers = 1) {
                          std::vector<std::string>({"z3"}));
   engine_op_desc.SetAttr("subgraph", std::string(block_->SerializeAsString()));
   engine_op_desc.SetAttr("engine_serialized_data", std::string(""));
+  int device_id = 0;
+  engine_op_desc.SetAttr("gpu_id", device_id);
 
   auto engine_op = framework::OpRegistry::CreateOp(engine_op_desc);