add GetMutableTensor test=develop

lite/api/cxx_api.cc

@@ -314,9 +314,16 @@ void Predictor::GenRuntimeProgram() {
 
 const lite::Tensor *Predictor::GetTensor(const std::string &name) const {
   auto *var = exec_scope_->FindVar(name);
+  CHECK(var) << "no variable named with " << name << " in exec_scope";
   return &var->Get<lite::Tensor>();
 }
 
+lite::Tensor *Predictor::GetMutableTensor(const std::string &name) const {
+  auto *var = exec_scope_->FindVar(name);
+  CHECK(var) << "no variable named with " << name << " in exec_scope";
+  return var->GetMutable<lite::Tensor>();
+}
+
 // get input by name
 lite::Tensor *Predictor::GetInputByName(const std::string &name) {
   auto element = std::find(input_names_.begin(), input_names_.end(), name);

lite/api/cxx_api.h

@@ -91,6 +91,9 @@ class LITE_API Predictor {
   std::vector<const lite::Tensor*> GetOutputs() const;
 
   const cpp::ProgramDesc& program_desc() const;
+  // get a mutable tensor according to its name
+  lite::Tensor* GetMutableTensor(const std::string& name);
+  // get a const tensor according to its name
   const lite::Tensor* GetTensor(const std::string& name) const;
   const RuntimeProgram& runtime_program() const;
 
@@ -142,8 +145,12 @@ class CxxPaddleApiImpl : public lite_api::PaddlePredictor {
   std::vector<std::string> GetInputNames() override;
   std::vector<std::string> GetOutputNames() override;
 
+  // get tensor according to tensor's name
   std::unique_ptr<const lite_api::Tensor> GetTensor(
       const std::string& name) const override;
+  // get a mutable tensor according to tensor's name
+  std::unique_ptr<lite_api::Tensor> GetMutableTensor(
+      const std::string& name) override;
 
   // Get InputTebsor by name
   std::unique_ptr<lite_api::Tensor> GetInputByName(

lite/api/cxx_api_impl.cc

@@ -101,6 +101,12 @@ std::unique_ptr<const lite_api::Tensor> CxxPaddleApiImpl::GetTensor(
   return std::unique_ptr<const lite_api::Tensor>(new lite_api::Tensor(x));
 }
 
+std::unique_ptr<lite_api::Tensor> CxxPaddleApiImpl::GetMutableTensor(
+    const std::string &name) {
+  return std::unique_ptr<lite_api::Tensor>(
+      new lite_api::Tensor(raw_predictor_.GetMutableTensor(name)));
+}
+
 std::unique_ptr<lite_api::Tensor> CxxPaddleApiImpl::GetInputByName(
     const std::string &name) {
   return std::unique_ptr<lite_api::Tensor>(

lite/api/paddle_api.h

@@ -94,6 +94,14 @@ class LITE_API PaddlePredictor {
   virtual std::unique_ptr<const Tensor> GetTensor(
       const std::string& name) const = 0;
 
+  /// Get a readonly tensor, return null if no one called `name` exists.
+  virtual std::unique_ptr<const Tensor> GetTensor(
+      const std::string& name) const = 0;
+  /// Get a mutable tensor, return null if on one called `name` exists
+  /// internal infereces API, not recommanded.
+  virtual std::unique_ptr<Tensor> GetMutableTensor(
+      const std::string& name) const = 0;
+
   /// Persist the optimized model to disk. This API is only supported by
   /// CxxConfig, and the persisted model can be reused for MobileConfig.
   virtual void SaveOptimizedModel(