C API: Do not take ownership of the TF_Tensors

Prior to this change, TF_*Run, TF_SetAttrTensor and TF_SetAttrTensorList
took ownership of the TF_Tensor*s of the feeds. This can make performance
client languages bothersome when the same Tensor is repeatedly fed into
multiple session executions as the memory for the feed tensor would need
to be re-allocated and filled in every time.

With this change, these functions no longer take ownership of the
TF_Tensor*.

The changes to the Go API implementation reflect the claimed benefits.
(Another step towards #10)
Change: 139169388

1 files changed, 11 insertions, 4 deletions

diff --git a/tensorflow/c/c_api_test.cc b/tensorflow/c/c_api_test.cc
index ca1324033d..ad0e6a7da8 100644
--- a/tensorflow/c/c_api_test.cc
+++ b/tensorflow/c/c_api_test.cc
@@ -45,6 +45,9 @@ TF_Tensor* TF_Tensor_EncodeStrings(const Tensor& src);
 
 namespace {
 
+typedef std::unique_ptr<TF_Tensor, decltype(&TF_DeleteTensor)>
+    unique_tensor_ptr;
+
 TEST(CAPI, Version) { EXPECT_NE("", string(TF_Version())); }
 
 TEST(CAPI, Status) {
@@ -259,8 +262,9 @@ TF_Operation* Placeholder(TF_Graph* graph, TF_Status* s) {
 }
 
 TF_Operation* ScalarConst(int32 v, TF_Graph* graph, TF_Status* s) {
+  unique_tensor_ptr tensor(Int32Tensor(v), TF_DeleteTensor);
   TF_OperationDescription* desc = TF_NewOperation(graph, "Const", "scalar");
-  TF_SetAttrTensor(desc, "value", Int32Tensor(v), s);
+  TF_SetAttrTensor(desc, "value", tensor.get(), s);
   if (TF_GetCode(s) != TF_OK) return nullptr;
   TF_SetAttrType(desc, "dtype", TF_INT32);
   return TF_FinishOperation(desc, s);
@@ -752,8 +756,7 @@ class CSession {
                   inputs_.size(), outputs_ptr, output_values_ptr,
                   outputs_.size(), targets_ptr, targets_.size(), nullptr, s);
 
-    // TF_SessionRun() takes ownership of the tensors in input_values_.
-    input_values_.clear();
+    DeleteInputValues();
   }
 
   void CloseAndDelete(TF_Status* s) {
@@ -1261,7 +1264,8 @@ TEST_F(CApiAttributesTest, Tensor) {
   const size_t ndims = TF_ARRAYSIZE(dims);
 
   auto desc = init("tensor");
-  TF_SetAttrTensor(desc, "v", Int8Tensor(dims, ndims, tensor), s_);
+  unique_tensor_ptr v(Int8Tensor(dims, ndims, tensor), TF_DeleteTensor);
+  TF_SetAttrTensor(desc, "v", v.get(), s_);
   ASSERT_EQ(TF_OK, TF_GetCode(s_)) << TF_Message(s_);
 
   auto oper = TF_FinishOperation(desc, s_);
@@ -1296,6 +1300,9 @@ TEST_F(CApiAttributesTest, TensorList) {
       Int8Tensor(dims1, ndims1, tensor1), Int8Tensor(dims2, ndims2, tensor2),
   };
   TF_SetAttrTensorList(desc, "v", tmp, TF_ARRAYSIZE(tmp), s_);
+  for (int i = 0; i < TF_ARRAYSIZE(tmp); ++i) {
+    TF_DeleteTensor(tmp[i]);
+  }
   ASSERT_EQ(TF_OK, TF_GetCode(s_)) << TF_Message(s_);
   auto oper = TF_FinishOperation(desc, s_);
   ASSERT_EQ(TF_OK, TF_GetCode(s_)) << TF_Message(s_);