Update on "Use object identity for deepcopy memo"

Copy of #126089, with some fixes & tests (TODO)

[TODO description]


[ghstack-poisoned]

test/cpp/api/CMakeLists.txt

@@ -10,6 +10,7 @@ set(TORCH_API_TEST_SOURCES
   ${TORCH_API_TEST_DIR}/functional.cpp
   ${TORCH_API_TEST_DIR}/init.cpp
   ${TORCH_API_TEST_DIR}/integration.cpp
+  ${TORCH_API_TEST_DIR}/ivalue.cpp
   ${TORCH_API_TEST_DIR}/jit.cpp
   ${TORCH_API_TEST_DIR}/memory.cpp
   ${TORCH_API_TEST_DIR}/meta_tensor.cpp

test/cpp/api/ivalue.cpp

@@ -0,0 +1,58 @@
+#include <gtest/gtest.h>
+
+#include <ATen/core/ivalue.h>
+
+#include <c10/util/flat_hash_map.h>
+#include <c10/util/irange.h>
+#include <c10/util/tempfile.h>
+
+#include <torch/torch.h>
+
+#include <test/cpp/api/support.h>
+
+#include <cstdio>
+#include <memory>
+#include <sstream>
+#include <string>
+#include <vector>
+
+using namespace torch::test;
+using namespace torch::nn;
+using namespace torch::optim;
+
+TEST(IValueTest, DeepcopyTensors) {
+  torch::Tensor t0 = torch::randn({2, 3});
+  torch::Tensor t1 = torch::randn({3, 4});
+  torch::Tensor t2 = t0.detach();
+  torch::Tensor t3 = t0;
+  torch::Tensor t4 = t1.as_strided({2, 3}, {3, 1}, 2);
+  std::vector<torch::Tensor> tensor_vector = {t0, t1, t2, t3, t4};
+  c10::List<torch::Tensor> tensor_list(tensor_vector);
+  torch::IValue tensor_list_ivalue(tensor_list);
+
+  c10::IValue::CompIdentityIValues ivalue_compare;
+
+  // Make sure our setup configuration is correct
+  ASSERT_TRUE(ivalue_compare(tensor_list[0].get(), tensor_list[3].get()));
+  ASSERT_FALSE(ivalue_compare(tensor_list[0].get(), tensor_list[1].get()));
+  ASSERT_FALSE(ivalue_compare(tensor_list[0].get(), tensor_list[2].get()));
+  ASSERT_FALSE(ivalue_compare(tensor_list[1].get(), tensor_list[4].get()));
+  ASSERT_TRUE(tensor_list[0].get().isAliasOf(tensor_list[2].get()));
+
+  c10::IValue copied_ivalue = tensor_list_ivalue.deepcopy();
+  c10::List<torch::IValue> copied_list = copied_ivalue.toList();
+
+  // Make sure our setup configuration is correct
+  ASSERT_TRUE(ivalue_compare(copied_list[0].get(), copied_list[3].get()));
+  ASSERT_FALSE(ivalue_compare(copied_list[0].get(), copied_list[1].get()));
+  ASSERT_FALSE(ivalue_compare(copied_list[0].get(), copied_list[2].get()));
+  ASSERT_FALSE(ivalue_compare(copied_list[1].get(), copied_list[4].get()));
+  // NOTE: this is actually incorrect. Ideally, these _should_ be aliases.
+  ASSERT_FALSE(copied_list[0].get().isAliasOf(copied_list[2].get()));
+
+  ASSERT_TRUE(copied_list[0].get().toTensor().allclose(tensor_list[0].get().toTensor()));
+  ASSERT_TRUE(copied_list[1].get().toTensor().allclose(tensor_list[1].get().toTensor()));
+  ASSERT_TRUE(copied_list[2].get().toTensor().allclose(tensor_list[2].get().toTensor()));
+  ASSERT_TRUE(copied_list[3].get().toTensor().allclose(tensor_list[3].get().toTensor()));
+  ASSERT_TRUE(copied_list[4].get().toTensor().allclose(tensor_list[4].get().toTensor()));
+}