From fabc058b40e1591efc13913977827148d5b75641 Mon Sep 17 00:00:00 2001
From: Chen Weihang <chenweihang@baidu.com>
Date: Tue, 21 Dec 2021 21:03:01 -0600
Subject: [PATCH] add copy constructor for densetensor (#38319)

---
 paddle/pten/core/dense_tensor.cc            |  3 +++
 paddle/pten/core/dense_tensor.h             |  5 ++---
 paddle/pten/core/tensor_meta.cc             |  6 ------
 paddle/pten/core/tensor_meta.h              |  7 +++++++
 paddle/pten/tests/core/test_dense_tensor.cc | 15 +++++++++++++++
 5 files changed, 27 insertions(+), 9 deletions(-)

diff --git a/paddle/pten/core/dense_tensor.cc b/paddle/pten/core/dense_tensor.cc
index 3237576cb6..4298906df0 100644
--- a/paddle/pten/core/dense_tensor.cc
+++ b/paddle/pten/core/dense_tensor.cc
@@ -38,6 +38,9 @@ DenseTensor::DenseTensor(intrusive_ptr<Storage> storage,
 DenseTensor::DenseTensor(intrusive_ptr<Storage> storage, DenseTensorMeta&& meta)
     : meta_(std::move(meta)), storage_(std::move(storage)) {}
 
+DenseTensor::DenseTensor(const DenseTensor& other)
+    : meta_(other.meta()), storage_(copy_intrusive(other.storage_)) {}
+
 int64_t DenseTensor::numel() const {
   if (meta_.is_scalar) {
     return 1;
diff --git a/paddle/pten/core/dense_tensor.h b/paddle/pten/core/dense_tensor.h
index 92c8e3d4bd..fbb39e6f17 100644
--- a/paddle/pten/core/dense_tensor.h
+++ b/paddle/pten/core/dense_tensor.h
@@ -62,9 +62,8 @@ class DenseTensor : public TensorBase,
   /// move constructor to support move semantics.
   DenseTensor(DenseTensor&& other) = default;
 
-  /// \brief We do not recommend deep copy of dense tensor because of its
-  /// efficiency and complexity across devices. The operation is disabled here.
-  DenseTensor(const DenseTensor& other) = delete;
+  /// \brief DenseTensor shallow copy constructor.
+  DenseTensor(const DenseTensor& other);
 
   /// \brief Destroy the tensor object and release exclusive resources.
   virtual ~DenseTensor() = default;
diff --git a/paddle/pten/core/tensor_meta.cc b/paddle/pten/core/tensor_meta.cc
index 3e06508be6..d8a3b5c9b2 100644
--- a/paddle/pten/core/tensor_meta.cc
+++ b/paddle/pten/core/tensor_meta.cc
@@ -38,10 +38,4 @@ bool DenseTensorMeta::valid() const noexcept {
   return valid;
 }
 
-bool operator==(const DenseTensorMeta& lhs, const DenseTensorMeta& rhs) {
-  bool ret = true;
-  return ret && (lhs.is_scalar == rhs.is_scalar) && (lhs.dims == rhs.dims) &&
-         (lhs.dtype == rhs.dtype) && (lhs.layout == rhs.layout) &&
-         (lhs.lod == rhs.lod) && (lhs.offset == rhs.offset);
-}
 }  // namespace pten
diff --git a/paddle/pten/core/tensor_meta.h b/paddle/pten/core/tensor_meta.h
index cc02c57a48..18daabca03 100644
--- a/paddle/pten/core/tensor_meta.h
+++ b/paddle/pten/core/tensor_meta.h
@@ -60,4 +60,11 @@ struct DenseTensorMeta {
   size_t offset{0};
 };
 
+inline bool operator==(const DenseTensorMeta& lhs, const DenseTensorMeta& rhs) {
+  bool ret = true;
+  return ret && (lhs.is_scalar == rhs.is_scalar) && (lhs.dims == rhs.dims) &&
+         (lhs.dtype == rhs.dtype) && (lhs.layout == rhs.layout) &&
+         (lhs.lod == rhs.lod) && (lhs.offset == rhs.offset);
+}
+
 }  // namespace pten
diff --git a/paddle/pten/tests/core/test_dense_tensor.cc b/paddle/pten/tests/core/test_dense_tensor.cc
index 2879a429d9..4a17046b2f 100644
--- a/paddle/pten/tests/core/test_dense_tensor.cc
+++ b/paddle/pten/tests/core/test_dense_tensor.cc
@@ -122,5 +122,20 @@ TEST(dense_tensor, resize) {
   CHECK_EQ(storage->size(), 6u);
 }
 
+TEST(dense_tensor, shallow_copy) {
+  const DDim dims({1, 2});
+  const DataType dtype{DataType::INT8};
+  const DataLayout layout{DataLayout::NHWC};
+  const std::vector<std::vector<size_t>> lod{};
+  DenseTensorMeta meta(dtype, dims, layout, lod);
+
+  auto alloc = std::make_shared<FancyAllocator>();
+  DenseTensor tensor_0(alloc, meta);
+
+  DenseTensor tensor_1(tensor_0);
+  CHECK(tensor_0.meta() == tensor_1.meta());
+  CHECK(tensor_0.release() == tensor_1.release());
+}
+
 }  // namespace tests
 }  // namespace pten
-- 
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