Allow Constant ops to share internal buffer (#4216)

* Move non-templated constructor implementation to the source file

* Optimize constant constructor for uniform constant

* Cleanup

* Much faster deserialize constant

* Adding unit tests

* Unit tests

* Update unit test

* Cleanup

* style

* Cleanup nbench output

* wip

* Fix specializations

* Change from unique to shared_ptr internally

* Enable copy of Constant

* cleanup Constant ctors

* Fix copy contructor

* Fix compile error
Co-authored-by: Scott Cyphers <diyessi@users.noreply.github.com>

src/ngraph/op/constant.cpp

@@ -52,8 +52,8 @@ op::Constant::Constant(const element::Type& type,
                        const std::vector<std::string>& values)
     : m_element_type(type)
     , m_shape(shape)
-    , m_data(new runtime::AlignedBuffer(
-          std::ceil(shape_size(m_shape) * m_element_type.bitwidth() / 8.f), host_alignment()))
+    , m_data(
+          new runtime::AlignedBuffer(shape_size(m_shape) * m_element_type.size(), host_alignment()))
 {
     NODE_VALIDATION_CHECK(this,
                           values.size() == shape_size(m_shape) || values.size() == 1,
@@ -290,15 +290,24 @@ op::Constant::Constant(const element::Type& type,
 op::Constant::Constant(const element::Type& type, const Shape& shape, const void* data)
     : m_element_type(type)
     , m_shape(shape)
-    , m_data(nullptr)
+    , m_data(
+          new runtime::AlignedBuffer(shape_size(m_shape) * m_element_type.size(), host_alignment()))
 {
-    size_t size = std::ceil(shape_size(m_shape) * m_element_type.bitwidth() / 8.f);
-    m_data.reset(new runtime::AlignedBuffer(size, host_alignment()));
+    size_t size = shape_size(m_shape) * m_element_type.size();
     std::memcpy(m_data->get_ptr(), data, size);
     constructor_validate_and_infer_types();
     m_all_elements_bitwise_identical = are_all_data_elements_bitwise_identical();
 }
 
+op::Constant::Constant(const Constant& other)
+    : m_element_type(other.m_element_type)
+    , m_shape(other.m_shape)
+    , m_data(other.m_data)
+    , m_all_elements_bitwise_identical(other.m_all_elements_bitwise_identical)
+{
+    constructor_validate_and_infer_types();
+}
+
 op::Constant::~Constant()
 {
 }
@@ -516,7 +525,7 @@ AxisSet op::Constant::get_axis_set_val() const
 shared_ptr<Node> op::Constant::copy_with_new_args(const NodeVector& new_args) const
 {
     check_new_args_count(this, new_args);
-    return make_shared<Constant>(m_element_type, m_shape, m_data->get_ptr());
+    return make_shared<Constant>(*this);
 }
 
 template <typename T>

src/ngraph/op/constant.hpp

@@ -49,9 +49,8 @@ namespace ngraph
                 Constant(const element::Type& type, Shape shape, const std::vector<T>& values)
                     : m_element_type(type)
                     , m_shape(shape)
-                    , m_data(new runtime::AlignedBuffer(
-                          std::ceil(shape_size(m_shape) * m_element_type.bitwidth() / 8.f),
-                          host_alignment()))
+                    , m_data(new runtime::AlignedBuffer(shape_size(m_shape) * m_element_type.size(),
+                                                        host_alignment()))
                 {
                     NODE_VALIDATION_CHECK(
                         this,
@@ -94,6 +93,8 @@ namespace ngraph
                 /// \param data A void* to constant data.
                 Constant(const element::Type& type, const Shape& shape, const void* data);
 
+                Constant(const Constant& other);
+
                 virtual ~Constant() override;
 
                 void validate_and_infer_types() override
@@ -374,11 +375,9 @@ namespace ngraph
                 static constexpr size_t host_alignment() { return 64; }
                 element::Type m_element_type;
                 Shape m_shape{};
-                std::unique_ptr<runtime::AlignedBuffer> m_data;
+                std::shared_ptr<runtime::AlignedBuffer> m_data;
                 bool m_all_elements_bitwise_identical;
                 bool are_all_data_elements_bitwise_identical() const;
-                Constant(const Constant&) = delete;
-                Constant operator=(const Constant&) = delete;
             };
 
             /// \brief A scalar constant whose element type is the same as like.

test/constant.cpp

@@ -1010,3 +1010,13 @@ TEST(constant, float16_vector_broadcast)
     EXPECT_EQ(p[2], float16(1));
     EXPECT_EQ(p[3], float16(1));
 }
+
+TEST(constant, shared_data)
+{
+    Shape shape{100, 200};
+    auto c1 = make_shared<op::Constant>(element::f16, shape, vector<float16>{123});
+    auto c2 = static_pointer_cast<op::Constant>(c1->copy_with_new_args({}));
+    const float* p1 = c1->get_data_ptr<float>();
+    const float* p2 = c2->get_data_ptr<float>();
+    EXPECT_EQ(p1, p2);
+}