Since C++11 we can now use move semantics (move constructor, move assignment operator). They provide a perfomance boost over copy semantics, but only work on rvalue references.<\/p>\n
\r\n#include <utility>\r\n#include <cstring>\r\n#include <memory>\r\n#include <mutex>\r\n#include <iostream>\r\n \r\nclass Matrix\r\n{\r\npublic:\r\n \/\/ Constructor\r\n Matrix(unsigned rows, unsigned cols) : m_Mtx(), m_Rows(rows), m_Cols(cols)\r\n {\r\n std::cout << "Matrix constructor" << std::endl;\r\n \r\n createMatrix();\r\n }\r\n \r\n \/\/ Copy-Constructor\r\n Matrix(const Matrix& other) : m_Mtx()\r\n {\r\n std::cout << "Matrix copy-constructor" << std::endl;\r\n \r\n {\r\n std::lock_guard<std::mutex> lock(other.m_Mtx);\r\n \r\n m_Rows = other.m_Rows;\r\n m_Cols = other.m_Cols;\r\n \r\n createMatrix();\r\n for (int i = 0; i < m_Rows; i++)\r\n {\r\n std::memcpy(m_Mat[i], other.m_Mat[i], m_Cols * sizeof(m_Cols));\r\n }\r\n }\r\n }\r\n \r\n \/\/ Move-Constructor\r\n Matrix(Matrix&& other) : m_Mtx()\r\n {\r\n std::cout << "Matrix move-constructor" << std::endl;\r\n \r\n {\r\n std::lock_guard<std::mutex> lock(other.m_Mtx);\r\n \r\n m_Rows = other.m_Rows;\r\n m_Cols = other.m_Cols;\r\n m_Mat = other.m_Mat;\r\n \r\n other.m_Rows = 0;\r\n other.m_Cols = 0;\r\n other.m_Mat = nullptr;\r\n }\r\n }\r\n \r\n \/\/ Destructor\r\n ~Matrix()\r\n {\r\n std::cout << "Matrix destructor" << std::endl;\r\n \r\n removeMatrix();\r\n \r\n m_Rows = 0;\r\n m_Cols = 0;\r\n m_Mat = nullptr;\r\n }\r\nprivate:\r\n void createMatrix()\r\n {\r\n m_Mat = new unsigned*[m_Rows];\r\n for (unsigned i = 0; i < m_Rows; ++i)\r\n {\r\n m_Mat[i] = new unsigned[m_Cols];\r\n }\r\n }\r\n \r\n void removeMatrix()\r\n {\r\n for(unsigned i = 0; i < m_Rows; ++i)\r\n {\r\n delete[] m_Mat[i];\r\n }\r\n delete[] m_Mat;\r\n }\r\n \r\n mutable std::mutex m_Mtx;\r\n unsigned m_Rows;\r\n unsigned m_Cols;\r\n unsigned** m_Mat;\r\n};\r\n \r\nint main()\r\n{\r\n std::cout << "== Step 0: Create baseMatrix (on stack) ==" << std::endl;\r\n Matrix baseMatrix(100000, 10000);\r\n \r\n std::cout << "== Step 1: Copy baseMatrix to destMatrix1 ==" << std::endl;\r\n Matrix destMatrix1(baseMatrix); \/\/ Very slow\r\n \r\n std::cout << "== Step 2: Move baseMatrix to destMatrix2 ==" << std::endl;\r\n Matrix destMatrix2(std::move(baseMatrix)); \/\/ Very fast\r\n \/\/ std::move() makes baseMatrix an rValue reference,\r\n \/\/ which is empty after the move-c'tor\r\n\r\n std::cout << "== Step 3: Cleanup in stack order ==" << std::endl;\r\n return 0;\r\n}\r\n<\/pre>\n\r\n== Step 0: Create baseMatrix (on stack) ==\r\nMatrix constructor\r\n== Step 1: Copy baseMatrix to destMatrix1 ==\r\nMatrix copy-constructor\r\n== Step 2: Move baseMatrix to destMatrix2 ==\r\nMatrix move-constructor\r\n== Step 3: Cleanup in stack order ==\r\nMatrix destructor\r\nMatrix destructor\r\nMatrix destructor\r\n<\/pre>\nThis example just contains the move constructor, but normally you want to implement a move assignment operator as well.<\/p>\n
Alternative<\/u>: Let the compiler implicitly create a move constructor \/ move assignment operator for you. Be aware of the requirements and restrictions.<\/p>\n
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