Optimize matrix_cl constructors #1420

Description

When constructing a matrix_cl from Eigen::Map it creates a copy of the data by calling .eval(). Instead of this the data in Map should be directly accessed.

When constructing a matrix_cl from a rvalue (temporary object), it uses blocking calls to OpenCL to avoid accessing these objects after they are destroyed. Instead these objects could be moved (or evaluated in case of Eigen expressions) on heap and deleted after the copy to OpenCL device is complete.

Example

int rows, cols;
double* data;
Eigen::Map<Eigen::MatrixXd> map(data, rows, cols);
matrix_cl(map);

Eigen::MatrixXd a, b;
matrix_cl(a + b);

Expected Output

Constructing matrix_cl from a Map is faster. Constructing matrix_cl from a temporary does not block.

Current Version:

v3.0.0