Support to Sparse Matrix CSC format

[aaamourao]

Hi, is vexcl going to support sparse matrices in CSC format (column major) in the near future?

[ddemidov]

Probably not, unless someone makes a pull request. CSC is not very effective for matrix vector product, especially on GPUs.

And even although vexcl supports CSR as input format, it converts it to (hybrid) ELL internally for better GPU performance. CSR is only used when the compute device is a CPU.