CSC kills the prospect of multithreading. Shouldn't Julia use CSR?

[gdalle]

@stevengj

In any case, one option is simply to use transpose(A), since Transpose{T, <:SparseMatrixCSC{T}} is effectively a CSR sparse matrix.

I seem to remember reading that this is not as efficient as it looks, eg here

What to do since CSR matrixes are not in Sparse Arrays?

I ran some benchmarks using the suggestions of @rdeits and @Oscar_Smith . The example matrix is the 2D finite-difference laplacian on a grid of 10,000 x 10,000 points. The “CSR” matrix is the transpose of the CSC matrix. Below are the benchmark results and a conclusion. All times are the minimum benchmark time: [Screen Shot 2021-01-30 at 1.09.31 AM] Thoughts? I can provide the pluto notebook upon request.

But I don’t know what those benchmarks are worth