Question about sparse format choice for RVV-accelerated SpMV

[Yash Kaushik]

Hi everyone,

I had another question while thinking about sparse matrix formats for RVV-targeted SpMV implementations.

Is CSR still generally considered the preferred storage format for SpMV on RISC-V Vector (RVV), or do formats like ELLPACK, COO, SELL-C-sigma, etc. tend to map better to RVV’s vector-length-agnostic execution model?

From what I understand, CSR is widely used because of its memory efficiency and generality, but I’m curious whether the irregular row lengths and indirect accesses become a bigger bottleneck on vector hardware specifically. On the other hand, formats like ELLPACK seem more vector-friendly due to their regular structure, even if they introduce padding overhead.

I would really like to understand how sparse format choices change when targeting RVV/vector architectures in practice, and what formats are typically preferred in production HPC or research implementations.

Thanks!