Module hyb 

HYB (Hybrid ELL+COO) sparse matrix format.

The HYB format splits a sparse matrix into two portions:

• An ELL (ELLPACK) portion storing the regular part: up to ell_width entries per row, padded with sentinel values (-1) for unused slots.
• A COO (Coordinate) overflow portion storing entries that exceed the ELL width.

This hybrid approach combines the coalesced memory access benefits of ELL (for rows with typical density) with the flexibility of COO (for rows with atypical density), yielding better performance than either format alone on matrices with irregular sparsity patterns.

The HybPartition enum controls how the ELL width is chosen:

• Auto uses the median row nnz (good default).
• Max uses the maximum row nnz (pure ELL, no COO overflow).
• Threshold(f64) uses a percentile of the row nnz distribution.
• Fixed(usize) lets the user specify the ELL width directly.

Structs

HybMatrix

A sparse matrix in HYB (Hybrid ELL+COO) format, stored on host.

HybStatistics

Statistics describing the quality of the HYB partition.

Enums

HybPartition

Strategy for partitioning non-zeros between ELL and COO portions.

Constants

HYB_ELL_SENTINEL

Sentinel value for unused ELL entries in the HYB format.

Functions

optimal_ell_width

Compute the optimal ELL width from a distribution of per-row nnz counts.