BLAS (OpenBLAS)

Improvements to OpenBLAS 0.3.30 on RISC-V boards — built via EasyBuild, deployed through EESSI with FlexiBLAS runtime swapping. Verification tools and A/B scripts live in the opensolvers/benchmarks repo (dgemm/, numpy/).

Base stack: GCC 14.3.0, OpenBLAS 0.3.30, EESSI 2025.06-001 (dev.eessi.io/riscv).

Improvements

Board / CPU Problem (stock 0.3.30) Fix Result
VisionFive 2 — SiFive U74 (scalar) No U74 kernel; falls back to generic RISCV64_GENERIC C 2×2 GEMM New 4×4 DGEMM micro-kernel in RV64 assembly, TARGET=U74 Single-core DGEMM ~1.4 → 1.77 GFLOP/s; 4-core DGEMM 6.31 GFLOP/s; HPL 1.69×
Orange Pi RV2 — SpacemiT X60 (RVV VLEN=256) RVV gemv_n zeroes an uninitialized vector register → dgemv returns NaN Backport upstream gemv_n fix; TARGET=RISCV64_ZVL256B Correct dgemv; see HPL and A/B tables below
Banana Pi F3 — same K1 / X60 SoC Same RVV gemv_n bug as RV2 Same easyconfigs#26444 fix Fix applies; peak results not yet recorded

X60 A/B — patched RVV vs scalar (Orange Pi RV2)

All runs use a fixed RVV OpenBLAS (gemv_n patch) swapped in via FlexiBLAS. Source: benchmarks/dgemm, benchmarks/numpy.

Probe Scalar (RISCV64_GENERIC) Patched RVV (ZVL256B) Speedup
bench_dgemm N=2048, 1 core 1.16 GFLOP/s 2.62 GFLOP/s 2.3×
NumPy A @ B N=4096, 8 threads 4.77 GFLOP/s 11.52 GFLOP/s 2.4×
NumPy eigvalsh N=2048, 8 threads 10.54 s 6.72 s 1.6×

X60 — isolating the gemv_n bug (difftest)

The benchmarks difftest tool dlopens a BLAS .so and reports NaN counts per routine:

Backend dgemv NaN dgemm NaN dgemv sum
Stock EESSI, default RVV 192 0 198.94 (wrong)
Stock EESSI, forced scalar 0 0 42.06549 (reference)
Patched RVV (gemv_n fix) 0 0 42.06549 (matches)

dgemm looks fine on the broken build — which is why a raw GEMM benchmark can pass while HPL and ELPA fail.

Packages

Target EasyBuild PR Upstream OpenBLAS Walkthrough
SiFive U74 easyconfigs#26436 OpenBLAS#5903 EESSI/docs#818
SpacemiT X60 easyconfigs#26444 OpenBLAS#5408, #5476 EESSI/docs#819

Build with eb --from-pr <num> --robot into an EESSI-extend user install, then flexiblas add / flexiblas default — no downstream rebuild.

Notes