FlexiBLAS

Licences

FlexiBLAS is a lightweight wrapper around the BLAS and LAPACK APIs.  It allows you to choose an implementation at run-time.  Our foss/2023a toolchain specifies FlexiBLAS as its BLAS/LAPACK library, with OpenBLAS as the default real implementation.  So for any software built with that toolchain, you can substitute OpenBLAS with BLIS or with Intel's MKL by setting the environment variable FLEXIBLAS:

module load Python/3.11.3-foss-2023a
# using OpenBLAS

# switch to Intel MKL
module load imkl/2022.0.2
export FLEXIBLAS=IMKL

# switch to BLIS
module load BLIS/0.9.0-GCC-12.3.0
export FLEXIBLAS=BLIS

# explicitly switch back to OpenBLAS
export FLEXIBLAS=OPENBLAS

# switch to our default (currently OpenBLAS)
unset FLEXIBLAS

For workloads which spend a considerable amount of CPU time doing linear algebra via BLAS or LAPACK, it may be worth benchmarking these options to see which performs the best.  Their relative performance can differ between different CPU types.

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