OpenBLAS/docs/extensions.md

OpenBLAS for the most part contains implementations of the reference (Netlib) BLAS, CBLAS, LAPACK and LAPACKE interfaces. A few OpenBLAS-specific functions are also provided however, which mostly can be seen as "BLAS extensions". This page documents those non-standard APIs.

BLAS-like extensions

Routine	Data Types	Description
?axpby	s,d,c,z	like axpy with a multiplier for y
?gemm3m	c,z	gemm3m
?imatcopy	s,d,c,z	in-place transposition/copying
?omatcopy	s,d,c,z	out-of-place transposition/copying
?geadd	s,d,c,z	ATLAS-like matrix add B = α*A+β*B
?gemmt	s,d,c,z	gemm but only a triangular part updated

bfloat16 functionality

BLAS-like and conversion functions for bfloat16 (available when OpenBLAS was compiled with BUILD_BFLOAT16=1):

• void cblas_sbstobf16 converts a float array to an array of bfloat16 values by rounding
• void cblas_sbdtobf16 converts a double array to an array of bfloat16 values by rounding
• void cblas_sbf16tos converts a bfloat16 array to an array of floats
• void cblas_dbf16tod converts a bfloat16 array to an array of doubles
• float cblas_sbdot computes the dot product of two bfloat16 arrays
• void cblas_sbgemv performs the matrix-vector operations of GEMV with the input matrix and X vector as bfloat16
• void cblas_sbgemm performs the matrix-matrix operations of GEMM with both input arrays containing bfloat16

Utility functions

• openblas_get_num_threads
• openblas_set_num_threads
• int openblas_get_num_procs(void) returns the number of processors available on the system (may include "hyperthreading cores")
• int openblas_get_parallel(void) returns 0 for sequential use, 1 for platform-based threading and 2 for OpenMP-based threading
• char * openblas_get_config() returns the options OpenBLAS was built with, something like NO_LAPACKE DYNAMIC_ARCH NO_AFFINITY Haswell
• int openblas_set_affinity(int thread_index, size_t cpusetsize, cpu_set_t *cpuset) sets the CPU affinity mask of the given thread to the provided cpuset. Only available on Linux, with semantics identical to pthread_setaffinity_np.