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Extensions

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.