OpenBLAS, a Basic Linear Algebra Subprograms Library

OpenBLAS is an open source optimized BLAS (Basic Linear Algebra Subprograms) library based on GotoBLAS2 1.13 BSD version.

Install OpenBLAS from source

• Step 1: Clone the source of OpenBLAS

git clone https://github.com/xianyi/OpenBLAS.git
cd OpenBLAS

• Step 2: Build the source

make -j4

Usage

Statically link with libopenblas.a or dynamically link with -lopenblas if OpenBLAS was compiled as a shared library.

Example of Matrix Multiplication in OpenBLAS

#include <cblas.h>
#include <stdio.h>
#include <sys/time.h> 
#include <stdlib.h>
#include <math.h>
void init_matrix(double* A, int dim1 , int dim2 ) 
{
  int mod = 100003, prod = 7 , e = 1 , i = 0, j = 0;
  for ( i = 0; i < dim1; ++i )
  {
	for ( j = 0; j < dim2; ++j )
        {
            e = (e*prod + 1)%mod; // random
            A[i*dim2 + j] = e * .91739210437;
        }
  }
}
int main(int argc, char** argv)
{
  int m , n , k , i , j , u , nrep = 1 , cnt = 0;
  double *A , *B , *C;
  if ( argc != 5 ) 
  {
    puts("Format: ./a.out number_of_iteration dimension_1 
          dimension_2 dimension_3");
    exit(0);
  }
  if ( argc == 5 ) 
  {
    sscanf ( argv[1] , "%d" , &m );
    sscanf ( argv[2] , "%d" , &k );
    sscanf ( argv[3] , "%d" , &n );
  }
  A = (double *) malloc( sizeof(double) * m * k );
  B = (double *) malloc( sizeof(double) * k * n );
  C = (double *) malloc( sizeof(double) * m * n );
  init_matrix ( A , m , k );
  init_matrix ( B , k , n );
  cblas_dgemm ( CblasRowMajor, CblasNoTrans, CblasNoTrans ,
         m , n , k , 1.0 , A , k , B , n , 0.0 , C , n );
  return 0;
}

Compile and run the above code:

gcc matrix_multiplication_openblas.c
./a.out 100 100 100