The following program computes the product of two matrices using the Level-3 BLAS function SGEMM,
The matrices are stored in row major order but could be stored in column
major order if the first argument of the call to cblas_sgemm
was
changed to CblasColMajor
.
#include <stdio.h> #include <gsl/gsl_cblas.h> int main (void) { int lda = 3; float A[] = { 0.11, 0.12, 0.13, 0.21, 0.22, 0.23 }; int ldb = 2; float B[] = { 1011, 1012, 1021, 1022, 1031, 1032 }; int ldc = 2; float C[] = { 0.00, 0.00, 0.00, 0.00 }; /* Compute C = A B */ cblas_sgemm (CblasRowMajor, CblasNoTrans, CblasNoTrans, 2, 2, 3, 1.0, A, lda, B, ldb, 0.0, C, ldc); printf("[ %g, %g\n", C[0], C[1]); printf(" %g, %g ]\n", C[2], C[3]); return 0; }
To compile the program use the following command line,
gcc demo.c -lgslcblas
There is no need to link with the main library -lgsl
in this
case as the CBLAS library is an independent unit. Here is the output
from the program,
$ ./a.out [ 367.76, 368.12 674.06, 674.72 ]