I have a problem using the sgemm function of cblas.
Here is the code:
#include <math.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <cblas.h>
#define MATRIX_DIM 5
int main(){
float *a_mat = calloc(MATRIX_DIM*MATRIX_DIM, sizeof(float));
float *b_mat = calloc(MATRIX_DIM, sizeof(float));
float *c_mat = calloc(MATRIX_DIM, sizeof(float));
int i,j;
for(i=0; i<MATRIX_DIM*MATRIX_DIM; i++) {
a_mat[i] = 1.0f;
b_mat[i] = 1.0f;
c_mat[i] = 0.0f;
}
cblas_sgemm(CblasRowMajor, CblasNoTrans,
CblasNoTrans, MATRIX_DIM, MATRIX_DIM,
MATRIX_DIM, 1.0, a_mat,
MATRIX_DIM, b_mat, MATRIX_DIM,
1.0, c_mat, MATRIX_DIM);
//RESULT PRINTING
printf("Printing A MATRIX: \n");
for(i=0; i<MATRIX_DIM; i++) {
for(j=0; j<MATRIX_DIM; j++){
printf("%0.1f ", a_mat[i*MATRIX_DIM+j]);
}
printf("\n");
}
printf("Printing B MATRIX: \n");
for(i=0; i<MATRIX_DIM; i++) {
for(j=0; j<MATRIX_DIM; j++){
printf("%0.1f ", b_mat[i*MATRIX_DIM+j]);
}
printf("\n");
}
printf("\nPrinting the Results: \n");
for(i=0; i<MATRIX_DIM;i++){
for(j=0; j<MATRIX_DIM; j++){
printf("%0.1f ", c_mat[i*MATRIX_DIM+j]);
}
printf("\n");
}
free(a_mat);
free(b_mat);
free(c_mat);
return 0;
}
I am pretty some of the arguments I put in are wrong, but I really don't know which. The results should be a 5x5 matrix filled with 5.0. Instead the program responds with this:
6.0 6.0 6.0 16.0 86.0
6.0 6.0 6.0 16.0 86.0
16.0 36.0 6.0 46.0 86.0
16.0 36.0 5.0 45.0 85.0
20.0 80.0 5.0 45.0 85.0
I know the rowmajor order or the transpose arguments might be wrong and I will figure those out later, but in this particular multiplication the answer should be 5.0 either way.
Thanks to @AndrasDeak in the comments, all I needed was to allocate more space on the two matrices, which I previously overlooked.
So basically change:
float *b_mat = calloc(MATRIX_DIM, sizeof(float));
float *c_mat = calloc(MATRIX_DIM, sizeof(float));
To:
float *b_mat = calloc(MATRIX_DIM*MATRIX_DIM, sizeof(float));
float *c_mat = calloc(MATRIX_DIM*MATRIX_DIM, sizeof(float));
Since those are supposed to be 2-dimensional matrices and not vectors.