Why do dgemm_itcopy and sgemm_itcopy get different results for a same matrix?

[Shan Kang]

Hi,

I wrote a very simple test apps. Here is the code:

#include <stdio.h>

#include <stdlib.h>

#include <cblas.h>

#include <lapacke.h>

#define SIZE1 8

#define SIZE2 8

double src[SIZE1*SIZE2];

double dst[SIZE1*SIZE2];

int my_print_array(double a[])

{

        for (int i = 0; i < SIZE1*SIZE2; i++)

                printf("%.0f ", a[i]);

        printf("\n");

}

int main(int argc, char **argv)

{

        for(int i=0; i<SIZE2; i++)

            for(int j=0; j<SIZE1; j++)

                src[i*SIZE1+j] = i*10+j;

        printf("src:\n");

        my_print_array(src);

        dgemm_itcopy(SIZE1, SIZE2, src, 8, dst);

        printf("dst:\n");

        my_print_array(dst);

}

The "sgemm_itcopy " test app is almost the same as the above code, except using "float" instead of "double" and using "sgemm_itcopy" instead of "dgemm_itcopy".

dgemm_itcopy results:

src:

0   1   2   3   4   5   6   7 

10 11 12 13 14 15 16 17 

20 21 22 23 24 25 26 27 

30 31 32 33 34 35 36 37 

40 41 42 43 44 45 46 47 

50 51 52 53 54 55 56 57 

60 61 62 63 64 65 66 67 

70 71 72 73 74 75 76 77

dst:

0   1   2   3   10 11 12 13 

20 21 22 23 30 31 32 33 

40 41 42 43 50 51 52 53 

60 61 62 63 70 71 72 73 

4   5   6   7   14 15 16 17 

24 25 26 27 34 35 36 37 

44 45 46 47 54 55 56 57 

64 65 66 67 74 75 76 77

It looks reasonable.

sgemm_itcopy results:

src:

0   1   2   3   4   5   6   7 

10 11 12 13 14 15 16 17 

20 21 22 23 24 25 26 27 

30 31 32 33 34 35 36 37 

40 41 42 43 44 45 46 47 

50 51 52 53 54 55 56 57 

60 61 62 63 64 65 66 67 

70 71 72 73 74 75 76 77

dst:

0   1   2   3   4   5   6   7 

10 11 12 13 14 15 16 17 

20 21 22 23 24 25 26 27 

30 31 32 33 34 35 36 37 

40 41 42 43 44 45 46 47 

50 51 52 53 54 55 56 57 

60 61 62 63 64 65 66 67 

70 71 72 73 74 75 76 77

The src and dst matrices are identical which is different from dgemm_itcopy.

I wonder whether it is an expected behavior or it is a bug.

I use the latest dev-branch code. dgemm_itcopy's implementation is "kernel/generic/gemm_tcopy_4.c" and sgemm_itcopy's implementation is "kernel/x86_64/sgemm_tcopy_16_skylakex.c".