Re: [Starpu-devel] Problem with partitioning matrix with starpu_matrix_filter_block

[Samuel Thibault <samuel.thibault@inria.fr>]

Hello,

Johan Mazel, le mer. 08 janv. 2020 23:12:46 +0100, a ecrit:
> If I try to use starpu_matrix_filter_block (for example by decommenting 
> line 51
> and 52 in test_starpu.c), I obtain the following results:
> * Worker 0 get values with index 0 -> 7.

The problem is not the partitioning: it is correct, as shown by
test_cpu: id (1804289383) ; nx: 2 ; ny: 4

The issue is in the data access in your test_cpu_func, you mustn't use
nx, but ld:

unsigned nx = STARPU_MATRIX_GET_NX(matrix_res);
unsigned ld = STARPU_MATRIX_GET_LD(matrix_res);
unsigned ny = STARPU_MATRIX_GET_NY(matrix_res);

for (j = 0; j < ny; j++) {
  for (i = 0; i < nx; i++) {
    printf("test_cpu: id (%u) ; res_m[%d,%d]: %lu\n", id, j, i, res_m[j*ld + 
i]);
  }
}

Since partitioning is done in-place, ld really mustn't be ignored (and
it shouldn't be ignored in the general case anyway, because you never
know when you would change your code in a way that makes taking ld into
account mandatory)

Samuel