Re: [Starpu-devel] Question about MPI usage

[Nathalie Furmento <nathalie.furmento@labri.fr>]

Xavier,

When you want to register a data that will be allocated only when it is 
used for the first time, you need to set the "home node", the 2nd 
parameter of starpu_xxx_data_register to -1.

Cheers,

Nathalie

On 31/01/2014 10:46, Xavier Lacoste wrote:
> Hi,
>
> I'm porting PaStiX multicore StarPU code to MPI StarPU.
> I register on each node local data and halo data (data that willl be read 
> used to update local data or that will be updated using local data).
> halo data is registered using NULL pointer :
>
>      starpu_matrix_data_register(&(Lhalo_handle[itercblk]), 0,
>                                  (uintptr_t)NULL,
>                                  (uint32_t)HCBLK_STRIDE(itercblk),
>                                  (uint32_t)HCBLK_STRIDE(itercblk),
>                                  HCBLK_COLNBR(itercblk),
>                                  sizeof(PASTIX_FLOAT));
>      starpu_data_set_rank(Lhalo_handle[itercblk], HCBLK_OWNER(itercblk));
>      starpu_data_set_tag(Lhalo_handle[itercblk],  HCBLK_GCBLK(itercblk));
>
> On the proc that possess the data, the same data is registered with an 
> allocated area (same owner/tag) :
>
>      starpu_matrix_data_register(&(L_handle[itercblk]), 0,
>                                  (uintptr_t)SOLV_COEFTAB(itercblk),
>                                  (uint32_t)SOLV_STRIDE(itercblk),
>                                  (uint32_t)SOLV_STRIDE(itercblk),
>                                  CBLK_COLNBR(itercblk),
>                                  sizeof(PASTIX_FLOAT));
>      starpu_data_set_rank(L_handle[itercblk], SOLV_PROCNUM);
>      starpu_data_set_tag(L_handle[itercblk], UPDOWN_LOC2GLOB(itercblk));
>
> When some tasks are submitted i get this error :
>
> [starpu][_starpu_mpi_irecv_data_func][assert failure] Invalid pointer to 
> receive data
>
> simple: starpu_mpi.c:487: _starpu_mpi_irecv_data_func: Assertion `req->ptr' 
> failed.
>
> When I look into starpu_mpi.c:1422 i found that it is due to 
> starpu_data_get_local_ptr() returns a NULL pointer:
>
>                                          if (found_req->user_datatype == 0)
>                                          {
>                                                  found_req->count = 1;
>                                                  found_req->ptr = 
> starpu_data_get_local_ptr(found_req->data_handle);
>                                                  fprintf(stdout, "%s:%d 
> found_req->ptr %p\n", __FILE__, __LINE__, found_req->ptr);
>                                          }
>
> I'm certainly doing an error somewhere, do you have any clue ? Is this the 
> NULL pointer i'm giving to starpu_matrix_data_register() ?
> I don't want to allocate this halo data before i need it... It should only 
> update my local data and be deleted, I was hopping that StarPU was going to 
> do that...
>
> Any Idea of what I'm doing wrong ?
>
> Regards,
>
> XL.
>
> PS: As we already gave all informations to starpu_mpi_task_build(), wouldn't 
> it be possible to only give the task to starpu_mpi_task_post_build() ? That 
> would make the code lighter :)
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