Open MPI logo

Open MPI User's Mailing List Archives

  |   Home   |   Support   |   FAQ   |   all Open MPI User's mailing list

Subject: Re: [OMPI users] MPI One-Sided Communication, indexed datatype and segmentation fault.
From: Ziaul Haque Olive (mzh.olive_at_[hidden])
Date: 2012-06-06 14:24:18


Hello Brian,

Actually, I am not modifying the local communication buffer that contains
the data. I am modifying the the buffer that contains the indices of the
data buffer(source_disp and target_disp).

in MPICH2 this is not a problem. I am not sure about Open MPI.

Thanks,
Ziaul

On Wed, Jun 6, 2012 at 1:05 PM, Barrett, Brian W <bwbarre_at_[hidden]> wrote:

> Ziaul -
>
> Your program is erroneous; you can not modify the local communication
> buffer of an MPI_ACCUMULATE call until after the next synchronization call
> (Section 11.3 of MPI 2.2). In your example, that would be after the
> MPI_FENCE call following the call to MPI_ACCUMULATE.
>
> Brian
>
> On 6/6/12 9:44 AM, "Ziaul Haque Olive" <mzh.olive_at_[hidden]> wrote:
>
> >Hello,
> >
> >I am not sure, if my code is correct according to Open MPI(v1.6). the
> > code is given as follows, I am doing MPI one-sided communication inside
> > a function - data_transfer. this function is being called inside a
> >fence epoch. inside data_transfer, I am allocating memory for
> >non-contiguous data, creating derived data type, using this datatype in
> >MPI_Accumulate, and after calling MPI_Accumulate, freeing the indexed
> >data type and also freeing the memory containing indices for indexed
> >data type. is it okay that I am freeing memory for derived datatype
> >before the closing
> >fence?
> >
> >I am getting segmentation fault with this code. if I comment out the
> >MPI_Accumulate call, then no seg-fault occurs.
> >
> >
> >
> >void data_transfer(void *data, int
> >*sources_disp, int *targets_disp, int *target, int size, int *blength,
> >int func, MPI_Op op, MPI_Win win, MPI_Datatype dtype){
> >
> > int i,j, index;
> > int tmp_target;
> > int *flag;
> > int *source_disp;
> > int *target_disp;
> > MPI_Datatype source_type, target_type;
> >
> >
> > MPI_Alloc_mem( size*sizeof(int), MPI_INFO_NULL, &source_disp);
> > MPI_Alloc_mem( size*sizeof(int), MPI_INFO_NULL, &target_disp);
> > MPI_Alloc_mem( size*sizeof(int), MPI_INFO_NULL, &flag );
> >
> > memset(flag, 0, size*sizeof(int));
> >
> > for(i=0;i<size;i++){
> > if(flag[i]==0){
> > tmp_target = target[i];
> >
> > index = 0;
> > for(j=i; j<size; j++){
> > if(flag[j]==0 && tmp_target == target[j] ){
> > source_disp[index] = sources_disp[j];
> > target_disp[index] = targets_disp[j];
> > //printf("src, target disp %d %d\n", j, disp[j]);
> > index++;
> > flag[j] = 1;
> > }
> > }
> >
> > MPI_Type_indexed(index, blength , source_disp, dtype,
> >&source_type);
> > MPI_Type_commit(&source_type);
> > MPI_Type_indexed(index, blength , target_disp, dtype,
> >&target_type);
> > MPI_Type_commit(&target_type);
> >
> >
> > MPI_Accumulate( data, 1, source_type, tmp_target, 0, 1,
> >target_type , op, win);
> >
> > MPI_Type_free(&source_type);
> > MPI_Type_free(&target_type);
> > }
> > }
> > MPI_Free_mem(source_disp);
> > MPI_Free_mem(target_disp);
> > MPI_Free_mem(flag);
> >
> >}
> >
> >void main(){
> > int i;
> > while(i<N){
> > MPI_Win_fence(MPI_MODE_NOPRECEDE, queue2_win);
> >
> > data_transfer();
> >
> > MPI_Win_fence(MPI_MODE_NOSUCCEED, queue2_win);
> > }
> >}
> >
> >thanks,
> >Ziaul
> >
> >
> >_______________________________________________
> >users mailing list
> >users_at_[hidden]
> >http://www.open-mpi.org/mailman/listinfo.cgi/users
>
>
> --
> Brian W. Barrett
> Dept. 1423: Scalable System Software
> Sandia National Laboratories
>
>
>
>
>
>
> _______________________________________________
> users mailing list
> users_at_[hidden]
> http://www.open-mpi.org/mailman/listinfo.cgi/users
>