[mpich-discuss] MPI One-Sided Communication, and indexed datatype

[Ziaul Haque Olive]

Thanks Jeff,

the code is quite large to post here. It is from graph500 benchmark's mpi
implementation. multiple files are required to build this code. I can send
the whole directory for debugging. what do you say?

Thanks,
Ziaul.

On Thu, May 31, 2012 at 8:51 PM, Jeff Hammond <jhammond at alcf.anl.gov> wrote:

> This is an interesting question.
>
> "Is it okay that I am freeing memory before the closing fence?"
>
> With respect to the memory associated with the MPI_Accumulate itself,
> the answer is clearly "no".
>
> MPI-2.2 11.3:
>
> "The local communication buffer of an RMA call should not be updated,
> and the local communication buffer of a get call should not be
> accessed after the RMA call, until the subsequent synchronization call
> completes."
>
> Freeing memory is obviously a modification.
>
> However, it seems you are freeing the MPI_Datatype used in this
> operation and the input arrays associated with it.
>
> From MPI-2.2 4.1.9:
>
> "Marks the datatype object associated with datatype for deallocation
> and sets datatype to MPI_DATATYPE_NULL. Any communication that is
> currently using this datatype will complete normally. Freeing a
> datatype does not affect any other datatype that was built from the
> freed datatype. The system behaves as if input datatype arguments to
> derived datatype constructors are passed by value."
>
> It would seem that your usage is correct.
>
> I cannot debug your code because it is incomplete and has a few bugs
> according to the C standard.  Can you post the code that actually
> results in the error you're seeing?
>
> There may be other issues with your code that others may point out.
> My email is not intended to capture all possible sources of error.
>
> Best,
>
> Jeff
>
>
> On Thu, May 31, 2012 at 6:23 PM, Ziaul Haque Olive <mzh.olive at gmail.com>
> wrote:
> > Hello,
> >
> > I am not sure, if my code is correct according to MPICH2(v1.4.1p1.). 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 before the closing fence.
> >
> > 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
> >
> > _______________________________________________
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>
>
>
> --
> Jeff Hammond
> Argonne Leadership Computing Facility
> University of Chicago Computation Institute
> jhammond at alcf.anl.gov / (630) 252-5381
> http://www.linkedin.com/in/jeffhammond
> https://wiki.alcf.anl.gov/parts/index.php/User:Jhammond
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