[mpich-discuss] (no subject)

[Chafik sanaa]

hi, thanks

2014-12-05 19:37 GMT+01:00 "Antonio J. Peña" <apenya at mcs.anl.gov>:

>
> Dear user,
>
> Please note that this mailing list is exclusively intended to discuss
> potential issues with the MPICH MPI implementation. Since your question is
> about general MPI usage, we cannot provide you with that assistance here.
> You will surely find assistance in this kind of topics in general
> programming forums such as stackoverflow, where some of our team members
> contribute as well. Also, web search engines are likely to be a good
> resource in your case.
>
> Best regards,
>   Antonio
>
>
>
> On 12/05/2014 11:50 AM, Chafik sanaa wrote:
>
> I have a table "tab[]" with 10 elements "0 | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8
> | 9 |" I am sending with the Scatterv function; 4 elements to the process 0
> "|0 | 1 | 2 | 3 | 4| "and 6 elements to process 1 "| 5 | 6 | 7 | 8 | 9 | ",
> after I did the summation of the value" add " to each element of the
> received table which gives me a new table "afteradd[] "for each process, I
> want this time collecting the both tables "afteradd[]" and send them to the
> process 0, after a little research I found that there's a GATHERV function
> which do that but I do not know how ?
>
> program:
>  #include <malloc.h>
> #include <stdlib.h>
> #include <stdio.h>
> #include <time.h>
> #include "math.h"
> #include "mpi.h"
>
>  int main(int argc, char** argv)
> {
>  int          taskid, ntasks;
>  int          ierr, i, itask;
>  int         sendcounts[2048], displs[2048], recvcount;
>  double       **sendbuff, *recvbuff,*afteradd, buffsum, buffsums[2048];
>  double       inittime, totaltime;
>  const int nbr_etat = 10;
>  double tab[nbr_etat];
>  for (int i = 0; i < nbr_etat; i++)
>  tab[i] = i;
>  int nbr_elm[2] = { 4, 6 };
>  int dpl[2] = { 0, 4 };
>  MPI_Init(&argc, &argv);
>  MPI_Comm_rank(MPI_COMM_WORLD, &taskid);
>  MPI_Comm_size(MPI_COMM_WORLD, &ntasks);
>  recvbuff = (double *)malloc(sizeof(double)*nbr_etat);
>  if (taskid == 0)
>  {
>  sendbuff = (double **)malloc(sizeof(double *)*ntasks);// run for 2 proc
>  sendbuff[0] = (double *)malloc(sizeof(double)*ntasks*nbr_etat);
>  for (i = 1; i < ntasks; i++)
>  {
>  sendbuff[i] = sendbuff[i - 1] + nbr_etat;
>  }
>  }
>  else
>  {
>  sendbuff = (double **)malloc(sizeof(double *)* 1);
>  sendbuff[0] = (double *)malloc(sizeof(double)* 1);
>  }
>
>  if (taskid == 0){
>
>  srand((unsigned)time(NULL) + taskid);
>  for (itask = 0; itask<ntasks; itask++)
>  {
>  int k;
>  displs[itask] = itask*nbr_etat;
>  int s = dpl[itask];
>  sendcounts[itask] = nbr_elm[itask];
>
>
>  for (i = 0; i<sendcounts[itask]; i++)
>  {
>  k = i + s;
>  sendbuff[itask][i] = tab[k];
>  printf("+ %0.0f  ", sendbuff[itask][i]);
>  }
>  printf("\n");
>  }
>  }
>
>  recvcount = nbr_elm[taskid];
>
>  inittime = MPI_Wtime();
>
>  ierr = MPI_Scatterv(sendbuff[0], sendcounts, displs, MPI_DOUBLE,
>  recvbuff, recvcount, MPI_DOUBLE,
>  0, MPI_COMM_WORLD);
>
>  totaltime = MPI_Wtime() - inittime;
>
>   buffsum = 0.0;
>  int add = 3;
>  afteradd = (double *)malloc(sizeof(double)*nbr_etat);
>  for (i = 0; i<recvcount; i++)
>  {
>  afteradd [i]= add + recvbuff[i];
>  }
>  for (i = 0; i<recvcount; i++)
>  {
>  printf("* %0.0f ", afteradd[i]);
>  }
>  printf("\n");
>  if (taskid == 0)
>  {
>  free(sendbuff[0]);
>  free(sendbuff);
>  }
>  else
>  {
>  free(sendbuff[0]);
>  free(sendbuff);
>  free(recvbuff);
>  }
>  MPI_Finalize();
>
>  }
>
>
>
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>
>
> --
> Antonio J. Peña
> Postdoctoral Appointee
> Mathematics and Computer Science Division
> Argonne National Laboratory
> 9700 South Cass Avenue, Bldg. 240, Of. 3148
> Argonne, IL 60439-4847apenya at mcs.anl.govwww.mcs.anl.gov/~apenya
>
>
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