Example
The all-gather version of Example Examples using MPI_GATHER, MPI_GATHERV . Using MPI_ALLGATHER, we will gather 100 ints from every process in the group to every process.
MPI_Comm comm;
int gsize,sendarray[100];
int *rbuf;
...
MPI_Comm_size( comm, &gsize);
rbuf = (int *)malloc(gsize*100*sizeof(int));
MPI_Allgather( sendarray, 100, MPI_INT, rbuf, 100, MPI_INT, comm);
After the call, every process has the group-wide concatenation of the
sets of data.