c++ - What is equivalent of socket programming's select() in MPI? -


in socket programming, have select() function allows simultaneously check multiple sockets. want know there such feature available in mpi library well?

in first loop of following code, sending multiple nonblocking send , receive requests 1 every other node. in second loop instead of waiting each node in sequential order, want start processing data of node sends data first. want know there way that? 

for(id=0; id<numtasks; id++){         if(id == taskid) continue;         if(sendcount[id] != 0) mpi_isend(sendbuffer[id], n*sendcount[id], mpi_double, id, tag, mpi_comm_world, &reqs[id]);         if(recvcount[id] != 0) mpi_irecv(recvbuffer[id], n*recvcount[id], mpi_double, id, tag, mpi_comm_world, &reqs[id]); }  for(id=0; id<numtasks; id++){         if(id == taskid) continue;         if(recvcount[id] != 0){                 mpi_wait(&reqs[id], &status);                 for(i=0; i<recvcount[id]; i++)                         splitdata(n, recvbuffer[id] + n*i, u[torecv[id][i]]);         } }

according given answers, have tried modify code still getting segmentation fault error during run time. please me figure out error.

for(id=0; id<numtasks; id++){         if(id == taskid) continue;         if(sendcount[id] != 0) mpi_isend(sendbuffer[id], n*sendcount[id], mpi_double, id, tag, mpi_comm_world, &reqs[id]);         if(recvcount[id] != 0) mpi_irecv(recvbuffer[id], n*recvcount[id], mpi_double, id, tag, mpi_comm_world, &reqs[id]); }  reqs[taskid] = reqs[numtasks-1]; for(i=0; i<numtasks-1; i++){         mpi_waitany(numtasks-1, reqs, &id, &status);          if(id == taskid) id = numtasks-1;         for(i=0; i<recvcount[id]; i++)                 splitdata(n, recvbuffer[id] + n*i, u[torecv[id][i]]); }

the closest equivalent mpi_waitsome, provide list of requests , returns @ least 1 request completed. however, there no timeout in select. there mpi_waitany, mpi_waitall mpi_testany, mpi_testall, mpi_testsome.

the any , some variants differ in way interface informs 1 or multiple completed requests.

edit: need use separate requests each operation, send , receive operations.


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