Hello, I think that the MPI open its sockets even though the number of processor is only 1 on the same machine? regards.
On Tue, Apr 8, 2014 at 9:43 AM, Hamid Saeed <e.hamidsa...@gmail.com> wrote: > Hello all, > > I have a very basic question regarding MPI communication. > > In my Task, what i am doing is.. > Comparing Scatterv and MPIO. > 1) In scatterv, I scatter all the data to the other ranks and SCAN for the > specific characters. > MPI_Scatterv (chunk, send_counts, displacements, MPI_CHAR, copychunk, > smallchunk_size, > MPI_CHAR, 0, MPI_COMM_WORLD); > & > 2) On the other hand using MPIO, I have the data available in the shared > memory and every rank searches in the specific chunk. > MPI_File_open(MPI_COMM_WORLD, "170mb.txt", MPI_MODE_RDONLY, MPI_INFO_NULL, > &in); > here i assign every processor to search in a specific "chunk" > > > My question is.. > > Why MPI_Scatterv using 1 processor takes more time then MPI_File_open? > How does MPI sending and receiving takes place? > > I think using 1 processor does not include physical sending and > receiving. Then why it consumes more clock? > > In the attachment you can observe the plots in which i performed some > tests using both algorithms. > > Kindly explain briefly the mpi communication using 1 processor and > multiple processors. > > > Thanks in advance. > > Regards > Hamid > -- Hamid
