parallel processing - MPI Parallelization time consumption -

parallel processing - MPI Parallelization time consumption -

i have 2 blocks of code consume 2 seconds each, in classic construction run sequentially, in 4 seconds

in mpi format, supposed consume 2 seconds takes 5 seconds

why?

int main ( int argc, char *argv[] ) { mpi_init( &argc, &argv ); mpi_comm_size(mpi_comm_world,&p ); mpi_comm_rank(mpi_comm_world,&id); if(id==0) { // 2 seconds block } if(id==1) { // 2 seconds block } mpi_finalize(); }

what take 5 seconds? if have measured time whole program, problem mpi_init() , mpi_finalize() time consuming. in order see speedup increment "blocks".

parallel-processing mpi