In this post, we will see Hello World program in MPI.
For How to install MPI on Linux (Ubuntu and Fedora), check following link:https://www.comrevo.com/2019/10/How-to-install-MPI-on-Linux-Ubuntu-and-Fedora.html
Program (helloworldmpi.c)
Program (helloworldmpi.c)
#include "mpi.h" int main(int argc, char **argv) { int rank, size; MPI_Init(&argc,&argv); MPI_Comm_rank(MPI_COMM_WORLD, &rank); MPI_Comm_size(MPI_COMM_WORLD, &size); printf("Hello world! Process of rank %d out of %d processes.\n",rank,size); MPI_Finalize(); return 0; }
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Output:
>>> mpic++ helloworldmpi.c >>> mpirun -np 5 ./a.out Hello world! Process of rank 0 out of 5 processes. Hello world! Process of rank 2 out of 5 processes. Hello world! Process of rank 3 out of 5 processes. Hello world! Process of rank 1 out of 5 processes. Hello world! Process of rank 4 out of 5 processes. |
Note:
Here, 5 is the number of processes. We compile program by mpic++. We get object file a.out. Then, we run it on many processes (in this example 5).
Function MPI_Comm_rank() gives rank of process. Ranks are in the range 0 to n-1.
Function MPI_Comm_size() gives number of processes.
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