A simple MPI program to compute the matrix matrix multiplication. Splitting the matrix A rowwise, and distribute it to different processes. Comparing the runtime using 1, 2 and 4 processors.

    int i, j, k;
    for (i = 0; i < N; i++) {
        for (j = 0; j < N; j++) {
            res[i][j] = 0;
            for (k = 0; k < N; k++)
                res[i][j] += mat1[i][k] * mat2[k][j];
        }
    }

Intel(R) Core(TM) i5-8250U CPU @ 1.60GHz
CPU(s): 8
Thread(s) per core: 2

$ mpic++ main.cpp -o exc
$ mpirun -np 4 exc

1. Chandresh Kumar Maurya, Assisant professor, IIT Indore link
2. Advanced Message Passing in MPI, Using MPI Datatypes with Opaque C++ Types, Paul Preney pdf link