meow c

#include <stdio.h>
#include <mpi.h>

int main()
{
	const int N = 4;

	int matrix[N*N] =
	{
		1, 5, 7, 8,
		7, 2, 3, 4,
		8, 1, 5, 2,
		2, 5, 0, 1
	};

	int vector[N] = {4, 3, 2, 1};
	int result[N];

    MPI_Init( NULL, NULL );

    int world_size, world_rank;
    MPI_Comm_size( MPI_COMM_WORLD, &world_size );
    MPI_Comm_rank( MPI_COMM_WORLD, &world_rank );

	if ( world_size < N * N )
	{
		MPI_Finalize();

		if ( world_rank == 0 )
			printf( "Error: Not enough processors\n" );

		return 1;
	}

	int local_data = matrix[ world_rank ] * vector[ world_rank % N ];
	int local_sum = 0;

	for ( int i = 0; i < N * N; i++ )
	{
		MPI_Send( &local_data, 1, MPI_INT, ( i / N ), 0, MPI_COMM_WORLD );

		if ( world_rank == ( i / N ) )
		{
			MPI_Recv( &local_data, 1, MPI_INT, i, 0, MPI_COMM_WORLD, MPI_STATUS_IGNORE );
			local_sum += local_data;
		}
	}

	MPI_Gather( &local_sum, 1, MPI_INT, result, N, MPI_INT, 0, MPI_COMM_WORLD );

	if ( world_rank == 0 )
	{
		for ( int i = 0; i < N; i++ )
			printf( "result[%i] = %i\n", i, result[i] );
	}

    MPI_Finalize();

	return 0;
}