For lab 4 I created a file:  lab4a.cpp

Compiled using: >mpiCC lab4a.cpp

Run using: >mpirun N a.out 

lab4a.cpp contains:

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

int main(int argc, char ** argv){
    int size, node, arr[size][size];

    MPI_Init(&argc, &argv);
    MPI_Comm_rank(MPI_COMM_WORLD, &node);
    MPI_Comm_size(MPI_COMM_WORLD, &size);
    std::cout << "Hello world from " << node << std::endl;

    MPI_Finalize();
    return 0;
}

keep getting an error after run:

"It seems that [at least] one of the processes that was started with
mpirun did not invoke MPI_INIT before quitting (it is possible that
more than one process did not invoke MPI_INIT -- mpirun was only
notified of the first one, which was on node n0).

mpirun can *only* be used with MPI programs (i.e., programs that
invoke MPI_INIT and MPI_FINALIZE).  You can use the "lamexec" program
to run non-MPI programs over the lambooted nodes."

why am i getting this error?  

i'm not sure why it's working now, but it's working now.  HAHA

i'm using mpiCC (make sure to capitalize the "CC") to compile cpp files.

mpicc is for .c files