Update mpi test program.

tests/hellompi/hellompi.cpp

@@ -0,0 +1,36 @@
+#include <mpi.h>
+#include <sys/types.h>
+#include <unistd.h>
+#include <iostream>
+
+int main(int argc, char** argv) {
+
+    // Initialize the MPI environment
+    MPI_Init(NULL, NULL);
+
+    // Get the number of processes
+    int world_size;
+    MPI_Comm_size(MPI_COMM_WORLD, &world_size);
+
+    // Get the rank of the process
+    int world_rank;
+    MPI_Comm_rank(MPI_COMM_WORLD, &world_rank);
+
+    // Get the name of the processor
+    char processor_name[MPI_MAX_PROCESSOR_NAME];
+    int name_len;
+    MPI_Get_processor_name(processor_name, &name_len);
+
+    // Print off a hello world message
+    std::cout << "Hello world from processor " << processor_name << " rank " << world_rank << " size " << world_size << std::endl;
+
+    std::cout << "Waiting for debugger to be attached, PID: " << getpid() << std::endl;
+
+    bool attached = false;
+
+    while (!attached) sleep(1);
+
+    // Finalize the MPI environment.
+    MPI_Finalize();
+}
+