Hello. I am getting an error that i wasn't getting before. ------------------------------------------------------------------------ test.c: In function 'main': test.c:63: error: 'MPI_COMM_WORLD' undeclared (first use in this function) test.c:63: error: (Each undeclared identifier is reported only once test.c:63: error: for each function it appears in.) test.c:111: error: 'MPI_INT' undeclared (first use in this function) ------------------------------------------------------------------------ line 63 : MPI_Comm_size(MPI_COMM_WORLD, &numnodes); line 111:MPI_Scatter( array, PARTS, MPI_INT, my_array, PARTS, MPI_INT, master, MPI_COMM_WORLD); I am under a 2.6.23-gentoo-r5 cluster with gcc version 4.2.2 (Gentoo 4.2.2 p1.0)