We will compile the following example source code (example.cpp):
#include <iostream> #ifdef HAVE_MPI#include <mpi.h>#endifint main() {#ifdef HAVE_MPI // initialize MPI MPI_Init(NULL, NULL); // query and print the rank int rank; MPI_Comm_rank(MPI_COMM_WORLD, &rank); std::cout << "hello from rank " << rank << std::endl; // initialize MPI MPI_Finalize();#else std::cout << "hello from a sequential binary" << std::endl;#endif /* HAVE_MPI */}
The code contains preprocessor statements (#ifdef HAVE_MPI ... #else ... #endif) so that we can compile either a sequential or a parallel executable with the same source code.
