MPI_MODE_RDONLY - read only
MPI_MODE_RDWR - read/write access
MPI_MODE_WRONLY - write only
MPI_MODE_CREATE - create file if it does not exist
MPI_MODE_EXCL - error if creating file that already exists
MPI_MODE_DELETE_ON_CLOSE - delete file on close
MPI_MODE_UNIQUE_OPEN - block file opening elsewhere
MPI_MODE_SEQUENTIAL - file will only be accessed sequentially
MPI_MODE_APPEND - set initial positions of all file pointers to EOF