HP-MPI Version 2.0 for Windows Release Note

However, if your application is written to explicitly handle the autodoubled datatypes (for
example, if a variable is declared real and the code is compiled -r8 and corresponding MPI calls
are given MPI_DOUBLE for the datatype), then the autodouble related command line arguments
should not be passed to mpif90.bat at link time (because that would cause the datatypes to
be automatically changed).
48 Fortran Command-Line Basics