Considerations for compiling Fortran code to 64bit?

I'm working on scientific/engineering programs written in fortran for a 32bit unix system and I have to recompile for a new 64bit cluster and having trouble making sense of errors and what c开发者_JAVA百科hanges I should make.

I compile Fortran programs for 32-bit or 64-bit OSes and haven't encountered any problems. What errors have you seen? Are you changing it to a parallel program?

A program implemented to the best design philosophy of Fortran >=90 requests numeric types according to the precision that it needs, e.g., using "selected_real_kind" to specify the number of digits needed in a real type. Then the compiler (on the OS and host computer) provides the requested precision if it can, or otherwise the program refuses to run. If the requested precisions are sufficient to compute the answer, this approach should make a portable program. It isn't perfect since the numeric computing model isn't totally specified.