Conditional Compile 32bit vs 64bit

[fbalderasintel]

Is there a way to Conditionally compile some Fortran code in 32 bit while the rest of the code compiles
as 64 bit ?

[TimP]

You've posed a confusing question.
If you mean use of 32- and 64-bit mode in different parts of the same project, it would require a change of compilers, which certainly could be done in a Makefile, but is not commonly useful.
If you mean changing data declarations between 32- and 64-bit data types, several ways are in routine use, such as
using -fpp -D64mode


#ifdef 64mode
integer,parameter :: intkind=selected_int_kind(12)
integer,parameter :: floatkind=selected_real_kind(12)
#else
integer,parameter :: intkind=selected_int_kind(6)
integer,parameter :: floatkind=selected_real_kind(6)
#endif

real(floatkind) yourfloatvars
integer(intkind) yourintvars
...

or set up a Makefile to invoke your compiler's options to promote default kinds to 64 bits.

Incorporating correction kindly pointed out in subsequent response

[fbalderasintel]

Sorry for the confusion, actually my first draft was so lengthy, that I thought it would be too confusing
so I went for the simple question approach, which I see was equally confusing. However you did cut through the haze and I appreciate that.

Actually, your second option is the one we've been looking for. Yes changing
data declarations. Thats what we need. Will try this...
Thanks.

[Les_Neilson]

Quoting fbalderasintel

Actually, your second option is the one we've been looking for. Yes changing
data declarations. Thats what we need. Will try this...
Thanks.

To state the obvious : You willneed to be careful to check if any variables are passed as arguments to a subroutine compiled with a different size. Otherwise you will get stack corruption.

Les

[fbalderasintel]

Thanks for the heads up on that one. Sometimes we focus on the problem at hand and get broadsided
by another.



The code snippet posted earlier gives me a compiler error on the last two lines.
But I don't think I should move those two lines inside the ifdef as that would
defeat the purspose. I'm now not sure if the snippet was just "conceptual" or
should actually compile.

error #6236: A specification statement cannot appear in the executable section.
error #6236: A specification statement cannot appear in the executable section.

This is the test console program "Hello World".
! I set up -fpp and x64Mode in the preprocessor property page
! For preprocessor I had to begin with non integer so used x64mode

program MixedBitMode

implicit none

! Variables

integer intkind,floatkind

#ifdef Dx64mode

intkind=selected_int_kind(12)

floatkind=selected_real_kind(12)

#else

intkind=selected_int_kind(6)

floatkind=selected_real_kind(6)

#endif

real(floatkind) yourfloatvars

integer(intkind) yourintvars

! Body of MixedBitMode

print *, 'Hello World'

end program MixedBitMode

[John4 · Accepted solution]

intkind and floatkind should be parameters, e.g.:

[fortran]#ifdef Dx64mode

integer, parameter :: intkind = selected_int_kind(12)

integer, parameter :: floatkind = selected_real_kind(12)

#else

integer, parameter :: intkind = selected_int_kind(6)

integer, parameter :: floatkind = selected_real_kind(6)

#endif
[/fortran]

Also, keep in mind that with you must enable cpp-like preprocessing. Alternatively, you could use compiler directives:

[fortran]!DEC$IF DEFINED(Dx64mode)

integer, parameter :: intkind = selected_int_kind(12)

integer, parameter :: floatkind = selected_real_kind(12)

!DEC$ELSE

integer, parameter :: intkind = selected_int_kind(6)

integer, parameter :: floatkind = selected_real_kind(6)

!DEC$ENDIF[/fortran]

In any case, the compiler defines certain variables by default (e.g.,_WIN64, _M_X64, etc.). Check "Building Applications>Preprocessing" in the documentation for further details.