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From: Thomas Koenig <tkoenig@netcologne.de>
Newsgroups: comp.lang.fortran
Subject: Re: in gfortran, is it faster compile times with *.mod files ?
Date: Tue, 12 Nov 2024 08:01:40 -0000 (UTC)
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Lynn McGuire <lynnmcguire5@gmail.com> schrieb:
> On 11/11/2024 4:01 PM, Thomas Koenig wrote:
>> Lynn McGuire <lynnmcguire5@gmail.com> schrieb:
>>> In gfortran, is it faster compile times with *.mod files ?  Or is it
>>> just as fast compiling to include the module interface information in
>>> each subroutine / function file ?
>> 
>> I haven't benchmarked this, but I think likely that there would only
>> be a small difference.  Usually, the front end only takes a small part of
>> compilation time (but there are pathological cases).
>> 
>> In general, modules are better because of automatic checking.
>> If you want to avoid recompilation cascades, submodules (where
>> you can separate the definition from the implementation) might
>> be worth looking into.
>> 
>>> Is there any chance that gfortran will automatically generate and use
>>> module files in the future like IVF ?
>> 
>> Not sure what you're asking for.  Can you give an example?
>
> 1. you compile abc.f in IVF
> 2. IVF automagically creates an abc__genmod.f90 file in your release 
> subdirectory with the subroutine / function module interface in it

I think I get the general gist (but it would help me understand
if you could post a complete example).

But gfortran currently does not have such a feature (which appears
to duplicate modules).  It is also not immediately clear what should
happen if, for example, a procedure uses a derived type from another
module... (This may not be relevant to your case, but as a compiler
writer, you have to think about this kind of thing :-|)

What would go wrong if you simply encapsulated abc.f in

      MODULE ABC
      CONTAINS
C  Your code here
      END MODULE ABC

?