itaps-parallel Fortran name mangling issues

[Tim Tautges]

Onkar,
   I understand your suggested solution, and agree that it would work. 
I just don't think it's the best one when you consider all the use 
cases.  The advantage of your approach is that you're guaranteed to have 
all implementations/services agreeing on the name mangling and function 
signatures.  The disadvantage is that services and apps require an 
extra, independent process to build part of their iMesh-dependent code. 
  While this extra step isn't that difficult, it presents an extra 
burden on users and on service/impl'n developers.  Furthermore, there's 
an alternative solution that buys us almost the same thing while 
preserving independence.  The disadvantage of this alternative solution 
is something controlled by us and can be minimized.

- tim

Onkar Sahni wrote:
> I think my point is being missed, here is my last attempt... if in case of
> MOAB "AC_CONFIG_HEADERS is called to produce MBCN_FCDefs.h" why not one
> can produce "ITAPS_FCDefs.h" in a central place and one central
> iMesh_protos.h includes ITAPS_FCDefs.h that is generated during as an
> install/build process (all ITAPS header files can live in one location,
> for example, /usr/local/itaps/headers).
> 
> In summary, user/app. would do following basic steps:
> 
> * Download itaps-headers (say in /<path-itaps-headers>/)
> * Run configure to generate ITAPS_FCDefs.h in /<path-itaps-headers>/ (an
> app./user would do this step with platform and compiler combination of
> their choice)
> 
> * Download any implementation/service (such as FMDB/MOAB/GRUMMP or iZoltan)
> * Run configure and compile it (point to /<path-itaps-headers>/ to get
> header files from central place)
> 
> * Write app. code like MHD solver
> * Build it and link with appropriate libs. (ofcourse fortran name mangling
> has to be consistent while compling app. code with ITAPS_FCDefs.h
> generated by app.)
> 
> Is this not possible?
> 
> - Onkar
> 
>> On Wed, 2008-11-12 at 16:53 -0500, Onkar Sahni wrote:
>>>> The FC_FUNC macro winds up getting defined by something; Autoconf's
>>> configure script does some work to define it. Or, like Onkar suggests,
>>> you can define some logic ahead of time to set whatever FC_FUNC does
>>> using logic like so...
>>>> #ifdef AIX
>>>> #define FC_FUNC(lowFunc,UPfunc) _lowFunc
>>>> #elif GFORTRAN
>>>> #define FC_FUNC(lowFunc,UPfunc) UPfunc
>>>> #elif ...
>>>> ..
>>>> .
>>>   So here is my question (basically what I was trying to ask in
>>> tele-con)
>>> which may or may not be possible:
>>>
>>>   Can "#define FC_FUNC............" be generated in a central place
>>> during
>>> the process to install and build itaps softwares (before building any
>> I don't think it can because its definition depends on the name mangling
>> properties of the fortran compiler being used at time of (configuration)
>> compilation. Yes, the number of possible definitions for FC_FUNC is
>> finite, but know which it should be set to for a given compiler (and
>> what to use in the way of a detecting that) varies from compiler to
>> compiler. The BEST you can achieve is to identify what FC_FUNC should be
>> identified for common cases or cases that you know of so that it doesn't
>> need to be re-computed with each configure/compile.
>>
>>> implementation/library or service). This would be an extra configure
>>> step in say /usr/local/itaps/headers (central location where all headers
>>> sit along with probably configure stuff) and this step would just
>>> generate a new header file say "itaps_fc_func.h".
>>
>>> Say if one uses gfortran then the header file generated in "central"
>>> place
>>> (as an extra step using configure in "central" place) will contain
>>> following lines and every service and implementation simply use it.
>>>
>>>   #ifndef _ITAPS_FC_FUNC_H_
>>>   #define _ITAPS_FC_FUNC_H_
>>>
>>>   /* following line is for specific platform, compiler... combination */
>>>   #define FC_FUNC(lowFunc,UPfunc) UPfunc
>>>
>>>   #endif
>>>
>>> - Onkar
>>>
>>>> The only issue I see with this approach is that you need to have
>>> defined
>>> ahead of time all the possible #ifdef #elif cases above and whenever you
>>> go to a new machine, then you'll have to re-visit this logic. So, I like
>>> the approach where Autconf's configure is used to set FC_FUNC.
>>>> Finally, whatever FC_FUNC is set to, it MUST match the actual name
>>> mangling used by whatever fortran compiler is being used to compile the
>>> code. So, it is not just a matter of everyone agreeing on an
>>>> implementation for FC_FUNC. FC_FUNC must also address whatever name
>>> mangling is being used by a given fortran compiler on a given platform
>>> when the code is getting compiled. For that reason, I think the best
>>> approach is the Autoconf approach.
>>>> Mark
>>>>
>>>>
>>>> --
>>>> Mark C. Miller, Lawrence Livermore National Laboratory
>>>> email: mailto:miller86 at llnl.gov
>>>> (M/T/W) (925)-423-5901 (!!LLNL BUSINESS ONLY!!)
>>>> (Th/F)  (530)-753-8511 (!!LLNL BUSINESS ONLY!!)
>>>>
>>>>
>>>
>>>
>>>
>> --
>> Mark C. Miller, Lawrence Livermore National Laboratory
>> email: mailto:miller86 at llnl.gov
>> (M/T/W) (925)-423-5901 (!!LLNL BUSINESS ONLY!!)
>> (Th/F)  (530)-753-8511 (!!LLNL BUSINESS ONLY!!)
>>
>>
> 
> 
> 

-- 
================================================================
"You will keep in perfect peace him whose mind is
   steadfast, because he trusts in you."               Isaiah 26:3

              Tim Tautges            Argonne National Laboratory
          (tautges at mcs.anl.gov)      (telecommuting from UW-Madison)
          phone: (608) 263-8485      1500 Engineering Dr.
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