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From: Brian W. Barrett (bbarrett_at_[hidden])
Date: 2006-12-14 17:28:25


On Dec 14, 2006, at 1:48 PM, Michael Galloway wrote:

> On Thu, Dec 14, 2006 at 02:01:54PM -0500, Michael Galloway wrote:
>> good day all, i've been trying to build ompi with the 6.2-X
>> version of the pgi
>> compiler set (pgcc 6.2-4 64-bit target on x86-64 Linux). i've
>> tried both 1.1.2 and
>> the current nightly build 1.1.3b2r12766, both fail with this error
>> from configure:
>>
>> *** Fortran 77 compiler
>> checking whether we are using the GNU Fortran 77 compiler... no
>> checking whether /opt/pgi/linux86-64/6.2/bin/pgf77 accepts -g... yes
>> checking if Fortran 77 compiler works... yes
>> checking /opt/pgi/linux86-64/6.2/bin/pgf77 external symbol
>> convention... single underscore
>> checking if Fortran 77 compiler supports LOGICAL... yes
>> checking size of Fortran 77 LOGICAL... 4
>> checking for C type corresponding to LOGICAL... not found
>> configure: WARNING: *** Did not find corresponding C type
>> configure: error: Cannot continue

It appears that this is being caused by a problem much earlier in the
configure process. For some reason I don't totally understand, the
configure script is finding the size of shorts, ints, longs, long
longs, void *s, etc. to be 2. This is rather unexpected on a 64-bit
machine, obviously. In testing with PGI 6.1-3 on x86_64, it looks
like the IPA option is causing this to occur -- if I remove the IPA
option from the flags, configure runs properly.

In my (somewhat humble) opinion, turning on such aggressive options
is dangerous when compiling Open MPI (or most MPI implementations).
With share memory and RDMA interconnects, assumptions compiler
writers make when running at such high optimization setting are
frequently not true for codes like Open MPI. And the performance
gain in compiling the MPI layer with such high optimizations is
frequently near zero (that being said, there is a significant
advantage to adding some optimization flags and not including
debugging symbols in the MPI library if you don't need them).

It should be safe to compile Open MPI without the IPA options and
still use IPA when compiling your application.

Brian

-- 
   Brian Barrett
   Open MPI Team, CCS-1
   Los Alamos National Laboratory