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Subject: Re: [OMPI users] Configure fail: OpenMPI/1.5.3 with Support for LSF using Sun Studio compilers
From: Terry Dontje (terry.dontje_at_[hidden])
Date: 2011-04-08 13:18:15

Paul and I have been talking about the below issue and I thought it
would be useful to update the list just in case someone else runs into
this problem and ends up searching the email list before we actually fix
the issue.

The problem is OMPI's configure tests to see if -lm is needed to get
math library functions (eg ceil, sqrt...). In the case that one is
using the Solaris Studio compilers (from Oracle) and one passes in the
-fast option via CFLAGS the -lm test in configure will turn out false
because -fast set the -xlibmopt flag which provides inline versions of
some of the math library function. Because of that OMPI decides it
doesn't need to set -lm for linking.

The above is problematic when configuring with -with-lsf because the lsf
library has a symbol of ceil that needs to be resolved (so it
needs -lm in the case of Studio compilers). Without the -lm the
configure check for lsf fails.

There are several work arounds:

1. Put LIBS="-lm" on the configure line. The compiler still will
inline the math function compiled in OMPI but linking of the ompi libs
with lsf libs will work because of the -lm.

2. In the CFLAGS add -xnolibmopt in addition to -fast. This will turn
off the inlining and cause OMPI's configure script to insert -lm.

3. Don't use -fast.

On 04/07/2011 08:36 AM, Paul Kapinos wrote:
> Hi Terry,
>>> so, the attached ceil.c example file *can* be compiled by "CC" (the
>>> Studio C++ compiler), but *cannot* be compiled using "cc" (the
>>> Studio C compiler).
>>> $ CC ceil.c
>>> $ cc ceil.c
>> Did you try to link in the math library -lm? When I did this your
>> test program worked for me and that actually is the first test that
>> the configure does.
>>> 5. Looking into configure.log and searching on `ceil' results: there
>>> was a check for the availability of `ceil' for the C compiler (see
>>> config.log.ceil). This check says `ceil' is *available* for the "cc"
>>> Compiler, which is *wrong*, cf. (4).
>> See above, it actually is right when you link in the math lib.
> Thankt for the tipp! Yes, if using -lm so the Studio C compiler "cc"
> works also fine for ceil.c:
> $ cc ceil.c -lm
>>> So, is there an error in the configure stage? Or either the checks
>>> in config.log.ceil does not rely on the avilability of the `ceil'
>>> funcion in the C compiler?
>> It looks to me like the lbat configure test is not linking in the
>> math lib.
> Yes, the is no -lm in configure:84213 line.
> Note the cheks for ceil again, config.log.ceil. As far as I unterstood
> these logs, the checks for ceil and for the need of -lm deliver wrong
> results:
> configure:55000: checking if we need -lm for ceil
> ....
> configure:55104: result: no
> configure:55115: checking for ceil
> ....
> configure:55115: result: yes
> So, configure assumes "ceil" is available for the "cc" compiler
> without the need for -lm flag - and this is *wrong*, "cc" need -lm.
> It seem for me to be an configure issue.
> Greetings
> Paul
> _______________________________________________
> users mailing list
> users_at_[hidden]

Terry D. Dontje | Principal Software Engineer
Developer Tools Engineering | +1.781.442.2631
Oracle *- Performance Technologies*
95 Network Drive, Burlington, MA 01803
Email terry.dontje_at_[hidden] <mailto:terry.dontje_at_[hidden]>