[Users] Any 64-bit issues I should be aware of?

[Ian Hinder]

On 21 Aug 2014, at 15:19, Ian Smith <the.pond at dsl.pipex.com> wrote:

> On 21/08/14 14:08, Erik Schnetter wrote:
>> Ian
>> 
>> We've been running on 64-bit systems since Cactus was designed... I
>> doubt that a 64-bit issue is the problem here.
>> 
>> (Historical factoid: This was one of the motivations for introducing
>> CCTK_REAL. The early Cray 64-bit systems defined the "integer" to be 64
>> bit, as one would naively expect. The Fortran standard the requires
>> "single precision" floating point numbers to be 64-bit as well, so that
>> one would want to use "single precision" on such a system, not "double
>> precision" that would have 128 bits and be very slow. So -- CCTK_REAL,
>> which has the same number of bits on all systems.)
>> 
>> Yes, we've encountered and dealt segfaults before. Can you give us more
>> information? I recommend you open a bug report on
>> trac.einsteintoolkit.org <http://trac.einsteintoolkit.org> where you can
>> easily attach information, and then attach your option list, parameter
>> file, machine configuration, as well as the exact commands you used to
>> build your executable and run your job.
>> 
>> -erik
> 
> Hi Erik,
> 
> OK, I saw the list of supported architectures and noticed it contains 
> IA64 but not AMD64 if I read it correctly.
> 
> I'll investigate and see if I can get more debug for you.  In the 
> meantime I have a 32-bit machine to run on so I can study the examples 
> as well.

Try to get a backtrace to find out where the segfault occurred.  You can set "ulimit -c unlimited" in the shell you use to run Cactus, and this should cause core dump files to be generated when the crash happens. You can then read these with gdb:

gdb exe/cactus_sim core.XXXXX

Then type "backtrace" to get the backtrace.

-- 
Ian Hinder
http://numrel.aei.mpg.de/people/hinder