ffc team mailing list archive

["Johannes Ring" <johannr@xxxxxxxxx>]

On Tue, March 31, 2009 10:23, Garth N. Wells wrote:
>
>
> Johan Hake wrote:
>> On Tuesday 31 March 2009 09:45:33 Johannes Ring wrote:
>>> On Mon, March 30, 2009 20:19, Johan Hake wrote:
>>>> On Monday 30 March 2009 20:06:04 Anders Logg wrote:
>>>>> The buildbot is not responding at the moment so I can't check the
>>>>> status.
>>>> All is green except:
>>>>
>>>> The DOLFIN macbot how is complaining about the trilinos demo and the
>>>> DOLFIN
>>>> linux64-exp which complains about:
>>>>
>>>> Traceback (most recent call last):
>>>>   File "./demo.py", line 8, in <module>
>>>>     from dolfin import *
>>>>
>>>> File
>>>> "/work/jhbuildbot/fenics/lib/python2.5/site-packages/dolfin/__init__.py",
>>>> line 16, in <module>
>>>>     from assemble import *
>>>>
>>>> File
>>>> "/work/jhbuildbot/fenics/lib/python2.5/site-packages/dolfin/assemble.py",
>>>> line 25, in <module>
>>>>     import cpp
>>>>   File
>>>> "/work/jhbuildbot/fenics/lib/python2.5/site-packages/dolfin/cpp.py",
>>>> line 25, in <module>
>>>>     import _cpp
>>>> ImportError:
>>>> /work/jhbuildbot/local/lib/openmpi/mca_paffinity_linux.so:
>>>> undefined symbol: mca_base_param_reg_int
>>>>
>>>> I know Johannes has tried to get into this but as far as I know with
>>>> no
>>>> success.
>>> This is a problem with PyDOLFIN and Open MPI 1.3. We (me and Johan) had
>>> success with a small hack this morning. By adding
>>>
>>>   import ctypes
>>>   ctypes.CDLL('libmpi.so', ctypes.RTLD_GLOBAL)
>>>
>>> before loading the cpp module in site-packages/dolfin/__init__.py the
>>> Python poisson demo ran just fine. Alternatively one should be able to
>>> use
>>> this instead:
>>>
>>>   import dl
>>>   import sys
>>>   flags = sys.getdlopenflags()
>>>   sys.setdlopenflags(flags | dl.RTLD_GLOBAL)
>>>
>>> but because of a bug in the python2.5 package in Hardy (missing dl
>>> module)
>>> we couldn't test this.
>>>
>>> It might also be possible to do this in C++ directly. Any suggestion on
>>> the best way to fix this issue? See also:
>>>
>>> http://fenics.org/pipermail/deb-dev/2009-March/000210.html
>>> http://www.open-mpi.org/faq/?category=running#loading-libmpi-dynamically
>>>
>>> Open MPI 1.3 is in Debian unstable so it would be great if we could fix
>>> this before the release.
>>
>> The point is that the shared mpi library needs to be loaded using the
>> flag
>> RTLD_GLOBAL. Otherwise the loaded mpi libraries will be loaded into
>> private
>> namespaces causing the undefined symbol link error.
>>
>> I do not understand why this is not a problem when only using DOLFIN and
>> not
>> PyDOLFIN. Probably the mpi library is only loaded one time to the right
>> namespace? Well that's how deep my understanding is of this :P
>>
>
> Things went sour when DOLFIN was compiled with Trilinos and Trilinos had
> MPI enabled. Could this be related?

Probably not. Trilinos is built with --disable-mpi on all the buildslaves.

Johannes

> Garth
>
>> The hack consist of:
>> Before we load the compiled c++ module, i.e., the _cpp.do, we load the
>> shared
>> mpi library using the above mentioned calls. The library stays in memory
>> and
>> is not loaded a second time when the _cpp.so module is loaded.
>>
>> This is my naive view of the problem and the why the hack works. It
>> could
>> probably be solved in a more gracious manner, e.g. before
>> PetscInitialize is
>> called in DOLFIN or maybe even better on the PETSc side?
>>
>> Cheers!
>>
>> Johan
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>> FFC-dev@xxxxxxxxxx
>> http://www.fenics.org/mailman/listinfo/ffc-dev
>
>
>