[Pyode-user] Problem with PyODE object deallocation and XODE changes

[John G. <glo...@gm...>]

Hello,

I'm working on a Google Summer of Code project on PaGMO
(http://sourceforge.net/apps/mediawiki/pagmo) where I need to
instantiate a large number of similar ODE worlds and objects running
in multithreaded environment. I ran into a problem with Python garbage
collection of some of the objects. Basically it seemed that sometimes
a world was being deallocated, calling dBodyDestroy and deallocating
memory for a body, but the Python object was still calling its own
dealloc and bodyDestroy (with a similar problem for Joints), and
crashing with a segmentation fault.

I have code that can reproduce it on OS X 10.5 with Python 2.6.5, but
the same code doesn't crash with the same Python version on Ubuntu, so
it could be something strange with Python garbage collection on the
Mac. However, the following minor fix sorts the problem out, so I was
hoping that it would be possible to get it checked in, unless someone
has an alternative.

cvs diff: Diffing src
Index: src/body.pyx
===================================================================
RCS file: /cvsroot/pyode/pyode/src/body.pyx,v
retrieving revision 1.8
diff -r1.8 body.pyx
59c59
<         if self.bid!=NULL:
---
>         if self.bid!=NULL and self.world:
Index: src/joints.pyx
===================================================================
RCS file: /cvsroot/pyode/pyode/src/joints.pyx,v
retrieving revision 1.14
diff -r1.14 joints.pyx
124c124
<         if self.jid!=NULL:
---
>         if self.jid!=NULL and self.world:

Also, I'm not sure if you are aware, but the PyBrain project
(http://pybrain.org/) has some small XODE additions, perhaps they
could also be included at some stage soon? Here's the diff:

cvs diff: Diffing xode
Index: xode/body.py
===================================================================
RCS file: /cvsroot/pyode/pyode/xode/body.py,v
retrieving revision 1.5
diff -r1.5 body.py
0a1,2
> #@PydevCodeAnalysisIgnore
>
205a208,217
>             elif (name == 'cappedCylinder'):
>                 radius = float(attrs.get('radius', 1.0))
>                 length = float(attrs['length'])
>                 if (density is not None):
>                     mass.setCappedCylinder(float(density), 3, radius, length)
>             elif (name == 'cylinder'):
>                 radius = float(attrs.get('radius', 1.0))
>                 length = float(attrs['length'])
>                 if (density is not None):
>                     mass.setCylinder(float(density), 3, radius, length)
214a227
>
Index: xode/geom.py
===================================================================
RCS file: /cvsroot/pyode/pyode/xode/geom.py,v
retrieving revision 1.5
diff -r1.5 geom.py
0a1,2
> #@PydevCodeAnalysisIgnore
>
72c74
<             raise NotImplementedError()
---
>             self._parseGeomCylinder(attrs)
88c90
<             j = joint.Joint(nodename, self)
---
>             j = joint.Joint(nodeName, self)
181a184,200
>     def _parseGeomCylinder(self, attrs):
>         def start(name, attrs):
>             if (name == 'ext'):
>                 pass
>             else:
>                 raise errors.ChildError('cylinder', name)
>
>         def end(name):
>             if (name == 'cylinder'):
>                 self._parser.pop()
>
>         radius = float(attrs['radius'])
>         length = float(attrs['length'])
>
>         self._setObject(ode.GeomCylinder, radius=radius, length=length)
>         self._parser.push(startElement=start, endElement=end)
>
236c255
<
---
>
245c264
<                 tri = int(attrs['ia'])-1, int(attrs['ib'])-1,
int(attrs['ic'])-1
---
>                 tri = int(attrs['ia']) - 1, int(attrs['ib']) - 1, int(attrs['ic']) - 1


Thanks,
John