pickle complexity limit?

[Mark Hahn]

I have a heavily interlinked dom like tree structure of objects.  A node
will link to many children redundantly and many children will reference
parents redundantly.  So there are many cycles of references.

When I tried to cPickle one of these structures with about 700 nodes the
python interpreter crashed.  I did a binary search limiting the number of
nodes added and it could handle 217 nodes. I switched to pickle and now it
gives a recursion limit exception instead of crashing.

I don't understand how this could happen with pickle.  Isn't it supposed to
stop when it runs into an object it has already pickled?  Couldn't it have
been coded in a stackless way?

What do I do now?   I don't want to recompile with a deeper stack as this
will obviously only help in limited cases, not solve the real problem.