Hi there, I'm doing some cleanup in the computation of the hash value for various parent in sage (see #8120 and followup). A technical question came up: suppose that some object is inserted is a hash table (eg: some cache) and that the whole table is pickled. Do we have to ensure that upon unpickling, the hash value of the object is kept ?
Currently most parents use one of the two following methods to compute a hash value: 1 - take the value of the hash of _repr_. This is slow and change after a renaming so this is not a good idea. Note that, caching the computed value can help to solve these two issues. However if no care is taken to ensure that the cached value is pickled, the hash value can change. 2 - ensure unique representation and return id. Of course we cannot ensure that this is stable during pickle/unpickle. Any comment or suggestion ? Florent -- To post to this group, send an email to [email protected] To unsubscribe from this group, send an email to [email protected] For more options, visit this group at http://groups.google.com/group/sage-devel URL: http://www.sagemath.org
