#18529: Topological manifolds: basics
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Reporter: egourgoulhon | Owner: egourgoulhon
Type: enhancement | Status: needs_info
Priority: major | Milestone: sage-6.10
Component: geometry | Resolution:
Keywords: topological | Merged in:
manifolds | Reviewers: Travis Scrimshaw
Authors: Eric Gourgoulhon, | Work issues:
Travis Scrimshaw | Commit:
Report Upstream: N/A | 0fb39df7fafe7f0a765bf73b3f34a6cb41e65c40
Branch: | Stopgaps:
u/tscrim/top_manifolds_refactor |
Dependencies: #18175 |
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Comment (by egourgoulhon):
Marco and I have discussed the thing this morning. It's clear that the
`multiprocessing` Python module relies on pickling; some references are
- https://docs.python.org/2/library/multiprocessing.html
- http://matthewrocklin.com/blog/work/2013/12/05/Parallelism-and-
Serialization/
- http://stackoverflow.com/questions/8804830/python-multiprocessing-
pickling-error
Therefore, unless one develops a brand new way of parallelizing Python
codes, good pickling is required for parallelization. Given the importance
of parallelization in tensor calculus, I am really considering reverting
to `UniqueRepresentation` for the manifold classes. The argument goes as
follows: from the [https://groups.google.com/forum/#!msg/sage-
devel/Vzfj1haZHho/ sage-devel discussion], we get that manifolds must
implement equality by identity (i.e. inherit from `WithEqualityById`),
mostly because there exist no algorithm to decide whether two given
manifolds are homeo/diffeomorphic (especially with manifolds with
incomplete atlases, as we manipulate them). Then to have good pickling,
i.e. to ensure `M == loads(dumps(M))`, the only way is to inherit from
`CachedRepresentation` as well. Having both `WithEqualityById` and
`CachedRepresentation` implies`UniqueRepresentation`.
--
Ticket URL: <http://trac.sagemath.org/ticket/18529#comment:79>
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