#18529: Topological manifolds: basics
-------------------------------------+-------------------------------------
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 tscrim):
Replying to [comment:76 egourgoulhon]:
> Another solution would be to revert to `UniqueRepresentation` for
manifolds (once again!). Since now the user creates manifolds via the
front-end function `Manifold` and not by a direct call to the manifold
class constructor, the main issue raised at the end of comment:31 could be
overcome by the handling of the cache in `Manifold`. In this way
> {{{
> sage: M1 = Manifold(2, 'M')
> sage: M2 = Manifold(2, 'M')
> }}}
> would result in two different objects, as desired, but
> {{{
> sage: M1 == loads(dumps(M1))
> }}}
> would still work, because the unpickling does not go through the
function `Manifold`.
This breaks pickling:
{{{
sage: class Foo(UniqueRepresentation):
....: def __init__(self, i):
....: pass
....:
sage: F1 = Foo(1)
sage: Foo._clear_cache_()
sage: F2 = Foo(1)
sage: F1 is F2
False
sage: F1 == loads(dumps(F1))
False
sage: F2 == loads(dumps(F1))
True
}}}
The reason is pickling still goes through the `UniqueRepresentation`
cache. I am still convinced we should not be using `UniqueRepresentation`
for the manifolds.
--
Ticket URL: <http://trac.sagemath.org/ticket/18529#comment:77>
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