#16275: Hom: introduce a check argument to simplify the unpickling detection
logic
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Reporter: nthiery | Owner:
Type: enhancement | Status: new
Priority: major | Milestone: sage-6.2
Component: categories | Resolution:
Keywords: homset, pickling | Merged in:
Authors: Nicolas M. Thiéry | Reviewers:
Report Upstream: N/A | Work issues:
Branch: | Commit:
u/nthiery/hom__introduce_a_check_argument_to_simplify_the_unpickling_detection_logic|
ae3ca8080a8412891722695d1e24e1dfe374d787
Dependencies: | Stopgaps:
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Comment (by nthiery):
Replying to [comment:9 SimonKing]:
> I think explicit is better than implicit. Moreover, it has another use
case (as demonstrated by Nicolas) and should also be faster than the old
solution. Hence, I am all in favour of the new solution.
Glad we are on the same line :-) And thanks for checking and investigating
further!
> The only problem is: (How) Do we care about old pickles whose unpickling
requires to skip the assertion, but which are unaware of the "check=False"
argument?
>
> I suggest the following scheme:
> {{{
> if check:
> if domain not in category:
> if domain's category is initialised:
> raise error, since that means we are not unpickling an
old pickle
> if codomain not in category:
> if codomain's category is initialised:
> raise error
> proceed with creating the homset
> }}}
> Hence, the assertion is skipped if this is explicitly requested, and
before raising an actual error it is verified if we need to skip the
assertion implicitly.
One thing: `domain not in category` will possibly call
`domain.category()` with the caveats that were mentioned on #14793.
Not sure how much we should care.
As to how important it is to actually do something about this: what's
the time period during which pickles may have been created that can't
be unpickled with the check=False approach?
Cheers,
Nicolas
--
Ticket URL: <http://trac.sagemath.org/ticket/16275#comment:16>
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