#15296: LinearMatroid can't use sets for fundamentals
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Reporter: Stefan | Owner:
Type: defect | Status: new
Priority: major | Milestone: sage-5.13
Component: matroid theory | Resolution:
Keywords: | Merged in:
Authors: | Reviewers:
Report Upstream: N/A | Work issues:
Branch: | Commit:
Dependencies: | Stopgaps:
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Description changed by Stefan:
Old description:
> Several methods in LinearMatroid have an option {{{fundamentals}}}.
> Internally, this gets used as a set, and we test things like {{{p in
> fundamentals}}}. Even though both {{{p}}} and the elements of
> {{{fundamentals}}} come from the same ring or field, it is not guaranteed
> (and sometimes false) that {{{p == q}}} implies {{{hash(p) == hash(q)}}}.
>
> The default behavior of these methods should therefore be to test for
> equality with each member of {{{fundamentals}}}, instead of relying on
> the {{{in}}} keyword. An optional argument (such as
> {{{use_fast_fundamental_test}}} with default option False can be used to
> speed up computations when appropriate.
New description:
Several methods in LinearMatroid have an option {{{fundamentals}}}.
Internally, this gets used as a set, and we test things like {{{p in
fundamentals}}}. Even though both {{{p}}} and the elements of
{{{fundamentals}}} come from the same ring or field, it is not guaranteed
(and sometimes false) that {{{p == q}}} implies {{{hash(p) == hash(q)}}}.
The default behavior of these methods should therefore be to test for
equality with each member of {{{fundamentals}}}, instead of relying on the
{{{in}}} keyword. An optional argument (such as
{{{use_fast_fundamental_test}}} with default option False can be used to
speed up computations when appropriate.
See #15297 for a change that makes the fast_fundamental_test work for a
larger group of fields.
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Ticket URL: <http://trac.sagemath.org/ticket/15296#comment:1>
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