#17548: Partitions() is buggy
---------------------------------+---------------------------
Reporter: ferriszorro | Owner: ferriszorro
Type: defect | Status: needs_work
Priority: major | Milestone: sage-6.5
Component: combinatorics | Resolution:
Keywords: Partitions | Merged in:
Authors: | Reviewers:
Report Upstream: N/A | Work issues:
Branch: | Commit:
Dependencies: | Stopgaps: #17637
---------------------------------+---------------------------
Description changed by jdemeyer:
Old description:
> There are various bugs in `Partitions`/`Compositions`, especially when
> many constraints are combined:
>
> {{{
> sage: C = Partitions(10, min_part=2, max_slope=-1)
> sage: [5,3,2] in C
> True
> sage: C.list()
> [[10], [8, 2], [7, 3], [6, 4]]
> }}}
>
> {{{
> sage: C = Compositions(5, max_part=2, min_slope=1, inner=[2])
> sage: [2,1,2] in C
> False
> sage: C.list()
> [[2, 1, 2]]
> }}}
>
> When slopes are equal, things often go wrong:
> {{{
> sage: C = Compositions(4, min_slope=0, max_slope=0)
> sage: [1,1,1,1] in C
> True
> sage: C.list()
> [[4], [2, 2]]
> }}}
>
> Contradictory length bounds still give results:
> {{{
> sage: C = Compositions(6, min_length=3, max_length=2)
> sage: [4,1,1] in C
> False
> sage: C.list()[0]
> [4, 1, 1]
> }}}
> {{{
> sage: C = Compositions(3, max_length=2, inner=[1,1,1])
> sage: [1,1,1] in C
> False
> sage: C.list()
> [[1, 1, 1]]
> }}}
>
> `max_part` is not respected:
> {{{
> sage: C = Compositions(4, max_part=2, min_slope=1)
> sage: [1,3] in C
> False
> sage: C.list()
> [[1, 3]]
> }}}
>
> Strange exception which really shouldn't be an exception:
> {{{
> sage: Compositions(10, inner=[1,1], max_slope=-1)
> ...
> ValueError: floor does not satisfy the max slope condition
> }}}
New description:
There are various bugs in `Partitions`/`Compositions`, especially when
many constraints are combined:
{{{
sage: C = Partitions(10, min_part=2, max_slope=-1)
sage: [5,3,2] in C
True
sage: C.list()
[[10], [8, 2], [7, 3], [6, 4]]
}}}
{{{
sage: C = Compositions(5, max_part=2, min_slope=1, inner=[2])
sage: [2,1,2] in C
False
sage: C.list()
[[2, 1, 2]]
}}}
When slopes are equal, things often go wrong:
{{{
sage: C = Compositions(4, min_slope=0, max_slope=0)
sage: [1,1,1,1] in C
True
sage: C.list()
[[4], [2, 2]]
}}}
Contradictory length bounds still give results:
{{{
sage: C = Compositions(6, min_length=3, max_length=2)
sage: [4,1,1] in C
False
sage: C.list()[0]
[4, 1, 1]
}}}
{{{
sage: C = Compositions(3, max_length=2, inner=[1,1,1])
sage: [1,1,1] in C
False
sage: C.list()
[[1, 1, 1]]
}}}
`max_part` is not respected:
{{{
sage: C = Compositions(4, max_part=2, min_slope=1)
sage: [1,3] in C
False
sage: C.list()
[[1, 3]]
}}}
This is horribly wrong:
{{{
sage: Compositions(7, max_part=4, inner=[1], min_slope=1).list()
[[3, 5], [1, 3, 4]]
}}}
Strange exception which really shouldn't be an exception:
{{{
sage: Compositions(10, inner=[1,1], max_slope=-1)
...
ValueError: floor does not satisfy the max slope condition
}}}
--
--
Ticket URL: <http://trac.sagemath.org/ticket/17548#comment:39>
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