#9941: faster multinomial_coefficients
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Reporter: pernici | Owner: AlexGhitza
Type: enhancement | Status: needs_work
Priority: minor | Milestone: sage-4.6.1
Component: basic arithmetic | Keywords:
Author: Yann Laigle-Chapuy | Upstream: N/A
Reviewer: | Merged:
Work_issues: |
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Changes (by fwclarke):
* status: needs_review => needs_work
Comment:
I've tested this, and confirmed that the "even_faster" patch is indeed
significantly faster and delivers correct results. It's ''almost'' a
positive review, except for two minor things:
1. Erroneous results are returned if `m` is zero. E.g.,
*
{{{
sage: multinomial_coefficients(0, 3)
{(3,): 1}
}}}
To be consistent with `multinomial([])`, which returns `1`,
`multinomial_coefficients(0, n)` should return `{(), 1)}` if `n` is zero,
and `{}` otherwise.
2. I don't understand the comment "`the very first step was mixed above"`,
the word ''mixed'' in particular.
One other thing that might be worth changing would be to allow
`multinomial` to take a tuple as its argument. Then
`multinomial_coefficients` could have a doctest like
{{{
sage: r = multinomial_coefficients(4, 3)
sage: all(multinomial(k) == v for k, v in r.items())
True
}}}
--
Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/9941#comment:4>
Sage <http://www.sagemath.org>
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