#19555: Implement a containment for cartesian_product
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Reporter: tscrim | Owner: sage-combinat
Type: enhancement | Status: needs_review
Priority: major | Milestone: sage-6.10
Component: combinatorics | Resolution:
Keywords: | Merged in:
Authors: Travis Scrimshaw | Reviewers:
Report Upstream: N/A | Work issues:
Branch: | Commit:
public/sets/contains_cartesian_product-19555|
6a440d55060e2a7debbed41b22990951d8a3c6a5
Dependencies: | Stopgaps:
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Comment (by tscrim):
Ahh...the speed of Cython. I created a new class in between
`ElementWrapper` and `CartesianProduct.Element` that has specialized
equality comparisons against the wrapped class.
Current:
{{{
sage: C = cartesian_product([ZZ, ZZ])
sage: c = C((1, 1))
sage: d = C((1, 1))
sage: e = C((1, 2))
sage: %timeit c == d
1000000 loops, best of 3: 183 ns per loop
sage: %timeit c == e
10000000 loops, best of 3: 183 ns per loop
}}}
vs old:
{{{
sage: %timeit c == d
1000000 loops, best of 3: 175 ns per loop
sage: %timeit c == e
10000000 loops, best of 3: 179 ns per loop
}}}
So we might loose up to ~2%, but I think this will get lost in noise if
someone is doing Cartesian products of things with any harder comparison
operators. (Although IMO the previous slowdown would likely have been
negligible in computations (at least I would recommend using `itertools`
and `tuple`s if this was an issue)).
As suggested in the parenthetical, if you wanted this to be a facade
parent for tuples, which is I think what you would end up with, then you
likely could just use `itertools`.
--
Ticket URL: <http://trac.sagemath.org/ticket/19555#comment:19>
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