Hi!
Thanks everyone for your input. We are banging hard on IntegerListLex
at Sage Days 64, and hopefully will get a correct and as fast as
previously implementation in the coming days. Don't hold your breath,
but the point is that it's likely that the "non lex is faster" is only
a temporary effect.
Btw: I'd like to thank Jeroen for his hard work on an alternative
polytope based implementation (#17920). Even with the hopefully
upcoming IntegerListLex, every bit of his work will be useful:
- Iteration over polytopes which is a generally useful feature
- Lots of documentation and tests that we will recycle
- An alternative implementation to run comparative tests
- The connection with polytopes, which will be useful for other
operations (counting, and maybe others)
Cheers,
Nicolas
On Wed, Mar 18, 2015 at 02:28:36PM +0100, Viviane Pons wrote:
> 2015-03-18 12:40 GMT+01:00 Mike Zabrocki <[1][email protected]>:
>
> That would make sense. My preference is that (at least for values less
> than 15) the default is that the output is sorted and this can be
> controlled by the optional parameter.
> I think about how many times that I test symmetric function identities
> on partitions and realize that patterns that indicate a relation to
> dominance order will be a lot less clear if the order is not something
> natural. I wouldn't want the interface to be too complicated, but the
> more I think about it the more I realize that my personal use of
> partitions is very dependent on this order.
>
> I would tend to agree with you. The order wasn't documented but I'm
> pretty sure many people writing some personal code using partitions
> still rely on the order somehow. I feel a good choice would be to give
> the "nice" order by default and some parameter to obtain the optimized
> one.
>
> On Wednesday, 18 March 2015 04:20:15 UTC-4, Samuel Lelievre wrote:
>
> Nathann Cohen wrote:
>
> Hello,
> > I think that Partitions should be output in either lex (or
> possibly reverse
> > lex) since this order is compatible with dominance order.
> I only want to bring to your attention that deciding in which order
> the partitions should be returned is not free in terms of
> computational time.
> The current implementation returns them in lex order, but returns
> *many* wrong answers too (see #17548).
> In order to fix that, Jeroen is re-implementing this feature through
> a
> routine that enumerates the integer points of a polytope (see
> #17920),
> probably without any control over the order in which they are
> returned.
> Thus, in order for Partition/Composition to return them in a
> specific
> order we must list them *all* before returning the first of them.
> This
> can really mean hours (or no results at all) instead of seconds on
> big
> instances.
>
> So would it make sense to have an optional parameter sorted=None,
> which one could set to 'lex' or 'revlex' to get them in a desired
> order.
> The documentation could warn about the issues you just raised.
>
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>
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Nicolas
--
Nicolas M. Thiéry "Isil" <[email protected]>
http://Nicolas.Thiery.name/
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