Re: [sage-combinat-devel] WeylCharacterRing regression
Yes, sorry for the typos. I know that it works if I specify the branching rule explicitly, but I was under the impression that the default (rule='default') would be able to figure that out by itself. On Sunday, December 9, 2012 1:18:14 AM UTC, bump wrote: > But anyway if you forget rule="levi" it hangs. So I think there is > something to be done in the matter of input checking. > It is true that before the patch you could do what you said and it > will work. I'll investigate some more. > -- You received this message because you are subscribed to the Google Groups "sage-combinat-devel" group. To view this discussion on the web visit https://groups.google.com/d/msg/sage-combinat-devel/-/dsz8l47FOWgJ. To post to this group, send email to sage-combinat-devel@googlegroups.com. To unsubscribe from this group, send email to sage-combinat-devel+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/sage-combinat-devel?hl=en.
Re: [sage-combinat-devel] WeylCharacterRing regression
I currently don't think there's a problem. You wrote:
sage: A3 = WeylCharacterRing('A3', style='coroots')
sage: A3 = WeylCharacterRing('A3', style='coroots')
sage: A4(1,0,0,0,0).branch(A3) # takes forever
There's three things wrong with your input, but presumably the relevant
one is that you forgot rule="levi".
The other two problems is that one of the rings should be A4,
and when using style="coroots" the correct syntax would be
A4(1,0,0,0) not A4(1,0,0,0,0) since the semisimple rank is 4.
But anyway if you forget rule="levi" it hangs. So I think there is
something to be done in the matter of input checking.
It is true that before the patch you could do what you said and it
will work. I'll investigate some more.
Dan
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Re: [sage-combinat-devel] WeylCharacterRing regression
> In sage-5.5.beta0 some stuff was merged that is supposed to speed
> up WeylCharacterRing, but I noticed the following taking forever now:
>
> sage: A3 = WeylCharacterRing('A3', style='coroots')
> sage: A3 = WeylCharacterRing('A3', style='coroots')
One of these should be A4.
> sage: A4(1,0,0,0,0).branch(A3) # takes forever
I'm not running 5.5.beta0 but I tried this with sage-5.4
with trac_13461 applied and can confirm there is a problem.
I'll try to figure what is causing this. Perhaps it is
best if the patch is backed out before the next beta.
Dan
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Re: [sage-combinat-devel] WeylCharacterRing
On Tue, Jan 03, 2012 at 01:17:14AM -0800, Bruce wrote:
> This seems to me to be either a bug or a deficiency:
>
> sage: KZ = WeylCharacterRing('A1',base_ring=ZZ,style="coroots")
> sage: KS =
> WeylCharacterRing('A1',base_ring=SFASchur(ZZ),style="coroots")
> sage: a = KZ([1])
> sage: KS(a)
>
> produces an error.
>
> More generally I was hoping that given (commutative) rings R and S and
> a ring homomorphism
> phi : R --> S that the category framework would then provide the
> homomorphism from
> WeylCharacterRing('A1',base_ring=R) to
> WeylCharacterRing('A1',base_ring=S)
> but in view of the above I have now lost confidence.
This would be a natural feature, but it is indeed not yet implemented.
It should not be difficult, but requires a bit of thought to integrate
properly in the coercion framework. Please create a ticket! Maybe this
will trigger a volunteer :-)
> Is there a simple way to achieve this? Here R would probably be
> symmetric functions and there are several definitions of the same
> homomorphism, depending on the choice of basis.
You can construct the homomorphism by hand, and register it:
sage: KZ = WeylCharacterRing('A1',base_ring=ZZ,style="coroots")
sage: KS = WeylCharacterRing('A1',base_ring=SFASchur(ZZ),style="coroots")
sage: a = KZ([1])
sage: phi = KZ.module_morphism(KS.monomial)
sage: phi(a)
s[]*A1(1)
sage: phi.register_as_coercion()
sage: KS(a)
s[]*A1(1)
Note that the registering must be done early in the Sage session
(before any coercion lookup between KZ and KS.
Cheers,
Nicolas
--
Nicolas M. Thiéry "Isil"
http://Nicolas.Thiery.name/
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Re: [sage-combinat-devel] WeylCharacterRing
Dear Bruce, dear Dan,
On Thu, Aug 19, 2010 at 07:19:44AM -0700, Bruce wrote:
> I have tried to construct the WeylCharacterRing with base_ring
> polynomials in q with integer coefficients. There were no complaints
> but it seemed to take q to be one of the monomials.
>
> # Defines the ring of polynomials in q with integer coefficients
> R. = ZZ[]
> # Defines the character ring
> KG2 = WeylCharacterRing("G2", base_ring = R, style="coroots")
>
> KG2(q)
>
> I don't know if this is a bug or an error on my part.
This sounds like a missing feature in the __call__/_call_ method of
KG2. The best fix would be to have, as has been planned some time ago,
WeylCharacterRing use categories (and by the way
CombinatorialFreeModule), and this would be automatically handled by
the coercion system.
Dan: do you have any chance for handling this?
Btw: as a bonus incentive, switching to CombinatorialFreeModule would
make WeylCharacterRing benefit from the upcoming arithmetic
optimizations that Christian Stump is currently polishing.
Cheers,
Nicolas
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