#12969: Coercion failures in symmetric functions
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Reporter: aschilling | Owner: sage-combinat
Type: defect | Status: needs_review
Priority: major | Milestone: sage-5.3
Component: combinatorics | Resolution:
Keywords: symmetric functions, coercion | Work issues:
Report Upstream: N/A | Reviewers:
Authors: Simon King | Merged in:
Dependencies: | Stopgaps:
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Changes (by {'newvalue': u'Simon King', 'oldvalue': ''}):
* status: new => needs_review
* author: => Simon King
Comment:
The attached patch seems to fix the problem.
Questions:
__Is there a speed regression? __
With my patch, the absence of a coercion from X to Y is ''only'' cached,
if no coercion path from X to Z (with Z different from Y) is temporarily
disabled. But if there ''really'' is no coercion from X to Y, then the fix
might involve a speed regression. Potential solution: If the old buggy
depth first algorithm would cache the absence of a coercion from X to Y,
while the new fixed version wouldn't, then we might investigate the paths
from X to Y again, right after re-enabling the other paths starting from
X.
__What about #5457__
I did not run the tests, yet. But the new test in my patch would fail
because of the deprecation warnings introduced by #5457. So, we must
decide whether making #5457 depend on this ticket or the other way around?
For the record: Without #5457, I now get
{{{
sage: H = MacdonaldPolynomialsH(QQ)
sage: P = MacdonaldPolynomialsP(QQ)
sage: m = SFAMonomial(P.base_ring())
sage: Ht = MacdonaldPolynomialsHt(QQ)
sage: m(P.one())
m[]
sage: Ht(P.one())
McdHt[]
}}}
and
{{{
sage: Ht.coerce_map_from(P)
Composite map:
From: Macdonald polynomials in the P basis over Fraction Field of
Multivariate Polynomial Ring in q, t over Rational Field
To: Macdonald polynomials in the Ht basis over Fraction Field of
Multivariate Polynomial Ring in q, t over Rational Field
Defn: Composite map:
From: Macdonald polynomials in the P basis over Fraction Field
of Multivariate Polynomial Ring in q, t over Rational Field
To: Symmetric Function Algebra over Fraction Field of
Multivariate Polynomial Ring in q, t over Rational Field, Schur symmetric
functions as basis
Defn: Generic morphism:
From: Macdonald polynomials in the P basis over Fraction
Field of Multivariate Polynomial Ring in q, t over Rational Field
To: Macdonald polynomials in the J basis over Fraction
Field of Multivariate Polynomial Ring in q, t over Rational Field
then
Generic morphism:
From: Macdonald polynomials in the J basis over Fraction
Field of Multivariate Polynomial Ring in q, t over Rational Field
To: Symmetric Function Algebra over Fraction Field of
Multivariate Polynomial Ring in q, t over Rational Field, Schur symmetric
functions as basis
then
Generic morphism:
From: Symmetric Function Algebra over Fraction Field of
Multivariate Polynomial Ring in q, t over Rational Field, Schur symmetric
functions as basis
To: Macdonald polynomials in the Ht basis over Fraction Field
of Multivariate Polynomial Ring in q, t over Rational Field
}}}
(the latter being the same as in vanilla sage)
--
Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/12969#comment:24>
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