#17971: Infinite recursion when taking a resultant over a complicated base ring
-------------------------------------+-------------------------------------
Reporter: pbruin | Owner:
Type: defect | Status: needs_review
Priority: major | Milestone: sage-6.6
Component: algebra | Resolution:
Keywords: infinite | Merged in:
recursion polynomial resultant | Reviewers:
Authors: Peter Bruin | Work issues:
Report Upstream: N/A | Commit:
Branch: | 09839726d16ef06a51f8acda28aab00d04e4efb4
u/pbruin/17971-infinite_recursion | Stopgaps:
Dependencies: |
-------------------------------------+-------------------------------------
Description changed by pbruin:
Old description:
> The following resultant computation leads to an infinite recursion:
> {{{
> sage: A.<a,c> = Frac(PolynomialRing(QQ,'a,c'))
> sage: B.<d,e> = PolynomialRing(A,'d,e')
> sage: R.<x> = PolynomialRing(B,'x')
> sage: (a*d*x^2+a+e+1).resultant(-4*c^2*x+1)
> Traceback (most recent call last):
> ...
> RuntimeError: maximum recursion depth exceeded while calling a Python
> object
> }}}
> We solve this by replacing a recursive call in
> `FractionField_generic._element_constructor_()` by a more direct
> construction of the element.
>
> This particular bug is also fixed (in a different way) by #17974, but the
> doctest and the shortcut added by this ticket are useful regardless of
> that.
New description:
The following resultant computation used to lead to an infinite recursion
before #17974 (merged in 6.7.beta0):
{{{
sage: A.<a,c> = Frac(PolynomialRing(QQ,'a,c'))
sage: B.<d,e> = PolynomialRing(A,'d,e')
sage: R.<x> = PolynomialRing(B,'x')
sage: (a*d*x^2+a+e+1).resultant(-4*c^2*x+1)
Traceback (most recent call last):
...
RuntimeError: maximum recursion depth exceeded while calling a Python
object
}}}
Although this particular bug is now fixed, the doctest and the shortcut
added by this ticket may still be useful.
--
--
Ticket URL: <http://trac.sagemath.org/ticket/17971#comment:4>
Sage <http://www.sagemath.org>
Sage: Creating a Viable Open Source Alternative to Magma, Maple, Mathematica,
and MATLAB
--
You received this message because you are subscribed to the Google Groups
"sage-trac" group.
To unsubscribe from this group and stop receiving emails from it, send an email
to [email protected].
To post to this group, send email to [email protected].
Visit this group at http://groups.google.com/group/sage-trac.
For more options, visit https://groups.google.com/d/optout.
