#18356: special resultants ``composed_sum`` and ``composed_product``
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Reporter: pernici | Owner:
Type: enhancement | Status: needs_work
Priority: major | Milestone: sage-6.7
Component: algebra | Resolution:
Keywords: | Merged in:
Authors: | Reviewers:
Report Upstream: N/A | Work issues:
Branch: | Commit:
u/pernici/ticket/18356 | 1898678cfccd18df76b57a015c03d96fb44542ae
Dependencies: | Stopgaps:
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Description changed by pernici:
Old description:
> Added ``composed_sum`` and ``composed_product``, implementing
> the algorithm in A. Bostan, P. Flajolet, B. Salvy and E. Schost,
> "Fast Computation of special resultants",
> Journal of Symbolic Computation 41 (2006), 1-29
> in the case of polynomials on integer or rational ring.
> This algorithm is asymptotically faster than using the ``resultant``
> method.
New description:
Added `composed_op` to compute the composed sum and the composed product,
implementing
the algorithm in A. Bostan, P. Flajolet, B. Salvy and E. Schost,
"Fast Computation of special resultants",
Journal of Symbolic Computation 41 (2006), 1-29
in the case of polynomials on integer or rational ring.
This algorithm is asymptotically faster than using the `resultant` method.
For instance
{{{
sage: p1 = minpoly(cos(pi/43))
sage: p2 = minpoly(cos(pi/47))
sage: time r1 = p1.composed_op(p2, '+')
Wall time: 105 ms
sage: time r2 = p1.composed_op(p2, '+', algorithm="resultant")
Wall time: 53.4 s
sage: r1 == r2.monic()
sage: r1.is_irreducible()
True
}}}
so `r1` is the minimal polynomial of `cos(pi/43) + cos(pi/47)`
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Ticket URL: <http://trac.sagemath.org/ticket/18356#comment:11>
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