#19587: Implement the Chow ring of a matroid
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Reporter: tscrim | Owner: tscrim
Type: enhancement | Status: positive_review
Priority: major | Milestone: sage-6.10
Component: matroid theory | Resolution:
Keywords: | Merged in:
Authors: Travis Scrimshaw | Reviewers: Rudi Pendavingh
Report Upstream: N/A | Work issues:
Branch: | Commit:
public/matroids/chow_ring-19587 | 7bb4a54b8c4c0fb622f9ea9bb7aeef2aec1518fa
Dependencies: | Stopgaps:
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Comment (by Rudi):
Thinking a bit about efficiency, this seems to insert a quadratic number
of relations:
{{{
L = [sum(gens[i] for i in flats_containing[x]) - sum(gens[i] for i in
flats_containing[y])
for j,x in enumerate(E) for y in E[j+1:]]
}}}
where a linear set of relations generates the same ideal J_M:
{{{
L = [sum(gens[i] for i in flats_containing[E[j]]) - sum(gens[i] for i in
flats_containing[E[j+1]])
for j in range(len(E)-1)]
}}}
But this does not affect the running time by much. The real pain seems to
be in the relations defining I_M.
I also see now that my plan for recursive calculation through truncation
does not make sense. Truncation really changes the relations which define
J_M, and does not just remove some of the relations.
--
Ticket URL: <http://trac.sagemath.org/ticket/19587#comment:3>
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