#8878: Use Dijkstra to discover shortest coercion path
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Reporter: nthiery | Owner: robertwb
Type: defect | Status: new
Priority: major | Milestone:
Component: coercion | Keywords: coercion, morphism
Author: Nicolas M. Thiéry | Upstream: N/A
Reviewer: | Merged:
Work_issues: |
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In #7420, it was discussed that the current coercion model is using depth
first search to find for coercion paths between different parents, and
that it would be better to use breath-first / Dijkstra to get a shortest
coercion path. For example, we obtained once a coercion path of length 20
among symmetric functions.
Patch under development on the Sage-Combinat server.
Note: the following issue is probably related:
{{{
A = CombinatorialFreeModule(QQ, ZZ, prefix = "A")
B = CombinatorialFreeModule(QQ, ZZ, prefix = "B")
C = CombinatorialFreeModule(QQ, ZZ, prefix = "C")
D = CombinatorialFreeModule(QQ, ZZ, prefix = "D")
def make_morph(X, Y):
X.module_morphism(Y.monomial).register_as_coercion()
make_morph(A,B)
make_morph(B,A)
make_morph(C,A)
make_morph(D,C)
d = D.monomial(1)
A(d)
B(d)
}}}
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Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/8878>
Sage <http://www.sagemath.org>
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