On Fri, 22 Aug 2014, Nathann Cohen wrote:

Does Sage has a function to check if poset A contains a subposet
isomorphic to subposet B?

Not... exactly. There is no Poset method that does that, but there is a
DiGraph method that does that. But then, it depends on what you call a
subposet of a poset.

It seems that neither definition is not what I was thinking. In principle the function I want could be done with something like

def has_isomorphic_subposet(A, B):
    for x in Subsets(A.list()):
        if A.subposet(x).is_isomorphic(B):
            return True
    return False

which is of course extremely slow.

In this definition i.e. lattice N_5 contains 4-element "diamond lattice".

--
Jori Mäntysalo

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