On Sat, 13 Dec 2014, Nathann Cohen wrote:
It is basically just self.lequal_matrix().inverse().change_ring(ZZ).
Oh. No Poset-specific algorithm. I see. Then we should earn a lot by
doing so.
But really, in the Poset class we are very very very far from having
implemented correctly all that should be.
Do you know the next operation that we should improve ?
Just now I am not running any specific calculation with posets.
Möbius function matrix depends on other parts. We can do a boolean matrix
--- take GF(2) as base ring --- but is it stored as bits packed to bytes
really?
Should we look at posets at all, or to have support for machine integer
matrix? It must be quite a big poset to have möbius function value bigger
than 2^31.
On the other hand, is this kind of matrix used in some other part of Sage?
And it must be converted to normal python integers when returning values
for the user.
* * *
Just guessing, but maybe is_isomorphic() and related functions could
benefit from nauty when it is installed. Is it automatically used on
(di)graphs?
--
Jori Mäntysalo
