id,summary,reporter,owner,description,type,status,milestone,component,version,severity,resolution,keywords,cc
5636,BGL isomorphism vertex invariant interface change,Evan Driscoll <driscoll@…>,Jeremiah Willcock,"(This is the last isomorphism ticket I think. :-))

I have one more suggestion about how to handle vertex invariants. To determine whether `u` and `v` should be considered equivalent by the isomorphism, instead of providing two functors `f` and `g`, calling `f(u)` and `g(v)` to get a pair of integers, and finally comparing the result, I think it would be cleaner to have a ""binary"" predicate `p` which would be called as `p(u,v)`. (In reality of course you'd probably want to have it receive `g1` and `g2` as well, so it'd really be a 4-arg function.) This should also let you get rid of the `vertex_max_invariant` parameter perhaps.

I'm not sure of how this would impact the performance or how you'd do sorting, but you could probably do it by doing an N^2 traversal and recording for each `u` in `g1` how many `v`s in `g2` are considered equivalent. This is a bit different from what you're doing now, I think.

(The benefit of this would be it becomes easier to impose extra conditions on the isomorphism. Instead of figuring out how to encode everything into an integer -- and worrying about the fact that you make an array of size `vertex_max_invariant`, so you can't even use all that much of that size -- you can just test it directly.)",Feature Requests,assigned,To Be Determined,graph,Boost 1.46.1,Problem,,,