Getting roots from tree sequence

[haono]

Hello,
Is there any way to obtain all the roots from a tree sequence without iterating over single trees?
Many thanks.

[benjeffery]

Hi @haono!
Thanks for your question. The TreeSequence doesn't store any cached information about roots, so to find them you have to work through the trees. Are you finding this to be a bottleneck? It shouldn't be that slow to go through the trees. Feel free to paste some code of how you're doing this if you want us to have a look.

[haono]

Thank you very much @benjeffery

[jeromekelleher]

In special cases you might be able to look at the oldest edges and reason about them, but it would be quite tricky I think. As @benjeffery says though, going through the trees should be quite a quick way to do this unless you've got a large number of roots.

[haono]

Thank you very much @jeromekelleher