Originally Posted by Taper_Mike
Do you know of anything I can read to learn more about this? Rollouts still seem to take a ton of time compared to XG.
I don't know any good summary about this, the online documentation at www.gnubg.org
is out of date.
The number of threads to use is set in Settings|Options|Other|Eval Threads. You should not set it higher than the number of cores in your machine.
Besides that, my experience (under linux) is that on an old dual core system a gnubg process running with 2 threads was very noticeable from other interactive usage (but fine for overnight rollouts), while on a Core i5, a rollout or 4ply analysis running with 4 threads doesn't harm basic GUI/editing/etc... usage. You'll have to experiment a little and see what suits you.
There must be some discussions about multiple threads issues at http://lists.gnu.org/archive/html/bug-gnubg/
Regarding the speed gap compared to XG, as Xavier pointed out, the latter is substantially faster anyway.