What do you mean here? Does each thread operate on a different part of your game tree. Or do they all perform parallel full chance sampled tree traversals? And if so, do you synchronize something?

I'm also using Java and I'm also trying to figure out the best options for multithreading for my cs cfrm implementation. I would like to know if it could screw up the algorithm if the regrets and average strategies are not updated atomically.
If the algorithm still converges if some values are sometimes not updated correctly, it would probably be the best option to let each thread do independent chance-sampled tree-walks without synchronization. Then we might still need to use the "volatile" keyword, but I'm not sure about that. Can anyone explain to me what exactly the "volatile" keyword does? My understanding is, that it prevents caching so that every thread always reads and writes the actual values directly from and to ram.