Question Running Large Calculation Without the Game Freezing?

I'm working on a board game, a replication of Othello, and I created a tree of all possible moves (with a few moves left) so that the AI I made can see the best possible move. However, the size of the tree grows exponentially with the amount of remaining moves. It can take a while to create the tree. That's fine. Even if I got the tree to work faster I would just increase its size. My problem is that the game freezes while it is running this calculation. I'd like the game to not freeze while this was happening.

I've read some about similar problems but I'm not sure if I understand the possible solutions correctly. I think my options are: One, do the calculation for making the tree in batches (a few each frame) so that the program could still run while doing the calculations. Two, use the jobs system for some sort of multi-hreading so that the main thread of the game could keep on while another thread built the tree. Am I understanding my options correctly? Do you have any advice where I can look for an overview of either method? For example, how do you do only some of the calculations each frame? Thank you.

 

Break the additions up to handle so many calcs per frame. It is turn based so if you did 20 a frame at one sec at 60FPS you could calculate 1200 nodes.

 

That should be the easiest. Pack your calculations into a Monobehavior where your variables you'd normally have in a loop or recursive call, are member variables instead. Then you just have the loop content in the Update() method.
Another, more concise option would be to use Coroutines.

The Job System would provide you actual multithreading and the powerful burst compiler. A speedup of factor 30 would not be surprising. However that is a significantly different way of thinking and unfortunately especially data structures like trees are not easy to represent (you cannot use classes or references - everything needs to be pretty much linear with the exception of the NativeHashMap).

One more option that is there: "Normal threads". It's only the Unity API (aka all methods of Unity's built in classes) which strictly forbids being called from foreign threads. As long as you stick to regular C# classes of your own (and stuff like List<>) you still have all regular tools of C# at your disposal. Here's some introduction to that: https://www.knowledgehut.com/tutorials/csharp/csharp-multithreading
You could start a singular thread just for your calculations, or employ multithreading with several custom threads if the work can be split up well (note: do not go overboard, unlike with Jobs where hundreds are okay, you shouldn't open more than a dozen threads).

 

Rather than using the (bloated) Thread namespace you could simply write an async/await-able method that runs in the background. That'll be the easiest route. Of course you'll be responsible for any race conditions etc whereas the Job system protects you from those, by enforcing strict coding guidelines which may seem counterintuitive at first.

 

coroutines, threads or async/await.

 

I'm a bit confused by what you mean by "Normal threads." Do you mean just using threads without using Unity's whole Job System?

 

Exactly, just like you would do it in any other C# application.

 

To anyone finding this thread later: I ended up using "normal threads" as DragonCoder suggested and it was much easier than I was worried it would be. This tutorial was helpful in going over the basics as well