draw detection

[lucasart]

draw detection

[stockfishdeveloper]

Ok, I'm going to work on recognizing insufficient material. I'll open a pull request when I'm done. By the way, a quick going-over of the search routine did not seem to have LMR. If you can verify this, I'll add it.

[lucasart]

thanks.

PS: search has reductions already. have a closer look.

[stockfishdeveloper]

OK

[stockfishdeveloper]

Alright, I did a rough draft of detecting insufficient material. It gives a score of 3 cp with KBvK and KNvK.
The diff is here: stockfishdeveloper/Demolito@master...stockfishdeveloper:insufficient_material_detection
Note: According to FIDE rules, KNNK is automatically a draw.
I'll open a pull request if you think this is good enough to commit.

[lucasart]

draw by chess rules should not be in the eval, but in the search. same as:

    if (ply > 0 && threadHistory[ThreadId].repetition(pos.rule50()))
        return DrawScore[us];

just need to extend it to include draw by insufficient material. best to make a wrapper function that handles all the cases: 3-rep, 50-move, insufficient material.

also, we should return the contempt score for draw by chess rules generally (3-rep, 50-move, insufficient material, stalemate). we don't want to special case or hardcode.

[stockfishdeveloper]

I tried putting the draw detection just after the 50-move rule detection--it didn't work.
I tried
if(pos.insufficient_material()) return some contempt factor;
But the output pvs were empty--because at every node it's getting a cutoff as it's insufficient material.

I'll work it out though.

BTW, I really appreciate your guidance--it's worth its weight in gold at this time in my career aspirations.

[lucasart]

The root node cannot be game over by chess rules, including draw by chess rules. If that happens, the GUI is bogus. You can safely assume that it only happens at interior nodes, in which case, it may truncate the PV, but that's essentially correct. Anyway, there's a ply > 0 condition to prevent pruning at root, just in case (as it can happen for two-fold repetition).

[stockfishdeveloper]

OK. Makes sense