How much ELO should I expect to gain from killer moves?

[abulmo2]

The one thing I don't understand is that I've seen several engines in the past few weeks, claiming to get +70 Elo from aspiration windows, while I've also seen engines that claim to get nothing from it. I've been experimenting with those (on top of both fail-hard and fail-soft alpha/beta), and the results are, at this point, that they _might_ make a positive difference, but probably not more than +20 Elo, when on top of a fail-soft alpha/beta.

A possible explanation is that aspiration windows is a generic term that cover various implementations. Not all of them are as worth 70 Elo.

[algerbrex]

Nope, but here's the code on GitHub now:

You store the killer move in the bèta-cutoff, which is correct. You also make sure they are unique, which is correct as well. What I don't see is you testing if the killer move is a quiet move. You only store a move as a killer move if it's not a capture.

The reason is that the PV-move / TT-move is ordered on top, all captures are already ordered behind that, and then there are unordered quiet moves that aren't captures. If one of those moves caused the bèta-cutoff, it's a killer; so it's ordered right behind all the captures. (Later this can be refined by ordering it right behind the good captures, before neutral captures and bad captures.)

Ah ok, I did end up noticing that after I posted the code, and so I'll run some more tests with the non-quiet moves filtered out. Thanks. Unfortunately, the preliminary test I've been running aren't super promising, but I'll do my due diligence and run some more to be sure.