No standard specification for Perft

[Michael Sherwin]

If you want perft to be a representative measure of the speed of an engine it should indeed focus more on capture-only generation. Perthaps it would be useful to define a function perft(N, M) which does N ply of full-width search followed by M ply of captures only.

Most people use perft only for testing correctness, however, to see if they get the right numbers.

And it would be useful to have an accurate count of the capture only nodes as well.

why?

perft is not a goal in itself. playing chess is the goal (or variants if that's your thing).

the only purpose of perft is to serve as unit test for the move generation (and move play/undo etc.).

in which valid use case do you need perft captures, that can't be verified by normal perft?

If an engine has a separate capture generator it might be good to see if the engine produces correct node counts there as well. And like HGM said it would be a way of testing engine performance minus eval more realistically.

Well, you must be doing it wrong, if you need to duplicate movegen code like this… Fix that instead of blaming perft.

-. --- - / .-- --- .-. - .... / .-. . ... .--. --- -. -.. .. -. --. / - --- ---

[Joost Buijs]

in my regular search I never promote to bishop because that is clearly a waste of time.

Is this really worth it? I always consider all legal moves in search and never even considered doing anything like that. Besides there are other ways to avoid wasting time on bishop underpromotions rather than completely pruning them.
There is a really really tiny fraction of games where it could matter, of course nothing that can be reliably measured.
And for analysis of course (but true, nobody would use my engine for analysis anyway

Testing with self-play shows that it helps my engine a tiny bit. I only do ALL under-promotions at the root.

Indeed there are positions where under-promotion to bishop secures the win, like this one:

[d]kb6/2P5/K7/2N5/8/8/8/8 w - -

These are very scarce and will probably never happen during normal play. I never found anything counter productive by not generating promotions to bishop. Of course it could be different for other engines.

[elcabesa]

In my engine I use perft and divide to test the correctness of the engine.
Whit this goal, I use the same move generator, do/undo move routines and the move selector. I tested my engine in a lot of random positions and checked the result against stockfish. This helped me validating the code.
Sometimes I used it to check the speed, but this is not the goal of my routine.