Tempo

[thomasahle]

Sunfish currently doesn't do 'tempo'. A mate in 6 is considered the same as a mate in 1.

[Ravenslofty]

I have this solved in my master. d6bb441

[thomasahle]

Interesting. Isn't it normally implemented by always subtracting a bit from the score returned in minmax?

[Ravenslofty]

Nope. If you always do that then you introduce a bug where a bad move searched shallowly is favoured over a good move searched deeply.

Matthew:out

[thomasahle]

But it doesn't have to be a big constant.
Otherwise, don't you have to do a lot of 'correcting' in the TT code, like
the describe on http://chessprogramming.wikispaces.com/Checkmate ?
Another approach I've thought about is to keep the global movenumber in the
Position representation. Then we could make MATE_SCORE-global_ply the value
of a checkmate. This might give new problems in TT though.

2014-03-13 18:16 GMT+01:00 ZirconiumX [email protected]:

Nope. If you always do that then you introduce a bug where a bad move
searched shallowly is favoured over a good move searched deeply.

Matthew:out

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Reply to this email directly or view it on GitHubhttps://github.com//issues/11#issuecomment-37559774
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Mvh. Thomas

[Ravenslofty]

Search deep enough and even 1 centipawn can make a difference.

It's better to have to deal with mate scores in the TT than having to deal with false mate scores in the TT.

Matthew:out

[thomasahle]

Have you tried testing the engines against each other and compared results?

[Recursing]

A mate in 6 is considered the same as a mate in 1.

I "solve" this in my rust engine by exiting the search early on mate found, which while not correct 100% of the time is a good approximation, makes the engine appear faster and can very easily be done by making _search yield the score

[thomasahle]

I like the way this is done in Micromax: https://home.hccnet.nl/h.g.muller/delay.html

But I haven't found a position where it matters in the current sunfish, so I can't really test whether it improves anything.