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Re: [gnugo-devel] set_depth_values()

From: Gunnar Farneback
Subject: Re: [gnugo-devel] set_depth_values()
Date: Sat, 13 Jul 2002 17:28:36 +0200
User-agent: EMH/1.14.1 SEMI/1.14.3 (Ushinoya) FLIM/1.14.2 (Yagi-Nishiguchi) APEL/10.3 Emacs/20.7 (sparc-sun-solaris2.7) (with unibyte mode)

Arend wrote:
> I just wanted to add some semeai depth values/node limit to
> set_depth_values in utils.c, but I don't get what this complicated code
> is trying to do. And frankly, I don't think I am the first one who doesn't.

It was much simpler in the beginning but has gradually become more
complex. I think Dan has done most of the tweaking there.

> Apart from atari-atari, the depth settings are exactly identical for
> levels 10 and 9.
> Levels 7 and 8 are identical apart from the setting of owl_node_limit.
> As this has a rather moderate jump from 450 to 400, whereas in the next
> step to level 6 it drops to 325, I can't see why this should make sense.

It is worth noticing that the depth values are not the only things
changing with the level. E.g. below level 5
find_more_owl_attack_and_defense_moves() is no longer called.

Ideally the levels should be related to the speed of the engine,
probably exponentially, while keeping the playing strength as high as
possible at each level. A doubling of the speed for every 2 or 3
levels would probably be appropriate.

I don't know how well the level system currently works, but something
like that should be the aim.

> Given that the existing code probably doesn't do what it wants to do,
> shouldn't we just use
> ..._depth = ..._DEPTH * level / 10
> and
> ..._node_limit = ..._NODE_LIMIT * pow(1.5, level - 10)
> and be done with it?
> This would have the advantage of being understandable, and I doubt it
> would give worse results than the current code.

I have nothing against simplifying the code if it can be made to work
well enough, but the formula for *_depth above doesn't look good. You
definitely don't want the main depth to fall lower than 6 or 7 or so
and some other depth parameters probably shouldn't fall all the way
down to 0 either. On the other hand you want some of the more
expensive depth parameters to fall off faster than the formula says
early on.


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