Author: Dave Gomboc
Date: 00:34:17 09/11/99
Go up one level in this thread
On September 11, 1999 at 02:28:00, Ed Schröder wrote:
>>There are only three choices here.
>>
>>(1) best <= alpha. We don't know anything about any of the moves. Yet I
>>believe Ed (and I thought you as well) said that if you take this 'best'
>>move and store it in the hash, it works well. In my test, it didn't.
>>
>>(2) alpha < best < beta. This is a move with an _exact_ score that is
>>correct. Also known as a PV-candidate move normally.
>>
>>(3) alpha < beta < best. This is a fail high move. It is better than the
>>best that is allowable. It is _not_ the best move at this level however,
>>it is just good enough to produce a score >= beta and terminate the search early.
>>This is the case that feeds (1) above at the previous ply. If we try
>>_another_move here we might get an even _bigger_ score here, and back up an even worse
>>score to the previous ply. But alpha/beta makes us stop _now_.
>
>I like to try this. One question: what is "best"?
>
>the score of the node?
>
>the best score sofar on this ply?
"best" is initialized to -oo before the subtrees are searched. At any given
time, "best" is the best backed-up score or bound from the subtrees that have
been searched.
>Ed
P.S. Why do I always see INF or INFINITY in people's code?
I always use "oo". :-)
Dave
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