Author: Robert Hyatt
Date: 05:56:56 07/30/99
Go up one level in this thread
On July 30, 1999 at 05:09:08, Herman Hesse wrote: >On July 30, 1999 at 02:36:56, Bruce Moreland wrote: > >> >>On July 30, 1999 at 00:28:06, Ed Schröder wrote: >> >>>Search the first iteration without alpha/beta. >>> >>>Ed Schroder >> >>This would hurt your "game in one second" performance :-) >> >>bruce > >He told you all once. When Rebel was released able to give senseful 4-move lines >for the first four moves. Four moves sorted into order. Only way was first >iteration(s) without alpha-beta. No person ever commented. > >Now he told you twice. Only comment is a weak joke. > >Your forum stultifies when on-topic reigns. The off-topicals were the ones that >saw and said so. Only dullness remains. Mr Schroder is sad about this. Possibly >why he drops ideas in, hoping for souls to respond. > >Low iterations without alpha-beta lead to more senseful move ordering from hash >when the PV is going to change in later iterations. This can save time. All >spelt out so even the slow ones can see. > >Herman Sorry, but this is _dead_ wrong. Otherwise we would just do the 'low iterations without alpha/beta' and then play the best move. Check out Rebel on any test suite. I'll bet you find it changing to the _right_ move at extreme depths and not at depth 1 or 2 or 3. Doing a 1/2 ply search without alpha/beta can help a bit with ordering the root moves, but _only_ a bit. Because all you learn is which moves seem to be best for 1-2 ply searches. (no, you won't do 3-4-5 ply searches at the root without alpha/beta and finish them in reasonable time). However, what is best at 2 plies has _nothing_ to do with what is best at 10, 11 or 12 plies... This is an _old_ idea. Ken Thompson did a 2 ply search without alpha/beta in Belle to order the ply-1 move list. I used his idea in Cray Blitz (I had the ability to use a 'true-value' search at the root by resetting alpha/beta to +/- infinity for each root move to get a score for each, useful for debugging and other things). It isn't 'new'. It isn't particularly 'great'. And it absolutely does _not_ let you see that all moves but one lead to mate. Because they all (but one) might lead to a mate in 10, and you won't see that with a 1-2-3 ply search, generally.
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