Author: Dan Ellwein
Date: 06:41:13 05/03/00
Go up one level in this thread
On May 03, 2000 at 01:21:58, Ed Schröder wrote: >On May 03, 2000 at 00:17:28, blass uri wrote: > >>On May 02, 2000 at 07:38:08, Ed Schröder wrote: >> >>>On May 02, 2000 at 06:26:34, Michael Neish wrote: >>> >>>> >>>>Hello, >>>> >>>>I wonder whether anyone could help me, or offer any suggestions as to the >>>>following little problem. >>>> >>>>The program I'm writing needs two ply to see what I think should take only one >>>>ply. >>>> >>>>In the position below White wins material by the blindingly obvious Bg5. >>>> >>>>[D]6k1/pp1nrppp/5rb1/P2P4/5BP1/5P2/4BK1P/R3R3 b - - >>>> >>>>However, if I set my program to look only one ply deep, it doesn't see this >>>>move, and prefers Bb5. At two ply, though, it sees it all right. I think one >>>>ply should be enough, as the Qsearch ought to take care of the ensuing >>>>exchanges. Indeed, other programs I have tried manage to find it easily enough >>>>in one ply. >>>> >>>>This might be a trivial position, but if it's taking longer than it should to >>>>see these tactics then I could be wasting plies in my search. >>>> >>>>By the way, in case anyone asks, I'm not doing anything unusual in Qsearch. I >>>>call Eval() first, return if it fails high, otherwise set alpha to the Eval() >>>>score if it's greater than alpha, and then search through the available >>>>captures. >>>> >>>>Thanks for your help. >>>> >>>>Mike. >>> >>>Rebel gives a bonus of 1.00 in eval for Bg5 assuming one of those rooks >>>get lost. A higher bonus is quite risky as the opponent often has an >>>escape. The effect in search is minor. It was effective in the days of >>>programs running at 5 Mhz hiting 5-6 plies only. Nowadays I would not >>>spend time on such (processor) time consuming cases. >>> >>>Ed >> >>I do not understand why not. >> >>If there is a long line when the final position is one of these cases >>you can have a better evaluation. >> >>Usually long lines are not forced so the effect may be better positional moves >>and not tactics. >> >>Uri > >Your point sounds very plausible but isn't true. Search solves these >kind of cases and you only end up with some speed loss. Running a >set of 500 positions only gave a few (non-important) different moves. > >That is one of the crazy things of CC, you have to go from scratch on >your code every 3-4 years as many things that were good then are >out-dated now because of increasing hardware (Mhz & Ram). > >A few days ago I wrote something about 1992 and one instruction making >Rebel (The ChessMachine then) stronger. It made me think about and as >a result I improved that piece of code with a net result of 28% speed >gain. The change would not have been a good idea in 1992. > >Search is a strange animal and hard to understand for the human brain. >It is full of unexpected surprises. I estimate that after 20 years >wrestling with search I only understand 5% (or so) of search. > >Ed Ed... sounds like there might be a correlation here between search and the human brain... in that we 'only' use about 5% of our brain... and... after many years of performing brute force/selective search techniques (going back to Shannon - 1950's), we only understand about 5% of what's really going on... well... any-way... just a thought :) PilgrimDan
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