Author: Ralf Elvsén
Date: 09:33:47 10/05/00
Go up one level in this thread
On October 05, 2000 at 11:48:46, Severi Salminen wrote: >Hi! > >I ordered a copy of Heinz's book in the library of my home town. A few question >about his AB explanation: > >1.He says: "While fail-highs with result>=beta place lower bounds on the real >scores of failed searches, fail-lows with result<=alpha place upper bounds on >them." > >So, what bound is he meaning (maybe my english is not so good): real scores of >failed searches? I thought that Alpha and Beta are the only bounds involved - >they are the lower and upper bounds of real score, aren't they. Does this imply >in negamax implementation? I know basically what fail-high (and fail-low) means, >but didn't understand this statement. > Assume you are in a position with beta = (say) 100. You search move A and get a score 150. Then you have a beta cutoff and exit that node. But this value 150 is a lower bound on the "true" score of that position because there might be moves you never serached with values of 200 or whatever. So 150 is a lower limit on the "true" value of the position. The reasoning is basically the same for the other case (if you think about it for a while): where did all those values <= alpha come from? Ralf
This page took 0 seconds to execute
Last modified: Thu, 15 Apr 21 08:11:13 -0700
Current Computer Chess Club Forums at Talkchess. This site by Sean Mintz.