Author: Angrim
Date: 13:13:59 01/13/00
Go up one level in this thread
On January 13, 2000 at 09:16:34, Robert Hyatt wrote: >On January 12, 2000 at 18:56:38, Nobuhiro Yoshimura wrote: > >>>>>>Regards Dan Andersson >>>>> >>>>> >>>>>Note that this is not easy to do. Because if you give the bonus at the root, >>>>>it affects the score at the tips of the tree below that root move. And thanks >>>>>to the hash table, you can now play the move at ply=3 at the root, and the >>>>>root move at ply=3, and the hash table will politely include the original bonus >>>>>due to the way hashing is about positions, not moves. >>>> >>>>I disagree, root move penaties are fairly easy to do right. >>>>If coded correctly a root move bonus/penalty will not change the values >>>>stored in the hash except as you would expect from changeing the search window. >>>>The score at the leaf nodes is not affected since you should >>>>be adding the bonus after you have searched the move. One thing you might >>>>have some trouble with is that the alpha-beta bounds have to be adjusted >>>>to take into account the amount that you will be adding to the score. >>>> >>>>For example, with alpha=100 beta=110 and a root bonus of +50 you need >>>>to search with a window of 50-60 so that the returned score(after bonus) >>>>will be in the correct range. >>>>then if it returns <=50 you failed low with <=100 >>>>if it returns 52 then you have a new best move with score 102 >>>>if it returns >=60 you failed high with a score of >=110 >>>> >>>>Also have to be carefull with this around forced win/loss values, since >>>>if your window was +win50 to +win1 and you give a 50 point bonus to a >>>>move you could be searching with a window of +win1 to +win1+50 <bad thing> >>>>So if alpha or beta is a win/loss value don't adjust it, and if the >>>>returned score is a win/loss value don't add the bonus. >>>> >>>>Hope this helps, >>>>Angrim >>> >>> >>>That is a known 'fix' but it has its difficulties... >> >>What kind of difficulties do you in mind? > > >speed for one. Now you maintain two scores. The score without the root bonus, >and the root bonus. You have to add them together everywhere you make a >decision, so that they can be used separately when hashing. Bob, you seem to be confused here, the root bonus is only used at the root, it is not passed into the search at all. Only after the move has been searched and has returned a value at the root level is the per-move bonus added. This should have been clear from the original post, and the description of how to adjust alpha-beta bounds to account for the bonus. >However, I think that scores added because of a move's position at the root >is probably a wrong idea anyway... unless the search depth is so low that >you get into tactical trouble by not developing. Matter of taste, I'm happy useing them and I use small enough bonuses that they don't get in the way when a position is tactical. Angrim
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.