Author: John Merlino
Date: 19:32:08 06/15/03
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On June 15, 2003 at 22:05:00, Rex wrote: >Thanks. Can you define Selective Search. Lower number ver higher number. I am >guessing the tree branch factor comes in play but not really sure if its greater >with the lower or higher number. Lower number = more pruning = deeper depth? >Is that it? > >tnx Perhaps you've noticed that Chessmaster 9000 reports search depths in an "X/Y" format. 'X' is defined as the brute force search depth. 'Y' is what Johan calls the "nominal search depth". What this amounts to is the MINIMUM depth that all "reasonable" or "promising" lines have been searched. The Selective Search value defines (Y - X), the difference between X and Y. So, in the opening position, with the default value of 9, you will see the following search depths be reported in order: 1/3, 1/4, 1/5, 1/6, 1/7, 1/8, 1/9, 1/10, 2/11, 3/12, etc.... If you change the selective search value to, say, 6, then you will see these depths reported in order: 1/3, 1/4, 1/5, 1/6, 1/7, 2/8, 3/9, 4/10, etc. Most independent testers have reported that higher selective search values can improve the quality of play at longer time controls, or for very lengthy analysis. Now that the default value is 9, many testers are satisfied with this. Some testers still prefer values in the 10-12 range, though.... jm
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