Author: Tord Romstad
Date: 01:48:41 03/10/04
Go up one level in this thread
On March 09, 2004 at 22:37:10, Jonathan Kreuzer wrote: >on an AMD 1.8ghz, time until mate in 9 is declared: > >Ruffian 1.01: 5.0 seconds >Slow Chess 2.89b: 7.4 seconds >Crafty : ??? seconds (let it run for 2 minutes) > >I've noticed that Crafty quite often has trouble declaring mate, and I've >wondered why (it doesn't hurt playing strength since Crafty is good at >finding the best move quickly.) I am not sure whether your guess is correct, but there is another possible explanation. My engine behaves similar to Crafty. It is usually good at finding the right move quickly, but often needs a very long time in order to find a mate. The current position is no exception. It finds Rxg7+ instantly, but needs exactly 3 minutes before it announces "mate in at most 110 moves". Mate in 9 is announced after 4m28s. The explanation for the long solution time is that my search is intentionally lazy for the winning side. When one side appears to be winning, all search extensions for that side are severely limited, and I search very few moves for the winning side in the qsearch (no checks at all, for instance). Instead, the search makes an effort to find hidden resources for the losing side. The idea is that it is more important to make sure there isn't a very deep refutation of the (apparently) winning line than to look for an even more crushing win. In practise, this seems to work very well, even in tactical test suites. I am sure my engine occasionally needs a handful more moves than necessary to checkmate its opponent, but who cares? Tord
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.