Author: F. Huber
Date: 07:03:00 11/10/03
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On November 10, 2003 at 03:11:53, Jouni Uski wrote: >I am surprised, that node speed is only about 25% of playing engines node speed! >How is this possible, when Chest needs only to check mate and not do any >position evaluation? > >Jouni Hello Jouni! Just as you, I was also rather surprised, when I saw these ´nodes/sec´ the first time in ChestUCI - but shortly said it´s almost the same as with Hiarcs: "rather slow, but very intelligent". ;-) I don´t know the full details of Chest´s mate solving process, but I´ve got some informations about this directly from Heiner Marxen by Email, and so I´ll try to explain it as good as I can: For every examined position Chest calculates a _lot_ of informations and stores them in the hash table - and that makes it rather ´slow´ (usually slower than other mate solvers with a factor of 3..5). On the other hand those _many_ informations make it possible for Chest to skip over a lot of positions or moves, which he hasn´t to recalculate again - and so Chest needs to examine only a _small_ fraction of nodes compared with other mate solvers (a factor of 10..20 or even more is not unusual) - look at the total nodes at the end of solving process and compare them with the nodes of other programs. And so the following calculation (e.g.) is rather simple: 5-times slower + 20-times less positions = 4-time faster in total! :) These two things may be main reasons for Chests excellent results in solving mate problems. Of course Chest has many other cunning tricks built in (e.g. special code for ´mate in 2´, different heuristic routines, ...), but these would be explained best by Heiner Marxen himself (probably needing a ´one year lecture´ on a University ;-)) - because I´m sure he is absolutely the _only one_, who really understands his own source code! ;-) I hope that I could clear up the situation a little bit - best regards, Franz.
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