Author: F. Huber
Date: 11:00:44 02/04/04
Hello friends of chess problems! Again there´s a new version of Chest/ChestUCI, and this team has now made a really big jump in its capabilities - at least an increase of 30 points! (no, not ELO but IQ! ;-)) For the new features this time it was necessary to make some bigger changes to Chest´s code itself, and once more I would like to thank Heiner Marxen, who is always very kindly helping me, whenever I want (or have) to make any changes in his Chest and get into troubles to understand his source code - and that really happens quite often! ;-) [Special note for Thomas Mayer: Is this ´thanking´ enough? ... WHAT? ... NOT? ... Ok, here´s a bit more: "Thanks to Heiner for making Chest - and thanks to God for making Heiner!" :-)] So what´s new in this version? 1) the maximum mate level (´SearchDepth´) has been increased from 30 to 62 moves (especially in view of the following feature) 2) there´s now a new problem type (´Special-Mate´) together with the three corresponding options ´ChecksOnly´, ´KingMobility´ and ´MaxMoves´, making it possible to solve now many mate problems, which could not be solved by the standard ´brute force´ method in a reasonable time. This is done through restrictions in Chest´s mate search to only such moves, which meet some special conditions, and this mode can sometimes reduce the solving time really dramatically! With ´ChecksOnly´ Chest makes only ´checking moves´, i.e. it searches only for solutions consisting of serial checks - and if such a solution exists, it will be found almost immediately. ´KingMobility´ restricts the mate search to those attacker moves, which don´t allow the opponent king more than an adjustable number (0-7, 8=off) of moves (or flight squares). And finally with ´MaxMoves´ you can limit even the total number of allowed opponent (or defender) moves (1-221, 0=off), which can further cut Chest´s search tree enormously. But there´s an important remark necessary: Of course in this ´Special-Mate´ mode Chest can only find such solutions, which exactly meet the adjusted conditions, i.e. in this case it can not be guaranteed, that there will be found any solution at all, or that a provided solution is the optimal (i.e. shortest) one. So this mode should only be used, if a mate problem can not be solved with the usual method in an acceptable time. Nevertheless, for _exactly_ those selected conditions Chest will indeed give all possible solutions (and also the shortest ones), and furthermore these solutions will of course also be _forced_ (i.e. a mate even with the optimum counter moves). Detailed informations about these new options can be found in the program description ´English.txt´, and the included test suite ´Mate.epd´ contains some mate problems, which have been solved with this special mode - simply search for lines with the character "@". Certainly the most spectacular example in my collection - I´ve already posted it a few days ago here - is the following "mate in 38", which is solved _immediately_ with the following settings ´C-/K1/X14´ (i.e. ChecksOnly=off, KingMobility=1, MaxMoves=14 at ´ProblemType=Special-Mate´). (In ´normal´ mode I probably won´t live long enough to see that solution :-)) 1R6/6pK/5p2/4p3/1B1p3n/8/p1p1pp2/1k3b2 w - - [Special note for Ed Trice: Excuse me, Ed - I know this is an absolutely (your words!) ´useless´ example, but who cares - except you? Most friends of mate puzzles _do_ love such ´strange´ positions, and Chest´s performance here is really fantastic! ;-)] Ok, now it´s your turn to experiment with these new options, and to find the appropriate parameter settings for difficult mate puzzles (something that would require a little experience, flair and also logic ;-)). As usual the new ChestUCI Ver.3.2 is available at: http://www.uciengines.de/UCI-Engines/Chest/chest.html Much fun with it, and best regards, Franz.
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