Author: Robert Hyatt
Date: 13:28:17 05/30/03
Go up one level in this thread
On May 30, 2003 at 11:02:05, Tim Foden wrote: >On May 30, 2003 at 10:46:41, Robert Hyatt wrote: > >>On May 29, 2003 at 07:33:59, Omid David Tabibi wrote: >> >>>On May 29, 2003 at 00:17:14, Robert Hyatt wrote: >>> >>>>On May 28, 2003 at 14:59:57, Uri Blass wrote: >>>> >>>>>I am too lazy to look at the source code of crafty to try to find what >>>>>formula is used by crafty for reducing the distance between the kings in >>>>>endgames like KQ vs KR to help it to win without tablebases. >>>>> >>>>>what is the formula that is used. >>>>>I decided to try something in movei and first tests suggest that it is slightly >>>>>productive but I want also to know what crafty does. >>>>> >>>>>Uri >>>> >>>> >>>>Distance is easy: >>>>max(abs(rankwhiteking-rankblackking),abs(filewhiteking-fileblacking) >>>> >>>>#define FileDistance(a,b) abs(File(a) - File(b)) >>>>#define RankDistance(a,b) abs(Rank(a) - Rank(b)) >>>>#define Distance(a,b) Max(FileDistance(a,b),RankDistance(a,b)) >>>> >>>>I use the three #defines above... >>> >>>In Image Processing, assuming that a and b are two pixels, >>>Max(FileDistance(a,b),RankDistance(a,b)) is called "chess distance" :) >> >> >>In graph theory it is often called "taxicab distance" since taxis have to >>follow streets rather than "as the crow flies". :) > >I thought taxi distance would be (FileDistance(a,b) + RankDistance(a,b)), >not Max(FileDistance(a,b), RankDistance(a,b)). > >Cheers, Tim. You might be right, now that I think about it. The "Distance" macro I use is obviously correct, since for any pair of squares a,b, the number of moves to reach from a to b is the max of the rank/file distances as given.
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