Author: Gerd Isenberg
Date: 13:22:30 02/19/04
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On February 19, 2004 at 14:39:16, Uri Blass wrote: >Today I have an array direction[64][64] that gives me different numbers for >different directions(possible directions are queen direction that get 0-7 knight >directions that get -2,identical squares that get -9 or no direction that gets >-1 ). > >I thought about the idea to change it to the following definition: > >#define direction((i)(j)) directionnumber[translate[i]-translate[j]+128] > >The result is that I can get instead of one array of 4096 entries >2 arrays when translate is an array of 64 entries and directionnumber is an >array of 256 entries. > >My question is if it is a good idea from speed point of view. >It will probably be a simple change when I only need to construct the 2 arrays >and the main problem is to construct the translate array. > >It is probably only few hours of work but I do not like to spend time on >constructing these arrays only to discover later that it is not productive so I >ask for your opinion about it. > >Uri Only some few more aspects in addition to Bob's answer .... If it is frequently used eg. with generated moves, i would say the extra memory references and instructions don't pay off. It may even be faster with a 16KByte 4096-int-array. I often found arrays of packed structs favorably with such 64*64 arrays with low ranges (eg. distance, taxidistance, unique distance relationship (see links below) or direction). With 0x88 there is also a fast substraction trick to get the direction... http://chessprogramming.org/cccsearch/ccc.php?art_id=245611 http://chessprogramming.org/cccsearch/ccc.php?art_id=245625 http://chessprogramming.org/cccsearch/ccc.php?art_id=245765
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