Author: Gerd Isenberg
Date: 11:59:47 12/06/05
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On December 06, 2005 at 13:03:16, Alessandro Damiani wrote: >On December 06, 2005 at 02:31:57, Gerd Isenberg wrote: > >>On December 05, 2005 at 17:23:16, Alessandro Damiani wrote: >> >>>Just wondering: does anyone use flood-fill to detect open files? >>> >>>Alessandro >> >>I do it indirectly, i have front-span and back-span of both white and black >>pawns. Oring all spans and the pawns itself gets a set of all pawn occupied >>files - and the complement is the open-file set. >> >>Direct calculation is like that: >> >>bb = allPawns; >>bb |= bb >> 8; >>bb |= bb >> 16; >>bb |= bb >> 32; >>bb = ~bb & 0xff; // if you only need a file-set, take it here >>bb |= bb << 8; >>bb |= bb << 16; >>bb |= bb << 32; >>openFileSet = bb; >> >>Gerd > >Thanks. Maybe it's faster than incremental updating. And since you use pawn >front- and back-spans, detecting open files is cheap. > >Do you use pawn front- and back-spans to determine both players' territory? Yes a kind of... i don't have my source handy - it is usefull for a lot of semi-open- and open-file stuff, together with attack-spawns. The question is always to store such things for some time or to save some memory writes and to do it on the fly when needed. Gerd > >Alessandro
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