Author: Tom King
Date: 14:10:43 03/10/03
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On March 10, 2003 at 17:06:10, Gerd Isenberg wrote: >On March 10, 2003 at 14:49:30, Tom King wrote: > >>Hi all, >> >>One search extension which most programs seem to use is the passed pawn pushing >>extension. When a move is made which is a passed pawn push to the 7th rank, we >>extend the search by a ply. >> >>My programs has got away without this extension for years. Or perhaps "got away" >>isn't right.. there have been losses which this extension might have prevented. >> >>Anyway, what do people think of this extension. Worth having? If so, what value >>would you attach to it? >> >>Regards (and hi to all), >>Tom >>tom@silentshark.co.uk > >Hi Tom, > >i do some fractional extensions with passers. Not only if they push or capture >foreward to the 6th or 7th rank, even if a opposite "guard" pawn in backward or >knight distance (re)captures (but no push) from it's base rank (own 7th rank) to >the "right" side, which establish an own passer on the 6th rank. I consider the >number of advanced passers per side, supporting and defending pieces. A lot of >code, specially at interiour nodes or near the root to look for further >recuductions of determined extensions. > >Even if these extensions work fine in some testpositions, i requires a lot of >effort to tune them for tournament play. Most often i do it by "gut feel". > >One thing i tried to control extensions with is to vary the amount of fractions >to become one ply. I tried to vary it by search depth and by the relative amount >of extensions so far. > >Regards, >Gerd Hi Gerd, Sounds like your passed pawn extensions are very sophisticated - doesn't this analysis slow up your search? I'm sure you are dead right about the test positions. I gave up with testsuites a while back, and now just use hundreds of test games to determine whether a change is beneficial or not. Regards, Tom
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