Author: Larry Coon
Date: 10:44:01 08/28/98
Go up one level in this thread
On August 28, 1998 at 05:35:47, Dan Newman wrote:
>>1. Is it safe to assume that "qsf" (queenside)and "tri"
>> (a1-d1-d4 triangle) indexing are never used in the
>> same tablebase file?
>
>Yes, that's my understanding too. When there are only pieces on
>the board there are more symmetries to play around with than when
>there are pawns, so we can use the "tri" indexing for one of the
>pieces. Since pawns are highly directional you lose a lot of the
>symmetry and must go to "qsf" indexing--which gives less than
>a third of the "compression" that "tri" gives.
Makes sense. So the general rule would be:
-- If there are -any- pawns, there will be one "qsf" (on
a pawn) and the rest will be "all."
-- If there are -no- pawns, there will be one "tri" (on
the last black piece) and the rest will be "all."
Sound better?
>>I'm unclear as to the order in which things are done here.
>>Let's say the following position appears:
>> 8/8/8/5kp1/8/6K1/8/8 w
>>
>>According to this I reverse the colors and reflect across the
>>X axis:
>> 8/8/6k1/8/5KP1/8/8/8 b
>>
>>and will now use the tablebase KPK.tbb. But since the indexing
>>in this tablebase is "all", "tri", "all", I -now- have to
>
> (should be "all qsf all" for KPK)
>
>>reflect about the Y axis, right? So this gives me:
>> 8/8/1k6/8/1KP5/8/8/8 b
>
>I get 8/8/1k6/8/1PK5/8/8/8 b (but I see by your indices below
>that you do too.)
You're right -- both the "tri" and the "KP" were
typos. Thanks for catching them -- shows what
happens when I type right before dinner.
>>and I can now look up my value in KPK.tbb[41][13][26]. Is this
>>the correct process?
>>
>
>Yes. (This always twists my brain into a pretzel--esp. the "tri"
>indices.)
But once you figure it out, it's an efficient and
elegant scheme. Thanks again.
This page took 0 seconds to execute
Last modified: Thu, 15 Apr 21 08:11:13 -0700
Current Computer Chess Club Forums at Talkchess. This site by Sean Mintz.