Author: Larry Coon
Date: 20:20:09 08/27/98
Go up one level in this thread
On August 22, 1998 at 14:30:15, Dan Newman wrote:
>Hi,
> Here's something I dug up from my files: SJE's readme.tb file.
>Hope this helps.
I've now had a chance to digest it completely, and it answered
almost all my questions -- thanks again.
However, I do have a couple of questions.
SJE's doc listed specs for only a few of the existing
tablebases. I think I can infer the pattern in the
remaining files, but I want to double check:
1. Is it safe to assume that "qsf" (queenside)and "tri"
(a1-d1-d4 triangle) indexing are never used in the
same tablebase file?
2. Is the order of array indexes always the reverse
order of the piece order in the tablebase name?
(eg: in KQRKR would they be bR, bK, wR, wQ, wK?)
3. Is the last black piece in the tablebase name
always the one with the "tri" or "qsf" index,
unless there's a pawn, in which case it's the
pawn?
4. Is it true that if the last piece is a pawn the
first index is always "qsf", otherwise it is "tri"?
So to continue with my example, for KQRKR it would be
the C array:
signed char KQRKR[10][64][64][64][64]
with the subscripts and scanning patterns: bR = "tri",
bK = "all", wR = "all", wQ = "all" and wK = "all",
respectively. Yes?
I have more questions about the following:
>Note that all the tablebases are constructed with White as the side with more
>material (e.g., better winning chances). If Black is the side with better
>material, then the colors are reversed and, if any pawns are present, the
>piece positions have to be reflected across the X axis prior to indexing.
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
reflect about the Y axis, right? So this gives me:
8/8/1k6/8/1KP5/8/8/8 b
and I can now look up my value in KPK.tbb[41][13][26]. Is this
the correct process?
Thanks again,
Larry Coon
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