Author: Dieter Buerssner
Date: 11:36:29 07/17/02
Go up one level in this thread
On July 17, 2002 at 04:22:44, Gerd Isenberg wrote:
>On July 17, 2002 at 02:23:52, Russell Reagan wrote:
>
>>Two things:
>>
>>1. How are most opening books stored? Are they in human readable move notation,
>>or a binary representation?
I guess, most will use a binary representation. But like in Gerd's case a
intermediate human readable intermediate representation (which might be a PGN
collection) probably is common, from which the binary representation is created.
>>
>>2. How do most programs interact with their book? I've heard of some schemes
>>where the book is loaded into the transposition table and it simply works
>>seamlessly from that. Is that the standard method?
>>
>>Russell
>
>I do it in the following way (kind of persistent hashtable):
>
>1. I use a readable file with all opening lines, algebraic notation with some
>optional tags (!,=,?). Each opening line is one physical line separated by
>CR/LF. They may include comments {some interpretable like +-, +=, ECO}.
Very similar here. Although I do not necessarily need them to be on seperate
input lines. Therfore some other means is needed to seperate the different
opening lines, for example one (or more) PGN tag.
>2. With this source file i generate a binary file. This binary represents an
>array of structs like a transpositions table does. With hash index modulo table
>size i seek to the appropriate struct, which containes hashkey, castle rights,
>color to move and ep-information and a (lseek) pointer to a dynamic struct
>placed in an appendix of the binary file.
Also very similar here.
>This dynamic structure contains all
>the necessary information about the position, all the moves (including
>probability to play) and also all source line indices that lead to this position
>(for bookeditor reasons).
However, I do not have a dynamical struct. The structs in the array have all the
information needed for one position and one move. My pointer (=file offset,
"lseek pointer") points is the start of a link list of additional moves of this
position and/or different positions with the same array index (=hash key modulo
number of entries in the array of structs). So I have to traverse the linked
list, to find all opening moves in one position. This may sound a bit costly
because of the several disk accesses, but is only a few milliseconds at max in
practice.
How do you work around the problem, that different position may yield to the
same index in the array of structs? From reading the above, I cannot see it.
Another possiblility would sort the structs by hash index, and use a binary
search to find the positions. No need for linked lists anymore, but some more
effort while creating the binary representation because of the additional sort
process, (or by generating it sorted from the beginning).
>3. If i probe the table and there is no hit, i try it with the black/white
>mirrored position, to look for reversed opening lines, where white possibly
>looses one tempo.
Did you check, if this is worth the work? Do you get now and then opening moves
by the probing of the mirrored position? How often? Once in 10 games, in 100
games? ...
Regards,
Dieter
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.