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Up Topic Rybka Support & Discussion / Rybka Discussion / Bitbases and Shredderbases
- - By h1a8 (***) [us] Date 2007-01-12 01:41
I discovered what both bitbases and Shredderbases are. They are very similar to Nalimov tablebases but with no distance to win.
SMK says,

"The Shredderbases work fine in combination with the Nalimov endgame databases. In the search the
Nalimov databases are no longer accessed when the corresponding Shredderbases are installed.
When the position on the chess board is already in the database, Shredder will access the
Nalimov databases as the Shredderbases only store if a position is won, draw or lost and not the
number of moves until mate

Thus Shredderbases are a kind of bitbases.
The disadvantage of bitbases is when there are many moves that win combined with the engine not knowing which moves are leading down (converging) can (not always though) make the engine draw by the 50move rule. The advantage of bitbases is that they are much smaller than regular tablebases. Thus making the lookup much faster as compared to Nalimov (can even fit into ram memory) .
Another advantage is when an engine looks through the bitbases first to find the win and then switch over to the Nalimov tablebases for conversion. Thus the bitbases work great in conjunction to the engine's thinking or the Nalimov tablebases.
The problem is that no engine (except shredder) is programmed to do this. I hope Vas can implement bitbase support for rybka and have rybka switch over to Nalimov when she sees what she wants. Also, I hope there is someone (if Vas can't) who can create bitbases for rybka or a universal bitbases.
Parent - - By ernest (****) [fr] Date 2007-01-12 12:34
I have seen a recent test of the 5-piece Nalimov EGTB on 2 x 4 GB USB key (of course also possible on 1 x 8 GB key).
Seems all the disk access inconveniences are gone!...
Which means bitbases are no longer needed.

For those who read German, see
Parent - By Uri Blass (*****) [il] Date 2007-01-12 22:38

It does not mean that bitbases are not needed because of the following reasons:

1)You talk about hardware that nobody or almost nobody has and people simply do not care about performance on hardware that they do not have.
2)if you think about a special hardware that the general public will have maybe in 2008 or 2010 then for that hardware it is possible to create bitbases for 6 piece nalimov EGTB.
Parent - By Vasik Rajlich (Silver) [hu] Date 2007-01-13 10:29
A few comments:

1) Tablebases and bitbases should definitely be compressed. In another thread here, people are discussing the logistics of downloading everything - apparently, 6 man TBs are 1.12 TB. That's just crazy.

2) Part of the compression can involve losing some information. That's fine - we're not doing a mathematical exercise, we're trying to play and analyze chess.

3) In general, even the most compressed format should not be kept in RAM in the typical position - the hash entries are going to be more relevant. However, for some specialized positions, it may make sense to allow users to do this.

4) I'd like to see an open standard. In the big scheme of things, the above issues are fairly minor and I'm willing to wait a bit.

Up Topic Rybka Support & Discussion / Rybka Discussion / Bitbases and Shredderbases

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