Author: Anthony Bailey
Date: 19:12:59 09/18/99
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On September 18, 1999 at 21:34:38, Eugene Nalimov wrote: >You can thank Compaq. Recently it stopped NT development on Alpha, and suddenly >we have huge Alpha NT servers that have nothing to do - now they will be used >only for testing service packs for already shipped products. So I was able to >use 2 such servers with 4 Gb of RAM each. Unfortunately, generator itself >doesn't use more than 1 CPU, and I don't want to spend time on that. But even >with 1 CPU I was able to generate KQQKQQ and KRRKRR; right now they are being >verified, and I think that tomorrow or on Monday I'll be able to download them. Excuse a question from a newbie... but why is that much (8Gb, you're implying) RAM required? It seems to suggest you are using quite a number of bytes to encode the current knowledge about each position in the tablebase whilst it is being generated. (I saw the number 1,546,346,34 bandied about for the number of positions in the thing.) Now, I expect I'm missing some reason why the following algorithm doesn't work... but if you start the process by going through each position in turn, counting the legal moves from it, there still aren't be more than 64 even for wild positions like kqq. And for each position you only have to know which of a few possible evaluations (I presume win/lose/draw suffices) applies so far, and how many more times you need to backtrack into the position in question until you've effectively covered all the moves forward from it. So that's one byte per position. I can see you need some kind of direction information (like moves to a finishing position) once the position is evaluated, but it seems you can generate that once per ply when you write the newly evaluated positions out to disk. (It's random look-up from the disk that you're trying to avoid by holding working information in RAM, right? You can afford to write a few Gb to disk linearly once per ply...?) Even if you can't, two bytes of RAM is going to suffice, it seems? I presume I've made some silly false assumption here. I confess to being completely new to all this (came in on the Kasparov vs World ship) and any citations of electronically available papers that describe the algorithms usually used would be great. - Anthony.
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