Saturday, April 28, 2012

Frequency of the diferent Nalimov EGTB 6 men





6-man EGTB collecting tip

by Cato the Younger » Thu Jan 05, 2006 4:37 pm

http://sites.google.com/site/chess2u/Nalimov-Endgame-Tablebases/frequency-of-the-diferent-nalimov-egtb-6-men

Collecting the entire set of 6-man EGTB is intimidating and impractical for most people who don't have the necessary 1.2 terabytes of free disk space on their hard drives. But there is a practical if imperfect solution to this problem: only collect the most important--that is to say, the most frequently occurring--combinations.



There are 365 possible 6-man combinations. If you collect just the top 20 of them, by my guess you will have over 56% of the 6-man situations that happen in engine vs. engine games. If you get ambitious and go for the top 50, you will have over 79%. But if you are super-inefficient and collect only the bottom 100 combinations you will have only 0.16% coverage! I mean really, what good is a KNNNNK tablebase to you unless you like horses?



Now there is one issue with this suggestion that I will let others elaborate: the "incomplete tablebases" problem. For example if you have a tablebase with pawns and don't have the one that it converts into following a pawn promotion, you could have some problems. But my general impression is that if you go for maximum coverage in statistical terms that's a better approach that getting all the pawnless combinations first, many of which hardly ever occur. KRRKBB for example happens less than once every 100,000 engine games!



According to my database, here are the top 100 most frequently occurring combinations, ranked in order. You really don't need much more than this, as these cover about 92% of all 6-man combinations that actually happen in engine games. (And for practical purposes you can toss out any 5+1 combinations I show here because if your engine can't solve those without help you need a new engine.)



KRP KRP

KRPP KR

KPP KPP

KRP KPP

KBP KNP

KBP KPP

KRPP KP

KRP KBP

KPPP KP

KQPP KP

KBPP KP

KBP KBP

KRB KRP

KNP KPP

KQP KQP

KQP KPP

KRBP KR

KNP KRP

KQRP KR

KRN KRP

KBPP KB

KNP KNP

KNPP KP

KBPP KR

KQP KRP

KRNP KR

KRPP KB

KQPP KQ

KQRP KP

KBPP KN

KQBP KP

KPPP KR

KNPP KB

KNPP KN

KQR KRP

KNPP KR

KQPPP K

KRPP KN

KRB KRN

KQRPP K

KQP KBP

KRPP KQ

KRPPP K

KQQP KP

KQPP KR

KRR KRP

KRRP KR

KPPP KB

KRBP KP

KQBPP K

KQNP KP

KQP KNP

KPPP KN

KRP KBN

KQQPP K

KQR KPP

KRB KBP

KRB KRB

KRB KPP

KQBP KB

KPPP KQ

KRBP KB

KRNP KP

KRBPP K

KBPPP K

KRN KRN

KRB KNP

KQB KQP

KBNP KR

KQPP KB

KQNPP K

KQRBP K

KQRP KB

KQB KPP

KRBP KQ

KQP KRR

KRN KPP

KBPP KQ

KQBP KN

KRN KBP

KQPP KN

KQBP KR

KRN KNP

KBNP KP

KQP KRB

KQN KQP

KPPPP K

KQRB KR

KRBP KN

KBN KBP

KQNP KB

KNPPP K

KNPP KQ

KQR KBP

KRRP KP

KQBP KQ

KRNPP K

KBNP KB

KQQ KPP

KQR KQP



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