Hash table entries and search extensions

Discussion of chess software programming and technical issues.

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rbarreira
Posts: 900
Joined: Tue Apr 27, 2010 3:48 pm

Hash table entries and search extensions

Post by rbarreira »

Does anyone modify the zobrist key based on whether extensions were allowed or not?

The search result will be different depending on this, so if we don't do it we might return an unextended branch from the hash table where we wanted a branch with extensions.
bob
Posts: 20943
Joined: Mon Feb 27, 2006 7:30 pm
Location: Birmingham, AL

Re: Hash table entries and search extensions

Post by bob »

rbarreira wrote:Does anyone modify the zobrist key based on whether extensions were allowed or not?

The search result will be different depending on this, so if we don't do it we might return an unextended branch from the hash table where we wanted a branch with extensions.
I've not tested the idea for obvious reasons, but the first downside would be a significant reduction in hash hit rate.