Author: Vincent Diepeveen
Date: 10:58:26 07/27/03
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On July 27, 2003 at 13:51:28, Sune Fischer wrote: Hello, Here what i write every few months in CCC. Because it is a few lines i will do it again. use a hashtable with n entries. then find index hashkey%n; %n is slower than a multiplication or an AND or a divide, but it's faster than a divide and multiplication and sub. Then sequential try 8 positions in a row. If each position is just 16 bytes that makes 128 bytes. About the cache line length at the average supercomputer or a P4. And just 2 cache lines of K7. I do not know about opteron. I guess it's also 128 bytes cache line length? Anyway just always replace the smallest depth out of those 8 positions. This works very well. If you want to keep inside 64 bytes then try 4 probes. I found by experimental data that 8 probes was optimal for DIEP. Best regards, Vincent > >I've been trying some different hash schemes, and the one >that should be the best completely fails to solve a few positions. > >Currently I use two tables, one of the criterias is to replace if it is the >same key (so I don't get the same key in both tables, same philosophy as with >killers moves), but only if the depth is greater or equal. > >For some reason this fails on fine70 and similar positions. >If I do always replace on top of _the same_ key, then it works fine!? >I don't see the logic in that, and I'd really prefer to keep the deeper entry, >obviously. > >Could this indicate a bug, or can it be explained/fixed? > >Currently I'm trying replace if LOWER bound (beta cut) or deeper, seems to work >well also, I still don't get it though. > >-S.
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