Author: Tom Kerrigan
Date: 13:05:33 04/12/00
Go up one level in this thread
On April 12, 2000 at 14:03:21, KarinsDad wrote: >On April 12, 2000 at 12:08:37, Tom Kerrigan wrote: > >[snip] >> >>I don't care for this method because you have to go through your entire hash >>table and set these bits. That takes about as long as clearing the hash table, >>which makes it unreasonable to have large hash tables for fast games. >> >>What you can do is take any leftover bits in your hash entries and use them for >>a counter. Every time you start a new search, you increment the counter. If you >>find an entry with an old counter value, you can toss it. >> >>-Tom > >I like it. What size counter do you use? 2 bytes? 4 bytes? How large does your >hash table get? > >KarinsDad :) I have a byte in my hash table entries to indicate what type of score the entry is (alpha, beta, pv). That only takes 2 bits, so i use the remaining 6 bits for a counter. So the counter can go to 64. I figure if an entry is lucky enough to avoid being clobbered for 64 searches, it deserves to stick around for one more. :) I usually set my general hash table size to 16MB. I have 128MB RAM, but I like to be able to just fire up my program with no swapping. I have no idea how fast I "burn" entries. Maybe I'll test that later on. -Tom
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