Author: KarinsDad
Date: 15:29:17 04/12/00
Go up one level in this thread
On April 12, 2000 at 16:05:33, Tom Kerrigan wrote:
[snip]
>
>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
What I would like to do is maintain entries in the hash that are still derived
from the current 0 ply node as opposed to entries that were not discovered in
the search off of the current 0 ply node.
For example (without an opening book):
Counter = 1
1. d4 the position after 1 ... d5 2. c4 Nf6 is in the hash and has a 1 counter
d4 move made, Counter now = 2
1. ... Nf6 the position 2. c4 d5 is a transposition in the hash, but has a 1
counter, so it may be overwritten since it's counter is not 2.
This seems to imply that you randomly get rid of nodes, even though they are
descendents of the current position (and in fact were found in the previous
search of the parent of the current position).
I'm trying to think up a way to avoid this. For example:
a b c d
\ / \ /
e f
\ /
g h
\ /
i
Node c is a descendent of i. If we make move g, it is still a descendent of g,
hence, it would be nice to not get rid of it since there is still a good chance
of transpositions from it later on. However, if we make move h, it may be a
descendent of h, or it may not, but who knows? Hence, if we make move h, I would
not mind getting rid of c.
I want to also take this idea farther based on the PV. The lower your ancestor
deviated from the PV on the tree, the more I do not care if I drop you from the
hash table.
I cannot think of how to use your counter method to accomplish this, but your
counter method can be used as a backup check (i.e. if I am currently creating
counter 7 nodes, I probably do not care as much about counter 2 nodes as much as
counter 5 nodes).
KarinsDad :)
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