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Vincent Diepeveen

Joined: 09 Mar 2006
Posts: 1738
Location: The Netherlands

Post subject: Re: Hash table division    Posted: Fri Apr 06, 2012 2:15 pm

Rebel wrote:
hgm wrote:
 Rebel wrote: And so it makes sense to declare a bigger odd-ply-HT than an even-ply-HT.

Not really. Number of stores in meaningless. Number of hits is only a little bit less meaningless. What really counts is how much search time the hits save you.

When you say 'odd ply', do you mean counted from the root or counting from the leaves?

From the root. The perfect search (except for the best move) goes like this:

odd - xxxxxxxxxxxxxxxxxxxxx (all moves searched) (no beta cut-off)
even - x (beta cut-off) (only one move searched)
odd - xxxxxxxxxxxxxxxxxxxxx (all moves searched) (no beta cut-off)
even - x (beta cut-off) (only one move searched)

etc.

Of course I agree with you that a faster search should be the end result and for me it does, I am just trying to explain the logic behind the approach.

On top of that consider the better flexibility how to profit from the available memory at your disposal. If your PC (for example) has 1GB you (probably) can only use a HT of 512MB. With 2 tables you can use 768MB, one of 512Mb and one of 256Mb.

Your table is split based upon expected outcome of what the position is, so positions >= beta in 1 table and positions <= alfa in 1 table?

That reduces of course the impact of a Zobrist error.

As for the 1GB size being able to use 768 in your approach versus less with 1 table,l that's not entirely true.

I can also use 919191 entries for hashtable easily if i want to.
No need for a slow modulo.

Take 32 bits of your zobrist key, multiply it by 919191 and then take the top bits, so forget about the lowest significant 32 bits.

It's one 32 bits multiplication. Sure that is slower than a single AND, but gives more flexibility
 Display posts from previous: All Posts1 Day7 Days2 Weeks1 Month3 Months6 Months1 Year Oldest FirstNewest First
Subject Author Date/Time
Ed Schroder Thu Apr 05, 2012 8:30 am
H.G.Muller Thu Apr 05, 2012 9:47 am
Steven Edwards Thu Apr 05, 2012 6:11 pm
Robert Hyatt Thu Apr 05, 2012 6:58 pm
Vincent Diepeveen Thu Apr 05, 2012 11:36 pm
Robert Hyatt Fri Apr 06, 2012 6:58 pm
Vincent Diepeveen Fri Apr 06, 2012 8:37 pm
Robert Hyatt Sat Apr 07, 2012 4:16 pm
Vincent Diepeveen Sat Apr 07, 2012 4:27 pm
Robert Hyatt Thu Apr 05, 2012 7:00 pm
Sam Hamilton Thu Apr 05, 2012 8:39 pm
Robert Hyatt Fri Apr 06, 2012 7:01 pm
Ed Schroder Fri Apr 06, 2012 1:29 pm
Vincent Diepeveen Fri Apr 06, 2012 1:33 pm
Ed Schroder Fri Apr 06, 2012 2:22 pm
Vincent Diepeveen Fri Apr 06, 2012 2:29 pm
H.G.Muller Fri Apr 06, 2012 1:35 pm
Vincent Diepeveen Fri Apr 06, 2012 1:37 pm
Ed Schroder Fri Apr 06, 2012 2:06 pm
Re: Hash table division Vincent Diepeveen Fri Apr 06, 2012 2:15 pm
Robert Houdart Fri Apr 06, 2012 2:24 pm
Vincent Diepeveen Fri Apr 06, 2012 2:47 pm
Ed Schroder Fri Apr 06, 2012 4:53 pm
Robert Houdart Fri Apr 06, 2012 5:24 pm
Sam Hamilton Fri Apr 06, 2012 5:29 pm
Vincent Diepeveen Fri Apr 06, 2012 8:33 pm
Sam Hamilton Sat Apr 07, 2012 1:39 am
Vincent Diepeveen Sat Apr 07, 2012 8:42 am
Sam Hamilton Sat Apr 07, 2012 3:11 pm
Ed Schroder Fri Apr 06, 2012 9:55 pm
Vincent Diepeveen Fri Apr 06, 2012 10:25 pm
Robert Houdart Fri Apr 06, 2012 10:27 pm
Ed Schroder Sat Apr 07, 2012 3:27 pm
H.G.Muller Fri Apr 06, 2012 4:24 pm
Ed Schroder Fri Apr 06, 2012 5:05 pm
H.G.Muller Sat Apr 07, 2012 12:43 pm
Vincent Diepeveen Fri Apr 06, 2012 5:14 pm
Robert Hyatt Fri Apr 06, 2012 8:44 pm
Vincent Diepeveen Thu Apr 05, 2012 11:15 pm
Ed Schroder Fri Apr 06, 2012 1:53 pm
Vincent Diepeveen Fri Apr 06, 2012 1:58 pm
Ed Schroder Fri Apr 06, 2012 2:10 pm
Vincent Diepeveen Fri Apr 06, 2012 2:23 pm

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