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Hash table division
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Vincent Diepeveen



Joined: 09 Mar 2006
Posts: 1738
Location: The Netherlands
PostPost subject: Re: Hash table division    Posted: Fri Apr 06, 2012 2:15 pm Reply to topic Reply with quote
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 Smile
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Subject Author Date/Time
Hash table division Ed Schroder Thu Apr 05, 2012 8:30 am
      Re: Hash table division H.G.Muller Thu Apr 05, 2012 9:47 am
      Re: Hash table division Steven Edwards Thu Apr 05, 2012 6:11 pm
            Re: Hash table division Robert Hyatt Thu Apr 05, 2012 6:58 pm
                  Re: Hash table division Vincent Diepeveen Thu Apr 05, 2012 11:36 pm
                        Re: Hash table division Robert Hyatt Fri Apr 06, 2012 6:58 pm
                              Re: Hash table division Vincent Diepeveen Fri Apr 06, 2012 8:37 pm
                                    Re: Hash table division Robert Hyatt Sat Apr 07, 2012 4:16 pm
                                          Re: Hash table division Vincent Diepeveen Sat Apr 07, 2012 4:27 pm
      Re: Hash table division Robert Hyatt Thu Apr 05, 2012 7:00 pm
            Re: Hash table division Sam Hamilton Thu Apr 05, 2012 8:39 pm
                  Re: Hash table division Robert Hyatt Fri Apr 06, 2012 7:01 pm
            Re: Hash table division Ed Schroder Fri Apr 06, 2012 1:29 pm
                  Re: Hash table division Vincent Diepeveen Fri Apr 06, 2012 1:33 pm
                        Re: Hash table division Ed Schroder Fri Apr 06, 2012 2:22 pm
                              Re: Hash table division Vincent Diepeveen Fri Apr 06, 2012 2:29 pm
                  Re: Hash table division H.G.Muller Fri Apr 06, 2012 1:35 pm
                        Re: Hash table division Vincent Diepeveen Fri Apr 06, 2012 1:37 pm
                        Re: Hash table division Ed Schroder Fri Apr 06, 2012 2:06 pm
                              Re: Hash table division Vincent Diepeveen Fri Apr 06, 2012 2:15 pm
                              Re: Hash table division Robert Houdart Fri Apr 06, 2012 2:24 pm
                                    Re: Hash table division Vincent Diepeveen Fri Apr 06, 2012 2:47 pm
                                    Re: Hash table division Ed Schroder Fri Apr 06, 2012 4:53 pm
                                          Re: Hash table division Robert Houdart Fri Apr 06, 2012 5:24 pm
                                                Re: Hash table division Sam Hamilton Fri Apr 06, 2012 5:29 pm
                                                      Re: Hash table division Vincent Diepeveen Fri Apr 06, 2012 8:33 pm
                                                            Re: Hash table division Sam Hamilton Sat Apr 07, 2012 1:39 am
                                                                  Re: Hash table division Vincent Diepeveen Sat Apr 07, 2012 8:42 am
                                                                        Re: Hash table division Sam Hamilton Sat Apr 07, 2012 3:11 pm
                                                Re: Hash table division Ed Schroder Fri Apr 06, 2012 9:55 pm
                                                      Re: Hash table division Vincent Diepeveen Fri Apr 06, 2012 10:25 pm
                                                      Re: Hash table division Robert Houdart Fri Apr 06, 2012 10:27 pm
                                                            Re: Hash table division Ed Schroder Sat Apr 07, 2012 3:27 pm
                              Re: Hash table division H.G.Muller Fri Apr 06, 2012 4:24 pm
                                    Re: Hash table division Ed Schroder Fri Apr 06, 2012 5:05 pm
                                          Re: Hash table division H.G.Muller Sat Apr 07, 2012 12:43 pm
                                    Re: Hash table division Vincent Diepeveen Fri Apr 06, 2012 5:14 pm
                  Re: Hash table division Robert Hyatt Fri Apr 06, 2012 8:44 pm
      Re: Hash table division Vincent Diepeveen Thu Apr 05, 2012 11:15 pm
            Re: Hash table division Ed Schroder Fri Apr 06, 2012 1:53 pm
                  Re: Hash table division Vincent Diepeveen Fri Apr 06, 2012 1:58 pm
                        Re: Hash table division Ed Schroder Fri Apr 06, 2012 2:10 pm
                              Re: Hash table division Vincent Diepeveen Fri Apr 06, 2012 2:23 pm
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