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Hash table division
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Sam Hamilton



Joined: 23 Jun 2006
Posts: 1095
PostPost subject: Re: Hash table division    Posted: Sat Apr 07, 2012 3:11 pm Reply to topic Reply with quote
diep wrote:
BubbaTough wrote:
diep wrote:
BubbaTough wrote:
Houdini wrote:
Rebel wrote:
Houdini wrote:
Rebel wrote:
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.

Why does it result in a faster search?

Because of testing, what else is the final measurement?

You didn't answer the question.
WHY would splitting up the hash table accelerate the search?


One possibility is if the hash associativity is the same (seems 4 is usual) then you are getting a better hit rate because none of the opposite color_to_move positions are competing for the same spots.

-Sam


The table is 2x smaller, don't forget to factor that in Smile


The total size allocated for hash is the same, its just a matter of what spot a position can go into. I would guess for most searches nowadays its about 50/50 between black and white to move, which Bob's results seem to support. So splitting the hash into 2 hashes may very well be a good idea, but they should probably be the same size for most.

-Sam


Ed's assumption is that his table is 1.5 times the size you can allocate.

He's using an AND instruction to find the index and if you have 1 GB of RAM in total then you can't use the entire RAM for hashtable.

So YOUR hashtable then is 512MB and HIS hashtable then is 768MB.

Get the idea?

Now Diep's hashtable implementation is slow anyway, so i 'waste' a single multiplication instruction (thanks to Dieter Buerssner for explaining that to me a year or 10+ ago) and can allocate 899MB maybe, so i beat both of you - that's not the discussion here Smile

You are using AND instruction?

p.s. Ed always got huge nps and remember that those cards he sold one day - chessmachine schroeder - they had in total like a 1MB ram or so - hashtable size matters a lot then.

p.s.2 unlike my expectation Kermit scored in the Muppet Show yesterday, so standings right now: Kermit 1, rest of the Muppet Show 0. Not bad knowing Kermit already lives for a while from his pension...


Ahhh...OK. Thanks for explaining it.

-Sam
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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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