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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 2:29 pm Reply to topic Reply with quote
Rebel wrote:
diep wrote:
Rebel wrote:
bob wrote:
Rebel wrote:
When implementing hash tables in the days that memory was limited (1 Mb if you were rich) I set-up my hash table data structure as follows:

- One hash table for odd plies
- One hash table for even plies

And where ever possible make the odd ply HT twice as big as the even ply HT because that one is accessed the most due to the AB behaviour. And it also worked great in case of a full HT. Anno 2012 I wonder if that's still the case.

Anyone using a somewhat similar system ?


You realize that if you do an even-ply search, 1/2 of the hash stores are going to be from that last layer of even-ply searches??? That is, for every depth N-1 node where N-1 is odd, you will always see a depth N search (and probe).

I don't see why this makes any sense at all...

I have a display, it gives the percentages how both HT tables fill and the odd-ply HT fills a lot faster than the even ply HT. It's exactly what one might expect from a well ordered search. And so it makes sense to declare a bigger odd-ply-HT than an even-ply-HT. Just try yourself.


Maybe Bob didn't understand you mean odd iterations versus even iterations.

That's of course possible. But I mean from the root.
Code:
ply-1 e2-e4  (odd)   --> into odd-HT
ply-2 e7-e5  (even)  --> into even-HT
ply-3 Ng1-f3 (odd)   --> into odd-HT
ply-4 Nb8-c6 (even)  --> into even HT

Hope that clears things up


Yes very clear - sorry for the confusion.

Note that it doesn't seem like a very efficient scheme at todays computing Ed.

As from the mainline you'll get a huge amount of nodes where the even/odd just is reversed thanks to mainline reasons.

Ack - i should say : *behind* the mainline you get a lot of nodes with a minimal search window where even/odd just is the reverse of the allnode/cutnode property from what you wrote down.

You basically sort it now colorbased if i may say so.
In Diep i'm not doing that.

In fact i take care that positions from black and white that are the same, get stored nearby each other.

Advantage is that i can reuse the evaluation value better then, as the evaluation from white is of course -black ones. As i store it always from white side viewpoint no big deal in fact.

Besides that of course we have already probably in one of our caches this c acheline now from the RAM, so if we nullmove we get our hashentry for near free from the hashtable.
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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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