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Hash table division
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Robert Hyatt



Joined: 27 Feb 2006
Posts: 15816
Location: Birmingham, AL
PostPost subject: Re: Hash table division    Posted: Fri Apr 06, 2012 8:44 pm Reply to topic Reply with quote
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.


See my response to Sam. I simply counted wtm and btm positions throughout the search (none in q-search since I don't hash there) and found a reasonable balance...

I'll post the numbers in a few minutes, will have to extract and format...

Here we go.

First postion is BTM, kopec#22. Searched to depth=22
wtm=10,718,001 btm=8,587,532
time=39.66 mat=0 n=118,450,786 fh=95% nps=3.0M

The "even plies" (wtm, since BTM was root) were bigger, but not by a lot.

Next position is WTM, kopec#24, searched to depth=19
wtm=5411683 btm=6442429
time=49.83 mat=0 n=109541418 fh=93% nps=2.2M

Even plies (btm this time) slightly larger.

Next (and final) position is wtm, kopec#21, searched to depth=20
wtm=6760964 btm=3109970
time=15.51 mat=0 n=53688784 fh=94% nps=3.5M

This time the odd plies (wtm) is bigger.

I ran the entire set and saw absolutely no consistency other than the totals seemed to bounce to favor one side or the other about equal numbers of times...

Here's a few others just for fun, but just the wtm/btm counters:

wtm=7060090 btm=6452962
wtm=3893962 btm=3689548
wtm=9946589 btm=16398992
wtm=4324817 btm=6880681
wtm=8218700 btm=5259557



Those last ones were searched with a fixed time limit rather than a fixed depth...

Seems to be no correlation between STM and node distribution, nor odd/even ply depth.
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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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