Computer Chess Club Archives




Subject: Re: Doesn't appear to work for me (full data)

Author: Uri Blass

Date: 16:57:54 11/21/02

Go up one level in this thread

On November 21, 2002 at 16:46:28, Omid David Tabibi wrote:

>On November 21, 2002 at 15:55:55, Uri Blass wrote:
>>On November 21, 2002 at 09:10:32, Omid David Tabibi wrote:
>>>On November 21, 2002 at 07:18:11, Uri Blass wrote:
>>>>On November 21, 2002 at 06:26:16, Uri Blass wrote:
>>>>>On November 21, 2002 at 06:25:17, Uri Blass wrote:
>>>>>>On November 21, 2002 at 04:52:13, Omid David Tabibi wrote:
>>>>>>>On November 20, 2002 at 22:05:29, Robert Hyatt wrote:
>>>>>>>>On November 20, 2002 at 16:55:41, Gian-Carlo Pascutto wrote:
>>>>>>>>>Nullmove in Deep Sjeng uses an algorithm of my own, but I can
>>>>>>>>>switch it back to other systems easily. I did so for running
>>>>>>>>>a few tests.
>>>>>>>>>I made a version which uses Heinz Adaptive Nullmove Pruning
>>>>>>>>>and a version which uses your verification nullmove.
>>>>>>>>This would seem to be a bit harder than at first glance.  They say that
>>>>>>>>if the normal null-move search fails high, then do a D-1 regular search
>>>>>>>>to verify that, but while in that verification search, no further
>>>>>>>>verification searches are done, meaning that the normal null-move search
>>>>>>>>fail-high is treated just like we do it today..
>>>>>>>>I'm going to experiment with this myself, just for fun, but it seems that you
>>>>>>>>need to pass some sort of flag down thru the search calls indicating that
>>>>>>>>you are either below a verification-search node or not so that recursive
>>>>>>>>verification searches are not done...
>>>>>>>Exactly!! (finally someone read the article carefully)
>>>>>>>See Figure 3 for detailed implementation (the flag you mentioned which is passed
>>>>>>>down as a parameter for search(), is called 'verify' in the pseudo-code).
>>>>>>>At first stage leave alone the zugzwang detection part (the piece of code at the
>>>>>>>bottom of Figure 3). Due to instablilities, some programs might do a needless
>>>>>>>re-search. First let the algorithm work fine in general, and then do the
>>>>>>>zugwzang detection part.
>>>>>>I let the algorithm to work without zugwzang detection and first results seems
>>>>>>not to be good
>>>>>>Some positions I get at the same depth and
>>>>>>the only position so far in the gcp test suite that I got at smaller depth for
>>>>>>tactical reasons is
>>>>>>[D]5rk1/1r1qbnnp/R2p2p1/1p1Pp3/1Pp1P1N1/2P1B1NP/5QP1/5R1K w - - 0 1
>>>>>>I am going to try it in 10 sedconds per move and get resulkts in half an hour.
>>>>>should be seconds,results,position
>>>>>I type too fast.
>>>>Here are the results of the new version:
>>>>1     39     39
>>>>2      9     48
>>>>3      8     56
>>>>4     11     67
>>>>5      6     73
>>>>6      6     79
>>>>7      5     84
>>>>8      4     88
>>>>9      4     92
>>>>10      2     94
>>>>results of the old version seem better:
>>>>1     40     40
>>>>2     17     57
>>>>3      8     65
>>>>4      7     72
>>>>5      6     78
>>>>6      4     82
>>>>7      8     90
>>>>8      2     92
>>>>9      3     95
>>>>10      1     96
>>>>Remember also that I tested the olf version at more than 10 seconds per move so
>>>>if it changed it's mind after 20 seconds from the right move to the wrong move
>>>>the position is counted as a failure.
>>>Did you use the exact implementation I described in Figure 3?
>>>BTW, you have to compare the algorithms at deeper searches. A fixed 10 ply depth
>>>will be fine.
>>Some notes:
>>I do not the exact implementation in figure 3.
>>1)I do not use null move pruning at depth=1 because I have other pruning and I
>>did not change it.
>>null move pruning is used by movei only when the depth is at least 2.
>>2)I did use research so I have not varaible to tell me about fail high and after
>>fail high, I trust the result of normal search(verify=false) with depth
>>that is reduced by 1.
>>3)I already tested it at 300 seconds per move(still without research) and I
>>expect to have results tommorow.
>>I am going to compare it with results of my previous version(null move pruning
>>I use also other pruning ideas that I did not change.
>I'm afraid that all these differences might result in a totally different
>structure. I strongly recommend you to try my exact implemenation first.

I am interested in the question if verification search can help movei to be
better so I compare time to get the solution and try first minimal changes.

1)If the target is to have something that is clearly superior to R=2 then I
believe that I already have it and not only because of R=3.

It means that I do not expect to do movei significantly better by removing

2)I am going to try later the following changes:

a)Replace depth>1 by (!verify||depth>1)
b)Maybe some changes of my pruning rules to try to make a) productive
c)Add research


This page took 0.06 seconds to execute

Last modified: Thu, 07 Jul 11 08:48:38 -0700

Current Computer Chess Club Forums at Talkchess. This site by Sean Mintz.