Computer Chess Club Archives




Subject: Re: listing a few beginner bugs in Omids 'research'

Author: Uri Blass

Date: 16:54:06 12/17/02

Go up one level in this thread

On December 17, 2002 at 19:16:26, Vincent Diepeveen wrote:

>On December 17, 2002 at 18:21:28, Uri Blass wrote:
>>On December 17, 2002 at 18:11:20, Vincent Diepeveen wrote:
>>>On December 17, 2002 at 17:30:36, Bruce Moreland wrote:
>>>if you go back in time a bit you see that i had
>>>major problems with Omids article and posted it here.
>>>there is more than just the problems you see there.
>>>also look at his homepage and get the positions he tested
>>>and then look to his node counts. for a mate in 2 position
>>>where i need like a couple of hundreds of nodes to get to 10 ply
>>>he needs 10 million nodes. then R=3 reduces that more.
>>>also his implementation is buggy of course. it doesn't take into
>>>account problems with transpositions. a classical beginners problem.
>>>But most important is that verification search is not something new
>>>it is a buggy implementation of something already described years ago
>>>with only 'novelty' that omid turns off nullmove *completely*
>>>after he finds a nullmove failure.
>>No he does not.
>>There is no point in the tree that he turns off nullmove completely.
>>>All with all a very sad article. The only good thing about it is
>>>the quantity of tests done.
>>>The test methods and the implementation and the conclusions are
>>>grammar school level.
>>>I do not know who proofread it, but it gotta be idiots or people who
>>>didn't care at all.
>>>Amazingly Bob defended Omid here and said nothing was wrong with
>>>the article.
>>Bob also found that verification search is good for crafty based on his post.
>>Bob is not the onlyone who defended Omid.
>>I also defend him and you are the only poster who attacks him(even posters who
>>said that it did not work for them did not say that it is very bad).
>>Most of what you say is not correct.
>You are dreaming.
>Ok to list a few bugs in his paper:
>  a) all his test positions are mates and he doesn't do
>     checks in qsearch so R=2 versus R=3 matters a lot because
>     of the extra ply you miss of the main search finding the
>     mate for you. So if your qsearch is so buggy it is logical
>     that R=2 works at depth==9 better than R=3 at depth==9,
>     this is *trivial*. It is so trivial that no serious researcher
>     should compare the same plydepths with each other without
>     taking into account time.

not all his test positions are mates
I believe that most of the test positions are not mates.

The fact that R=2 works at depth=9 better than R=3 at depth=9 is not the point
of the research.

>     Because we are going to conclude that minimax search is better
>     than alfabeta for sure.
>  b) now already assuming the bug in his comparision is there to
>     compare depth==9 with depth==9 instead of the factor time,
>     then the bug is that he is just testing mates so reduction
>     factor matters. It is trivial to try adaptive nullmove then.
>  c) there is major bugs in the program Genesis looking at the
>     branching factor differences between R=1, R=2 and R=3.
>     I do not know a single serious chess program that has
>     such a difference.

Genesis is not his serious program but it does not mean that there are bugs in

>  d) Genesis needs way too much nodes to get to a decent plydepth
>     when compared to even programs doing checks in their qsearch
>     and extensions in nominal search. For mate in 2 he needs like
>     10 million nodes to get to depth == 10.

You look at the wrong positions
The time that it needs to get depth 10 in mates in 2 are not interesting and can
be ignored but there are enough positions that are not forced mates.

>  e) illegal position in his testset.

He replied that this was simply old positins in his site and he did not use the
illegal position.
>  f) his algorithm is not new. It is a rewrite of something already
>     existing and he rewrote it wrong. He has a bug in his verification
>     search. You can easily proof it by using transpositions.

I do not know what you talk about.
>  g) It won't detect a zugzwang for sure simply because of transposition
>     bugs. Therefore the only claim can be that it is enhancing tactical
>     abilities of his program.

It can detect zugzwang but only if there is not more than one zugzwang in the
same line.

 Therefore it is crucial to also test
>     different forms of adaptive nullmove (with different depths to
>     go from R=3 to R=2).
>  h) It is unclear why he concluded verification search is better using
>     his own data.
>       a) more Fullwidth search than verification
>          clearly finds more positions.

he did not compare verification search with R=3 but only verification search
with R=2.
There is no conclusion if verification R=3 is better than R=3 based on the

The games that he did were against R=2 and not against R=3.

>       b) R=3 uses less nodes than his verification search.
>     it is very unclear how he concludes then that verification search
>     is better. It's topping nowhere a list of 'this works better'.

>   i) Even from where i sit and without having genesis i can already smell
>      that adaptive nullmove works better than his own verification search.
>      his beloved verification search you can easily write down what it is
>      doing on paper. It's simply avoiding to nullmove last few plies
>      initially. So there is always a form of adaptive nullmove that is
>      going to completely outgun it simply.

It does not avoid nullmove and it is using always R=3 after null in the search.
If you use always R=3 after null then you can expect to use R=3 in most of the
tree when you search deep enough.
>   j) the testset is just basically mating positions in all tests.
>      that's a very dangerous ground to conclude things.
>Note that at depth == 10 ply i solve with diep with R=3 i solve far more
>positions in way less nodes than this guy ever will. This testset is just
>too simple.

Your comparison is wrong.
genesis is not a top program and omid never claimed that it is a top program.
If you have better qsearch and better order of moves and better extensions you
may solve more positions with less nodes.

I also remember that genesis does not do check extensions except the last ply
but it proves nothing.

Part of the programmers of good amateur found that the idea is productive for
them(I do not say that it is productive for everyone but I do not see the point
of attacking genesis when Omid has a better program that is not public).

It is better in the future to use also other programs before publishing but Bob
found that it is also good for crafty in test suites and games.


This page took 0.02 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.