Strelka cannot see mate in 1

[Uri Blass]

[d]k7/2Q5/8/2N1K3/8/8/8/8 w - - 0 1

All programs that I tried except strelka and rybka beta can see the mate.


1.Qc7-d8+ Ka8-a7 2.Qd8-a5+ Ka7-b8 3.Qa5-b4+ Kb8-a7 4.Qb4-b7#
+- (#4) Depth: 1 00:00:00

(, 06.03.2008)

Note that 3...Ka7 is wrong in this line because 3...Kc7 avoids mate in 1.

Uri

[hgm]

How do you know it does not see the mate. It might simply be that it does not go for fastest mate (and by symmetry, for black does see no reason to delay the mate, explaying the move 3. ..., Ka7).

[Uri Blass]

How do you know it does not see the mate. It might simply be that it does not go for fastest mate (and by symmetry, for black does see no reason to delay the mate, explaying the move 3. ..., Ka7).

I guess that you are right and all the mate scores are equal for it.
The surprising thing is that with this behaviour it can practically win games even when the oppoent does not resign and not because of the 50 move rule.

If I run it in console mode then strelka announce mate in 4 and it get this score in the first iteration but looking at the code
I see that it is simply using the length of the pv to decide about the mate score.

Uri

[hgm]

I guess it gets it in the first iteration because of check extensions (checks in QS) and mate-threat extensions and such.

In a real game the problem might be smaller, because even in the face of extensions it will still be likely to see the closest mate first. The problem here is that you start so close to the mate that even deeper mates are already within the horizon in the first iteration.

[GenoM]

it does not go for fastest mate

This is right. If Strelka sees any mate it goes for it no matter if there is shortest path.

[rightrook]

Hi...Dedicated machines do that a lot...they often prefer taking a longer way to checkmate even in a very simple problem set up...

regards

Robert

[T Barack]

Is Strelka a legal engine now ?
And if the clone engines can be talked about freely in ccc?

But I still have read some old threads in ccc as follows:

Have you seen the threads in Rybka forum?
Some guys disassembled Strelka 1.0 or 1.8, i don't remember which one exactly, and posted results in a thread.

There were:
1)Huge segments of data with same values. Means-Rybka eval and material imbalance tables were copied.
2)Segments of code that corresponded to the search. Was the same. Two different search functions do not produce the same assembly code. Even if you give a same algorithm and they have 2 (equivalent!) implementations, they are very unlikely to produce the same assembly code. If the algorithm is complex enough. Rybka's search is complex enough, so we have to deal with something extraordinary here.

Then, there were a couple of threads where people posted positions were Rybka had faulty evaluation/bug, and Strelka too. They tried other engines -none produced the bug. It's not the same eval, the same line-its a BUG.


Some people claim everything is a clone. For them-evidence is a blind belief in good Vasik and evil russians. When they see same UCI strings and similar playing style, it's over. You cannot change their mind.

In the begining Vas was not saying Strelka is a clone. He was saying that, say, displaying +-320 as a mate score is very natural (he said it's something like the biggest value you can store in a hash entry), not implementing underpromotion is very natural too, and people should not make claims about clone based on that. However, after they posted the search stuff and the data tables, he pretty much changed his opinion.

I don't know what is enough evidence for you. For me, however, same assembler footprint for the SEARCH, same CONSTANTS, same BUGS is more than enough.

Is that true?

[pedrox]

Of course Strelka is a legal engine, you can download it and play with it and you will have no problem with the law as a result.

There is a lot of information on how it's done Strelka, so everyone can consider whether it is a clone or not, at least until there is a complait and a ruling by a judge.

Talking about a murder does not make one a murderer, and in CCC you are or you should be to able to speak freely of what you want, always you not break the rules of the forum.

[T Barack]

Of course Strelka is a legal engine, you can download it and play with it and you will have no problem with the law as a result.

There is a lot of information on how it's done Strelka, so everyone can consider whether it is a clone or not, at least until there is a complait and a ruling by a judge.

Talking about a murder does not make one a murderer, and in CCC you are or you should be to able to speak freely of what you want, always you not break the rules of the forum.

I agree, totally. But someone else would not. They still consider Strelka as a illegal clone and the clone engine will break the rules of the forum, right ?

[pedrox]

But my words do not give place to doubts, I would not support take a engine, change the author's name and publish it with another name.