Another issue is how well the engine does analysis working backward through a game. This is not a skill that is used during an engine tournament. There are also skills that are important for engine matches, but much less so for analysis, like time management.
So much as we might like there to be a strong correlation between the two, it may not really exist.
>you are generally looking for the best move (which may be impossible to find)
Especially if it's a bishop underpromotion. :-P
>the best move (which may be impossible to find)
Surely you recall the Harrwitz-Staunton repartee (from Bird's Chess History and Reminiscences):
Staunton pretended sometimes not to see Harrwitz, and would look round the room and even under the chairs for him when he was sitting at his elbow, which greatly annoyed Harrwitz, who, however, sometimes got a turn, and was not slow to retaliate. In a game one day, Staunton materially damaged his own prospects by playing very tamely and feebly, and testily complained - "I have lost a move." Harrwitz told the waiter to stop his work, and search the room until he had found Staunton's lost move, and his manner of saying it caused a degree of merriment by no means pleasing to the English Champion.
It does not mean that always the better engine in games is better for analysis but when there is a big gap it is clear that the better engine is better.
3000 engine may be better than 3100 engine for analysis but
I do not believe that 2700 engine can be better than 3100 engine for analysis.
branching factor is clearly unimportant because branching factor tell you nothing about playing strength.
smaller branching factor can be result of better order of moves or better pruning that prunes only additional bad moves and in this case it helps and smaller branching factor may be result of unsound pruning that prunes good moves and in this case it may be counter productive also for games.
In correspondence games the target is also to win against the opponent and not to find the best move and it is better to avoid serious blunders.
If you cannot trust non rybka engines in the task of avoiding serious blunders then you certainly need rybka to avoid them.
Zappa also has some intangible advantages when it comes to doing analysis:
- It is much better at remembering the results of multiple variations when doing backward analysis. We all know how frustrating it is to check out a sideline and then come back to the mainline and see that Rybka has forgotten why the position is so good or so bad.
- Zappa allows more flexibility in controlling the engine. Zugzwang in an endgame position? Turn off null move. Think there is a potential mating sequence? Turn on mate extensions. etc.
Of course there are limits to this. You can't expect to compete doing analysis with an engine that is 300 Elo in the hole.
Rybka certainly has her uses. There is no engine better at doing overnight forward searches from the root to try to find deep opportunities or traps. But saying branching factor is unimportant is, I think, a mistake when looking at an engine's suitability for analysis. Rybka seems to have the lowest branching factor for a top engine. Zappa is on the other end of the scale (Anthony didn't get around to adding futility pruning until after the match in Mexico). In my opinion, the fact that these two approaches give results that are at least in the same ballpark Elo wise means it makes sense to look at both of them.
As far as correspondence games go, if you're happy getting mostly draws and a few wins from opponent blunders, avoiding bad moves is a reasonable strategy. In tournaments when you need a high score to win, this may not be the best strategy.
1)For the future rybka3 is relevant so the gap to zappa may be 150-200 elo.
2)It is possible to achieve lower branching factors by many ways so the analysis is important and not the branching factor.
lower branching factor may mean some unsound pruning so you do not find some good moves and it also may mean good pruning when you prune only illogical moves and reduce almost always illogical moves so I cannot say if smaller branching factor is good or bad.
Bigger branching factor can be achieved by good extensions when the extension help or by extending too much when the result is that you cannot see deep enough in the important lines.
Only knowing the branching factor simply tells me nothing.
You can say that rybka may sometimes miss good moves regardless of time that zappa finds and this may be a relevant comment.
I have been playing Zappa against the predominantly Rybka engines in the CB engine room, and have not had a problem maintaining a winning percentage well above 50% with average hardware. This is done by favoring openings that lead to positions that are closed and/or require king attacks where Zappa seems to outperform Rybka. Will this change when R3 comes out? I suspect not, but we shall see.
I would be very happy if people would use only Rybka to do their analysis. Every engine has weaknesses, and once these are identified, anyone who is overly reliant on this one engine will be susceptible to exploitation of those weaknesses.
I may be wrong but I guess that things are going to be changed with rybka3.
100 elo improvement is not nothing but maybe larry can say if there is improvement in rybka in king attacks or in closed positions.
Maybe R3 will cure all of its R2.3.2a's problems and be a more well rounded engine, but given the way that Vas and Larry test I tend to doubt this. Their tests allow very weak play in a minority of positions to be counterbalanced by stronger play in the majority of positions. This approach tends to allow weaknesses that occur in only a small percentage of positions. The trick is to be able to find these positions where they occur close to the starting position so that they can be exploited.
By the way, I do not think it would be impossible to come up with a set of openings which allow movei to be very competitive with Rybka. I have previously posted some games that reached these types of positions. Of course this would be easier if movei was 10X faster. :-)
I searched in your post and finding the link
I did not work recently about movei and I will probably not do it in the near future and
it is encouraging to see that movei can beat rybka in the right type of positions.
As I think you've stated in the past, Movei would probably be very competitive if it were 10X faster. That's obviously much more easily said than done. Adding in MP capability and taking advantage of 64-bit processing would probably get you about half way there (in a geometric sense).
>Their tests allow very weak play in a minority of positions to be counterbalanced by stronger play in the majority of positions. This approach tends to allow weaknesses that occur in only a small percentage of positions.
Yes, it is interesting that the VR/LK testing régime seems not to actually look at any positions (unless Iweta is still doing this). My own personal methodology has been loath to tend toward this extreme.
I believe that Larry does not test random changes but test changes that he believes in them.
Changes that he believes in them are probably based on positions when rybka went wrong so
I believe that he looked at positions before deciding what changes to test.
This is a very interesting statement. As we all know, a lot of draws occur when an engine unwittingly locks up the position. Rybka was probably worse than most in this regard because for instance it would frequently lock up its attacking pawns in opposite castled positions, thereby killing off its own attack. Do you believe you have made good progress in preventing this from happening? I suspect that fixing this one problem might add a few Elo points all by itself, since it is seen so frequently.
>...we should have "contempt" for everyone and everything!
LOL. This would make a great public relations quote on Rybkachess.com :-)
Also does this make a difference in analysis (displaying not 0.00 for repetition)?
Jeroen has stated on multiple occasions that the Zappa team lost the book battle convincingly. This would imply that Rybka lost the over the board battle even more convincingly...
>Jeroen has stated on multiple occasions that the Zappa team lost the book battle convincingly.
In fact, he said: Zappa won the match because it made fewer mistakes. If we would reverse the openings and replay the match, I fear it could be something like 7-3 for Zappa.
See also this thread about the book battle.
wow, didnt know that. kudos to jeroen.
"This would imply that Rybka lost the over the board battle even more convincingly..."
i dont think we can make that determination over a sample size of 10 games.
For the 10 game match, Zappa started in the hole on many of the games and still came out with a positive score. It was the better engine during this 10 game match.
maybe zappa was better given those match conditions, but not because it "won the match." by that logic, if fritz were to win a 2 game match against rybka, one would say "how do i know that? fritz won the match." 10 games simply isnt enough.
ok, i'll concede that. but only due to sample size. :-)
what do u mean by crush? can u give quantify this? such as an elo or expected score rating (overall a large sample size, of course)?
didnt someone say erdo has extensive knowledge of what positions rybka 2.3.2 plays poorly, and used that knowledge to construct an "anti-rybka" book for the mexico match?
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