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Hi all,

Do pardon my ignorance. In a completed game, if I wanted to know the best move say on 25th move. What is the difference between
(a) if I use "analysis' mode to analyze 25th move and
(b) I let the engine to play at 25th move

both setting at say 18 plys?

Thank you!

Yours sincerely,
Kah Huat, Koh
- from Singapore

I personaly think that there is no difference at all for most of the engines....

As Dr.Wael Deeb said, for most engine there is no different. But for Rybka 3 there is a small difference because the contempt factor is not the same for playing (0.15) and analysing (0.0). I already checked that for some positions you can get different results. For example this one (if I remember well) with 256Mb hash

2b1q3/p7/1p1p2kb/nPpN3p/P1P1P2P/6P1/5R1K/5Q2 w - -

e5 seems stronger than Rf6+ but both win I guess. Rybka 3 choose e5 or Rf6+ depending on if you play or analyse.

genorb wrote:As Dr.Wael Deeb said, for most engine there is no different. But for Rybka 3 there is a small difference because the contempt factor is not the same for playing (0.15) and analysing (0.0). I already checked that for some positions you can get different results. For example this one (if I remember well) with 256Mb hash

2b1q3/p7/1p1p2kb/nPpN3p/P1P1P2P/6P1/5R1K/5Q2 w - -

e5 seems stronger than Rf6+ but both win I guess. Rybka 3 choose e5 or Rf6+ depending on if you play or analyse.

For analysing with Rybka 3,set the contempt factor to 0.0....

Dr.Wael Deeb wrote:

genorb wrote:As Dr.Wael Deeb said, for most engine there is no different. But for Rybka 3 there is a small difference because the contempt factor is not the same for playing (0.15) and analysing (0.0). I already checked that for some positions you can get different results. For example this one (if I remember well) with 256Mb hash

2b1q3/p7/1p1p2kb/nPpN3p/P1P1P2P/6P1/5R1K/5Q2 w - -

e5 seems stronger than Rf6+ but both win I guess. Rybka 3 choose e5 or Rf6+ depending on if you play or analyse.

For analysing with Rybka 3,set the contempt factor to 0.0....

I know thanks, this was to answer to Kah Huat, Koh.

I was also mentioning this because if you run automatized test suites under, for example, the classic Shedder GUI, then you are using the playing mode and you are not analysing (I do not know about Fritz GUI). So at the end of some tests, I saw that Rybka 3 did not find the best move, then I loaded those positions and analyzed them and Rybka 3 found the solution. Then I understood that contempt can play a role. Of course Rybka 3 will not go from a bad move to a good one just because of this contempt issue I guess, but still there is some slight differences, especially for test suites if the GUI use play mode. The same would go for automatized game analysis under Shredder GUI I guess (I would have to check). I would not be surprised if the play mode is also used. This mean that with Shredder GUI (at least) if you want to use those automatized tools (that are nice by the way), it's perhaps better to create a new Rybka 3 personnality where you set contempt play to 0 instead of 0.15. This is what I did. I hope I was clear with that explanation... not sure though

genorb wrote:

Dr.Wael Deeb wrote:

genorb wrote:As Dr.Wael Deeb said, for most engine there is no different. But for Rybka 3 there is a small difference because the contempt factor is not the same for playing (0.15) and analysing (0.0). I already checked that for some positions you can get different results. For example this one (if I remember well) with 256Mb hash

2b1q3/p7/1p1p2kb/nPpN3p/P1P1P2P/6P1/5R1K/5Q2 w - -

e5 seems stronger than Rf6+ but both win I guess. Rybka 3 choose e5 or Rf6+ depending on if you play or analyse.

For analysing with Rybka 3,set the contempt factor to 0.0....

I know thanks, this was to answer to Kah Huat, Koh.

I was also mentioning this because if you run automatized test suites under, for example, the classic Shedder GUI, then you are using the playing mode and you are not analysing (I do not know about Fritz GUI). So at the end of some tests, I saw that Rybka 3 did not find the best move, then I loaded those positions and analyzed them and Rybka 3 found the solution. Then I understood that contempt can play a role. Of course Rybka 3 will not go from a bad move to a good one just because of this contempt issue I guess, but still there is some slight differences, especially for test suites if the GUI use play mode. The same would go for automatized game analysis under Shredder GUI I guess (I would have to check). I would not be surprised if the play mode is also used. This mean that with Shredder GUI (at least) if you want to use those automatized tools (that are nice by the way), it's perhaps better to create a new Rybka 3 personnality where you set contempt play to 0 instead of 0.15. This is what I did. I hope I was clear with that explanation... not sure though

Hi Fabian,
You were more than clear and I agree with you....

Dr.Wael Deeb wrote: Hi Fabian,
You were more than clear and I agree with you....

Thanks!! Sometime I realize that my english is not always as good as I would like, this is why I am not always sure if I am clear

Thank you, guys!! Your help is much appreciated.


Best Regards,
Kah Huat, Koh