Fritz (12) and the limit strength feature

[Alexander Schmidt]

Does anyone know how to use UCI Limit strength features under Fritz? In the engineoption menu the feature is not available, so it must be somewhere else.

Under Training -> Rated games Fritz loads the UCI engine, sends the correct ELO value to the engine and then calculates itself. The UCI engine sleeps.

I really don't like that I implement some nice ELO feature, and the user thinks the stupid blunder moves by Fritz are done by my engine...

[kinderchocolate]

As far as I can remember, only Arena properly supports the UCI strength limit option. By the way, I've been studying how you implemented limit strength features and might include one of yours in my new GUI application.

[Alexander Schmidt]

If a GUI has no special implementation of the limit strength feature the options UCI_LimitStrength and UCI_Elo should at least appear in the engineoptions menu.

Shredder has also a good implementation.

[kinderchocolate]

How do you limit the strength? You slow the search, limit the number of nodes etc. But is this enough? And how do you tune and verify the parameters are correct?

[Alexander Schmidt]

The strength reduction is done only by limitation of the nodes per second. It works for SlowChess, with modern engines it is tricky because of presearch functions.

The tweaking is don by games against Emulations of dedicated machines in the range between 1450 and 2450 SSDF ELO. This games where played with the 2.96LS, the formula was simplyfied in the last versions, but the difference is tiny.

Code: Select all

1464 ELO Mephisto III*
1824 ELO Rebel 5 Emulation
1904 ELO MM IV Emulation**
1971 ELO Dallas Emulation
1974 ELO MM V Emulation**
2030 ELO Roma 32Bit Emulation
2445 ELO Resurrection Fruit 2.1***



                               Rtng    Score     12345678901234567890123456789012345678901234567890   Perf Chg
----------------------------------------------------------------------------------------------------------------
 1: Mephisto III                1464  27,5 / 50   11011111011=10=11001=100=00=10011=1=0=10010001=011   1500 +25
 2: Mysticum SlowChess ELO 1464 1464  22,5 / 50   00100000100=01=00110=011=11=01100=0=1=01101110=100   1428 -25
----------------------------------------------------------------------------------------------------------------
50 games: +24 =9 -17

                                Rtng    Score     12345678901234567890123456789012345678901234567890   Perf Chg
----------------------------------------------------------------------------------------------------------------
 1: Mysticum SlowChess ELO 1824 1824  32,5 / 50   =01=10110111101=0110110=110=1=101111=1011011100110   1934 +75
 2: Mephisto Rebel 5            1824  17,5 / 50   =10=01001000010=1001001=001=0=010000=0100100011001   1714 -75
----------------------------------------------------------------------------------------------------------------
50 games: +24 =7 -19

                                Rtng    Score     12345678901234567890123456789012345678901234567890   Perf Chg
----------------------------------------------------------------------------------------------------------------
 1: Mysticum SlowChess ELO 1769 1769  25,5 / 50   100=11=11001====101=010=10=1010=0011110001010101=0   1831  +5
 2: Mephisto Rebel 5            1824  24,5 / 50   011=00=00110====010=101=01=0101=1100001110101010=1   1817  -5
----------------------------------------------------------------------------------------------------------------
50 games: +16 =11 -23

                                Rtng    Score     12345678901234567890123456789012345678901234567890   Perf Chg
----------------------------------------------------------------------------------------------------------------
 1: Mephisto MM IV              1904  26,5 / 50   0010===10011=011011011=011101==01001001=1011=01==0   1925 +15
 2: Mysticum SlowChess ELO 1904 1904  23,5 / 50   1101===01100=100100100=100010==10110110=0100=10==1   1883 -15
----------------------------------------------------------------------------------------------------------------
50 games: +22 =11 -17

                                Rtng    Score     12345678901234567890123456789012345678901234567890   Perf Chg
----------------------------------------------------------------------------------------------------------------
 1: Mysticum SlowChess ELO 1927 1927  26,5 / 50   0011100=01=11100001=0=11==1===1==11=001=1====01001   1948 +15
 2: Mephisto Amsterdam          1927  23,5 / 50   1100011=10=00011110=1=00==0===0==00=110=0====10110   1906 -15
----------------------------------------------------------------------------------------------------------------
50 games: +22 =17 -11

                                Rtng    Score     12345678901234567890123456789012345678901234567890   Perf Chg
----------------------------------------------------------------------------------------------------------------
 1: Mephisto Dallas 16Bit       1971  25,0 / 50   ===11==110=1=1111=01==0=100100000011=0=011=0000110   1971  +0
 2: Mysticum SlowChess ELO 1971 1971  25,0 / 50   ===00==001=0=0000=10==1=011011111100=1=100=1111001   1971  +0
----------------------------------------------------------------------------------------------------------------
50 games: +25 =14 -11

                                Rtng    Score     1234567890123456789012345678901234567890123   Perf Chg
---------------------------------------------------------------------------------------------------------
 1: Mephisto MM V               1974  22,0 / 43   1=1011101011=001010011=0110=0=000==11=00011   1981  +4
 2: Mysticum SlowChess ELO 1974 1974  21,0 / 43   0=0100010100=110101100=1001=1=111==00=11100   1967  -4
---------------------------------------------------------------------------------------------------------
43 games: +18 =8 -17

                                Rtng    Score     12345678901234567890123456789012345678901234567890   Perf Chg
----------------------------------------------------------------------------------------------------------------
 1: Mysticum SlowChess ELO 2030 2030  29,0 / 50   ==10011=1011=0=01=1=101001=1111=1=1=1=0=11=0001010   2087 +40
 2: Mephisto Roma 32Bit         2030  21,0 / 50   ==01100=0100=1=10=0=010110=0000=0=0=0=1=00=1110101   1973 -40
----------------------------------------------------------------------------------------------------------------
50 games: +16 =14 -20

                                Rtng    Score     12345678901234567890123456789012345678901234567890   Perf Chg
----------------------------------------------------------------------------------------------------------------
 1: Mysticum SlowChess ELO 2011 2011  25,5 / 50   0110==010===1=11010=010==1100101010100110=10=10110   2037  +5
 2: Mephisto Roma 32Bit         2030  24,5 / 50   1001==101===0=00101=101==0011010101011001=01=01001   2023  -5
----------------------------------------------------------------------------------------------------------------
50 games: +22 =11 -17

                                   Rtng    Score     12345678901234567890123456789012345678901234567890   Perf Chg
-------------------------------------------------------------------------------------------------------------------
 1: Mysticum SlowChess ELO 2445    2445  26,0 / 50   1001==01010=10=00110==0011=1=1=110==101=0=10=11==0   2459 +10
 2: Resurrection Fruit 2.1 203 MHz 2445  24,0 / 50   0110==10101=01=11001==1100=0=0=001==010=1=01=00==1   2431 -10
-------------------------------------------------------------------------------------------------------------------
50 games: +22 =16 -12


Here some fast games:


                                Rtng    Score     12345678901234567890123456789012345678901234567890   Perf Chg
----------------------------------------------------------------------------------------------------------------
 1: Mephisto III                1464  27,5 / 50   0011101011===001011011101011101=1010000=1111100=0=   1500 +25
 2: Mysticum SlowChess ELO 1464 1464  22,5 / 50   1100010100===110100100010100010=0101111=0000011=1=   1428 -25
----------------------------------------------------------------------------------------------------------------
50 games: +28 =7 -15

                                Rtng    Score     12345678901234567890123456789012345678901234567890   Perf Chg
----------------------------------------------------------------------------------------------------------------
 1: Mysticum SlowChess ELO 1824 1824  28,5 / 50   0=1111=1=11==0=1011=0010=0=111110110==110010000101   1874 +35
 2: Mephisto Rebel 5            1824  21,5 / 50   1=0000=0=00==1=0100=1101=1=000001001==001101111010   1774 -35
----------------------------------------------------------------------------------------------------------------
50 games: +21 =11 -18

                                Rtng    Score     12345678901234567890123456789012345678901234567890   Perf Chg
----------------------------------------------------------------------------------------------------------------
 1: Mysticum SlowChess ELO 2030 2030  26,0 / 50   1111000000111001010==1111101010=0101=0==1101000101   2044 +10
 2: Mephisto Roma 32Bit         2030  24,0 / 50   0000111111000110101==0000010101=1010=1==0010111010   2016 -10
----------------------------------------------------------------------------------------------------------------
50 games: +31 =6 -13



A quick test of SlowChess 1000 ELO against Microchess 1976, just to be sure that SlowChess 1000 ELO is able to lose against this weakest thing available:

                                Rtng    Score     12345678901234567890123   Perf Chg
-------------------------------------------------------------------------------------
 1: Mysticum SlowChess ELO 1000 1000  18,0 / 23   =1=1=10111=111011111110   1310 +94
 2: Microchess 1976             ????   5,0 / 23   =0=0=01000=000100000001    780 -94
-------------------------------------------------------------------------------------
23 games: +11 =4 -8

It is hard to classify ELO values of 1000, so maybe at this level the values are not exact.


*Mephisto III = The Glasgow Emulation at 3,05 MHz. (Mephisto III runs at 6,1 MHz, the Glasgow Emulation is 2x faster because it is 16Bit instead of 8Bit)
**The MM Emulations where not able to play all games because they hang at some positions. Thats why there are less than 50 games.
***Resurrectiion Fruit 2.1 = Fruit 2.1 at the speed of a Resurrection 203 MHz. In the middlegame it plays like the Resurrection, in the endgame it is 5-6% faster which should not have much influence on the strength. The Resurrection Fruit `05 is listed in the SSDF list with 2395 ELO. Fruit 2.1 is around 50 ELO weaker in all ratinglists. Because the SSDF once reduced all ELO values by 100 I have to add this 100 ELO again. So this version should have quite exactly 2445 SSDF(old) ELO.

[kinderchocolate]

I see your idea. Just curiosity, the point of reducing strength is to allow a human beat the engine. If the engine isn't calibrated against humans on a real human playing scale, how accurate would that be? For example, if I was a 1400 rated and I played a LS engine 1400 rated. If I don't score around 50%, would that cause any problems?

[Alexander Schmidt]

It is of course dificult to compare. One human of1400 ELO maybe beats a computer of 1400 ELO easily, another human will lose. One will try some anti computer chess strategy, another is not aware of such things.

I just can try to get as close as possible to the human values. The ssdf values from the past where quite good calibrated to the human rating because the "new chess playing machines " where allowed to play in human tournaments. Of course I am interested in feedback about the strength of the ELO levels

[kinderchocolate]

I've played your LS engines. In fact I downloaded your engines every time you announced on talkchess. I think the reduced difficulty achieved isn't as consistent and smooth as I would have thought. For example, the LS feature in Shredder is better. I felt a bit artificial, I don't know how to express it but it's like Carlsen deliberately make very stupid mistakes because you have a gun pointing at him.

Would randomly selecting inferior PV lines in multipv mode work better?

[Alexander Schmidt]

Thanks for the feedback. At what strength and timecontrol did you play?

I didn't observe silly mistakes, probably mainly because I tested with long timecontrol.

[kinderchocolate]

I tested your engines with a human (myself). I wouldn't play it with a long control, every game was played at 5 minutes or something like two seconds per move. Maybe you should try a bit more in shorter control. Nobody would bother to sit and play a computer for a standard control. I also don't find much improvement in your LS settings against the default settings in Stockfish.