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first25plus5 wrote:Something pointed out in Robin Smith’s book “Modern Chess Analysis” (Gambit books, 2004) are ‘ruler flat’ evaluations which indicate fortress draws. (or the evaluation tendency to ‘settle’ approximately so).
This evaluation behavior is further examined in a paper with later engines “Detecting Fortresses in Chess” (Guid & Bratko, 2012).
Example is if an evaluation eventually stabilizes at approximately say +2.24 and maintains this for some time then this behavior strongly indicates a fortress draw, despite a high evaluation for White.

From the article:

6 CONCLUSIONS

We introduce a novel idea for detecting fortresses in the
game of chess. We demonstrate that a heuristic-searchbased
program is able to detect fortresses on the basis of
backed-up values obtained at different levels of search.
If a particular position is a fortress, the program is not
able to show any progress towards a win and thus the
backed-up values cease to change significantly from a
certain search depth on.

Calling this idea "novel" in 2012 seems dubious, at best. Probably should not comment further...

Thank you for that.
I gleaned over the test suite with analysis and diagrams on the web (http://privat.bahnhof.se/wb432434/pos.htm), these are all open positions, except for #14. That means that in the remaining 15 positions stockfish should be irrefutable by humans. I checked that conjecture and indeed in 8(!) out of 15 cases the commentators got it wrong or backwards. How many points would you give for that??
I personally enjoyed this rebuttal the most:

[d]1rN1r1k1/1pq2pp1/2p1nn1p/p2p1B2/3P4/4P2P/PPQ1NPP1/2R2RK1 b - - 0 1

1..Rxbc8 2.Nf4 (allegedly the refutation) Nxf4! 3.Bxc8 Nxg2!

In #14 the alleged best move 1.Nb1, played by Kasparov, is neutralized outright by 1..b5 and black is well.
[d]r3r1k1/ppqbbpp1/2pp1nnp/3Pp3/2P1P3/5N1P/PPBN1PP1/R1BQR1K1 w - - 0 1


In #16 after 34.Qxc5 (stockfish) resigning is an option.
[d]2r2k2/5p2/2Bp1b1r/2qPp1pp/PpN1P3/1P2Q3/5PPP/4R1K1 w - - 0 1

Interestingly with the help of stockfish you might save even this position against a strong human master. Since after the 34. Rc1(?) Qxe3 35.Nxe3(?!) Bd8 36.Rc4(?!) Ba5 37.Nc2(?!) g4 38.Nxb4(??) it follows 38...Rb8 39.Bb5 Bxb4 40. Rxb4 f5! and white is only minimal better (stockfish).

Never trust your test suite.

zullil wrote: Calling this idea "novel" in 2012 seems dubious, at best. Probably should not comment further...

Yes... it's one of those things that make me wonder how it got past the referee. As it is, the paper points out some obvious points and proceeds to offer no real idea for how to handle fortress detection.
Saying that the engines "detect" the fortress by having a flat eval seems rather generous; I'd call not returning a draw score a sign of not detecting the fortress.
Still, the paper has a list of interesting fortress positions that I might use if/when I go back to tinkering with fortress detection.

MEA - Multiple move EPD Analyzer beta interface can be found here.

https://mea.bitballoon.com/

Ferdy wrote:MEA - Multiple move EPD Analyzer beta interface can be found here.

https://mea.bitballoon.com/

Thanks

Ferdy wrote:MEA - Multiple move EPD Analyzer beta interface can be found here.

https://mea.bitballoon.com/

Will try.