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Member since Dec-31-08 · Last seen Oct-21-16
About Me (in case you care):

Old timer from Fischer, Reshevky, Spassky, Petrosian, etc. era. Active while in high school and early college, but not much since. Never rated above low 1800s and highly erratic; I would occasionally beat much higher rated players and equally often lose to much lower rated players. Highly entertaining combinatorial style, everybody liked to play me since they were never sure what I was going to do (neither did I!). When facing a stronger player many try to even their chances by steering towards simple positions to be able to see what was going on. My philosophy in those situations was to try to even the chances by complicating the game to the extent that neither I nor the stronger player would be able to see what was going on! Alas, this approach no longer works in the computer age. And, needless to say, my favorite all-time player is Tal.

I also have a computer background and have been following with interest the development in computer chess since the days when computers couldn't always recognize illegal moves and a patzer like me could beat them with ease. Now it’s me that can’t always recognize illegal moves and any chess program can beat me with ease.

But after about 4 years (a lifetime in computer-related activities) of playing computer-assisted chess, I think I have learned a thing or two about the subject. I have conceitedly defined "AylerKupp's corollary to Murphy's Law" (AKC2ML) as follows:

"If you use your engine to analyze a position to a search depth=N, your opponent's killer move (the move that will refute your entire analysis) will be found at search depth=N+1, regardless of the value you choose for N."

I’m also a food and wine enthusiast. Some of my favorites are German wines (along with French, Italian, US, New Zealand, Australia, Argentina, Spain, ... well, you probably get the idea). One of my early favorites were wines from the Ayler Kupp vineyard in the Saar region, hence my user name. Here is a link to a picture of the village of Ayl with a portion of the Kupp vineyard on the left:

You can send me an e-mail whenever you'd like to aylerkupp(at)

And check out a picture of me with my "partner", Rybka (Aylerkupp / Rybka) from the Masters - Machines Invitational (2011). No, I won't tell you which one is me.


Analysis Tree Spreadsheet (ATSS).

The ATSS is a spreadsheet developed to track the analyses posted by team members in various on-line games (XXXX vs. The World, Team White vs. Team Black, etc.). It is a poor man's database which provides some tools to help organize and find analyses.

I'm in the process of developing a series of tutorials on how to use it and related information. The tutorials are spread all over this forum, so here's a list of the tutorials developed to date and links to them:

Overview: AylerKupp chessforum (kibitz #843)

Minimax algorithm: AylerKupp chessforum (kibitz #861)

Principal Variation: AylerKupp chessforum (kibitz #862)

Finding desired moves: AylerKupp chessforum (kibitz #863)

Average Move Evaluation Calculator (AMEC): AylerKupp chessforum (kibitz #876)


ATSS Analysis Viewer

I added a capability to the Analysis Tree Spreadsheet (ATSS) to display each analysis in PGN-viewer style. You can read a brief summary of its capabilities here AylerKupp chessforum (kibitz #1044) and download a beta version for evaluation.


Chess Engine Evaluation Project

The Chess Engine Evaluation Project was an attempt to evaluate different engines’ performance in solving the “insane” Sunday puzzles with the following goals:

(1) Determining whether various engines were capable of solving the Sunday puzzles within a reasonable amount of time, how long it took them to do so, and what search depth they required.

(2) Classifying the puzzles as Easy, Medium, or Hard from the perspective of how many engines successfully solved the puzzle, and to determine whether any one engine(s) excelled at the Hard problems.

(3) Classifying the puzzle positions as Open, Semi-Open, or Closed and determine whether any engine excelled at one type of positions that other engines did not.

(4) Classifying the puzzle position as characteristic of the opening, middle game, or end game and determine which engines excelled at one phase of the game vs. another.

(5) Comparing the evals of the various engines to see whether one engine tends to generate higher or lower evals than other engines for the same position. If anybody is interested in participating in the restarted project, either post

Unfortunately I had to stop work on the project. It simply took more time that I had available to run analyses on the many text positions for each of the engines. And, it seems that each time that I had reasonably categorized an engine, a new version was released making the results obtained with the previous version obsolete. Oh well.


Ratings Inflation

I have recently become interested in the increase in top player ratings since the mid-1980s and whether this represents a true increase in player strength (and if so, why) or if it is simply a consequence of a larger chess population from which ratings are derived. So I've opened up my forum for discussions on this subject.

I have updated the list that I initially completed in Mar-2013 with the FIDE rating list through 2014 (published in Jan-2015), and you can download the complete data from It is quite large (135 MB) and to open it you will need Excel 2007 or later version or a compatible spreadsheet since several of the later tabs contain more than 65,536 rows.

The spreadsheet also contains several charts and summary information. If you are only interested in that and not the actual rating lists, you can download a much smaller (813 KB) spreadsheet containing the charts and summary information from You can open this file with a pre-Excel 2007 version or a compatible spreadsheet.

FWIW, after looking at the data I think that ratings inflation, which I define to be the unwarranted increase in ratings not necessarily accompanied by a corresponding increase in playing strength, is real, but it is a slow process. I refer to this as my "Bottom Feeder" hypothesis and it goes something like this:

1. Initially (late 1960s and 1970s) the ratings for the strongest players were fairly constant.

2. In the 1980s the number of rated players began to increase exponentially, and they entered the FIDE-rated chess playing population mostly at the lower rating levels. The ratings of the stronger of these players increased as a result of playing weaker players, but their ratings were not sufficiently high to play in tournaments, other than open tournaments, where they would meet middle and high rated players.

3. Eventually they did. The ratings of the middle rated players then increased as a result of beating the lower rated players, and the ratings of the lower rated players then leveled out and even started to decline. You can see this effect in the 'Inflation Charts' tab, "Rating Inflation: Nth Player" chart, for the 1500th to 5000th rated player.

4. Once the middle rated players increased their ratings sufficiently, they began to meet the strongest players. And the cycle repeated itself. The ratings of the middle players began to level out and might now be ready to start a decrease. You can see this effect in the same chart for the 100th to 1000th rated player.

5. The ratings of the strongest players, long stable, began to increase as a result of beating the middle rated players. And, because they are at the top of the food chain, their ratings, at least so far, continue to climb. I think that they will eventually level out but if this hypothesis is true there is no force to drive them down so they will stay relatively constant like the pre-1986 10th rated player and the pre-1981 50th rated player. When this leveling out will take place, if it does, and at what level, I have no idea. But a look at the 2013 ratings data indicates that, indeed, it may have already started.

You can see in the chart that the rating increase, leveling off, and decline first starts with the lowest ranking players, then through the middle ranking players, and finally affects the top ranked players. It's not precise, it's not 100% consistent, but it certainly seems evident. And the process takes decades so it's not easy to see unless you look at all the years and many ranked levels.

Of course, this is just a hypothesis and the chart may look very different 20 years from now. But, at least on the surface, it doesn't sound unreasonable to me.

But looking at the data through 2015 it is even more evident that the era of ratings inflation appears to be over. The previous year's trends have either continued or accelerated; the rating for every ranking category, except for possibly the 10th ranked player (a possible trend is unclear), has either flattened out or has started to decline as evidenced by the trendlines.

Any comments, suggestions, criticisms, etc. are both welcomed and encouraged.

------------------- Full Member

   AylerKupp has kibitzed 9422 times to chessgames   [more...]
   Oct-21-16 Carlsen - Karjakin World Championship (2016) (replies)
AylerKupp: <Absentee> You've come to think of the free live feed as an acquired right, when it was only the blessed result of the lack of commercial interest.> I would think that most rights were acquired over time. And a right (although privilege might perhaps be a more appropriate
   Sep-23-16 J Torres Santiago vs Tito Kahn, 2016
AylerKupp: <<Sally Simpson> Here he is 300 pts. below his opponent, again he plays the Morra and sacrifices his chess set.> Thanks. Good to know in case I ever meet him across the board. :-)
   Sep-19-16 The World vs N Pogonina, 2010 (replies)
AylerKupp: <cro777> Comments on Schwetlick vs. Dronov, correspondence (part 2 of 2) Komodo opts for a completely different approach, replying at d=30 and earlier to 11.cxd5 with 11...Nxd5, resulting in a completely different game and no knight sacrifice on f2. It evaluates the ...
   Sep-10-16 AylerKupp chessforum (replies)
AylerKupp: <zanzibar> I did as you said and started the Stockfish 7 analysis after 45...Ra8. My Stockfish found 46.f3 immediately as White's best move with an eval of [+4.97] but it didn't find Black's 46...f6 until d=20 after 7 seconds and evaluated the eventual position at [+8.71] . ...
   Sep-04-16 Chess Olympiad (2016) (replies)
AylerKupp: <gopi11>, <Brankat> You might like this page better: . It lists the teams by standings orders as well as the game results for each of the team's players.
   Sep-02-16 Ghitescu vs Fischer, 1960
AylerKupp: <Sally Simpson> Yeah, it's like me getting questions about how to write short posts.
   Aug-30-16 Team White vs Team Black, 2015 (replies)
AylerKupp: <auh2o> To me the interesting part of the game started with 32.Bxe5 when White gets 2 pawns for the bishop, the initiative, and a beautifully posted (although not for long) Ne6. Alas, Team Black had apparently evaluated this position all the way to its conclusion and ...
   Aug-26-16 Fischer vs Petrosian, 1966 (replies)
AylerKupp: They were probably pretty close in playing strength. Although FIDE did not start to formally publish its rating list until 1970, Dr. Elo created several unofficial rating lists from 1967 to 1998. In his first list from June 1967 ( ), he ...
   Aug-22-16 Sinquefield Cup (2016) (replies)
AylerKupp: <<Sally Simpson> j'adoube> Great, just great. Too bad that non-chessplayers would not get it.
   Aug-19-16 Rubinstein vs Gruenfeld, 1929 (replies)
AylerKupp: Regardless of whether Gruenfeld had theoretical chances for a draw at the later stages of the game, from a practical perspective, entering into an endgame against Rubinstein with an inferior pawn structure was ill advised. Even with BOC.
(replies) indicates a reply to the comment.

De Gustibus Non Disputandum Est

Kibitzer's Corner
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Premium Chessgames Member
  juan31: To < AylerKupp>

In < Golden Executive forum > <Game Prediction Contest> for the <London Chess Classic 2015> tournament. Round 1 will be played next Friday December 4 16:00 GMT(UTC +0:00).

Carlsen, Caruana, Nakamura, Anand, Topalov, Grischuk, Giri, Aronian, Vachier-Lagrave, Adams.

Rounds: 9

The full pairings are released; the game prediction contest is open right now.

Just post your predictions before each round begins.

Premium Chessgames Member
  Golden Executive: Merry Christmas and a Happy New Year 2016 to you and yours <AylerKupp>!
Premium Chessgames Member
  WinKing: Merry Christmas & Happy Holidays to you <AylerKupp>!
Premium Chessgames Member
  wordfunph: <AylerKupp> Merry Christmas!
Jan-02-16  Dionyseus: <AylerKupp> My computer analysis shows that Fischer could have drawn the first game in his 1972 match against Spassky with 31...Ke7. I posted my analysis at Spassky vs Fischer, 1972
Apr-12-16  thegoodanarchist: Anyone know the last time a human beat one of the top programs in a game?

I was looking at Karjakin vs Deep Junior, 2004 when the question popped into my head.

Apr-12-16  Karposian: <tga> I think it may have been this game:

Ponomariov vs Fritz, 2005

Ponomariov had a bit of luck, though. Fritz made a strange blunder: 39..Bc2?

Apr-12-16  Karposian: Hi, <AylerKupp>. I was just wondering if you have read this Chessbase article that came out a couple of days ago?

It's about the ELO Rating System, and the tendency for higher rated players to underperform relative to the theoretical ELO probability, and for lower-rated players to overperform:

I thought you perhaps would find it interesting, considering your work with your game prediction spreadsheet.

Premium Chessgames Member
  AylerKupp: <thegoodanarchist> I'm assuming that you mean a "normal" game and not an odds game or a game with another engine assisting a top player like the 2014 Nakamura – Stockfish match or this year's Nakamura – Komodo match. Here is a link to a list of recent Komodo vs. human handicap matches: And these might be the latest victory by a human (GM Petr Neuman vs. Komodo 9, 2015, 2- and 1-pawn odds). Neuman won the match +3, =2, -1.

But, to try to answer your question, no, I don't know the last time that a human beat a computer in a non-odds match. I suspect that <Karposian> might be right and Ponomariov vs Fritz, 2005 might have been the last time. At least according to this article:

Quite a difference from today's GOTD: Bronstein vs M20, 1963 !

Premium Chessgames Member
  AylerKupp: <Karposian> No, I had not read that Chessbase article. Thanks for the link!

I had read Sonas' earlier article,, that described a similar effect, although not as pronounced. And also this article,, which also shows a similar effect but for a different reason, indicates the consequences, and alludes that this might be the reason for ratings inflation at the top level.

What makes Viswanath's article difference is that he associates the discrepancy between theoretical and actual performance to young players. But I don't know if the results he sees are literally due to "age" or if by "young" it could mean new to the game, not necessarily chronological age. If the latter is the case then it could simply mean that the formulas for estimating a young/new player need to be adjusted by, for example, having more K-factors than the 3 currently in use and using extrapolation to try to compensate for the lag between the young/new player's calculated rating and this effective rating due to his relatively fast rate of improvement. And his sample size is fairly small, 100 games, so I'm not sure if his results are statistically significant.

There are several errors in his article which make me wonder a little bit. For example, early on he says that "The original ELO formula proposes that a player who is 100 points higher rated should win a game with a 64% probability, and a 200 point difference gives approximately a 75% chance of winning for the higher rated opponent." This is not correct; a player who is 100 points higher rated had a win <OR> draw probability of 0.64, not a win probability of 0.64, which is definitely not the same thing. And originally Dr. Elo used a normal distribution for his calculations and it wasn't until later that a logistic distribution was found to give a better result between predicted and actual performance. But this is a minor point and only really significant when the rating differences are large.

Apr-13-16  thegoodanarchist: <AylerKupp: <thegoodanarchist> I'm assuming that you mean a "normal" game and not an odds game or a game with another engine assisting a top player like the 2014 Nakamura – Stockfish match>

Yes, in fact I almost typed "normal game" in my post, but figured you would assume it.

Apr-13-16  thegoodanarchist: <Karposian: <tga> I think it may have been this game:

Ponomariov vs Fritz, 2005 >

Cool, thank you!

Premium Chessgames Member
  WinKing: Only 2 more days!!!

♘Norway 2016♘ !!! Norway 2016 !!! ♗Norway 2016♗

This tournament will run from April 19th thru April 29th 2016.

Participants include: Magnus Carlsen, Vladimir Kramnik, Anish Giri, Li Chao, Maxime Vachier-Lagrave, Levon Aronian, Veselin Topalov, Pavel Eljanov, Pendyala Harikrishna & Nils Grandelius


<<> Norway 2016! <>>

< 3 Prediction Contests: (Win virtual medals - Gold, Silver & Bronze) >

User: lostemperor - Predict the order the players will finish. (3 categories to medal in)

User: Golden Executive - Predict the result 1-0, 1/2, or 0-1 (3 categories to medal in)

This year will be the 10th Anniversary for this contest! (from 2007 to 2016 - 10 years running)

User: OhioChessFan - Predict the result 1-0, 1/2, or 0-1 & the number of moves. (4 categories to medal in)

All three of the organizers <lostemperor>, <Golden Executive> & <chessmoron> have confirmed they will be running their contests for this event.


Also don't forget about <chessgames> ChessBookie game for this event. He can't wait to take some or all of your chessbucks. ;)

ChessBookie Game

Don't miss out on the fun for this Super Event!!!

Premium Chessgames Member
  zanzibar: Hi <AK>, just a note saying hello as a placeholder for any questions you might have re: filter program.


Premium Chessgames Member
  zanzibar: Just wondering, <AK>, if you plan on writing PGN parsing code in your steering program?

By this I mean, to the level of knowing if a move is legal or not, and to be able to map each move in an engine variation to a FEN yourself.

If you intend to write code at that level of detail, are you planning on using bitboards?

Premium Chessgames Member
  AylerKupp: <zanzibar> Thanks for responding. To answer your questions first, I did write a PGN parser (actually two) using Visual Basic for Applications (VBA). The first one was for my Analysis Tree Spreadsheet (ATSS, see my header above) and converts a *.pgn file into a *.csv file suitable for importing into Excel (I consider myself an Excel junkie). For each game certain fields in the game's header plus the game's moves fit into a single line of the *.csv file. This version of the PGN parser still does not handle comments since I've never been sufficiently motivated to fix it and something else always seems to be more important.

This PGN Parser version optimistically assumes that that the game moves in the *.pgn file are legal so it does not make legality checks. But as part of the ATSS (which has a viewer) I did implement sort of a legality move checker since each time a move is made it has to figure out the square that the moved piece came from. I think that I used a 12x12 square board (so that I didn't have to make special checks for a knight placed in a corner) and I indicated for each square whether it was empty or occupied by a piece or pawn.

I was proud that the move checker was table driven with a minimum of special coding. For each piece (and pawns) I had a table describing the pieces' move capabilities with special coding only for castling and pawn moves, captures (including en passant), and promotions. So that serves a similar purpose, if no source square can be found for the specified piece being moved then it's an illegal move. It shouldn't be too difficult to convert the needed VBA code to Python code.

The second PGN parser is a modification of the first which I'm using for the development of what I call the Single Game Predictor (SGP) for attempting to predict the results of individual games in major tournaments, a contest currently hosted by User: golden executive. It differs from the first PGN parser in that it looks and saves different fields and skips all the game moves. And, since it skips game moves, it doesn't care about legal or illegal moves.

As far as the SGP itself, it's proven to be more difficult and time consuming than I thought. I created a prototype that I used in 2 tournaments, and it successfully predicted 72% of the game outcomes in one and 69% of the game outcomes in the other. But I realized that the approach I used there was a dead end and I restarted with a different approach. And then my hard drive crashed and I didn't have any up to date backups (of course!) so I had to take my drive to a data recovery specialist that I hope will be able to recover most of the data. In the meantime, I'm writing a description of the SGP, what I have done and what I think I need to do so that when I get my data back (you have to be optimistic about these things!), I can proceed at a faster rate. I hope to have it finished in time for the London Classic in early Dec-2016.

As far as your filter program, could tell me in general terms what it does and how it's structured? I understand if you are hesitant to do so since I don't know what plans, if any, you have for it but I would be interested and appreciate anything that you are willing to share at this time. I was thinking of trying to write something like it to automate the data gathering for various tournaments so that I can validate the predictive ability of the SGP.

Premium Chessgames Member
  zanzibar: <AK> that's a lot to mull over...

We have different approaches, and toolsets, it seems. I don't use Excel so much, but rely on Octave for analysis (basically a Matlab clone).

None of the software I'm been writing uses any board representation - I generally treated the PGN movelist as a string for the PGN module I use. It was a practical decision, since I mostly wanted to map each game into an object where I could manipulate the tags (e.g. for normalization, etc.).

I do have some specialized routines to strip out comments and variations in order to compare the movelist strings between games, looking for duplicates or divergences etc.

This module has served me in good steed, and allowed me to work through a lot of Bistro stuff.

My recent engine steering program was cobbled together quickly too, in about a week. It's design goal is two-fold, to look for combinations, and to do "blunder"-checks.

This is a work-in-progress, but I'll be glad to describe it in the rough. It's really very simple-minded. So far, the vast bulk of the work is just getting the framework setup and working.

The first thing I did was attempt to replicate ChessTempo or Chess Tactics Server: (CTS) (CT)

One idea is to scan games looking for those that end in a mate, or a mate-in-progress. The idea is to backtrack from the end of the game until there isn't a forced mate, and go forward one ply.

This works rather well, until the mates are longish. Then a player might find suboptimal moves that still preserve the mate.

I could replicate <CT>, and diverge from the gameplay - but I haven't done so as yet. Besides, sometimes there's lessons to be learned from the different approaches.

Next, I added another routine to try to filter combinations, again searching from the end of the game, backwards.

Here I looked for moves that I denote as "sharp". That means running the engine in MPV mode, say 3. Then the main line (ML) is required to be demonstrably better than the other lines, by some programmable threshold.

That's what I mean by "sharp". There's a best move, and it's incontestable.

In addition, I require the game to be "won", as defined by another threshold.

Having found such a position in a game, I then backtrack again, as long as the position is sharp.

Doing so, I unwind the combination, hopefully back to it's start.

I would rate this effort a provisional success as well, especially given how crude the heuristic is.

Feeling a little bit overconfident, since I used a tactics-rich dataset for testing, I then decided to filter Sinquefield 2016.

Utter failure, only one game (Topalov--Svidler (R1)) makes the cut.

The reason, of course, is that super-GM's rarely make outright tactical blunders in classic games.

So, a refinement for my filtering-program was necessary. The idea is to find interesting positions, but with much lower thresholds.

Again, I look for "sharp" positions - but now I play the game forwards, and look at all positions, starting at move 10. The threshold is lowered to 0.75 at the moment. No win is required, just a clear "best-move".

This effort yields some modest results.

At this level of play, the hits are few enough that it's quite manageable to hand scan the games. I did this, using it to guide me to certain games, where I could compare my results with the kibitzing on <CG>.

It seems to be somewhat useful, though definitely still in need of refinement.

Premium Chessgames Member
  AylerKupp: <zanzibar> Your experience with the Sinquefield Cup 2016, like unfortunately many things, reminds me of a story.

Many decades ago when I was a young programmer I was working on systems software for automatic test equipment. The other software group, applications, wrote the actual code (in BASIC) to test the missile and aircraft modules on loan to us from the US Navy. All the applications code had supposedly been thoroughly tested.

The newly-promoted and equally young, supervisor of the applications software group (Jim) and I were sent to the big Navy base in Norfolk, VA for the first installation of the system. Nothing worked and the poor applications software supervisor was under a lot of stress. The applications software had indeed been "thoroughly" tested but, since the modules the US Navy lent us were working modules, the only software paths that were tested were the ones that verified that the modules were good. Now, with faulty modules being tested, all the fault isolation code that had never been run before was being run for the first time, and needless to say, most of it didn't work.

The bosses back home suggested to Jim that he run the test code that he had written since at least he was familiar with it. It also didn't work for the same reason. In exasperation Jim blurts out "There can't be anything wrong with this code, I wrote it."

At that point I put my hand on his shoulder and said "Jim, there are two things that a programmer must have, one is a sense of humor and the other is a sense of humility". Writing software, as I know you know, can be a humbling experience. And it is always in need of refinement.

Premium Chessgames Member
  AylerKupp: Back to chess. To answer your question about "insane levels of depth", for analyses during team games or as part of a Chessgames Challenge I often run the engines overnight (they don't seem to need sleep), about 8 hours or so. The depths that they reach depends on the engine and the position and they vary. I can't give you details because of the aforementioned disk crash (I'm still waiting hoping that at least some of my data is recoverable) but I typically aim to run Rybka to search depths at least in the mid 20-ply, Komodo and Houdini at least in the late 20 and early 30 ply, and stockfish in the early to late 30-ply, sometimes to the early 40-ply. Other engines I run somewhere in between. And, <RandomVisitor>, with his more powerful hardware, can get to deeper depths in the same or less amount of time.

The driving factor is what I've often said before, I let the engines analyze until I run out of either time or patience. That's how I arrived at these heuristics; the top engines are usually fairly evenly matched and they are rated by playing games with each other under the same time control. So I would think that the level of confidence that one can have in various engines' evaluations for analyses run for the same amount of time should be comparable. So the different search depths that various engines reach in the same amount of time should be comparable.

Some day as part of another project I will try to have various engines run an analysis on the same position(s) for the same length of time and see what search depths the various engines can reach in the same amount of time. The problem is that new engine versions are being released all the time, so it's a struggle to try to keep up.

With regards to the Stockfish issue, I have no idea. Perhaps it's just a hiccup which, in theory, should occasionally happen to all engines. And good luck to anyone who tries to find the cause without an extensive log file.

And I'm pleased to meet all your alter egos. :-)

Premium Chessgames Member
  zanzibar: <AK> a familiar programming story...

I have to say that I'd pretty good at finding bugs in programs - given my talent at putting them in there in the first place.

I'd like to return to the discussion of depth at some point in the future. I didn't follow your links previously, but I just took a quick look.

It seems your approach is designed for correspondence play - where the goal is to find the best possible move with unlimited time/computing power.

This is, of course, different than my design goals of finding combinations in games and/or interesting positions.

The discussion of depth would involve my other goal, which is using engines to optimize my own play. Note that this might not be the same as finding the optimal move for each and every position in a game(*).

(*) For openings, yes. For endgame play, where heuristics are more readily apparent, maybe. But for middlegame play?

Premium Chessgames Member
  zanzibar: Here's another example of Stockfish 7's fishiness (fishyness?)...

Nakamura vs R Aloma Vidal, 2016

Load the game up and jump to the ending, then back up to after Black's 45th move:

click for larger view

r4r2 /PKRR1pp1/4p1k1/4P2p/7P/6P1/5P2/8 w - - 0 46

Crude player that I am, I would likely have played the coarser 46.Rxf7 instead of Nakamura's more refined 46.f3 - which is better according to Stockfish 7?

Left to its own devices, it also finds 46.f3 as best (even allowing the engine a full 5minutes to cook on my laptop -

<+12.00 Nodes 1277494 (3924kn/s) Time 325.59s

1 ... 29 ... +11.98 ... 46.f3 f6 etc.

2 ... 29 ... +_7.64 ... 46.Kc6 Rae8 etc.

3 ... 28 ... +_7.40 ... 46.Kb f6


Ah, but put the GUI in trial mode with the engine running, play 46.Rxf7, wait a moment or two, and then back up to the same position.

How does Stockfish 7 evaluate the position now?

Do the experiment, and let me know how your setup compares the same position under these two conditions - I'd be mighty interested.

Premium Chessgames Member
  AylerKupp: <zanzibar> I did as you said and started the Stockfish 7 analysis after 45...Ra8. My Stockfish found 46.f3 immediately as White's best move with an eval of [+4.97] but it didn't find Black's 46...f6 until d=20 after 7 seconds and evaluated the eventual position at [+8.71]. The evals continued to climb and I stopped it at d=28 after 02:09 with an eval of [+77.37], although I'm not sure if that high eval is an artifact of the Syzygy tablebases.

I'm not sure what you mean by putting the GUI in trial mode. I use Arena 3.5 as my GUI and it doesn't have a "trial mode", at least not that I know of. But I set up the position assuming that White played 46.Rxf7 instead of 46.f3, cleared the hash table, and restarted the analysis. The results were similar; Stockfish evaluated the line starting with 46...Rxf7 (what else?) at [+1.62], d=8 immediately and then the evals started to climb and at d=20 the eval had reached [+8.29] after 3 seconds, not that much different than the [+8.71] it reached at d=20 after 46.f3. At d=28 after 01:00 the eval had reached [+46.97], again suggesting a Syzygy tablebase artifact.

I then restarted the analysis without clearing the hash table and it immediately (00:00) reached d=33 with an eval of [+123.41] which I know to be an Syzygy artifact indicating a forced win. Which makes sense since all the information from the previous run was still in the hash table.

I then went back to the position after 45...Ra8 without clearing the hash table. The hash table is now mostly invalid because it contained positions reached after 46.Rxf7 Rxf7 but Stockfish still found 46.f3 immediately with an eval of [+4.97], but didn't consider 46...f6 to be among its top 3 moves until I stopped it at d=29 after 02:59 when it reverted to 46.Rxf7 as being White's top move after 02:59, evaluating it at [+52.10]. It first reached a winning (artificial) eval of [+123.39] at d=30 after 04:24.

So I'm not sure what you're implying. If you're implying that Stockfish's evaluations and top moves are different under the different setups, that's to be expected. Chess engines, particularly multi-core chess engines, are non-deterministic; if you run an analysis of the same position on the same computer to the same search depth you will get different evaluations and likely different move rankings. Not MAY, WILL. Guaranteed. This has to do with the engine's pruning of its search tree, the ordering of the moves, and the influence of higher priority system processes interrupting the engine's executing threads, causing different move orderings. And Stockfish, because it probably has the most aggressive search tree pruning of all the top engines (that's why it gets to deeper search depths faster than any other engine I know), is more susceptible to this phenomenon than the other engines. So, if this is the Stockfish behavior you're seeing, don't consider it a "bug" or "fishy", just think of it as a "feature". :-)

Premium Chessgames Member
  diceman: Ayler/Zanzibar

Ever see a position like this?

click for larger view

Black to move.

Black is up material, but white has just played Qh6 threatening mate in one.

Premium Chessgames Member
  diceman: Some thoughts:

1)It's from an offhand, Game in 15 minutes game. (I was black)

2)I won in about 16 moves after
...Qd4+ (found out later with the
computer it's the only move to not get mated.

3)I let Fritz look at it for a while
and it only got to 20 ply and had
white lost at (-25).

4) I would have thought a computer
would easily find a win (or loss)
in a position with mate in one on the board.

A few horizon spite checks and game over.

5) I wondered if it could be used as a tactical test to "test" engines? (seemed like it was a workout for my
"pedestrian" Fritz)

6) I wondered if there had been something similar among top Grandmasters? (mate in one, unless you can win with a counterattack, obviously with some depth to the counterattack)

7) While Fritz hasn't given me the answer yet, my feeling is black has a forced mate before white can move.

Premium Chessgames Member
  diceman: Ok, one of the reasons this takes long to calculate is sometimes the mate threat needs to be removed and that just makes it a game where black is up material.

For example:

28...Qd4+ 29.Qe3 Qxb2+ (now white has no mate in one) 30.Ne2 d2 31.Nd3 Bxd3 32.Qh6 d1N+
(32.Qh6 reestablishes mate in one threat) 33.Kg3 Qxe5+ 34.Nf4 Qe1+ 35.Kg4 Ne3+ 36.Kg5 Qa5+ 37.Kh4 Nf5+ 38.Kg4
Nxh6+ 39.Kf3 Be4+ 40.Ke2 Qa2+ 41.Ke3
Rfe8 42.Ne6 Rad8 43.Nd4 g5 44.h3 Nf5+
46.Nxf5 Qd2#

Even though black is up heavy material
still some cute moves there like:




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