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Play a slight variant of chess for computer resistance

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Play a slight variant of chess for computer resistance

Postby kflyer » Mon Nov 28, 2016 10:23 pm

Hi, I'm a new member and I joined because this site seems to have lasted many years and to have a dedicated membership. Given that, I'd like to see if the site admin, and any number of members, would be interested in having this site developed to allow playing of a variant I've found out about that cannot be played by computer engines.

Of course, most variants can't be played by computer engines. This one however looks and feels so much like chess that it almost seems to be a natural extension of chess. I know the inventor and he did post an article on chessbase.com about it (apparently he was invited by Frederik Friedel of chessbase to post the article). This happened in early 2014. The inventor hasn't had time to promote it, but I am so taken by it that I want to see if a site like this that plays only correspondence would have any interest.

The basic rule changes are this: the first 16 moves of the game (8 moves by White, 8 moves by Black) are normal chess rules. Thus all chess openings are played as normal up to the 16th ply inclusive. After that, each player has 12 chances to play an "option" on his or her move. An option is simply a play of 2 moves, with certain restrictions (1st move cannot give check or capture, if a single piece is moved twice it cannot capture on the 2nd move either, but the 2nd move can give check).

The key thing is that you have to judge when it is best to use your 12 options, and when it is better to pass and just do a single normal chess move. Saving options for the endgame makes them more powerful, but if you try and save them all, you could get swamped in the middlegame.

After Black's 32nd move, each player gets 4 more options. This helps to ensure that options are available in the endgame.

That is basically it, although there are a few other minor points, including a very neat "en passant" rule when a player moves a single piece twice in an option play. I can send the admin or anyone else here a complete document of the rules, and it also describes how a game is annotated. And I have a copy of a Word document of 2 annotated games that the inventor played against a 1700 level player that I can also provide to anyone here.

Any programmer who writes computer chess engines will have great trouble writing a strong engine for this variant. That's because of 2 things: first, the search tree grows exponentially, and second, there is no good algorithm for an engine to figure out whether to use or to save options in a specific situation. Humans have greater intuition for these kind of decisions.

The site developers would have to write new code to handle allowing the playing of options and saving of games in a slightly modified pgn format (basically, a move where an option is played has the moves separated by a comma, i.e. 9.Ne4,f4 means White played Knight to e4 and pawn to f4).

This site could go down in history as being the first place where players could play Option Chess online. I'd be willing to play any number of games against any number of opponents. The play is very challenging, some of the lines of analysis in the annotated games I mentioned will floor you!

Since everyone here obviously loves to analyze chess, and Option Chess is really just extended chess (no fairy pieces with weird moves, no larger board), this site seems ideal to make history with Option Chess. Thanks for reading, cheers!
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Joined: Mon Nov 28, 2016 9:51 pm

Re: Play a slight variant of chess for computer resistance

Postby kflyer » Thu Jan 05, 2017 1:55 am

Ok... almost 1200 views and no replies. I'm seriously considering offering some kind of incentive for people to play this, such as... giving N players (to be determined how many) the chance to play me at this game at typical correspondence time controls, with prize money to the first person to defeat me (and I have to respond to moves in the order they were made). I'm an 1800 level chess player and there is no computer engine that can play this game, so someone would win money for sure.

But before I do that, let me reproduce the Option Chess problem that the game's inventor put into his chessbase.com article. Those of you with the time and inclination to investigate this variant can take a half hour and see how it works for yourself. Here's the FEN position:

4rQ2/pk1q2P1/1pp5/3p4/2P1P1b/P2RnN2/3RrN1p/7K b - - 0 50

As the author notes, in standard chess this is rather non-descript and has no mating or winning lines. A normal chess engine gives Black about a pawn edge, with the following best line: 1.... Rxd2 2.Rxd2 Qe7 3.Qxe7+ Bxe7 4.Ng5 Nf5 5.Ne6 Bf6 6.Kg2 Bxg7 7.Nxg7 Nxg7 8.Kg3 Nf5+ 9.Kg4 Nd6 10.a4 Nc4 11.Rd3 Rg8+ 12.Kf3 Rh8 13.Kg3 Nd6.

But in Option Chess, it is Black to move and mate in three! But you need to know how many Options (double moves) each player has remaining: for Black it is 3, for White it is 4.

Here is the text of the solution taken directly from the chessbase.com article... this will give you some idea of the new possibilities this variant introduces:

"First let’s examine two options that do not work: 1...Qh3, Re1+. At first glance, it appears the queen cannot be captured because only one move of a double move may capture. Because of the check the black rook must be captured, while a non-capturing, non-checking move may being played first. However, this is mistaken. White can play 2.Ng1, Nfxh3, and all of Black’s threats are gone. So White didn’t have to capture the rook, he could block it instead, which allows capturing of the queen.

Here's the second option that doesn't work: 1.... Qh3, Qg2+. This is a legal move, but it allows the special en passant capture of 2.Nxh3e.p. Also take note that 1.... Qh3, Qxf3+ is an illegal move because if a single piece is moved twice, neither of its moves may be a capture.

The solution begins with 1…Qh3, Bxf2. Note that White’s king has not been put in check, but there are mate threats on g2 and f1. And in this case, Black’s queen cannot be captured. White cannot play 2.Ng5, Ngxh3 because a piece being moved twice cannot capture at all, not even on the second move. White could try something desperate like 2.Rd1, Rg1, but this is taken care of by 2…Qxf3+. White could try 2.Rd1, g8=Q but this runs into 2…Qxf3+ and if now 3.Rg1, Qg2, Black has the incredible 3…Re1,Qxg2#.

Even the remarkable 2.Rd1, Rxe3 doesn't quite work despite removing the powerful knight. Black cannot play 2.... Re1+, Qf1+ because both moves are checks. But Black has immediate mate anyway with 2.... Be1, Qg2#. The Be1 move is cute, uncovering the rook to support the Queen's mating move. And White cannot play 3.Nh4, Nxg2 because the second move is a capture making the move illegal.

White’s best chance seems to lie with 2.g8=Q, Qff7+. This attempts to avert mate by chasing the Black king with checks. But alas, there is a white pawn on a3 that prevents either rook from getting in some checks and contributing to this effort. And so Black replies 2...Ka6, Qxf3+.

Now White is reduced to desperado measures and Black still has one Option token remaining: 3.Qg2, Qb7+ trying to stop the one-move mate on g2. But Black uses that last Option token to play 3…. Ka5, Qxg2#. This is mate because the other White queen can’t make the ricochet move 4.Qg7, Qxg2 because the rules stipulate moving a piece twice disallows either move from being a capture.

Just in time, Black uses his last option to secure mate."

I hope some of you will look at this and appreciate it. This variant seems optimal for correspondence play, and there is no computer program that can dominate it.
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Joined: Mon Nov 28, 2016 9:51 pm

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