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Chess and problem rambles by PW

28 Jan. 2018 – New digital subscription for ‘The Problemist’

The Problemist is undoubtedly one of the best chess problem magazines in the world. Produced by the British Chess Problem Society, each issue contains top-quality articles, news reports, original compositions (in six sections), selected problems (typically prize-winners), and tourney awards. Further, each instalment is bundled with The Problemist Supplement – also with originals and articles – which caters for newcomers to problems and is expertly edited by our own Geoff Foster. Starting from this year, you can subscribe to the electronic version of the publication at a greatly reduced rate. The annual membership cost is £5 (about AU$8.60) and it obtains six issues of the magazine in the PDF format. This is excellent value when you consider that the normal subscription is £25 for the hard copies (which is still available). Go to the British Chess Problem Society site for details on how to become a member.

Ilija Serafimović
Youth Chess Composing Challenge 2016
2nd Place, 1st Hon. Mention
Mate in 2

Here are two selections from the November 2017 issue of the publication. The first features in the inaugural C. J. Morse Award for two-move tasks and records, named in honour of the late Sir Jeremy Morse. Two-movers from any sources (not just The Problemist) that demonstrate a maximum effect of some sort were eligible for this tourney, which covers the 2012-2016 period. Instead of the award winner, I will quote one of the top eleven entries mentioned, by a young composer who was a successful entrant in our Guided Chess Problem Composing Competition. This delightful work by Ilija brings about a terrific number of knight promotions. The key is thematic, naturally – 1.g8(S)! with the threat of 2.Bg3. Two defences by the a8-rook allow White to deliver knight promotion mates: 1…Ra4 2.c8(S) and 1…Re8 fxe8(S). Black can also defend by promoting various pawns to knights, and these moves result in different queen mates: 1…f1(S) 2.Qd4, 1…gxh1(S) 2.Qg6, and 1…d1(S)+ 2.Qxd1. (Also, 1…Re7 2.Bxe7.) The total of six knight promotions (three white and three black) constitute a new record for single-phase two-movers.

Vasil Krizhanivsky
The Problemist 2015
1st Prize
Helpmate in 2
6 solutions

All originals published in The Problemist automatically take part in its (mostly) annual informal tourneys. Given the quality of the problems that such a prestigious journal attracts, the prize-winners in these tourneys invariably impress. The helpmate above won the 2015 two-move section by achieving what could be a first: a doubling of the cyclic Zilahi theme without the use of twins. In the first three solutions, the white officers rotate their roles in getting captured by the black queen and giving mate: 1.Qxe4 Rf6 2.d5 Sc6, 1.Qxd4 Bf5 2.Qf4 Rd5, and 1.Qxd6 Sc6+ 2.Ke6 Bf5. In each phase, the white piece that’s not part of the Zilahi scheme (i.e. it is not captured and doesn’t mate) always moves to guard flights. Hence there’s a formally perfect 3x3 cyclic change of functions (sacrificed/guard/mate) for the three white pieces. Such a theme rendered would be sufficient to make a very good helpmate, but here the composer has managed to produce another 3x3 cycle of function change that again incorporates a Zilahi. In this second triplet of solutions, it’s the black king that commences the cyclic play by making the thematic captures: 1.Kxe4 Re6+ 2.Kf4 Se2, 1.Kxd4 Bd3 2.Re3 Rxd5, and 1.Kxd6 Sb5+ 2.Kc6 Bxd5.

12 Mar. 2018 – Stockfish and a modern classic more-mover

The rise of chess engines in the last decade or so is an interesting topic from which I’ve been somewhat insulated, because of my focus on problem chess. Frequenting the Chess.com site has helped me to catch up with the advances of these incredible programs, which perform at superhuman levels on modest hardware. Thus I learnt that Stockfish, one of the strongest engines with an Elo rating of around 3500, is open source software that is accessible for free. And you don’t even have to install it on your computer; you can play against Stockfish directly on Chess.com, or set up a position on the site for the engine to analyse.

As a problemist, I was naturally curious to see how efficiently Stockfish deals with long directmate problems. And the answer seems to be “very.” It solved the great majority of more-movers of up to about 12 moves that I tested in mere seconds, and even cooked a few. (Note that when you run Stockfish on Chess.com, its speed still depends on your own computer’s processing power.) Although this is impressive, Stockfish is of course no substitute for a specialised problem solver like Popeye, which uncovers all of the variations in a problem and provides certainty to its soundness. Stockfish is designed to keep looking for the best move indefinitely, or it stops analysing according to a time-limit, so you can’t tell if any forced mating sequence it has found is in fact the shortest possible. Furthermore, Stockfish can be inconsistent in being unable to crack some not-very-long directmates in a reasonable time. Here is an excellent 9-move problem that stumped the engine, but was solved by Popeye in less than eight minutes.

Theodor Siers
Die Schwalbe 1935
Mate in 9

White’s plan is to mate on e7 with the bishop, while avoiding stalemate from capturing the knight. Black is almost in zugzwang, since most knight moves allow the bishop mate and 1…Sd5/Sc6 is answered by the waiting move 2.Bc5, after which the knight must unguard the mating square. However, White has to move the king first to fend off 1…Sc2+. 1.Kb2? fails to 1…Sxd3!+ 2.K-any Sc5 3.Bb4 Sxe4!, creating an escape square on f5 for the black king. White therefore plays 1.Kb1!, but after 1…Sd5, 2.Bc5? is premature because of 2…Sc3+!, again winning the vital e4-pawn. If 2.Kc2? instead, Black counters with the resourceful 2…Se3+! 3.K-any Sf5!, which simultaneously protects e7 and attacks g7, thus dislodging the white rook. So where should the white king go? No progress is made if it stays on the queen-side, because the black knight can continue to switch between b4 to block the bishop and d5/c6, where the knight either checks directly or (if White plays Bc5) executes a fork that will give the piece access to e4 or f5, as previously seen. Correct is 2.Kc1! forcing 2…Sb4, and then 3.Kd1! Sd5.

At this point, you might guess that the theme of the problem is that the white king marches all the way from a1 to h1 without leaving the first rank. Hence not 4.Bc5? or 4.Ke2? because of 4…Sc3+ again, but 4.Ke1! Sb4 5.Kf1! Sd5 6.Kg1! Sb4 7.Kh1! Sd5, and finally the king is safe from checks by the pesky knight – 8.Bc5 S-any 9.Bxe7. The solution exploits a curious geometric feature: h1 is the only white square on the board that cannot be attacked in one move by a knight on either d5 or c6. The maximum-length orthogonal trip by the white king is superbly engineered in this first-rate composition.

When Stockfish tackled this position, it took a few minutes to find a forced mate in 13, starting with 1.Rxh7. After a couple of hours, it picked the right first move, 1.Kb1!, but based that on a wrong continuation, 1…Sd5 2.exd5?, which lets the black king escape to f5, and this leads to mate only on move 12. Are there directmates even shorter than this 9-mover that cannot be solved – within an hour, say – by Stockfish? With few clues on what would give the engine trouble, I threw some random 7- and 8-move problems at it, but most were handled quickly. Then it occurred to me that I could try using the current problem by Siers but with the first few moves of its solution shaved off; at which point of the shortened variation will Stockfish get it right? As it turns out, the engine found the solution only at the mate-in-5 stage. That means the shortest forced-mate sequence I know of that cannot be solved by Stockfish is a mate-in-6, with the white king starting on d1 and the black knight on d5. Can anyone unearth a mate-in-5 position that is too difficult for Stockfish!?