Find the forced win
25 Jul '20 17:36White to move. Find the forced win.
26 Jul '20 01:511 edit 26 Jul '20 07:30
Reveal Hidden ContentReveal Hidden Content 26 Jul '20 16:562 editsReveal Hidden Content 28 Jul '20 04:201 edit@bigdoggproblem saidHa, it just came up on LiChess, so I had a fairly easy time with that one.
DT has it (mostly*) right, and I'm sure PL got it too.
Stumbled upon this one doing lichess.org puzzles. Liked how a nice idea tumbled out of a seemingly mundane position.
* [hidden]White does not have to lose the h2 pawn at the end[/hidden]
Reveal Hidden Content 29 Jul '20 13:48 30 Jul '20 01:54@deepthought said
I had this problem come up (except I interposed black and white) and it illustrates the difficulty I have with LiChess problems:[fen]8/6R1/pnk1pN1r/1p2P2p/1Pp3pP/P7/K5P1/8 w - - 0 1[/fen] White to play and win.
I'll give people a chance to solve it and then say where I have a problem with how they implement this on LiChess. I'm expecting a variation three moves deep.
Reveal Hidden Content 31 Jul '20 09:47@bigdoggproblem saidIs the correct answer. But on LiChess you only have to find the first move when the system moves the knight to d5 and you have to find the move Nxh6, so 1. Ng8 Nd5 2. Nxh6, presumably this is Stockfish's Principal Variation. So the problem with the way they set their puzzles is that what the move that Stockfish thinks is best is the one for which the resultant position 20 moves down the line gets a higher score in it's evaluation function isn't necessarily the most challenging to a human. In the case of this problem the point lies in the variation you gave. The first move Nb8 was my first thought, but I realised the rook isn't trapped, and then I wondered about checkmate but the knight blocks the rook's influence over the seventh rank. Then I managed to synthesize the two ideas and got it. The difficult move to find is the second one, 2. Ne7+, but one only needs to find the first one to think one's solved the problem on LiChess. Assuming they rate their puzzles using the same method that players are rated then puzzles like this will tend to be underrated as there's people who solve the whole problem like you and people who solve it by getting the first move. There, gripe over.
[hidden]1.Ng8 Rh8 2.Ne7+ K~ 3.Ng6+ wins the R[/hidden]
31 Jul '20 23:47@deepthought saidProbably they have a bot finding the puzzles in the first place. Hard to make a bot that finds the best "educational" variation.
Is the correct answer. But on LiChess you only have to find the first move when the system moves the knight to d5 and you have to find the move Nxh6, so 1. Ng8 Nd5 2. Nxh6, presumably this is Stockfish's Principal Variation. So the problem with the way they set their puzzles is that what the move that Stockfish thinks is best is the one for which the resultant position ...[text shortened]... ve the whole problem like you and people who solve it by getting the first move. There, gripe over.
02 Aug '20 21:52@bigdoggproblem saidAgreed, but they could have a way of alerting that particular situation so a moderator can make a decision about the best line. As things stand there's just a "do you like this" vote, which doesn't cover that particular base.
Probably they have a bot finding the puzzles in the first place. Hard to make a bot that finds the best "educational" variation.
Back to Top