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Re: Engines can't solve this puzzle (even not Stockfish 5)
Posted: Wed Jul 23, 2014 12:56 pm
by vittyvirus
hgm wrote:vittyvirus wrote:I wonder why does Stockfish completely give up at this position? And why don't engines find the mate in 18 at 36 ply?
Because when strong engines such as Stockfish say they searched 36 ply, it only means they searched one selected branch 36 ply. Almost all other branchess in the tree will have been searched to only 9 ply or so. If the mate is in there (which it will be, if the branch leading to it will not in some way achieve something very good in these first 9 ply), it is still very far beyond the horizon indeed.
I get it now... You are a great person. Seriously. I'd love to meet you someday and talk about Micro-max and other things...
Re: Engines can't solve this puzzle (even not Stockfish 5)
Posted: Wed Jul 23, 2014 2:50 pm
by lech
vittyvirus wrote:hgm wrote:vittyvirus wrote:I wonder why does Stockfish completely give up at this position? And why don't engines find the mate in 18 at 36 ply?
Because when strong engines such as Stockfish say they searched 36 ply, it only means they searched one selected branch 36 ply. Almost all other branchess in the tree will have been searched to only 9 ply or so. If the mate is in there (which it will be, if the branch leading to it will not in some way achieve something very good in these first 9 ply), it is still very far beyond the horizon indeed.
I get it now... You are a great person. Seriously. I'd love to meet you someday and talk about Micro-max and other things...
It means Stockfish needs 36 / 9 * 36 = 144 plies to solve it.
Why?
Stockfish has a very poor tool (code) for zugzwang positions.
Re: Engines can't solve this puzzle (even not Stockfish 5)
Posted: Thu Jul 24, 2014 9:02 am
by vittyvirus
lech wrote:vittyvirus wrote:hgm wrote:vittyvirus wrote:I wonder why does Stockfish completely give up at this position? And why don't engines find the mate in 18 at 36 ply?
Because when strong engines such as Stockfish say they searched 36 ply, it only means they searched one selected branch 36 ply. Almost all other branchess in the tree will have been searched to only 9 ply or so. If the mate is in there (which it will be, if the branch leading to it will not in some way achieve something very good in these first 9 ply), it is still very far beyond the horizon indeed.
I get it now... You are a great person. Seriously. I'd love to meet you someday and talk about Micro-max and other things...
It means Stockfish needs 36 / 9 * 36 = 144 plies to solve it.
Why?
Stockfish has a very poor tool (code) for zugzwang positions.
And the MAX_PLY for stockfish is probably set to 120, isn't it?
Re: Engines can't solve this puzzle (even not Stockfish 5)
Posted: Thu Jul 24, 2014 10:00 am
by lech
vittyvirus wrote:lech wrote:vittyvirus wrote:hgm wrote:vittyvirus wrote:I wonder why does Stockfish completely give up at this position? And why don't engines find the mate in 18 at 36 ply?
Because when strong engines such as Stockfish say they searched 36 ply, it only means they searched one selected branch 36 ply. Almost all other branchess in the tree will have been searched to only 9 ply or so. If the mate is in there (which it will be, if the branch leading to it will not in some way achieve something very good in these first 9 ply), it is still very far beyond the horizon indeed.
I get it now... You are a great person. Seriously. I'd love to meet you someday and talk about Micro-max and other things...
It means Stockfish needs 36 / 9 * 36 = 144 plies to solve it.
Why?
Stockfish has a very poor tool (code) for zugzwang positions.
And the MAX_PLY for stockfish is probably set to 120, isn't it?
Indeed, but such a high level is probably out of range for today computers to find and display a difficult solution.
Maybe the next generations of people will be able to enjoy the Stockfish's full abilities.
If you want be strong you don't need to be nice. The Elo gain (top) doesn't mean: I can solve each position now.
People love horses with tails even if it don't help to be fastest.
Re: Engines can't solve this puzzle (even not Stockfish 5)
Posted: Thu Jul 24, 2014 10:13 am
by hgm
lech wrote:Stockfish has a very poor tool (code) for zugzwang positions.
This is not really a zugzwang position, is it? If black is null-moving he is mated in no time (through Nd2 or Qxc1).
Re: Engines can't solve this puzzle (even not Stockfish 5)
Posted: Thu Jul 24, 2014 10:46 am
by lech
hgm wrote:lech wrote:Stockfish has a very poor tool (code) for zugzwang positions.
This is not really a zugzwang position, is it? ...
Is today thursday or not?
Re: Engines can't solve this puzzle (even not Stockfish 5)
Posted: Thu Jul 24, 2014 12:06 pm
by Uri Blass
hgm wrote:lech wrote:Stockfish has a very poor tool (code) for zugzwang positions.
This is not really a zugzwang position, is it? If black is null-moving he is mated in no time (through Nd2 or Qxc1).
I do not see how black is mated after null move and it seems to me that black can save itself by stalemate before Nd2(after 1.axb8=N c3 2.Na6 null)
Re: Engines can't solve this puzzle (even not Stockfish 5)
Posted: Thu Jul 24, 2014 12:52 pm
by vittyvirus
lech wrote:vittyvirus wrote:lech wrote:vittyvirus wrote:hgm wrote:vittyvirus wrote:I wonder why does Stockfish completely give up at this position? And why don't engines find the mate in 18 at 36 ply?
Because when strong engines such as Stockfish say they searched 36 ply, it only means they searched one selected branch 36 ply. Almost all other branchess in the tree will have been searched to only 9 ply or so. If the mate is in there (which it will be, if the branch leading to it will not in some way achieve something very good in these first 9 ply), it is still very far beyond the horizon indeed.
I get it now... You are a great person. Seriously. I'd love to meet you someday and talk about Micro-max and other things...
It means Stockfish needs 36 / 9 * 36 = 144 plies to solve it.
Why?
Stockfish has a very poor tool (code) for zugzwang positions.
And the MAX_PLY for stockfish is probably set to 120, isn't it?
Indeed, but such a high level is probably out of range for today computers to find and display a difficult solution.
Maybe the next generations of people will be able to enjoy the Stockfish's full abilities.
If you want be strong you don't need to be nice. The Elo gain (top) doesn't mean: I can solve each position now.
People love horses with tails even if it don't help to be fastest.
Yes! But Stockfish 'thinks' he (or she?) has figured out 120 plies in less than a second or two on my system.
Re: Engines can't solve this puzzle (even not Stockfish 5)
Posted: Thu Jul 24, 2014 1:02 pm
by hgm
If you can null move you should not be able to see stalemate. Stalemate is the ultimate zugzwang.
But even if you would, stalemate is a poor result for black. The normal evaluation puts black very much ahead because of all the material he has. So the null move would fail low.
Re: Engines can't solve this puzzle (even not Stockfish 5)
Posted: Thu Jul 24, 2014 1:15 pm
by Uri Blass
hgm wrote:If you can null move you should not be able to see stalemate. Stalemate is the ultimate zugzwang.
But even if you would, stalemate is a poor result for black. The normal evaluation puts black very much ahead because of all the material he has. So the null move would fail low.
The null search check if there is a threat not relative to the static evaluation but relative to the score of the search.
The score of the search is a draw even at small depth so the null search find no threat.
There is a solution to the problem and it is not to use null move pruning when the number of legal moves of the opponent is small(Movei does it) but most programs do not use the number of legal of moves of the opponent to decide if to use null move pruning.