Problem 25843

[drahacikfm]

Shouldn't the generator have rejected this problem for two different reasons?
1) Black is up a bishop and a pawn in the starting position.
2) The alternate winning move 1...Re5+ wins a whole rook, so Black will be up a rook, bishop, and a pawn.

It's mate in 2. I thought the generator allows alternate material-winning moves only for mate in 1 positions.

[richard]

Hi Drahacik,

I have a fairly large "position is winning" margin at the moment for the starting position analysis (only a bit less than a Rook - I think there is an argument that this number is too big and should be brought down closer to +3, this is especially noticeable in the end game with a reasonable number of pawns still in play).

The alternative material-winning moves kick in for mate in 3 and higher, so mate in 1 and 2 have it disabled (Mate in 1s are the only mates that allow a mate in n+1).  I'd be happy to change this in the next verification run if you think it is too annoying to have to find a mate in 2 over a material win (I think Mate in 1 is reasonable, but agree that mate in 2 might have been pushing it).

Re5+ is also mate in 9 here so due to the bug previously mentioned I probably wouldn't have seen this one even with the ignore level set at mate in 1.

Richard.

[drahacikfm]

Ok, I didn't check this one with Rybka, so I didn't know that 1...Re5+ is mate in 9!  Now it makes sense that the generator did not reject this problem.  Anyway, I got this problem correct