Bug in Mephisto Master

[Larry]

This bug was pointed out by a guy over on schachcomputer.info
last week:
[fen]8/1k6/8/8/8/6K1/7P/8[/fen]

White to move.
1.a8=Qch Kg3
2.Qf3ch ?? Kxf3 draw

For this bug to work, the power saving feature of the
Master must be set to zero, ie, "-PS: 0" via the "SEL" option group.
As pointed out, the bug has probably escaped attention all along
because games are normally resigned at this stage.
The board can be rotated and/or colors reversed, the bug
still does it's dirty work.
So that's it, guys. Sorry to spoil your day....
Larry
PS This bug is not in the Master's big brother, Atlanta, because
the Atlanta does not have the same power saving feature. I also
could not find it in little brother Cougar, which of course runs on
a different processor and has a different menu.

[spacious_mind]

Adding to Larry's post.

Try this position with Master or Milano Pro:

[fen]8/8/4k3/1n4p1/n7/P3K3/P7/8 w - - 0 1[/fen]

This was played at 30 seconds per move. Not sure if at longer times the same bad move is played. The actual game was MP against Master.

PS0 is of course the setting.

the move played is g4 ??

Which of course shows that neither of these computers realize that 2 Knights cannot win a game !


[fen]8/8/5k2/8/p7/2r1RK2/P7/1b6 w - - 0 1[/fen]

This position is for the Magellan lovers! Also 30 seconds per move. I have not tried it at a higher setting. Magellan plays Rxe3 which of course is a draw. Rule of Bishop does not match promotion square not understood by Magellan.

Best regards,

NIck

[Queegmeister]

Does not know insufficient material draw with 2 KINGS !! UGH !

Much to my dismay - a game (I misplayed) went to 2 kings and the GM continued on moving its king - OH NO !! How much effort would it take to have programmed in the very few insufficient material draws - what are there - 4 - ? Bishop , Knight , K vs K , 2 knights ? 20 minutes worth of effort to prevent this embarrassment.

Mike

[xerxes]

neither of these computers realize that 2 Knights cannot win a game !

2 Knights CAN win when their opponent has a pawn left. But it's very difficult and no sane human playing Black would allow their own pawn to be captured in this position!

[Queegmeister]

Obviously - I am well aware of this point. that is why I did not list 2 knights vs pawn. - the whole point being is the minute amount of effort it would have taken to program in these few situations.

Queeg

[xerxes]

Obviously - I am well aware of this point. that is why I did not list 2 knights vs pawn. - the whole point being is the minute amount of effort it would have taken to program in these few situations.

Queeg

I was replying to spacious_mind, not to you!

[spacious_mind]

Obviously - I am well aware of this point. that is why I did not list 2 knights vs pawn. - the whole point being is the minute amount of effort it would have taken to program in these few situations.

Queeg

I was replying to spacious_mind, not to you!

Well I don't use tablebases so I wouldn't know how. Not sure how someone would force a mate from this position. Perhaps you can show how:

Black to move

[fen]8/8/4k3/8/n2n2K1/P7/P7/8 w - - 0 5[/fen]

regards,

[xerxes]

Not sure how someone would force a mate from this position.

The technique is to use one knight to blockade the pawn(s) whilst the king and the other knight force the enemy king into a corner. Then the blockading knight hops over to deliver checkmate before the pawn can queen. Without the pawn, it is impossible to mate the king with 2 knights against best defence because it will be stalemated in the corner. The existence of the pawn prevents the stalemate.

Here is an example - http://www.chessgames.com/perl/chessgame?gid=1151993

Driving the king into the corner is the difficult bit. There are many examples from Grandmaster play when the player with the knights failed to win. In some configurations it is impossible to do it in 50 moves. In your example, the tablebase claims mate in 46 moves after Ke5. Who are we to argue!

[spacious_mind]

Not sure how someone would force a mate from this position.

The technique is to use one knight to blockade the pawn(s) whilst the king and the other knight force the enemy king into a corner. Then the blockading knight hops over to deliver checkmate before the pawn can queen. Without the pawn, it is impossible to mate the king with 2 knights against best defence because it will be stalemated in the corner. The existence of the pawn prevents the stalemate.

Here is an example - http://www.chessgames.com/perl/chessgame?gid=1151993

Driving the king into the corner is the difficult bit. There are many examples from Grandmaster play when the player with the knights failed to win. In some configurations it is impossible to do it in 50 moves. In your example, the tablebase claims mate in 46 moves after Ke5. Who are we to argue!

Thanks! Wow 46 moves! I think I will take the draw Yes I figured you would have to force the King to that a1 square, it is the forcing piece that is not so easy with a 50 move rule.

ps. thinking about it. this would perhaps only work if the pawns are not advanced. ie if the pawns are advanced to for example a4 and a5 or a5 and a6 as start position then a win would probably not be possible.

Best regards,

Nick

[Queegmeister]

Sorry no offense intended

I guess sometimes I should just keep quiet.

Mike