wrote in message ...
In article ,
Bill Smythe wrote:
White: Kc7, Rh1, Bh8, pawns on b3,b5,c2,d6,e2,e6,h2.
Black: Ka1, Rb2, Nb1, pawns on a2,a3,b7,e4,h4.
White mates in five.

You've scared me away from trying it, so let me just ask: Is the
underpromotion needed only because White is trying to mate in five,
or does White actually fail to win if he doesn't underpromote?

The only way I see that white can win is by underpromoting to
a *rook* not a second bishop. Also, I can't see how to do it in
five moves in all lines.

1.e7 b6
2.e8=R h3 (not 2...e3 3.Rxe3 h3 4.Rc3 and either 4...Rxb3 5.Rxb3# or
4...Rxc2 5.Rxc2#)

A. 3.d7 e3 4.Re5 Rxc2+ 5.Rc5+ Rb2 6.Rc3 Rxe2 7.Rc2#
B. 3.Re5 e3 4.Kxb6 (4.d7 transposes into A) Rxc2
5.Rxe3+ Rb2 6.Rc3 Rxe2 7.Rc2#

Oh, I think I got it! There is a way to mate by underpromoting
to a second bishop! The solution is most unexpected.

SPOILER WARNING (Turns out I still can't do it in 5 moves!)

..

..

..

..

..

..

..

..

..

..

..

..

..

..

..

1.d7 b6 2.d8=B h3 3.Bh4 e3 4.Be1 Nd2 5.Bxd2#
............... e3 3.Be7 h3 4.c3 Rc2 5.Bxa3 Rb2 6.e7 Rxe2 7.c4 Rb2 8.Bxb2#
............... e3 3.c4 h3 4.c5 bxc5 5.Bdf6 c4 6.Bc3 cxb 7.Be1 Nc3 8.Bxc3#

Darn! I still can't get it in five moves.

In article , I wrote:
Anyone know an endgame study in which underpromotion to a bishop on the
same color is the only way to win (or draw)?

I posted this question on the Chess Problem Discussion Board and Bojan Basic
posted some brilliant examples.

http://rebnora.com/discussion/viewtopic.php?p=613#613
--
Tim Chow tchow-at-alum-dot-mit-dot-edu
The range of our projectiles---even ... the artillery---however great, will
never exceed four of those miles of which as many thousand separate us from
the center of the earth. ---Galileo, Dialogues Concerning Two New Sciences

In artikel schreef Glenn C.
Rhoads:

1.d7 b6 2.d8=B

You need a different promotion after b6. The bishop promotion only works after
1. .. h3

S
P
O
I
L
E
R
S
P
A
C
E
S
P
O
I
L
E
R
S
P
A
C
E
S
P
O
I
L
E
R
S
P
A
C
E
S
P
O
I
L
E
R
S
P
A
C
E
S
P
O
I
L
E
R
S
P
A
C
E

1. d7! h3 2. d8=B b6/e3 3. Bh4 e3/b6 4. Be1 Sd2/Sc3 5. Bd2/Bc3#
1. .. e3 2. d8=R h3/b6 3. Rd3 b6/h3 4. Rc3 Rb3/Rc2 5. Rb3/Rc2#
1. .. b6 2. d8=S h3/e3 3. Sc6 e3/h3 4. Sd4 Rb3/Rc2 5. Sb3/Sc2#

Joost
--
Du hast mein Herz zerrissen, meine Seele geraubt
Das es so enden würde hätt` ich nie geglaubt [Aus der Ruinen -]
Ohne Rücksicht auf Verluste, hast Du meine Welt zerstört [L'Âme Immortelle]
Eine Welt, die vor kurzem nur uns beiden hat gehört

"Glenn C. Rhoads" wrote:
.... The only way I see that white can win is by underpromoting to
a *rook* not a second bishop. Also, I can't see how to do it in
five moves in all lines. ....
.... Oh, I think I got it! There is a way to mate by underpromoting
to a second bishop! The solution is most unexpected. ....
.... Darn! I still can't get it in five moves. ....

Well, you have an imperfect perception of one-third of the concept, and
something roughly (VERY roughly) in the ballpark of another third.

Perhaps that statement gives too much away.

Bill Smythe

Harold Buck writes:

In article ,
"Bill Smythe" wrote:

"Jud McCranie" wrote:
What do you think the combined value of two bishops on the same color
is? 4-5 points?

If a bishop is worth 3 points, then I'd say two of them on the same color
would be about 3.1. So would nine of them, for that matter.

I think you'd be very wise not to play for money under
those conditions.


As I'm sure you know, K+B+RP vs K , where the B is the wrong color for
the RP, is drawn, provided the defending K can get to the queening square.
The same is true of K+B+B+B+B+B+B+RP vs K , if all the Bs are the wrong
color. This says something about the value of multiple same-colored
bishops.

Yes, "Before the endgame the gods have placed
the middlegame".


Well, surely the value depends on the stage of the game. If I managed to
get two extra white-square bishops in the first 15 moves, I think
they'de be worth more than 3.1. They sure aren't each much *less*
valuable than a pawn in that situtation.

I'd say the extra bishop is worth about - a bishop.

The opponent has to avoid a bishop for knight exchange,
or then I "really" do have an extra piece. Similarly for
a bishop vs bishop exchange of the right colour. Hence
he is restricted in what he can do, and this is an extra
advantage for the side with the extra bishop.

Imagine being in a position where nf3 or nc3 effectively
loses a piece. The stronger side can also threaten
to sacrifice the bishop for two pawns and win the endgame.
With these kind of threats the stronger side should be
able to get the initiative

I expect that the side with the extra bishop could win
most of these in the middle game, but, for example, the
three bishops vs two bishops endgames with a reasonable
number of pawns on each side should be an easy win. Or
the monochrome bishop pair vs a bishop of the same colour
or knight.


William Hyde
EOS Department
Duke University

I put in some 2-same colored bishop positions into CM
and let it play them out. While recognizing that the engine
is not optimized to play this correctly, this experiment
suggests a value for the two bishops of around 5.
Certainly the answer 3.1 is too low for middle game type
positions - the bishop's mobility makes it pretty easy to
trade off.

"Jud McCranie" wrote in message
...
On Thu, 30 Sep 2004 16:39:38 -0500, Harold Buck
wrote:

Well, surely the value depends on the stage of the game. ...

I was not necessarily wondering about underpromotion to a B. In
Fisher Random chess, the two bishops must be on opposite colors, but
what if that rule wasn't applied, and one side had opposite colored
bishops and the other had same colored bishops. Opposite colored
bishops would be a definite advantage, but how much?

---
Replace you know what by j to email

On Fri, 01 Oct 2004 18:58:19 GMT, "David Kane"
wrote:

I put in some 2-same colored bishop positions into CM
and let it play them out.

That's a good idea!

While recognizing that the engine
is not optimized to play this correctly, this experiment
suggests a value for the two bishops of around 5.

That's in the range I guessed. Two bishops on the same color do have
the advantage of being able to support each other on a diagonal.


---
Replace you know what by j to email

..
Tim Chow wrote:


LOL!


Tien Chow -- a very unusual name in America.

..
I mistakenly thought you were guessing about "Tim" Chow. Upon reflection,
this makes little sense, as it could easily have been Tom, for example. Or
Ted. Or Terry.
Or Thad. Theodore. Thurmond. "Mr. T."




"Bill. or George -- anything but Sue!"

"NoMoreChess" wrote:
I mistakenly thought you were guessing about "Tim" Chow. Upon
reflection,
this makes little sense, as it could easily have been Tom, for example.
Or
Ted. Or Terry.

No guesswork involved. He signed "Tim Chow" to the post I answered.

Bill Smythe