robison@eosp1.UUCP (Tobias D. Robison) (12/05/84)
This is my detailed analysis of my game with Phoenix. Jonathan
Schaeffer has not had time to add his comments, and I have not
had time to add comments based upon Phoenix's analytical
output; however, I think the game is of interest, and
hope you enjoy reading it.
Tobias D. Robison -- Phoenix (programmed by Jonathan Schaeffer)
June 12, 1984 to October 4, 1984. (White wins)
French Defense
1. P-K4 P-K3
2. P-Q4 P-Q4
3. N-QB3 N-QB3
Phoenix adopts a solid defense that tends to lead to
closed games. In general, computers do better in open
positions, for reasons which I shall discuss later. However,
Phoenix has apparently been quite successful playing the French,
and in this game it will do a good job of opening up the position.
Phoenix's 3rd move is questionable, since it blocks the QB pawn,
which usually should go to QB4 in the French.
4. P-K5
Attempting to close the position. White is hoping that it will take
Phoenix a long time to move its QN and play P-QB4, in which case
the center may be very solid.
4. ... B-QN5
5. P-QR3 BxNch
6. PxB
This exchange creates opportunities for both sides. The pawn on
QB3 protects the center, and white may be able to attack on the QN
file. Black can post a knight on its QB5, and the isolated white
QRP will be a target. On balance, the position of the Q-side pawns
favors black, but in playing against a computer, the cramping effect
on black may be what matters.
6. ... KN-K2
7. B-KN5
Pinning the knight with these goals: to postpone ... N-KB4, and
... P-KB3; to further cramp black. In fact, black does not appear
to suffer from this pin.
7. ... P-KR3
Black is vulnerable to attack on the K-side, so this move is good
news for white. If black later moves the KBP, the K-side will be
weak on the white squares near the king.
8. B-R4 O-O
Castling K-side is risky in a closed position like this with
little piece protection on the K-side. In some variations of the
French, black castles much later than this, or not at all,
preferring the safety provided by the pawn block in the center.
The position is now of a type that is very dangerous for computer
programs. Even if it takes white a while to launch a K-side
attack, it will take blkack longer to defend; any attack must be
anticipated, or vigorously countered. White, having an advantage
in space, can shift pieces to either side of the board more
quickly. A computer is unlikely to make good decisions about
how much of its force to commit to each side of the board,
in reaction to what white does.
Black's best chance in this position is to open it up. In an open
position, it is much easier to move pieces from side to side,
and attacks and defenses develop more quickly. Black does in fact
open the board quite a bit while white aims at the K-side.
9. P-KB4 P-KB3
Black will open the K-side, but as a result of moving both the
KBP and KRP, its king is not well-protected. White is poorly
developed, having invested several moves in keeping the position
closed while grabbing more space. The speed of development is
relatively unimportant, IF the position stays closed.
10. N-KB3 N-KB4
11. B-B2 PxP
12. BPxP B-Q2
The KB file contains an unusual array of pieces. Black's KN is
strong, but neutralized somewhat by the white KN and QB.
13. B-Q3 B-K1
The black QB strengthens the weak white squares. The bishop would
be an important factor in black's defense if it remained on the
K-side. But at K1, it interferes with the Q and QR, and thus
hampers the defense. Since this B will soon go to QR5, black has
lost a tempo.
White's KB on Q3 is not really attacking the knight; it is simply
aiming at the black K-side beyond the knight.
14. P-KR3 N-QR4
White prepares P-KN4. Driving the black knight away will allow a
strong attack, but at some risk of also exposing white's king.
Black's QN moves toward to the black strongpoint QB5. Although this
knight is on the Q-side, it could control critical center squares
and hinder white's attack from its QB5.
15. O-O B-QR5
Black's bishop is not well-placed here. Although it will exert
pressure on white's QBP, it is basically out of the defense.
16. Q-K2 P-QB4
White is now trying to complete his development before playing
P-KN4, while avoiding exchanges or traps in the center that would
weaken any attack. Q-K2 looks wrong, since it provokes the strong
P-QB4. White did not want to allow 17 ... P-B5; 18. BxN, RxB,
preferring to preserve the bishop. However that exchange would
leave black with even less K-side protection, and might have been
fine for white. (If instead 18. ... PxB, white's passed KP is
strong, and black's K-side is still weak.)
17. Q-Q2 PxP
Now white has lost a tempo, and black has another open file to work
with.
18. PxP R-QB1
It looks like black is pinning white down to the defense of the
QBP, but the game now moves to the K-side. White was worried
about 18. ... N-B5; 19. BxN/4, PxB, which gives black good Q-side
pawns and a chance of using the long diagonal from its QR1 to KR8.
White might have answered N-B5 with Q-K2.
19. P-KN4!
Played after a lot of calculation. Still, this is very risky,
since black can analyze six half-moves deep, which white generally
can not. However, it seems necessary for white to attack before
getting pinned down defending the Q-side.
19. ... N-K2
20.B-R4 N/4-B3
Black has lost more tempi moving this knight. On QB3, the knight
ties white's knight down a little to defend the QP. White must
also worry about a future exchange sac: ... RxN with the threat
of dissolving white's center and penetrating to white's exposed
king.
21. P-N5 P-KR4
This is the slow-developing attack. White plans to play P-KN6,
Q-N5, QxRP, and Q-R7 mate. Slow and unforced as this plan is,
it is hard to defend. Black had to play P-KR4 to avoid losing
material, or allowing 21. ...PxP; 22. QxP with a strong attack at
KR7.
22. P-N6 Q-N3
It is not easy to get the queen into the K-side defense. Instead,
black applies counter-pressure on the center from the Q-side,
temporarily.
23. QR-QN1 Q-B2
This exchange again cost black a tempo, since 22 ... Q-B2 would
leave white's QR at QR1. The rook is now on an open file, and
black's queen is defending a pawn and preventing white's rook from
reaching the seventh rank.
24. Q-KN5 N-B4
25. QxRP N-R3
Black's knight maneuver was pretty much forced to prevent mate.
26. B-N5!
White continues to attack before black can consolidate.
BLACK
---------------------------------
| | | r | | | r | k | |
---------------------------------
| p | p | q | | | | p | |
---------------------------------
| | | n | | p | | P | n |
---------------------------------
| | | | p | P | | B | Q |
---------------------------------
| b | | | P | | | | |
---------------------------------
| | | | B | | N | | P |
---------------------------------
| P | | P | | | | | |
---------------------------------
| | R | | | | R | K | |
---------------------------------
WHITE
26. ... RxN
Black offers a rook for knight and pawn. Black's alternatives
are dreary. If black simply waited for white to play BxN, PxB;
QxRP, white would be two pawns up, with excellent prospects.
White cannot play 27. RxR, NxQP; for example:
28. R-B4, QxKP. Or,
28. R-K3, NxQBP.
However, 27. QxR, NxQP; 28. Q-B4, appears to defeat the sacrifice
(the knight is pinned against the unprotected bishop on white's
QR4). The text also works:
27. BxN!
White refuses the exchange and offers a piece. There are two
deadly threats:
(1) with the black knight gone, white may play R-KB7.
(2) White can mate at KR7 if black does not take the bishop.
27. ... RxRch
If either black rook moves to KB1, white plays 28. B-N5 and mates.
28. RxR
Now if 28... R-B1; 29. B-N5, and black must give up its queen to
prevent mate on the KR file.
28. ... PxB
29. R-B7 N-Q1
Black has to give up its queen to prevent mate. For example,
if 29. ... Q-N3; 30. QxRP, QxQPch; 31. K-R1 and black cannot stop
Q-R7 mate.
30. RxQ RxR
31. QxRP N-B3
Black could not play BxBP; its rook is pinned to the second rank to
prevent white from mating.
32. Q-B4 R-KN2
33. Q-B6 R-K2
Now all of black's pieces are nearly immobile.
34. P-KR4
BLACK
---------------------------------
| | | | | | | k | |
---------------------------------
| p | p | | | r | | | |
---------------------------------
| | | n | | p | Q | P | |
---------------------------------
| | | | p | P | | | |
---------------------------------
| b | | | P | | | | P |
---------------------------------
| | | | B | | | | |
---------------------------------
| P | | P | | | | | |
---------------------------------
| | | | | | | K | |
---------------------------------
WHITE
There is no defense against the advance of white's KRP.
34. ... P-QR3
35. P-KR5 resigns
- Toby Robison
decvax!ittvax!eosp1!robison
or: allegra!eosp1!robison
(maybe: princeton!eosp1!robison)