The Milov vs. Rybka Handicap Match
By IM Larry Kaufman
Although Rybka has played no less than thirteen official matches at various
handicaps with titled players (ten of the matches with GMs) in the past year
and a half, the match from Septermber 14-18 with Vadim Milov was our first match
with an Elite (FIDE 2700+) GM, Milov being rated number 28 in the world at 2705.
As usual, the match was played at my home in Potomac, Maryland, USA and broadcast
on the Internet.

Rybka opponent Vadim Milov, rated 2705
The time limit was the FIDE standard 90 min + 30 sec. Rybka played on a 3 GHz
Octal computer, using only 3-5 man endgame tablebases and a small handicap opening
book I wrote. The version was a slightly modified Rybka 3 default, differing
mainly in that the value of the exchange was lowered, which probably only affected
play in the exchange handicap games. A contempt setting of 50 was used in all
games. The eight game match consisted of three parts:
-
Two normal chess games where the only "handicap" was Milov's
getting white in both games. He lost the first of these and drew the second
by reaching a pawn down endgame that was easy to hold.
-
Two games at the classical "pawn and move" handicap (f7 removed).
Here the first game ended in an early draw by perpetual check when Milov
returned his pawn to drive Black's king out into the open, but he could
not find any way to achieve more than a slightly preferable position. The
second game was a disaster for Rybka; the position became very closed early
on, but Milov was able to calmly build up an attack on the kingside (where
he had an extra pawn), while Rybka just made delaying moves until it was
too late to get counterplay.
- Four games at odds of the exchange (Rybka removed a1 rook, Milov b8 knight).
Here Rybka drew three times and lost once. In one of the draws Rybka had good
winning chances, and in the one she lost she had good drawing chances.
Click to replay
and download the games
So
Milov won the match by 4.5-3.5, the first match victory by a human over Rybka,
except for a knight odds match with an FM. With a little better luck or perhaps
a little better play by Rybka the match could easily have ended in a tie score.
Although Milov made some mistakes (who doesn't?), I don't think he made any
errors that I would call "blunders". In general he played very well,
used his time properly, and tried to avoid complicated tactics as much as possible,
which is of course the proper strategy against a computer. His preparation for
the match failed him once, in the drawn game at pawn and move, when Rybka's
opening move (1...Nc6) already surprised him.
Before the match, my expectation was that we would win the white handicap-only
games by 1.5-0.5 or 2-0 but lose the pawn and move games by a similar score,
leaving the match to be decided by the exchange handicap games. This is indeed
what happened. It was my opinion (as well as the opinion of Milov, Rybka, and
Howard Staunton in the days when these handicaps were common) that pawn and
move handicap is larger than the exchange handicap, although the difference
now seems quite small. The exchange is nominally more than a pawn (two pawns
according to textbook count), but it is worth somewhat less in the opening,
while the f7 handicap is worse than just a pawn due to playing black and the
exposed king. Both handicaps seem to be worth about 1.5 pawns overall, maybe
a bit less in the case of Exchange handicap.
Here are some conclusions I've drawn from the match:
1. We need to do more to avoid blocked positions. Rybka 3 is much better than
earlier versions in handling this, especially with a high contempt setting.
But when down in material (as in handicap games), Rybka often tries to close
the position to make a draw more likely. We need to remedy this before playing
more matches (especially handicap matches) with humans.
2. We need a special opening book to play for a win with black in normal chess.
When White plays very conservatively, it's not easy to win as Black with normal
defenses. The drawn game we had in the non-handicap game was an Exchange Slav.
3. I should have set contempt higher in the handicap games. I don't know if
it would have made a difference, but it might have avoided some blocking moves.
4. Although pawn (f7) and move handicap is quite playable, there are just a
few playable defenses to 1.e4, which means a lack of variety. If a GM is well-prepared
in the opening, it would be quite difficult for Rybka to do well at this handicap
in a serious match like this one. I think we were too generous to offer this
handicap to an Elite GM at a standard time limit. More appropriate would be
either the f2 or c7 pawn I think.
5. The Exchange handicap proved to be both interesting and competitive. Although
Black is surely winning from the start, at least Rybka can use her first move
and extra minor piece to play actively in the opening. However there is one
big problem that I underestimated before the match. White cannot castle long
without a rook on that wing, but Black can, and did in two of the four games.
With his knight missing from b8, castling long is easy for Black to do. In rook-odds
games long ago, some players allowed White to play Kc1 in one move, but this
would be impossible for a normal Rybka to consider. The handicap is already
decisive materially, and for Black to have a choice of where to castle while
White does not makes it too much. So if the exchange handicap is used in future
matches, I think that Black should not be allowed to castle long, as if the
a8 rook had already moved.
6. Milov felt that now that he has played Rybka and learned her weaknesses
he would like to try a rematch with only the white pieces advantage. He felt
that with a copy of the program to be used, access to comparable hardware, and
enough prize money to justify spending a month or so in preparation he could
play a competitive match. I don't believe that the white advantage is enough
for any human to score more than 30% or so, even with massive preparation, especially
if we add more incentive to avoid closed games. But I'd welcome the chance to
try to prove this, so anyone interested in sponsoring such a match please let
me know.
7. One idea for future matches could be called "dynamic handicaps".
The first game would be played with the GM just playing white. If he wins he
must play black next, if he draws the next game is played the same way (GM is
white again), but if he loses the next game is played with some small handicap
(maybe two moves, maybe severe book restriction). Each win by the engine increases
the handicap (from a set list of handicaps) and each win by the GM decreases
it. This would insure an interesting and varied match regardless of the level
of the GM or the time limit.
8. What FIDE rating would Rybka 3 on an Octal computer like mine get if allowed
to play with the top five players in many tournaments? Although the computer
vs. computer rating lists suggest a rating of around 3200, there is some evidence
that engine vs. engine play overstates rating differences between computers
by 25% or so. This would imply a rating of around 3100. We can try to estimate
from these matches by assigning rating values to the handicaps based on results
in engine vs. engine play, for example by using the Monte Carlo feature on Rybka
3. I don't have much data at serious time limits, but extrapolating from fast
results I would say that the exchange handicap is worth perhaps 450 and the
f7 handicap 500 when the recipient is 2700. The White only handicap is around
50. So the average handicap in the eight games works out to 363 Elo, which when
added to 2705 (Milov's rating) gives 3068. The performance rating for the match
is about 3025. However our performance rating calculated this way in the other
three matches played with Rybka 3 or a version close to it was somewhat better
than this, so I think it is fairly safe to say that against top human players
Rybka should perform somewhere between 3000 and 3100 FIDE.
Replay games provided by Holger Lieske, SysOp on Playchess
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