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Up Topic Rybka Support & Discussion / Rybka Discussion / Rybka vs Benjamin II - Match at Draw Odds
- By Vasik Rajlich (Silver) [hu] Date 2008-01-03 13:50
Rybka vs Benjamin II - Match at Draw Odds

On Jan 3-6, 2008, Rybka will take on Grandmaster Joel Benjamin in an 8-game match at draw odds. GM Benjamin will have white in every game, and draws will be counted as wins for him. I'd like to thank Larry Kaufman for organizing the match, GM Benjamin for his participation, and our sponsors for making it all possible.

This is the fourth long match between Rybka and a grandmaster, and the first involving draw odds. Reports about the first three matches can be found here:

A Full Pawn - Rybka vs Benjamin
Everything but a Pawn - Rybka vs Ehlvest II
Match at Pawn Odds - Rybka vs Ehlvest

Draw odds is an interesting handicap, with three very attractive properties:


It could be argued that the previous handicaps were a bit artificial - it's unlikely that a grandmaster would take great professional pride in winning with a pawn-odds handicap. In contrast, the situation of needing or wanting to draw with white does occur in tournaments and matches, and the ability to draw on demand with white is part of a grandmaster's repertoire. I suspect that many grandmasters would indeed take pride in their ability to draw with white on demand.


The draw, and the draw offer, is a sort of ugly stepchild of chess. In what other sport do the combatants ever have occasion to agree about anything? In what other sport do the combatants make friendly offers to each other? In a draw-odds match, there is nothing to agree about or otherwise discuss - play continues until someone begs for mercy.


Humans are better than computers are understanding the drawing barrier, and this match will give us some data about this superiority.

In fact, for this reason, making predictions about the outcome of this match is tricky. Let's consider various paper-napkin calculations.

In the CEGT 2-CPU G/120 list, Rybka played 150 games against engines rated <2800. These engines, all signficantly stronger than Benjamin, drew or won 24.5% of their games against Rybka. Assuming that Rybka's increased incentive to win and Benjamin's increased incentive to draw roughly offset each other, this would suggest that Benjamin should be more than happy with just 2 points in this upcoming match.

This calculation, however, doesn't completely sound right, and a similar calculation in a related topic fails. Let's consider the question of how Benjamin would be expected to score if he received both pawn and draw odds. If we take the value of a pawn as 300 Elo (as engine vs engine simulations suggest), then Benjamin with an extra pawn should perform as a 2900 player. If we take Rybka's games from the same CEGT list against engines rated between 2866 and 2906, we see that these engines drew or won 50.6% of their games against Rybka. In fact, however, in his last pawn-odds match against Rybka, Benjamin drew or won a whopping 75% of his games. The 8 games of that match are not a big sample size, but my impression is that it was no fluke and that Benjamin could have continued drawing games against Rybka at that 75% clip under those conditions.

From the above results, we'll try one final paper-napkin calculation. Benjamin's ability to draw games at pawn odds seems to be roughly 200 Elo above that of a computer of comparable strength. Let's generalize this and assume that Benjamin's ability to draw games in general is 200 Elo above that of a computer of comparable strength. In this case, and given that he will have white in every game, Benjamin can be expected to perform in the upcoming match at an approximate Elo of 2850. Engines rated between 2830 and 2866 in the above CEGT list drew or won 42.6% of their games against Rybka, suggesting that Benjamin can expect to score 3 or 4 points in this match.

Of course, these calculations are based on some unproven and even questionable assumptions. We'll know more about this topic in a few days.
Up Topic Rybka Support & Discussion / Rybka Discussion / Rybka vs Benjamin II - Match at Draw Odds

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