Hi Tim Just,
I have examined the April 2005 “TD Corner” by Tim Just on the USCF web site, and would like to offer my opinions on what I see in the three different possible pairing suggestions (A, B, and C) for round 5.
I think the answer to the question, “Can you spot the human’s handiwork?”, is “Yes.” It seems to me that B is by a human.
The question, “Which of the other two pairings is more correct?” is also an interesting question!
I first did the pairings by hand, and came up with pairings as in C. After analysing A and B, I then entered the entire crosstable into SwissSys and it also generated C.
[Note, while entering the round by round results and doing the pairings for the next rounds, SwissSys did not generate the same pairings as in the crosstable for rounds 3 and 4. I know I looked at one such pairing, and thought the crosstable had it correct and SwissSys was incorrect.]
I think the title to the discussion should be:
How do you choose the odd Chessplayer(s) and his opponents?
Let me first explain how and why the suggested pairings were made, starting with C, then B, and finally A.
Pairings C
The first thing to notice is that there are an even number of contestants for round five, so we don’t need to determine who gets a bye.
In the top group with four players, Stanislav has played all three of the other players in the group, so he must be one of the two odd players. We then pick the lowest player in the group as the other odd player, Christopher. In doing so, we notice that the other two players in the top group have the color distribution, WBWB, so one of them will get WBWBB which violates the “alternation of colors” rule. I will discuss this later, as this is the key for Pairings A.
Since Stanislav is the higher of the two odd players, he is paired against the only player with 2.5 points, who is Aleksanda. Here too, the colors are not ideal, as Stanislav has BWBW and Aleksanda has BBWW. Aleksanda cannot have three Whites in a row, so Stanislav ends up BWBWW and also does not have “alternation of colors”.
We now try to pair Christopher in the next group of players with two points. The first attempt is to try to pair him with William, the highest ranking player in the group, but then we notice that the other two players have already played each other. Since the group cannot be paired with Christopher against the highest player, we then look for an alternate pairing with these four players. Since Christopher has already played Rajen, we then pair Christopher with Dushyan, and notice quite nicely that Rajen and William can be paired with each other.
In looking at the four players at the bottom of the crosstable, we see that Lawrence has already played Richard and Andrew. The only other possible pairing is Lawrence and Walt, and then we see that Richard can be paired with Andrew.
Determining the colors for each game by these pairings is not an issue as we simply follow the equalizing, alternating, and not-three-in-a-row rules.
Pairings B
The pairings here chose the odd players as in C.
The first mistake to notice is that Aleksanda is given three whites in a row. I’m hoping that no pairing software voluntarily violates this rule, otherwise the manufacturer should be notified! This is my first clue that these were by a “carbon based unit” and not a “silicon beast”.
The next difference from C is in pairing Christopher as the odd player into the players with two points. He is paired against William, and then the other two players in the group are treated as odd players and dropped down. This violates the rule that says players should be paired as close to possible with players in their own scoregroups.
After that mistake, we then try to pair Rajen with the highest player at 1.5 points, but notice the colors are BWBB and WWBB. We really don’t want to give a player three Blacks in a row, so we pair Rajen with Richard.
Next we would like to pair Dushyan with Lawrence, but then notice that we cannot pair the last two players (not to mention that colors are horrible for Dushyan and Lawrence). We next try Dushyan with Walt, and again notice that the last two players have already played, so we then try Dushyan with Andrew and notice that Lawrence and Walt can be paired.
Pairings A
Stanislav is one of the odd players. We would like to choose Christopher as the other odd player, but notice Andelo and Igo colors are WBWB. We therefore choose Igor as the odd player and can pair Angelo and Christopher with good colors. We do this realizing that the rating difference between Igor and Christopher is 191. We might make a different decision if the difference was greater than 200!?
We then try to pair Stansilav with Aleksanda, but notice the colors here are BWBW and BBWW. Since the pairing would need to give Aleksanda Black, Stansilav would end up with BWBWW and this violates the alternation of colors rule. Since we have two odd players dropping down from the top group, we notice that the colors work better if we pair Igor with Aleksanda.
We now need to pair Stanislav with the group at two points. He has already played William, so we pair him against Rajen and notice once again that the colors work out nicely! Dushyan and William are then paired as the other players at two points.
The last four players are paired as described in A.
Note, with these pairings, ALL the colors work out nicely following the equalization and alternation of colors rules!
Analysis
When I first looked at the A pairings, I thought they could not be correct. What is the logic in pairing the highest ranking player in a 4-player scoregroup down 2 scoregroups, and even then he is not paired with the highest player in that group! It also seemed wrong to choose the second odd player in the top scoregroup as Igor. I mention this while noticing that Igor has a rating of 2264 and Christopher has a rating of 2073, almost a 200 point difference.
But the logic involved in doing the pairings for A seem to be adhering strictly to the letter of the rules without necessarily adhering to its intent. I came to this conclusion by closely examining the rules 29D1 which makes reference to 29E and 29E3, and 27A.
29D. The odd player.
29D1. Determination.
… Care must be taken in doing this that the odd player can be paired in the next score group, that the remaining members of both affected score groups can be paired with each other, that the odd player has not played all the members of the next lower group, and that the color consequences are acceptable (29E, 29E3).
29E. Color allocation.
… the director, after the first round, tries to alternate colors by giving as many players as possible their due (correct or expected) color, round by round.
29E3. Due colors in succeeding rounds.
As many players as possible are given their due colors in each succeeding round, so long as the pairings conform to the basic Swiss system rules. See also 27A.
27A. Basic Swiss system rules.
27A5. Alternating colors.
Players receive alternating colors whenever practical.
I think it could be argued that the colors are not acceptable in Pairings C in that two players do not follow the “Basic Swiss” rule of alternating colors. If an alternate method of choosing the odd players and the odd players opponents can be made where ALL the players in the event follow the “Basic Swiss” rules, then aren’t those better pairings?
I really do think that Pairings C are more correct than pairings A. I say this especially since we have rules about transpositions and interchanges that adress what happens if the switch is more than 80 points or more than 200 points. If the point difference between Igor and Christopher was more than 200 points, it really wouldn’t make sense to basically switch these two players in deciding who is the odd player to be dropped down, just to make alternation of colors work properly. Now, if it was needed so that a player did not have 3 colors in a row, then maybe pairings as in A would be more correct.
Perhaps this all boils down to the interpretation in 29D1: “and that color consequences are acceptable”. Is it acceptable to violate the “Basic Swiss” rule of alternation of colors in order to chose the lowest rated player in the scoregroup as the odd player?
Two further notes about the crosstable. I notice that Albert withdrew from the tournament after round 3 while leading the tournament!? Also, Christopher, with two points, was given a full point bye in round 4!?
Could you give a bit more information about this crosstable?
Was this from an actual event?
What pairings were made at the tournament?
Did someone complain?
Which pairing software did the A pairings?
Regards,
Tom (WildTommy) Ewers
