Accelerated vs Abominated Swiss Pairings :)

[Kevin Bonham]

In round two there are couple of 0.5 v 0 pairings, where the 0.5's drew against each other in round one (top half pairing).

So in my opinion the two 0.5 ers are downfloaters as they playing someone on 0 who are also top halfers.

Correct.

[Garvinator]

Acceleration for round three was not as bad as I thought. I could see cases for why sp paired as being played, so left the draw as generated with limited time to make changes.

Now having had a few minutes to do some checking, I only get a couple of differences.

The two bottom half players are on boards 2 and 3 because of draws and losses in the top half. I would have paired 3 and 9, but as most of the other pairings are still the same, it does not appear to make much difference.

Back to normal pairings tomorrow for rounds 4-7.

[Kevin Bonham]

Garvinator mentioned this thread in the context of comments about the pairings for the 2011 Begonia where the same simplified two round system that I disparaged above was again used.

Some impacts in this year's event included:

* When the "acceleration" was removed in round 3 this created a scoregroup of 20 players of whom five were bottom-halfers. Of the five pairings where both players were top halfers, three were drawn, but all the mismatches were won by the stronger player. This meant that after round 3 the acceleration had culled the lead group to seven players, but had proper acceleration been used (including not removing the acceleration after round 2) there would have been eight all-top-half pairings involving at least one player on 2, most likely culling the lead group to something like 3-4 players instead of seven. Most likely that would have sped up matches between the winner and defeated strong players bouncing back.

* Also the top-halfers left on 3/3 included the 6th through 10th seeded of the 2/2 top-halfers. With true acceleration three of those players would be in the bottom half of their scoregroup and likely only about one would get through. Instead the tournament had a round 4 perfect score group consisting largely of players who weren't there on either merit or rating as demonstrated in the tournament. This further slows up getting matches that strongly test the winner.

* The completely absurd pairing Solomon vs Gray (though those two had one very interesting game in the past), in which a top-halfer on 1 was paired with a downfloating bottom-halfer on 1.5. Under true acceleration this would only have happened if no bottom-halfers were on 2 after round 2 - unlikely given the size of field.

* Very strong 2300s players who had dropped points wasted kicking 1500s who had already dropped points down to 1/3. Ideally those 2300s should be playing the 1500s who haven't dropped points (thus making sure those players get kicked out of the perfect score group, unless someone is performing way off the scale in one direction or another) while the 2100s on 2 are mostly getting sorted out of the 100% group.

[Oepty]

One thing that appears to have gone wrong with the accelerated pairings is the inclusion of Peter Miitel and Enoch Fan in the top group for pairings in Rd2. Both these players were in the bottom section in round 1 and beat lower rated players. I realise that things were complicated with the late addition of the Hamilton - Voon pairing in the first round, who both should have been in the top section but I don't know why the other 2 were included. Also Max Mollard who was held to a draw by Garvin was included with the top half players who drew although Garvin was not.
The order of the pairing of the bottom half of the top group also looks strange.
Scott

[Garvinator]

One thing that appears to have gone wrong with the accelerated pairings is the inclusion of Peter Miitel and Enoch Fan in the top group for pairings in Rd2. Both these players were in the bottom section in round 1 and beat lower rated players. I realise that things were complicated with the late addition of the Hamilton - Voon pairing in the first round, who both should have been in the top section but I don't know why the other 2 were included. Also Max Mollard who was held to a draw by Garvin was included with the top half players who drew although Garvin was not.
The order of the pairing of the bottom half of the top group also looks strange.

I think this is all caused by what number was chosen as the cut off point for top half/bottom half. Before the tournament that number was set at 64.

After the addition of Hamilton and Voon, that number should have changed to 66 so that all players around the top half/bottom half cut off stay on the same side of the acceleration cycle.

By not making this change, it would push the original seed 63 and 64 into the bottom half as they would become seeds 65 and 66.

Why this change was not made I have no idea. Easy to make an oversight like this when attempting to use a new pairing program you do not trust (Tornelo).

[Garrett]

I agree that accelerration should be applied until all lower half players have dropped at least half a point.

[Oepty]

I think this is all caused by what number was chosen as the cut off point for top half/bottom half. Before the tournament that number was set at 64.

After the addition of Hamilton and Voon, that number should have changed to 66 so that all players around the top half/bottom half cut off stay on the same side of the acceleration cycle.

By not making this change, it would push the original seed 63 and 64 into the bottom half as they would become seeds 65 and 66.

Why this change was not made I have no idea. Easy to make an oversight like this when attempting to use a new pairing program you do not trust (Tornelo).

Garvin, I think your numbers are slightly wrong, I think it was 62, top 31 boards or half the field as initially paired, which was also all those over 1600. There was then 2 more pairings made. Robert Bailey played on board 27 despite being lower rated, I guess he was a replacement for someone who didn't turn up or something like that. Also the wrong James Watson was put in the draw so he wrongly played in the top part as well. This means the number should not have changed with Watson and Bailey just being replaced by Hamilton and Voon in the top section.
Scott

[Bill Gletsos]

According to the SP files I have the cutoff was 64.

Notice in round 1 that Justin Tan played Nigel Barrow.
He is ranked 8th in round 1 yet he really should have been ranked 18th.
As such he played out of order on board 8 in round 1 as they apparently used the NSW Justin Tans rating.

It appears they made a similar error with James Watson using the NSW James Watson's rating.
As such James was ranked 19th in round 1 instead of 106th.

[Oepty]

According to the SP files I have the cutoff was 63.

Notice in round 1 that Justin Tan played Nigel Barrow.
He is ranked 8th in round 1 yet he really should have been ranked 18th.
As such he played out of order on board 8 in round 1 as they apparently used the NSW Justin Tans rating.

It appears they made a similar error with James Watson using the NSW James Watson's rating.
As such James was ranked 19th in round 1 instead of 106th.

It was clearly 62 for the first round before the Hamilton - Voon pairing was added. I also by counting players in the second round draw get to 64 players being paired as though they have been in the top section and Kordahi who was in the top section for the first round who had a second round bye. Board 41 looks a bit odd, I am guessing Ghobrial was initially given a 1 point bye in round 1.
I am certainly no expert on accelerated pairings and maybe I have something wrong but I don't think 63 was the number used for either round unless Tornelo or something else made errors. As Tornelo was supposed to be doing the pairings I wonder how relevant the number 63 in SP really is.
Scott

[Bill Gletsos]

I am certainly no expert on accelerated pairings and maybe I have something wrong but I don't think 63 was the number used for either round unless Tornelo or something else made errors. As Tornelo was supposed to be doing the pairings I wonder how relevant the number 63 in SP really is.

I made a typing error.
SP has it set to 64
Sorry for the confusion.

[Oepty]

I made a typing error.
SP has it set to 64
Sorry for the confusion.

That makes more sense, thanks Bill.
Scott

[Pepechuy]

The problem with not removing the bounts point is that some players can perceive favoritism.
For the situation you describe (24 players, wide difference in playing abilities, it seems it was 5 rounds but you do not say it explicitly), I think it would be best to use the Amalfi system.

[Sergio Pagano]

The problem with not removing the bounts point is that some players can perceive favoritism.
For the situation you describe (24 players, wide difference in playing abilities, it seems it was 5 rounds but you do not say it explicitly), I think it would be best to use the Amalfi system.

I agree. The Amalfi system seems working fine in situations like the described one. See for instance this tournament held in Italy last year (5 rounds, 20 players rating interval 2258 - 1371): http://www.torneionline.com/tornei_d...=c&ord=c&sen=a

[Kevin Bonham]

Typical example - actually worse than typical because it's a double-point version - of an Abominated Swiss draw in the current South African Open (saw Nigel Short complaining about it on Twitter) :

http://chess-results.com/tnr172929.a...flag=30&wi=984

Top half has been accelerated by two add-on points for the first three rounds and then the acceleration has been removed. The round three draw contained 17 bottom-halfers who had 2/2 and 16 top-halfers who had 0/2. With the stronger (and perhaps in cases underrated) end of the bottom-halfers thus playing the weaker (and perhaps in cases overrated) end of the top-halfers, the rating differences in the 16 bottom-vs-top halfer games in round 3 weren't great, and five of the bottom halfers won. The 17th bottom halfer was downfloated to play another bottom-halfer on 1.5 and also won.

Result: six bottom-half players go into the 3/3 scoregroup and with the acceleration removed they are playing GMs and IMs for no reason and most likely making the IMs' GM norm chances much more difficult (if there are norms in the event; I don't know if there are or not). Also there are two all-bottom-half 2.5/3 pairings that may well produce winners who then have to play GMs in round 5. The top two GMs in the 3/3 scoregroup do play top-halfers, but low rated ones who have had stellar results in the first three rounds and under a better acceleration system would play the third or fourth players from the top group.

[Kevin Bonham]

Copied from FIDE Congress thread:

There was an excellent presentation on Accelerated Pairings by IA Otto Milvang (Norway). He reported on testing of various possible computerised acceleration systems using simulations based on actual tournament fields according to how well they scored on maintaining the relationship between rating and score, reducing average rating differences and mismatches and increasing norm chances. He described most existing acceleration systems as based on "faith and guesses" rather than empirical evidence. In testing, the following system, which he called the Baku System, performed extremely well for events of 9+ rounds:

* Give top-half players one notional bonus point for rounds 1-3
* Reduce the notional bonus to half a point for 4-5
* Remove the notional bonus point for remaining rounds.

He also found that one notional bonus point for rounds 1-2 with half a bonus point for 3 worked quite well. This is compared to the round 1-2 only system as seen in a certain Australian event, which performed so badly in terms of the round 3 comedown that it was not even taken seriously for further testing.

His report is at http://pairings.fide.com/meeting-minutes/2016.html (links from point 2).