Accelerated Pairings

Running Chess Tournaments
1

Someone recently asked me about accelerated pairings not being announced in advance. Of course the idea behind accelerated pairings is to eliminate multiple perfect scores in an event, and create a sole winner. With a sole winner there is no need for any tie-breaks, which may be preferable.

However, it does bring up 2 questions to my mind. First if you are likely (or certain) to use accelerated pairings, then why not included that fact in your TLA and other advance publicity? Secondly if you have a split schedule [3-day & 2-day for example] is there any requirement to use accelerated pairings for both schedules? Say a 3-day schedule had only 12 players, while the 2-day had 128 in a 5 round event: accelerate both or just the 2-Day?

Larry S. Cohen

2

That might depend on when the merge occurs. If the schedules merge after 2 (or more) rounds, using accelerated pairings in only one of the two schedules might be possible. If the merge occurs after just 1 round, it would be silly and illogical. In fact, there would be no decent way to pair round 2, because you would be mixing accelerated and unaccelerated players.

Recall that accelerated pairings are used in rounds 1 and 2 together, and 1 and 2 only. And the method for pairing round 2 depends on whether round 1 is accelerated.

With standard pairings, round 1 is paired half-vs-half, and in round 2 players with the same scores are paired.

With accelerated pairings, round 1 is paired by quarters (1st quarter vs 2nd, and 3rd vs 4th). In round 2, players with unequal scores are paired. Top-half losers play bottom-half winners. (Only the top-half winners and the bottom-half losers are paired by equal scores.)

Beginning in round 3, standard pairings and accelerated pairings are done the same way. Players are paired by score groups, half-vs-half within each score group.

The reason accelerated pairings tend to reduce the number of perfect scores is that, in round 2, many of the round 1 losers will defeat round 1 winners, thus leaving them all with 1 point out of 2.

Barring upsets, with accelerated pairings, after round 1 the 1st and 3rd quarters will have 1 point, and the 2nd and 4th quarters will have 0. Then after round 2, where the 2nd quarter is paired against the 3rd, both of these quarters will stand at 1-1 (the higher-rated losers will defeat the lower-rated winners). Only the top eighth (the top half of the 1st quarter) will have 2-0, and only the bottom eighth (the bottom half of the 4th quarter) will have 0-2.

So, with 32 players for example, after 2 rounds you will have:

  • Standard pairings:

  • ----- 8 players at 2-0

  • ----- 16 players at 1-1

  • ----- 8 players at 0-2

  • Accelerated pairings:

  • ----- 4 players at 2-0

  • ----- 24 players at 1-1

  • ----- 4 players at 0-2

Now, if you tried to merge accelerated and non-accelerated after round 1, how would you pair round 2? Pair all players by score, as in standard pairings? Or pair top-half losers vs bottom-half winners, as in accelerated pairings? Or pair unaccelerated players against each other by score, and accelerated players against each other the accelerated way? That third alternative would amount to postponing the merge until after round 2, even though all the round 2 games would be played at the same time, in the same room, at the same time control.

Obviously, then, if you merge after round 1, you are doing something that really doesn’t make sense.

Bill Smythe

3

Accelerated pairings do not have to be announced in advance, but if you are pretty sure that you’re going to be using them it’s a good idea to announce them. If you are planning a five round, one section tournament, are expecting 75 entries, and plan to use accelerated pairings, you should announce that fact.

If you are considering accelerated pairings remember that they only work well in tournaments where most all players have reasonably accurate ratings, and where there is a large spread in the ratings distribution. They can be counterproductive in tournaments where a lot of players are unrated, or have provisional ratings based on only a few games, and also in class tournaments where most all the players in the tournament or section have ratings relatively close to each other. For accelerated pairings to work well you need the top quarter to beat the second quarter and the third quarter to beat the bottom quarter in round one, and then for the second quarter to beat the third quarter in round two. If this doesn’t happen you might actually wind up with more perfect scores after round two than you would have had with standard pairings.

4

I doubt ANTD Cohen needs to be reminded of the mechanics of accelerated pairings, but please remember that they do absolutely nothing to enhance the chances that there is just one winner. Draws happen.

Alex Relyea

5

There is a difference between having only one perfect score and having only one winner. Accelerated pairings reduce the probability of multiple perfect scores, but you could always have a multi-way tie for first with, say, 4.5 out of 5. In fact, by cutting down the pool of perfect scores more quickly, accelerated pairings may actually increase the chances of having multiple first-place non-perfect-score winners.

Some players (and TDs) throw around the phrase “accelerated pairings” as though they provide a magic panacea for all pairing problems. Nothing could be further from the truth. In a class tournament (with, say, sections at 200-point intervals) the ratings are close enough together so that the bottom half winners (3rd quarter) are likely to clobber the top half losers (2nd quarter). Then you could end up with 3/8 of the players at 2-0, as opposed to 1/4 with standard pairings or 1/8 with accelerated pairings that work right.

Bill Smythe

6

Actually I was not aware that Mr. Cohen was an ANTD. As such I am sure you are right; he already knows this. However, my post was aimed not just at Mr. Cohen, but at anyone else who might read this topic, and who might not be aware of how accelerated pairings work.

No system can enhance the chances that there will be a sole winner, and no one is claiming that accelerated pairings can do so. It is theoretically possible that all games in a tournament will end in draws, and that all entrants will therefore be co-winners. What accelerated pairings can do is eliminate, or at least minimize the chances that there will be multiple perfect scores.

7

I started this topic mostly because of the idea [which I had never considered before] only accelerating one of the two schedules [3-day & 2-day] for an event.

Also, I got into a discussion with someone who hates accelerated pairings. Considering in Both January and February he played in events with unannounced accelerated pairing, it is understandable that he is upset. He actually withdrew from one of the events in protest after the second round [bye in Rd1]. I thought it important to remind TDs and organizers that if you are likely to use accelerated pairings, then you should include this in advance publicity. Something that looks to have disappeared since it is no longer a USCF requirement.

Larry S. Cohen
ANTD & Chess Organizer

8

I agree that, if accelerated pairings are likely, it would be a good idea to mention this possibility in all pre-event publicity.

The main point of my post was to point out that, if there are two schedules, and if the merge occurs after just the first round, then it would be completely illogical to use accelerated pairings in only 1 of the 2 schedules. In fact, such an act would show that the person who thought it up either did not understand accelerated pairings or did not think through the idea thoroughly enough.

Accelerated pairings are, in my opinion, highly overrated. They will reduce the likelihood of multiple perfect scores, but not the likelihood of multiple first-place finishers, as a couple of others have also pointed out here.

Far better, as a way to avoid multiple perfect scores, is to hold the event in two or three sections, so that the number of players in each section is below the boiling point.

One problem with accelerated pairings is that, for the vast majority of participants (all but the top eighth and the bottom eighth), the 3rd round in an accelerated event feels pretty much the same as the 1st round in a standard event. In effect, for this 3/4 majority, the result of accelerated pairings is essentially to simply interchange the order of the first 3 rounds: the 2nd round comes first, then the 3rd, then the 1st.

Bill Smythe

9

Has anyone used accelerated pairings in a score-based prize tournament? It would be interesting to see the reaction of players in class sections to have the organizer working actively against there being a 5-0 score by using accelerated pairings. If playing in such a tournament, a player should know in advance whether accelerated pairings were going to be used.

10

Recent score-based events at this venue have used accelerated pairings and two sections, and the phrase “accelerated pairings possible” has been included in the tournament announcement. There’s one today, I’ll be heading for it within the next two hours. These tournaments have been drawing around 40-60 players.

Bill Smythe

11

Far better, as a way to avoid multiple perfect scores, is to hold the event in two or three sections, so that the number of players in each section is below the boiling point.

Bill Smythe
[/quote]
Agreed, but the reason accelerated pairings exist is to give the TD another way to deal with a situation where the number of entries far exceeds the organizer’s projection. If you are planning a five round, one section tournament with expectations that 25 or maybe 30 players will enter, and 64 actually do, as happened to me one time, accelerated pairings give you a useful option.

12

I once was an organizer of a tournament for which I had hired an NTD as chief TD. He opted to use accelerated pairings even though the number of entries vs. number of rounds wouldn’t have necessarily required it. He felt it would make for better pairings overall.

During the event, someone came up to me and commented they were so glad accelerated pairings were being used, it made perfect sense, because blah blah blah. Not five minutes later someone else came up and started complaining that accelerated pairings made absolutely no sense in this event because blah blah blah.

You can’t please everyone.

13

It doesn’t make for better pairings overall. It only reduces the odds of multiple perfect scores.

Bill Smythe

14

“Better” is a relative term. As Mr. Neilly’s example shows, what one person may find to be better another may find to be worse. In general, though, I would say that if it looks like you can get by without using accelerated pairings you’re probably better off not using them. I have run into considerably more players who for one reason or another dislike accelerated pairings than I have encountered people who like them. Using accelerated pairings almost always generates more complaints than kudos.

15

It does reduce the odds of multiple perfect scores. It does not reduce the odds of a tie. Just that the tie won’t be with two players 5-0 or 7-0. So it does even reduce the use of tie breaks (in an event which will need to use tie breaks). It just means that two perfect scores won’t have one declared above the other based on whom they each played.

16

I will take a wild guess …the player that hates accelerated pairings is high rated. Our club uses accelerated pairings. So that u1600 players do not get crushed in first two rounds and leave. At least if you lose in round three you don’t feel as if your weekend was wasted

17

I’m confused. I just glanced at Mr. Bell’s tournament history and I don’t see anything terribly recent that looks like accelerated pairings.

Alex Relyea

18

main line chess club been a while since I played there. They always use accelerated pairings. I’m using their justification