Odd number of teams for Swiss Tourney

[Hanoi5]

The setting is the following: 7 teams will be playing 5 rounds of a Swiss tournament. Each round will take 8 boards.

 

- Is it better a bye or a three-way table (for the bottom three)?

- How will the movement for the 3-table work? 4 boards against each? How is it scored? The other 2 teams are getting VP's from an 8-board chart, so how is that supposed to work?

- Should there be repetition of matches? If not for some rounds, at which point can teams play against each other again? There was a round robin previously so all the teams met before.

 

Thanks for your help.

[Gerardo]

The setting is the following: 7 teams will be playing 5 rounds of a Swiss tournament. Each round will take 8 boards.

 

5 rounds are a lot. Ideally, # rounds ~ ceil(log₂ # teams).

In the last round you'll have the first playing with the bottom, unless you allow replays (then it is Danish, not Swiss).

 

- Is it better a bye or a three-way table (for the bottom three)?

- How will the movement for the 3-table work? 4 boards against each? How is it scored? The other 2 teams are getting VP's from an 8-board chart, so how is that supposed to work?

- Should there be repetition of matches? If not for some rounds, at which point can teams play against each other again? There was a round robin previously so all the teams met before.

 

Thanks for your help.

 

I'd say 3-way, but not sure.

A 3-way takes 2 rounds, as each team faces 2 opponents.

Not sure how to score. I know you get an IMP diference for each team, my first instinct would be to VP that using same scale but 2x # boards, 16 in this case.

I think Danish allows last round replay only.

[TimG]

The setting is the following: 7 teams will be playing 5 rounds of a Swiss tournament. Each round will take 8 boards.

 

- Is it better a bye or a three-way table (for the bottom three)?

- How will the movement for the 3-table work? 4 boards against each? How is it scored? The other 2 teams are getting VP's from an 8-board chart, so how is that supposed to work?

- Should there be repetition of matches? If not for some rounds, at which point can teams play against each other again? There was a round robin previously so all the teams met before.

A three-way lasts two round so each match involves the same number of boards as a head-to-head match -- no need for any VP scaling.

 

As a participant, I'd much rather a three-way to a bye. Why sit out a round? Especially when not every team will get a bye.

 

What is the rationale behind the switch from round robin to Swiss? It seems to me much better to have a complete round robin rather than have each team miss a single other team.

[Hanoi5]

What is the rationale behind the switch from round robin to Swiss? It seems to me much better to have a complete round robin rather than have each team miss a single other team.

 

Switch? There was no switch. The tournament was set for 4 Swiss sessions but with only 7 teams a complete round robin was done first and then the 5 Swiss rounds.

[TimG]

There was a round robin previously so all the teams met before.

 

 

What is the rationale behind the switch from round robin to Swiss? It seems to me much better to have a complete round robin rather than have each team miss a single other team.

 

 

Switch? There was no switch. The tournament was set for 4 Swiss sessions but with only 7 teams a complete round robin was done first and then the 5 Swiss rounds.

 

Ahh, I read this to mean that in previous runnings of this event, the conditions of contest called for a round robin, not that in earlier stages of this event there had been a round robin.

[gnasher]

With the scenario you describe, I would play a round robin with longer matches, or two round robins, or a round robin followed by knockout for the top two or four teams.

 

The usual reasons for playing a Swiss are:

- It's a reasonably fair way to produce a winner from a large number of teams

- It ensures that teams don't have to play many matches against teams that are markedly better or worse, thereby making the event more enjoyable for most.

Neither of these applies here, so there's no particular benefit to playing a Swiss. All it does is unfairly disadvantage the two teams who don't play the weakest team.

 

Regarding the original question of whether to have a three-way or a sit-out, I'm sure that most competitors would prefer to play than to sit out.

[Bbradley62]

Definitely 3-way over bye.

 

How's this for an odd (but maybe the most fair) format? In each of the 4 sessions, play a Mitchell movement with each team playing 4 boards against each of the other 6 teams. At the end, you will have played a 16-board match against each of the other teams.

 

Edit: I guess it wouldn't quite be a Mitchell, but I'm sure you get the idea.

Re-edit: Each round, EW pairs move up one table; boards move down, skipping two tables.

[NickRW]

Stronlgly suggest you consider a round robin of 6 rounds at 6 or 7 boards instead of using a Swiss for this low numer of teams.

[Free]

If you want to play the swiss, I'd definitely choose for the 3-table.

 

Put the teams in the following order (NS vs EW):

table 1: A vs B

table 2: B vs C

table 3: C vs A

 

Now let them all play the same 8 boards. The pairs will compare their scores with their teammates, and get a result on 8 boards.

 

Example scores for 1 deal:

1. A +100 (B -100)

2. B +100 (C -100)

3. C -50 (A +50)

This will give A +150 on this board, B 0, and C -150. Total points will always add up to 0.

 

Not sure where in the ranking you should use the 3-table. Perhaps the top teams should play this way, perhaps the middle, perhaps the bottom teams, no idea.

[Fluffy]

Definitely 3-way over bye.

 

How's this for an odd (but maybe the most fair) format? In each of the 4 sessions, play a Mitchell movement with each team playing 4 boards against each of the other 6 teams. At the end, you will have played a 16-board match against each of the other teams.

 

Edit: I guess it wouldn't quite be a Mitchell, but I'm sure you get the idea.

Re-edit: Each round, EW pairs move up one table; boards move down, skipping two tables.

I think this only works for 5 teams

 

Not yet fully sure, but I think for 7 teams boards have to move down 3 tables, the movement seems to fit then, and IMO is the best solution, 24 boards per session and you play against everyone with no byes.

[Bbradley62]

I think this only works for 5 teams

 

Not yet fully sure, but I think for 7 teams boards have to move down 3 tables, the movement seems to fit then, and IMO is the best solution, 24 boards per session and you play against everyone with no byes.

"down, skipping two tables" and "down 3 tables" are the same thing. Works well for 7 teams.

[barmar]

A three-way lasts two round so each match involves the same number of boards as a head-to-head match -- no need for any VP scaling.

But there are an odd number of rounds, so the last round has to be a 3-way with half as many boards against each team.

 

Played in a Swiss on Sunday with 7 rounds of 8 boards and an odd number of teams. Before the last round, the TD asked if a team was willing to volunteer to drop out (they would get a win for the last round, but no VPs), so he wouldn't have to do a one-round 3-way. I don't know if anyone took him up on it.

[Free]

But there are an odd number of rounds, so the last round has to be a 3-way with half as many boards against each team.

Read my post! Please! So everyone can stop whining about half the number of boards...

[gordontd]

Read my post! Please! So everyone can stop whining about half the number of boards...

I've read it, but it doesn't make sense, because you are suggesting that we have different opponents from our team-mates. Shouting at us to read it doesn't make it meaningful.

[Fluffy]

"down, skipping two tables" and "down 3 tables" are the same thing. Works well for 7 teams.

Ahh right sorry, I think your solution looks much better than anything proposed, If you have segment lenght problem you can just play 2, 3 or 4 boards whatever you want. This system is specially indicated for 5 teams where the bye is trully awful.

[Free]

I've read it, but it doesn't make sense, because you are suggesting that we have different opponents from our team-mates. Shouting at us to read it doesn't make it meaningful.

So everyone ignores it because it feels weird, great. We've used this method to play with 3 teams a lot in the past and you get a representative result. If you don't want to use a simple and working solution where you get a result and nobody has to sit out, fine by me. If you want to explore some new grounds, continue reading.

 

Yes, you are playing against opponents from a different team, but so are the other 2 teams. In the end you don't need to modify the number of boards and you can compare 2 scores which resemble your own team's capabilities. Your team has played the NS and the EW hands. It doesn't matter if you play against 2 pairs of the same team or not. You compare the scores of your team, and calculate the imp difference. With that imp difference you calculate your own VPs (if you'd win 17-13, you just get 17). Eventually, you don't win/lose a 3-table match against 1 team, each team just gets it's own VP score. Moreover the average VP score usually will be 15 (unless one team gets beaten up like it would lose 25-0 for example).

[TylerE]

The way it's around here, which seems fair to me, is as follows:

 

First 3-way: Random draw (last 3 teams numerically, random team #s)

 

Subsequent 3-ways: Bottom 3 teams in overall rankings

 

If playing an odd number of matches:

Before the last round, the very bottom team is awarded a tie, the other two bottom teams play a normal match.

[Gerben42]

I suggest not to have a Swiss with the number of rounds more than half the number of teams. Just play a heptagon movement, if needed in two 24-board sessions. Letting a team sit out for 8 boards (1 hours) is not even worth discussing I think.

 

I.E. What Fluffy said :)

[gordontd]

If you don't want to use a simple and working solution where you get a result and nobody has to sit out, fine by me.

There already exists such a solution, routinely used. Your method does not seem to be an improvement on it.

[Free]

There already exists such a solution, routinely used. Your method does not seem to be an improvement on it.

So why don't you explain it and help the OP instead of targetting someone's (in your eyes) inferior method? How will you let all people play at the same time without a sit out and without changing the number of boards?

 

Unless I'm missing something, this is theoretically impossible if you want pairs of one team to play only against pairs of one other team. This is also known as the pigeon whole principle.

[gordontd]

So why don't you explain it and help the OP instead of targetting someone's (in your eyes) inferior method?

Sure. You get the bottom three teams to play two half-matches, using an appropriate VP scale that gives them up to 10 VPs for each half. The movement within the three tables is a mini American Whist.

 

Imagine you are playing 8 board matches. The three teams in the triple will have 12 boards in play - four on each table. After playing four boards against one of their opposing teams, the EW pairs take the completed boards back to their team-mates (for them to play), and then go on to play at the third table. After playing both half-matches they return to their team-mates to score up.

 

You need to have spare boards available for the extra half-set, and it's a good idea for them to be very high numbers so they don't get confused with other boards in play.

[RMB1]

I don't read posts with large bold letters in, or the posts they refer to, so I might be repeating what has already been said.

 

You would do well to get an extra team, or play an extra round and play a complete movement. You can play six rounds with seven teams, where matches are completed after one or two rounds.

 

AvB/BvC/CvA DvE/EvD FvG/GvF

AvC/BvA/CvB DvF/FvD EvG/GvE

 

AvD/DvG/GvA BvE/EvB CvF/FvC

AvG/DvA/GvD BvF/FvB CvE/EvC

 

AvE/EvF/FvA BvD/DvB CvG/GvC

AvF/EvA/FvE BvG/GvB CvD/DvC

 

Playing 5 rounds with 7 teams with 3-way matches involves 15 matches as part of the 3-ways, leaving only 6 assignments for the rest of the matches, so this will not work. You need to play some "long triangles" with 3-way matches spread over two rounds, and indeed you must play two long triangles during four of the five rounds. This is almost the schedule above for six rounds: one team must play in the long triangle for the first four rounds. You can then play a "short triangle" 8 board 3-way for the final round. You can try to preserve some of the Swiss element, but it will be a sham.

 

So in round 1: three teams start a long triangle, two head-to-head matches. Round 2: complete first long triangle, winners and losers of head-to-head play another head-to-head match.

 

For rounds 3/4, one team stays in the triangle, joined by two teams who have not played yet; the other four teams play their possible unplayed matches (two head-to-head matches in each round).

 

In round 5, the team who stayed in the triangle before must play in the short triangle with the two teams who have not played in the triangle. The remaining two head-to-head matches can be assigned on Swiss basis.

 

Alternatively, round 5 could be a Danish round. 1st v 2nd, 3rd v 4th and remainder in the short triangle, ignoring previous assignments.

[Free]

Sure. You get the bottom three teams to play two half-matches, using an appropriate VP scale that gives them up to 10 VPs for each half. The movement within the three tables is a mini American Whist.

 

Imagine you are playing 8 board matches. The three teams in the triple will have 12 boards in play - four on each table. After playing four boards against one of their opposing teams, the EW pairs take the completed boards back to their team-mates (for them to play), and then go on to play at the third table. After playing both half-matches they return to their team-mates to score up.

 

You need to have spare boards available for the extra half-set, and it's a good idea for them to be very high numbers so they don't get confused with other boards in play.

If I understand this correctly, it looks like you're using the same principle as I do for seating, and swap around after 4 boards so you can compare the teams against each other based on 4 boards...

 

The difference is that you compare AvsB, BvsC and AvsC based on 4 boards and need to change VP scales or divide the total by 2, while my method just calculates the scores team per team based on 8 boards and needs no rescaling or different VP scales.

[gordontd]

If I understand this correctly, it looks like you're using the same principle as I do for seating, and swap around after 4 boards so you can compare the teams against each other based on 4 boards...

 

The difference is that you compare AvsB, BvsC and AvsC based on 4 boards and need to change VP scales or divide the total by 2, while my method just calculates the scores team per team based on 8 boards and needs no rescaling or different VP scales.

Yes, but for me it's not teams if you don't play the same boards against the same team as your team-mates.

 

I thought this process of having a short triple was universal. I'm surprised that you appear not to know it. It's not complicated when you're prepared for it - we always carry three table cards, with 0-10 VP scale on them, to any Swiss Teams we run.

[Cascade]

It should be possible to do one of the following:

 

1. Play a three-team match with two half matches for each team against each of the other two teams

 

2. Similar to 1. but over two rounds play a full match against each other team. This method has obvious problems if there is scheduled an odd number of rounds. Perhaps you can play the half matches at the end.

 

Either of these methods can be programmed so that when you play the three-way matches you are playing in 2. two other teams that you have not played and in 1. two other teams that you have played at most for a half match in a previous three-way.

 

The first method for small fields has the potential to break down quickly if you want to avoid replays.

 

As an aside does anyone know of a good discussion of algorithms to make a Swiss Draw? I am particularly interested in any tricks to make an algorithm more efficient when making a draw around the half way point - round n for 2n teams - which is where algorithms seem to have problems.