[hrothgar]

Vampyr, on Feb 19 2010, 06:05 AM, said:

Would it have been "fairer" for us to miss out, since our Swiss points would not have been very many? Would it have made it a "better" event? What do these words mean?

I don't recall anyone using the word "fairer" to describe a Strength of Schedule adjustment; not did anyone use the expression better.

I made a very specific claim: Incorporating a Strength of Schedule adjustment increases the accuracy of a Swiss Teams format.

If you don't really care which team places where, don't use one. If, on the other hand, you think that its valuable that a tournament produces an accurate ranking of the skill level of the various teams...

[hotShot]

The swiss format is a theoretical equivalent of a sorting algorithm, that will bring everything into the correct order within log2( Number of objects ) steps.

To work properly it is necessary that the comparison function can give a true answer about which object is "larger" than the other. Unfortunately the remaining randomness of bridge distorts that comparison function.
On a small number of boards, the better team/pair will not necessarily win.

The algorithm is designed to use only wins and losses. The amount of a win should not mean anything. So using IMPs, VP or MPs for more than to determine the winner, leads to an additional distortion of the result.

To make a good swiss you should only count the wins and losses to determine the ranks. If everybody is playing duplicated boards, one could use the MPs/IMPs as a tiebreaker for those who have the same number of wins, but it will reintroduce a little more randomness to the final result.

[hrothgar]

hotShot, on Feb 19 2010, 03:12 PM, said:

To make a good swiss you should only count the wins and losses to determine the ranks. If everybody is playing duplicated boards, one could use the MPs/IMPs as a tiebreaker for those who have the same number of wins, but it will reintroduce a little more randomness to the final result.

"Good" is defined how?

Also, do you have any kind of analysis that backs up this assertion? (It seems very counter intuitive to me)

I can certainly believe that it would be better to use BAM scoring on individual boards. However, I don't think that the same logic should carry over to entire matches.

[helene_t]

hotShot, on Feb 19 2010, 01:12 PM, said:

The swiss format is a theoretical equivalent of a sorting algorithm, that will bring everything into the correct order within log2( Number of objects ) steps.
[.....]
The algorithm is designed to use only wins and losses. The amount of a win should not mean anything. So using IMPs, VP or MPs for more than to determine the winner, leads to an additional distortion of the result.

To make a good swiss you should only count the wins and losses to determine the ranks. [....]

It's not the idea of Swiss that it should resemble a sorting algorithm.

The idea is that having two top pairs play each other provides more information about their relative strength than having them both playing against weaker pairs. Also, if each table has a NS pair and an EW pair of approximately the same strength, the strength of the EW line and the NS line will be similar so the comparison of an NS score to an EW score is fair.

I am pretty sure that using IMPs is more efficient than counting wins/losses.

[mycroft]

Swiss works wonderfully as a sorting algorithm - but only for the extreme ends. Not perfectly accurately, true, but for "on the day".

If you run N rounds for 2^N pairs (in WIN/LOSS), you'll get a top team and a bottom team. Top team wins. You can't say with any certainty at all who's second, however. Overswiss a round, and you get #2. Another round, you get 3 and 4.

However, if you leave the sorted-out pairs in the swissing, you muck up the results (especially if you enforce a no-playback rule). So you need to remove the winner and last place from the game after N rounds, and the next pair after N+1, ... Nobody's going to go for that.

So we overswiss and leave the polluting pairs in the mix; the "fair" movement is damaged. It's damaged more (in a purely theoretical sense) by VPs (although that removes the "single-elimination" feel of a pure W/L swiss), more yet by non-duplicated boards, and so on...all of which works to the advantage of the pairs that aren't the best. You know, N-1/N% of the paying customers?

Curling bonspiels do a couple of interesting formats - either N games guaranteed (for 3: A (winners), B (lost first match), C (lost second match, irrelevant of what happened in 1), producing an A winner, a B winner, and a C winner) or N-ple knockout (where when you lose the first match, you drop into B, when you lose in B, you drop into C.) Notice how both of these require the A winner to play fewer (frequently much fewer) games than the C winner (in curling, this is considered a plus from the A winner's perspective - more drinking time).

(Note: qualifiers, unlike bonspiels, tend to work as a full-RR into Page playoffs: 1v2, 3v4; winner of 3v4 plays loser of 1v2 for the right to play the 1v2 winner in the final. To determine a "best team", this actually works very well; you have to have the "win the big games and against the fishes" skill to lead the RR because being 1 or 2 is a distinct advantage (two wins v three, can lose the first one if you come back to beat them on the revenge), but you still have to win two or three big games to win the event. It only works with prequalifiers, though, as the size of the RR has to be limited).

But all of that theory is irrelevant in Real Life. In Real Life, people like Swiss events because they like playing against people of their level (and swissing does do a good job of "bucketing" skill levels fairly quickly), and because of match awards. Swiss pairs has the added benefit that you don't have to find teammates you're willing to play with all day - I'm surprised it hasn't just exploded here (I guess BKOs will still award more monsterpoints, and the one-session swisses, well you have a team already; and Sunday will never change. Oh well). Also, the fact that it's a poor method of determining the winner is a plus for the 3rd-6th (or so) teams, who have a good chance of winning (and a good chance of being 10th, but still).

[Gerben42]

I think anyone who has played Swiss Teams knows that it's extremely random. I still feel sorry for Fluffy for his Estoril tournament, for example.

One of my positive Swiss experiences was the mixed teams in Pula. I ended up 2nd although I think my team wasn't remotely among the best 10. But we got easy opponents and some luck in the last round.

HotShot has shown the decisive point. In a swiss tournament, you cannot have VPs for it to be fair.

Quote

Consider two teams which finished close to each other in the standings. We probably only care about teams that finished close to the top, so consider two such teams (say 1st and 2nd place).

For each of these teams, we can compute the "strength of schedule" that they faced, in the simple way proposed. All this means is, you take all the opponents faced by each team and sum up their final victory points. To remove the effect of facing each other (if they did play each other) I suggest ignoring the teams in question. So:

For team one, compute the total of the final VPs of all teams they played except for team two.
For team two, compute the total of the final VPs of all teams they played except for team one.

My claim is that if team one has a substantially weaker strength of schedule according to this formulation, then something has gone wrong. The team that placed second can easily be a better team, yet they had to play against much stronger opposition and therefore couldn't rack up as many VPs.

I've done that for the Estoril transnationals and the result was quite shocking.

[FrancesHinden]

Short (one day, so up to 50 board) Swiss pairs events in the format played in England i.e.
- 7x7 or 8x6 or 6x8 matches
- matchpoints converted to VPs
- assignments one round in arrears

are very very random. Just look at all the 1-day county events and see how lots of different pairs win them, including pairs who you don't see doing well more than once, or in any other type of event.

Longer events (2-3 day ones) and/or not converting to VPs and using current match assignments are much better.

It's a pity that the EBU has reduced the amount of current-match assignmenting it does.

[gordontd]

FrancesHinden, on Feb 24 2010, 10:34 PM, said:

It's a pity that the EBU has reduced the amount of current-match assignmenting it does.

Assigning?

[Mbodell]

I think Swiss pairs are a fun sounding format, and I certainly enjoyed them online (MP or IMP, it doesn't really matter either can be the basis of swiss pairs).

In the ACBL there are three obvious problems:

1. They are unfamiliar. So you are less likely to see them.

2. They require pre-duplicated board sets to play more or less barometer style. This should be done for all events IMO (for fairness and event integrity - certainly more important than cell phone bans), but it is a problem for organizers in the ACBL tradition.

3. I've heard the master point awards are off in that the master point awards are based on number of tables more so than number of players so you will not award as many points in a 400 person swiss pair than you do for a 400 person swiss team. This is problematic if your goal as event organizer is to maximize the number of master points that are awarded.

But really, I think it is good that different locations are offering different events.

In terms of making swiss teams more fair and accounting for SoS, that's what the ?Zeligmo? (I forget the spelling) method does where it uses the swiss results recorded to then "simulate" what would happen if a complete round robin were to be played. The results of that calculated full round robin are then used to compare the team. I'm sure someone here remembers the article in question which studied one of the big European team competitions.

[Vampyr]

FrancesHinden, on Feb 24 2010, 10:34 PM, said:

Short (one day, so up to 50 board) Swiss pairs events in the format played in England i.e.
- 7x7 or 8x6 or 6x8 matches
- matchpoints converted to VPs
- assignments one round in arrears

are very very random.  Just look at all the 1-day county events and see how lots of different pairs win them, including pairs who you don't see doing well more than once, or in any other type of event.

But... by adding all of these one-day county events it's not as if the EBU are eliminating the longer ones. And the "lots of different pairs winning" cannot be a drawback in terms of getting bums on chairs. Top players like you, Frances, need to remember that there has to be events in which the little guys can enjoy themselves and hope to win, or there will be no events at all.

Quote

Longer events (2-3 day ones) and/or not converting to VPs and using current match assignments are much better.

It's a pity that the EBU has reduced the amount of current-match assignmenting it does.

It is a shame. And why is it so difficult? They could post the assignments around the room as they do in Swiss teams, or just project them onto a wall.

[Vampyr]

Mbodell, on Feb 24 2010, 11:34 PM, said:

I think Swiss pairs are a fun sounding format, and I certainly enjoyed them online (MP or IMP, it doesn't really matter either can be the basis of swiss pairs).

In the ACBL there are three obvious problems:

1. They are unfamiliar.  So you are less likely to see them.

This is why the ACBL also don't hold multiple teams events. Why they play two-winner movements and magically come up with a single winner. Why most (if I am not mistaken) clubs use hand-dealt cards and don't provide hand records. The "not invented here" syndrome is rather prevalent in North America.

Quote

2. They require pre-duplicated board sets to play more or less barometer style.  This should be done for all events IMO (for fairness and event integrity - certainly more important than cell phone bans), but it is a problem for organizers in the ACBL tradition.

This is true; you need about 1/(number of boards per round/2) the number of sets of boards as you have tables, for either Swiss pairs or Swiss teams. At the Brighton congress this requires someone to be working almost full-time between the two weekends preparing the boards. Do the ACBL not have the manpower? They don't even offer prizes at most events; surely they could afford people to prepare the hands.

Quote

3. I've heard the master point awards are off in that the master point awards are based on number of tables more so than number of players so you will not award as many points in a 400 person swiss pair than you do for a 400 person swiss team.  This is problematic if your goal as event organizer is to maximize the number of master points that are awarded.

Who awards the masterponts -- the ACBL? So... do they not have the power to create the masterpoint formulae?

I think that it would be incredibly dreary to have to play most of my bridge in the ACBL, especially as "bracketed knockouts" have become so prevalent. And I don't understand the appeal (except for the apparently inflated number of masterpoints awarded). Most people I know would not show up to an event if they were not guaranteed to be able to enter the top flight.

Quote

But really, I think it is good that different locations are offering different events.

In terms of making swiss teams more fair and accounting for SoS, that's what the ?Zeligmo? (I forget the spelling) method does where it uses the swiss results recorded to then "simulate" what would happen if a complete round robin were to be played.  The results of that calculated full round robin are then used to compare the team.  I'm sure someone here remembers the article in question which studied one of the big European team competitions.

People will be less likely to want to play if the results are not immediate and transparent to the players. Surely having people motivated to come to play is more important than deciding which is the "best" of the four top teams who showed up.

[McBruce]

I run a Swiss Pairs at the ACBL club I direct about once every two months. a short 2.5 hour mid-week evening game where we normally play 20-21 boards. This allows a five-round Swiss Pairs with four-board rounds, and without a dealing machine I spend about three hours pre-duplicaing 5 sets, which is enough for about 10-12 tables, our usual turnout.

ACBLScore awards the same overalls as for a club game for this event, plus reasonable match awards. Usually 95+% of the pairs win some points, and with the match awards added there are usually more points paid out in total. You do need to use software dedicated to Swiss Pairs and transfer only the final results to ACBLScore.

The key is in instructing players at the start. They need to know that:
--basic scoring is in matchpoints, so pairs strategies apply
--everyone is playing the same boards at once, with multiple copies of the same board around the room (so no loud comments)
--it's vital to pass boards down one table immediately once you have completed them and scored the result
--your matchpoint score in each round is converted to VPs in such a way that you need about 66% in a round to score a 20-0 blitz
--after round one, pairs are given new opponents based on their position in the standings

Players do enjoy the format, especially the feedback they get in later rounds by moving to a lower numbered table after a win. Even players who insist on a North-South or a stationary table at teams seem to enjoy the variety and excitement of vying for the right to play at "table 1."

Of course, after the first round, once play begins, you announce that even if you don't place in the overall awards, the winning pair in each match gets a match award.


As for the weaknesses of Swiss events in general, I think players tend to overestimate the difference between leaders and challengers. If you have the lead in a Swiss Teams event and play the 2nd place team, you're probably 3-8 VPs ahead of the 3rd vs 4th match. Your expectation in VPs, compared to the next few teams down the line, is probably negative. but your average expected VP result is probably 12-8 while 3rd vs 4th is maybe about 13-7: a difference of only one VP.

[Cascade]

What is the advantage in playing Swiss Pairs in converting scores to VPs?

I am particularly interested in MP scoring compared with carrying through the raw matchpoint score or percentage.

[gordontd]

Cascade, on Feb 27 2010, 06:06 PM, said:

What is the advantage in playing Swiss Pairs in converting scores to VPs?

I am particularly interested in MP scoring compared with carrying through the raw matchpoint score or percentage.

If you score in matchpoints or %, every board carries equal weight as in other matchpoint events. That sounds like a desirable thing in a matchpoint event, but the problem is that with fewer rounds, and longer ones than is usual in other matchpoint events, it's possible to have a very good or very poor match and for this to have a disproportionate effect on your final score.

This is especially so in the early rounds when strong pairs can meet very weak pairs. I once started a Swiss Pairs playing against a pair who it turned out had never played in anything other than an occasional club duplicate before, and we scored 94% on our seven-board match. I'm happy we only got 20 VPs for that.

Having said that, I've played in and run both sorts of events (when Bridgemates were first introduced the only software that scored Swiss Pairs didn't convert to VPs), and I think there are advantages and disadvantages to each.

[FrancesHinden]

Vampyr, on Feb 25 2010, 01:07 AM, said:

I think that it would be incredibly dreary to have to play most of my bridge in the ACBL, especially as "bracketed knockouts" have become so prevalent. And I don't understand the appeal (except for the apparently inflated number of masterpoints awarded). Most people I know would not show up to an event if they were not guaranteed to be able to enter the top flight.

You need to remember that there have to be events in which the little guys can enjoy themselves and hope to win, or there will be no events at all.

[nige1]

mrdct, on Feb 15 2010, 08:25 PM, said:

Over the last 10 years or so imp-scored swiss pairs has become the overwhelmingly most popular form of two-session pairs event in Australia with many, if not most, congresses (two day red-point bridge event typically with pairs on Saturday and teams on Sunday) ditching the traditional matchpoints pairs event for imp-scored swiss pairs.
This format, where you are still matchpointing across the field, I haven't seen before; but it might appeal to players who still want to risk their contracts for overtricks and play in anti-percentage NT contracts.

Match-pointed pairs or board-a-match teams require different skills from imped pairs and and teams. In the former, each board has roughly the same weight, and an extra overtrick or undertrick may be crucial, inflating the skill factor.

A Swiss competition is a good compromise between a Knockout and a Round-robin. If you only have time to play a fixed number of boards, and you are choosing between these three formats, then Swiss is best. Results of Swiss competitions correlate best with "God's order".

[blackshoe]

nige1, on Feb 27 2010, 06:38 PM, said:

Results of Swiss competitions correlate best with "God's order".

Who? What?

[Siegmund]

Aaaah! We have a Loki worshipper in our midst.

[Vampyr]

FrancesHinden, on Feb 27 2010, 08:06 PM, said:

Vampyr, on Feb 25 2010, 01:07 AM, said:

I think that it would be incredibly dreary to have to play most of my bridge in the ACBL, especially as "bracketed knockouts" have become so prevalent. And I don't understand the appeal (except for the apparently inflated number of masterpoints awarded). Most people I know would not show up to an event if they were not guaranteed to be able to enter the top flight.

You need to remember that there have to be events in which the little guys can enjoy themselves and hope to win, or there will be no events at all.

Well, I can scarcely argue with that! But I think that this is a little different, because people are entering an event that they have no chance of winning, no matter how well they do. That's why I don't understand the popularity of such events.

[TimG]

Vampyr, on Feb 28 2010, 03:16 AM, said:

FrancesHinden, on Feb 27 2010, 08:06 PM, said:

Vampyr, on Feb 25 2010, 01:07 AM, said:

I think that it would be incredibly dreary to have to play most of my bridge in the ACBL, especially as "bracketed knockouts" have become so prevalent. And I don't understand the appeal (except for the apparently inflated number of masterpoints awarded). Most people I know would not show up to an event if they were not guaranteed to be able to enter the top flight.

You need to remember that there have to be events in which the little guys can enjoy themselves and hope to win, or there will be no events at all.

Well, I can scarcely argue with that! But I think that this is a little different, because people are entering an event that they have no chance of winning, no matter how well they do. That's why I don't understand the popularity of such events.

I'm not sure whether you're talking about entering an open event that they have no chance of winning or entering a bracketed/flighted event which, because they are in a non-top bracket/flight, they have no chance of winning the whole thing.

But, either way I can understand why the events might be popular. In an open event, people can compare their result to how they expected to do, they get to play against a few good (or great) opponents along the way which is a draw for some, and they get token awards (match or section awards) along the way.

In a bracketed/flighted event, there is the chance to win the bracket/flight in which they are entered. And, you still get the token awards along the way. People choose to play games against less than great players all the time.

Do not discount the social aspect of either event.