What if too few players register in a two-stage tournament

[dschingis27]

Here is a quirky two-stage tournament that I created and that is still running. https://boardgamearena.com/tournament?id=567401 It tells us a little bit about what happens when fewer than the intended number of players register in a two-stage tournament.

What I wanted to have:
21 groups of 4 players, best 2 per group go to the KO stage. Group distribution is done by Serpentine.
- 1st places go directly into KO round 2.
- 2nd places start before in KO round 1, except the 2nd place with best Elo also starts in round 2.
(In that way it makes a difference if you get 1st or 2nd in your group and we can avoid some unwanted BGA quirks about matchmaking in the KOs.) https://boardgamearena.com/forum/viewto ... 480#p89480

The intended number of players was 84, however, I am always very tolerant with the minimum number of players because I see no good reason to take a tournament away from people who registered, even if the tournament turns out shorter and a bit odd. I set the minimum player number to 42.

Here is what happened:
- Only 62 players registered, that means not even enough were there to create 21 groups of 3 players.
- I expected that maybe a 21st group with only 2 players would be created, however, only 20 groups of 3 players were created.
- 2 players were seeded directly into the 2nd tournament stage, the KO stage, they missed the initial group stage completely.
- Surprisingly, the 2 seeded players were rank 21 and 22 in the original Elo ranking of participants, I suspect this has to do with Serpentine.
- Other than that, everything went normal and as intended, all 1st places were seeded into KO round 2, and the 2nd places started in KO round 1.

I think we can learn 3 things from that:
- If too few players register for a two-stage tournament, BGA makes sure that it can still happen, however, with some seeding to make it work.
- A group where everyone advances to the next stage is never created. I suspect there is a hard rule to prevent that.
- The seeded players are not necessarily plausible, it may even depend on the group distribution mechanism.

I don't think anything needs to be done about this. I am happy that these tournaments actually start and work out. It's a bit of an obscure edge case.

[BananaHarambe]

I have experimented with this as well. For your desired structure a minimum of 63 players would have been ideal so that everyone gets to play Stage 1. Like you said, one group only had 2 players so they automatically advance.

I made a 8 group tournament with 32/32 signups and 4 players from each group advance into Swiss. The idea was to play some warmup games in groups, but Stage 1 was completely skipped and it went straight to Swiss. So it is correct that Stage 1 will be skipped for each group that does not need to eliminate any players.

Interesting idea to use 21 groups with 2 advancing to make a bracket. 21-1-10 = 32 players in Round 2.

Sharing one of my Group Stage setup tricks: Swiss 2 groups, 7 from each group advance to SE. Configure so that each group will have one X-0 undefeated player that gets to skip a round in the Stage 2 bracket. I would host 64 players with 5 match Swiss Stage 1 so each group of 32 players makes a 5-0 winner and has 5 players with 4-1 who advance, plus a lucky 3-2 player.

[tbhp]

- Surprisingly, the 2 seeded players were rank 21 and 22 in the original Elo ranking of participants, I suspect this has to do with Serpentine.

That makes sense. Serpentine inverts the order on each pass, so that the groups don't end up having decreasing Elo ranks, but rather the same average for each group.

So it starts assigning players to each group, starting from highest Elo to lowest, then once it's finished putting one player in each group, instead of starting again from the top, it climbs back up. Then it keeps doing that for as many passes as are required, going up and down like a snake.

By doing this, it ensures that for each two successive passes, the cumulative Elo ranks are the same for each group. In your case, the sum after two passes is always 43 (player 21 is paired with player 22, player 1 is paired with player 42, and so on).

Since the group of player 21 is the last that was assigned a player, and there are 62 players in total, that's the group that ends up not having a third player. That would also have been true without using serpentine, except player 21 would have been paired with player 42.

I made a 8 group tournament with 32/32 signups and 4 players from each group advance into Swiss. The idea was to play some warmup games in groups, but Stage 1 was completely skipped and it went straight to Swiss. So it is correct that Stage 1 will be skipped for each group that does not need to eliminate any players.

I like this idea warmup games. Makes things fun and relaxed in the first stage, before things get serious in the second stage. It can seem a bit absurd, but it fits the spirit of some games.

It seems like a limitation that the site doesn't allow organizers to do something like that.

[RazorOz]

I have experimented with this as well. For your desired structure a minimum of 63 players would have been ideal so that everyone gets to play Stage 1. Like you said, one group only had 2 players so they automatically advance.

I made a 8 group tournament with 32/32 signups and 4 players from each group advance into Swiss. The idea was to play some warmup games in groups, but Stage 1 was completely skipped and it went straight to Swiss. So it is correct that Stage 1 will be skipped for each group that does not need to eliminate any players.

Interesting idea to use 21 groups with 2 advancing to make a bracket. 21-1-10 = 32 players in Round 2.

Sharing one of my Group Stage setup tricks: Swiss 2 groups, 7 from each group advance to SE. Configure so that each group will have one X-0 undefeated player that gets to skip a round in the Stage 2 bracket. I would host 64 players with 5 match Swiss Stage 1 so each group of 32 players makes a 5-0 winner and has 5 players with 4-1 who advance, plus a lucky 3-2 player.

The thing on this is there really needs to be an option to have a two phase tournament where you have like Swiss with cut, so it's 1 giant league, which then cuts to x, this actually a very common way for tournaments to work in real life, which isn't currently possible on BGA as you have to set a number of groups which can't be 1. I actually think this would be a pretty popular way of running tournaments too.

Currently the whole multiple phase tournaments can be used to your advantage, to force settings you'd want that otherwise wouldn't be possible, but it comes at a considerable cost of it tends to make your tournaments more vulnerable and prone to breaking, they can be very reliant on perfect numbers or they all fall apart.

[dschingis27]

It seems like a limitation that the site doesn't allow organizers to do something like that.

Well, it's just one of the many seemingly arbitrary/unnessecary limitations of tournaments on BGA.

- There can't be a group where no one gets eliminated. (Would be nice to have the option.)
- There can't be a group stage tournament with only one group in stage 1 (Why oh why?).
- There can't be double-/multi-round robins where everyone plays each other more than once.
- Related to the last point, there is no intrinsic "Best-of-X" setup for 2p knock-out matches.
- There can be at most 15 players in a round robin group. (Ok, I guess there must be some limit, but why 15?)
- There must be at least 3 games in a Swiss System (hence e.g., preventing a Final Four KO tournament where there are only 2 semi finals and then the final plus bronze medal game).
- No intrinsic ability to have different player counts or different game options in different tournament stages.

While some of the above can really be an implementation problem, most limits feel arbitrary (there MUST be someone eliminated, there MUST be more than one group in group stage 1, there MUST be at most 15p in round robin groups, there MUST be at least 3 games in Swiss, why oh why?)

[tbhp]

- There can't be double-/multi-round robins where everyone plays each other more than once.
- Related to the last point, there is no intrinsic "Best-of-X" setup for 2p knock-out matches.

This is a bit of a glaring oversight when you think about it, considering a competition as popular as the Champions League is more or less set up that way.

- There must be at least 3 games in a Swiss System (hence e.g., preventing a Final Four KO tournament where there are only 2 semi finals and then the final plus bronze medal game).

I guess they didn't think that far when they decided it. It's weird though, because there are Swiss system tournaments where there are not enough games for a single undefeated player to be declared. That's allowed. Your suggestion on the other hand is guaranteed to result in a neat 1,2,3,4 ranking, yet it's not allowed.