Thursday, January 28, 2016

WER: Editing Matches 2 — Cascades

Last week, I talked about editing matches in WER and what to do when you only have one or two tables to fix. This week, I'm going to take the ideas and processes there a little bit further and talk about what scorekeepers call "cascades" or "cascading repairs." They're not nearly as intimidating as they sound.

Common issues that lead to cascading re-pairs are accidental drops and bye issues (which usually only happen at GPs, Opens, Invitationals and the like), and dealing with them uses a similar process to dealing with incorrect results. There are just a few more things to consider and a few more tables to re-pair.

The Theory of Cascading

It's round six of an Open. A player comes up to the stage because his name isn't on the pairings. At the end of the last round, he had 9 match points, still potentially in contention to make Day 2, and he doesn't know why he was dropped.

You can't just pair him against the player with the bye (if there is one), because he's supposed to be paired in this round according to his record, which means he should be paired against someone that has about 9 match points, and 0 and 9 are very different. But all the players with 9 points are already paired. Telling him he can't keep playing isn't an option either, especially if he was dropped as a result of a mistake the scorekeeper made.

You need to pair him with an appropriate opponent, which means you're going to have to stop a match where at least one player has 9 points (and, if you're lucky, that player's opponent has 6 points) and pair him with that player.

Now you have a different player who isn't paired that you need to find a match for. If you're lucky, he has 6 match points (and you have match where a player with 6 match points is paired against a player with 3 match points). You can stop that match and pair your floating player with 6 match points against a player from that match with 6 match points.

Now you have a third player who isn't paired. See where this is going? Eventually, you can break a match in which a player has 0 match points and either pair that player with the existing bye or assign him or her a bye, whichever the case may be.

However, following these steps in this order is extremely time consuming. By the time you get to the second or third match, there's a good chance that match has already started playing, and stopping matches that are in progress is a Bad Thing.

It might be tempting to delete the pairings, re-add the player to the event, and re-pair the entire round, but that's time consuming in a different kind of way: it causes a delay to the entire event instead of just a few matches, and it can be confusing for players.

We'll get to what steps to follow instead in just a second.

A Few Words on Accidental Drops

Players being dropped when they didn't mean to drop is one of the leading causes of cascading re-pairs. Before you start breaking tables though, you might want to figure out what happened that led to the drop — it might give you some insight into what you're going to have to do or offer an easier solution.

It's important to note that you don't want to spend a ton of time on this, especially if the round clock is already ticking: your Prime Objective is to get players in seats and playing Magic, and trying to get to the bottom of what happened delays that. You can always go back to the slips later to figure out what happened, and this is a useful learning exercise ... but it's secondary to fixing the problem.

That said, these are the common issues I run into:
  • Someone made an incidental marking in the drop box.
  • A name on the drop sheet was illegible, or I misread it.
  • I misclicked.
  • The players marked the wrong drop box.
  • The player no-showed and didn't tell anyone he didn't want to drop.

In most situations, you're going to be doing the same thing. Start by letting the Head Judge know what's going on, even if the mistake was yours. If the mistake wasn't yours, he or she may have a reason to not let the player re-enter the event (but in most cases, if it's the beginning of the round after they were accidentally removed, re-entering them is the best choice).

Re-adding Dropped Players

This is almost always the first step in dealing with a cascade, and you want to do this before you start fiddling with pairings because you can't add a player in the middle of editing matches. You need the missing player in the event for your match-editing efforts to be effective.

To do this, go to the Players tab in WER:

By default, this screen will show you Active players. Click in either the All or Inactive circles above the player list to find the players that have been removed. If your event is large, you can use the search box above that to narrow down the results.

Double-click on the player you want to re-add. Their information will populate in the fields to the left. Make sure you're re-adding the correct player, then click the "Re-Enroll" button.

You'll be prompted to make a choice about what to do with the player. Assigning them a bye for now is fine; you're going to fix pairings in a second.

Crafting Correct Pairings

I use crafting here because there is a bit of an art to identifying the optimal matches to break and re-pairings to implement. There are "rules," of course, but every actual, live tournament is different. They have different matches with draws. They have different pair-downs. The player you need to re-add has a different record. This means that what you will and won't be able to do can vary pretty wildly. Once you have the missing player added back in you're going to want to do the following:

  1. Figure out how many and which matches you need to break.
  2. Send a judge to stop those players from playing.
  3. Do some computer stuff.
  4. Send players to their new, correct tables. If it's possible, send a judge with each match to take care of their time extension.
In later rounds and with players with better records, the complexity of cascades increases. More changes are necessary, and there are a high number of possible matches that could work.

Figure out how many and which matches to stop.

Honestly, this is the hardest thing about cascading re-pairs.

If you get stuck on this, or if pairing up, down and with draws doesn't make sense to you, just split one match per occurring match-point score in the event that's equal to or less than the match points of the player you had to re-enroll. When you get to re-creating the pairings, you can work from top to bottom, and everything will be Fine. 

For most situations, you'll be breaking a number of matches equal to the number of rounds the dropped player has won plus one. In our example from earlier, that's going to be four matches: one with 9-point players, one with 6-point players, one with 3-point players and one with 0-point players.

Depending on how your pairings break down, this number may fluctuate some. Still using that previous example, if there are paired-down matches in all of those brackets and no bye, you might only break three matches (a 9-point vs 6-point match, a 6-point vs 3-point match, and a 3-point vs 0-point match; the 0-point player is assigned the bye).

These two things — match points and pair-downs, are going to be your bread and butter of cascades at most events.

At larger events draws can also play a part in which matches you split. You can pair a player with 9 match points against a player with 6, 7, or 8 match points. If that player's initial opponent had 6 match points, you can pair him or her against someone with 3, 4, or 5 match points, and so on.

This gives you some flexibility, which might reduce the number of matches that you have to re-pair. However, this can be pretty tricky to figure out. If pairing this ways with draws trips you up, you can ignore them and still end up with a reasonable set of pairings.

Finally, keep in mind that your cascaded pairings don't have to be 100% perfect. Every player should paired in their bracket, or paired-up or paired-down in a way that makes sense based on their match points. If you end up with an extra pair-up or pair-down when everything is said and done, it's not the end of the world, especially if it means that fewer matches are disrupted.

Send a judge to stop those players from playing.

The computer stuff here can take a minute or a few, and, unlike with a simple flipped result, it's more important to re-seat the players concurrently with performing the re-pair. Because of this, as soon as you identify the matches you want to split, it's important to send a judge to stop those matches.

Seriously. This is super important. If you get through all the re-pairing only to discover that one of the matches you wanted to change has already started playing, one of two things has to happen: you either have them stop anyway (which is a Very, Very Bad Thing), or you have to start over (which costs a lot of time).

As soon as you know what tables you want to split up for the cascade, get those players up to the stage.

Do some computer stuff.

After you've figured out what needs to happen, making the computer match is the easy part.

First, you're going to either:
  • Print or grab a copy of the current pairings
  • Make a backup of the tournament
  • Do both of those things
(I strongly recommend doing both.) This will help you if Bad Things happen and you need to re-create the round as it was before you started changing things.

Second, you're going to break all the matches you decided to break. Finally, you're going to re-pair all of the floating players. All of this happens in the Edit Matches interface, which you can get to by clicking "Edit Matches" on the Rounds tab. That button is above the grid that shows you current matches and results.

The interface looks like this:

Current matches show up on the left side, while unpaired players show up on the right.

Breaking Matches

To break a match, click on it on the left so that it's highlighted in green, then click the Un-Match button. You want to do this for all the tables you identified earlier. Byes also show up here. If you assigned the re-enrolled player with a bye earlier, you'll have to un-match that "table" as well.

*If you're not sure what matches you should break, this screen can be a useful tool for figuring it out. Current match points display with each player in the grid on the right, in descending order. You can see what the new pairings will look like — in this case a player with 3 match points will be paired against a player with 1 match point, and two players with 0 match points will be paired.

Creating New Matches

Once that's done, you should be able to go through the players on the right side from top to bottom, pairing them as you go. I always like to start with the player I had to re-add to the event.

To do this, click the check boxes next to the names of the players that you want to pair, then click the Match button. When you're down to one player, the Grant Bye button will also be active. These matches will fill in the tables that you split, from lowest number to highest. So, in the screenshot above, that first match would be assigned to Table 2.

Something else to keep in mind ... the first box you check will be the top player on the match result slip and the left player on the matches screen when you're done with all of the re-pairing. If you're manually creating new match result slips, this should be the first player you list.

Speaking of time extensions ...

Send players to their new matches.

I like to do this as I go. As soon as I pair a match, I call those players' names (they're standing in front of the stage because I sent a judge to stop their match earlier), and tell them their new table number, then proceed to pairing the next match.

This is more helpful when the cascade affected more matches: it means that the time extension on the first match to get re-paired is shorter than the time extension on the last match to get re-paired. But sometimes I'm done re-pairing before all the players are at the stage, or I only had to fiddle with two tables. Do what you're comfortable with, what reduces confusion for the players and judges involved, and what's efficient.

The only really tricky thing about cascading re-pairs is optimizing the matches that you end up splitting. Even then, the "optimal" set of re-pairs isn't the only way to get to a good set of pairings when you're done — if you have to split one or two more matches to simplify the process, that's OK. It's way better than re-pairing the entire tournament. Just make sure you get those matches stopped ASAP :)

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