Draw System for League Phases of European Cups 2024 onwards

[FEPG]

I've released the initial version of the new simulator. For now, it doesn't follow the procedure UEFA are going to use. Instead, matches are drawn randomly by pot pairs.

The first stage is match drawing, which now takes mere couple of seconds, thanks to eye's suggestion to draw pot pairs in order (as seen in the visualisation).

The second stage is scheduling, which it takes a bit longer, but it's probably fine since UEFA don't usually release the schedule until the day after the draw & it's unlikely to be different this time.

[ThreeLions]

I've released the initial version of the new simulator. For now, it doesn't follow the procedure UEFA are going to use. Instead, matches are drawn randomly by pot pairs.

The first stage is match drawing, which now takes mere couple of seconds, thanks to eye's suggestion to draw pot pairs in order (as seen in the visualisation).

The second stage is scheduling, which it takes a bit longer, but it's probably fine since UEFA don't usually release the schedule until the day after the draw & it's unlikely to be different this time.

I ran this last night and schedule still hasn't been generated. Is this normal?

[FEPG]

I've released the initial version of the new simulator. For now, it doesn't follow the procedure UEFA are going to use. Instead, matches are drawn randomly by pot pairs.

The first stage is match drawing, which now takes mere couple of seconds, thanks to eye's suggestion to draw pot pairs in order (as seen in the visualisation).

The second stage is scheduling, which it takes a bit longer, but it's probably fine since UEFA don't usually release the schedule until the day after the draw & it's unlikely to be different this time.

I ran this last night and schedule still hasn't been generated. Is this normal?

This is expected (for now). It normally takes from 2 minutes to 1 hour to generate the schedule. Give it some time.

[Ambro]

It took around 4-5 mins for me. Great work @FEPG

[FEPG]

It took around 4-5 mins for me. Great work @FEPG

Cheers, mate.

[elkjiaer is back]

We still do not have any info from Uefa regarding the actual draw procedure.
But As mentioned in my previous post this year the problem is much more complex.
One thing to reflect upon: in the past seasons Uefa was drawing the groups, but not the calendar order . As a matter of fact it took Uefa 2 days last season to reveal the fixtures after the draw took place.
My concern is the following: if Uefa only draws the 144 fixtures, and then the full match calendar is performed separately by Uefa , can we always guarantee that the 144 fixtures result in a suitable calendar fullfilling all requirements? (home/away in first 2 and last 2 matchdays, maximum 2 home/away consecutive matches etc).

Regarding first part of the problem. How is Uefa going to perform the draw? If we assume it follows the same process as previous years, then the main question is if they will draw one pair at the time (first home and then away team, 144 times) or , given a random team picked from a bowl, they will pair of its 8 opponnets and then continue. Any thoughts on that? I Do not see uefa drawing pairings directly and I still like the idea of a pre-determined match schedule, but again I do not see Uefa going that way

[Sagy]

We still do not have any info from Uefa regarding the actual draw procedure.
But As mentioned in my previous post this year the problem is much more complex.
One thing to reflect upon: in the past seasons Uefa was drawing the groups, but not the calendar order . As a matter of fact it took Uefa 2 days last season to reveal the fixtures after the draw took place.
My concern is the following: if Uefa only draws the 144 fixtures, and then the full match calendar is performed separately by Uefa , can we always guarantee that the 144 fixtures result in a suitable calendar fullfilling all requirements? (home/away in first 2 and last 2 matchdays, maximum 2 home/away consecutive matches etc).

Regarding first part of the problem. How is Uefa going to perform the draw? If we assume it follows the same process as previous years, then the main question is if they will draw one pair at the time (first home and then away team, 144 times) or , given a random team picked from a bowl, they will pair of its 8 opponnets and then continue. Any thoughts on that? I Do not see uefa drawing pairings directly and I still like the idea of a pre-determined match schedule, but again I do not see Uefa going that way

My guess is that they will use a version of a preset schedule and draw the 36 teams (by pot) to fill spots A1-A9, B1-B9, C1-C9, D1-D9 with a computer “alerting” them of a team is drawn into a spot that can lead to a conflict (e.g., they will be assigned to the next available spot).

I don’t think that they want to take the time to do 144 physical draws with all the unique setup for valid matchups before each of the draws.

[FEPG]

We still do not have any info from Uefa regarding the actual draw procedure.
But As mentioned in my previous post this year the problem is much more complex.
One thing to reflect upon: in the past seasons Uefa was drawing the groups, but not the calendar order . As a matter of fact it took Uefa 2 days last season to reveal the fixtures after the draw took place.
My concern is the following: if Uefa only draws the 144 fixtures, and then the full match calendar is performed separately by Uefa , can we always guarantee that the 144 fixtures result in a suitable calendar fullfilling all requirements? (home/away in first 2 and last 2 matchdays, maximum 2 home/away consecutive matches etc).

Wiesing's theorem states that for any undirected graph, the chromatic index (the minimum number of colours needed for an edge colouring) is either equal to the maximum degree of the graph Δ(G) or Δ(G)+1.

For 8-regular graphs (where every vertex has the same degree 8) with 36 vertices, the chromatic index is 8, meaning it is possible to colour their edges with 8 colours. A colour represents a matchday.

However, notice the "undirected" part, which means it does not take home/away constraints into account. In my simulator, it sometimes takes a very long time to construct a schedule after all matches have been drawn & there has never been a precedent where this hasn't occurred. If, theoretically, it is impossible to construct a schedule with home/away constraints, that might explain why UEFA includes the following paragraph in the Champions League regulations:

In principle, a club does not play more than two home or two away matches in a row and each club plays one home match and one away match across the first two matchdays and across the last two matchdays. The UEFA administration may derogate from these rules if necessary.

I don't think it would be a significant issue if one of the clubs has to play 3 consecutive away matches, for example.

Regarding first part of the problem. How is Uefa going to perform the draw? If we assume it follows the same process as previous years, then the main question is if they will draw one pair at the time (first home and then away team, 144 times) or , given a random team picked from a bowl, they will pair of its 8 opponnets and then continue. Any thoughts on that? I Do not see uefa drawing pairings directly and I still like the idea of a pre-determined match schedule, but again I do not see Uefa going that way

This article explains how the draw will be conducted. Essentially, they will select 36 teams one at a time & a computer will determine their opponents. The scheduling aspect isn't mentioned, but it's likely to take place within the next day or two, as usual.

[kosovo]

We still do not have any info from Uefa regarding the actual draw procedure.
But As mentioned in my previous post this year the problem is much more complex.
One thing to reflect upon: in the past seasons Uefa was drawing the groups, but not the calendar order . As a matter of fact it took Uefa 2 days last season to reveal the fixtures after the draw took place.
My concern is the following: if Uefa only draws the 144 fixtures, and then the full match calendar is performed separately by Uefa , can we always guarantee that the 144 fixtures result in a suitable calendar fullfilling all requirements? (home/away in first 2 and last 2 matchdays, maximum 2 home/away consecutive matches etc).

Regarding first part of the problem. How is Uefa going to perform the draw? If we assume it follows the same process as previous years, then the main question is if they will draw one pair at the time (first home and then away team, 144 times) or , given a random team picked from a bowl, they will pair of its 8 opponnets and then continue. Any thoughts on that? I Do not see uefa drawing pairings directly and I still like the idea of a pre-determined match schedule, but again I do not see Uefa going that way

I think it's still early, we'll probably won't have anything concrete until the play-offs. As far I've seen from UEFA's broadcasting assets, the draw will go this way:
- Teams will be assigned into pots, the draw will start with Pot 1;
- One team will be drawn from the pot (using balls);
- Then it's the computer part, the program will assign the opponents automatically (short interval) in H/A/H/A/H/A/H/A order (1 pair at a time);
- Next team will be drawn until the pot is emptied;
- After the entire pot is emptied, the fixture matrix for X pot will be completed;
- The draw continues with the next pot

Sadly as I said it's still early, the qualifiers just started and I bet the detailed procedure is still in the making from UEFA.

[fabiomh]

....
This article explains how the draw will be conducted. Essentially, they will select 36 teams one at a time & a computer will determine their opponents. The scheduling aspect isn't mentioned, but it's likely to take place within the next day or two, as usual.

In theory, the fixtures could be predetermined the day before, and when each team is selected, the computer could retrieve their pre-stored opponents.
Who knows!

[diyx]

....
This article explains how the draw will be conducted. Essentially, they will select 36 teams one at a time & a computer will determine their opponents. The scheduling aspect isn't mentioned, but it's likely to take place within the next day or two, as usual.

In theory, the fixtures could be predetermined the day before, and when each team is selected, the computer could retrieve their pre-stored opponents.
Who knows!

This opens the door for manipulation, and everyone knows that. It would look very suspicious if the "draw" is basically just an announcement of the pairings.

[fabiomh]

....
This article explains how the draw will be conducted. Essentially, they will select 36 teams one at a time & a computer will determine their opponents. The scheduling aspect isn't mentioned, but it's likely to take place within the next day or two, as usual.

In theory, the fixtures could be predetermined the day before, and when each team is selected, the computer could retrieve their pre-stored opponents.
Who knows!

This opens the door for manipulation, and everyone knows that. It would look very suspicious if the "draw" is basically just an announcement of the pairings.

Agree.
What I mean is that if you see the ball with the team selected and then the computer says who are the opponents,
you never know if the computer determined them in that moment or the day before.
This can be suspicious. the computer might determine in that moment, but some people might suspect it was predetermined.

On the other hand, as already told in all the previous posts in this thread, the fixtures of the league stage is a really hard job;
it cannot be solved by a simple draw, it has to be driven by a computer.
So I can't see an easy solution by a real "draw".

[Francisco]

....
This article explains how the draw will be conducted. Essentially, they will select 36 teams one at a time & a computer will determine their opponents. The scheduling aspect isn't mentioned, but it's likely to take place within the next day or two, as usual.

In theory, the fixtures could be predetermined the day before, and when each team is selected, the computer could retrieve their pre-stored opponents.
Who knows!

This could be a bit like they did por the portuguese league matches schedule for the season. There are a number of predetermined (by computer) combinations of games possible.
What they draw is the number of the combination that will be used.
I don't know how many there were but this year the draw gave us combination 102345 (or something like that) and they just showed the match schedule for the season. There is no way for us to know if combination 102345 was any different from combination 543201 because these are not published in any way....

UEFA will know the 36 teams for each league before the draw, and a computer will have time (theoretically) to calculate days before the draw the number of possible matches combinations.
Imagine there is only 1000 possible combinations for those 36 teams that comply with the rules.
They will then draw 3 balls to give one of the numbers from combination 000 thru 999, and the selected "???" combination will have automatically a map of pre-determined matches.
It's a system the public won't like because it doesn't look clearly and may clearly be pre-arranged, but it's one of the most probable ways to have a draw for this complicated 36 league system.

[Sagy]

I still believe that they will have a schedule of all the games with place holders (e.g. A1-C7 = first team from pot A hosting 7th team from Pot C) and draw the 36 balls one after the other starting with Pot A. The role that the computer will play is to alert with a team that in drawn in position x has to be placed in position y for its Pot to avoid an immediate issue or a deadlock.

[fabiomh]

I still believe that they will have a schedule of all the games with place holders (e.g. A1-C7 = first team from pot A hosting 7th team from Pot C) and draw the 36 balls one after the other starting with Pot A. The role that the computer will play is to alert with a team that in drawn in position x has to be placed in position y for its Pot to avoid an immediate issue or a deadlock.

Well, I have some concern about it.
It depends on the complexity of the algorithm to be used.

What you are suggesting would be the perfct solution, the "real draw", and requires the computer is alerting in advance that a certain move will cause a deadlocks some steps ahead.
This requires the most complex algorithm, the one which explores completely all the paths of the combinations tree to say if that step in the tree has still valid paths.
Many of us suggest this is too complex, there are a lot of possible paths to explore (I am not able to estimate the order of the number) and it requires too much time, memory and so it could be very hard to implement.

The Plan B could be some euristhic method which predetermines one or more possible fixtures.
Of course in this case it would not be a "real draw".

EDIT:
Just now I am thinking there could be a way in the middle, a plan C - thanks to Francisco post

Let us suppose Plan A is impossible because the possible combinations are something like 10^10 or 10^20, and so it is not possible to run live the algorithm during the draw.

0. The euristhic can predetermine an high number of fixtures, let me say 1,000 or 10,000 or as much as possible (PFS = predetermined fixtures set).

1. The first team X is selected.
2. Then you see which are the possible opponents Y1, ..., Yn in the fixtures in the PFS.
3. You draw Yk the first opponent of X only between Y1, ..., Yn.
4. Then you discard from the PFS all the fixtures where X and Yk does not match.
5. Go back to step 1. or 2. and go forward
until there is only one remaining fixture in the PFS.

When there is only one remaining fixtures in the PFS, you can complete the fixture.