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Thread: War matchmaking explained

  1. #1
    Centennial Club Greentangent's Avatar
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    War matchmaking explained

    Firstly I am not affiliated with supercell and do not have access to game code; just a simple CofC rainman who is unsatisfied with matchmaking. I lead several war clans from ranges of levels 50+ to levels 100+. I have seen clan balance in war come and go. I hope that by posting a statistical analysis of war matchmaking that players and developers alike will be able to understand and improve on game mechanics.

    "So we appear to be in a rut of unbalanced war matches lately and no one likes ruts. Basically this is because there are not many clans similar to ours (number of th10, th9, th8 & th7). CofC tries to match us with an equal clan, but because there are so few other clans that are our equal we are being randomly matched with clans that are significantly stronger or weaker. In contrast, the composition of th10, th9, th8 & th7 that we had around one month ago was very common and we were finding very balanced matches and thus winning because we are awesome. The below diagram illustrates this theory. The left square is our current range of matches. The colored circles are opponents. The game randomly picks a match from our range of opponents. The right square is our old composition. It is an algorithm which takes the geometric mean (assigning low weight to outliers) of the sum of our members' average building/troop/spell levels. This gives us a number and we are paired with a random clan from a range of other clans NEARBY (rarely equal to) that number. "

    "Tonight we had a very long search for war and finally found a pretty wonky match (40 th10 vs our 13 th10). I have made another graph to explain how matchmaking works using an iterative algorithm (again, in theory). On the left is the time it takes to search for a match. On the bottom is relative clan strengths (cumulative building/troop/spell levels) with us at a middle strength of five. Every few minutes of the search where no opponents are found in a nearby strength range, the range expands and the search starts again. Eventually after 30 minutes of iterations we are searching a huge range of clan strengths and matched with the first possible opponent, who is most likely to be far too strong or far too weak since they were found in the last iteration. One simple way to abuse this algorithm is to cancel the search after 5-10 minutes and just try again later."

    "Finished a plot that illustrates why we are encountering too weak or too strong matches recently. Note the recent dramatic increase in number of th10 and decrease in number of th7. This makes us very unbalanced and the matching algorithm for wars may only work well for ideally balanced clans. The flat green line represents the trend of our composition a few weeks ago during a solid win streak. The high slope red line represents our current composition."

    Update: After several matches using my suggestion, we have only seen balanced matches. Went from consistent totally unbalanced matches (40 th10 vs 13 th10) to consistent matches with almost identical clans. All the "solutions" for future updates are amusing, but this is the only functional method of finding a good match if you are having balance problems.

    Update: Dozens of matches later, using this method we have not experienced a single mismatch.

    Start search, wait ~10 minutes, cancel and restart. This prevents the matching algorithm for searching for clans far out of your range.

    Note: Attaching a relevant quote.
    Quote Originally Posted by xTrain View Post
    Great thread and insight...

    In regards to this, does anybody know what a "common" clan looks like in order for a quick and easy match up? Our clan is a size of 10 right now, eventually heading to 15. My main concern is that our top guy is level 140, close to a maxed out TH10. We have 4 strong TH9's that are all close to max, and the rest are strong TH8 and 1 TH7.

    What kind of TH levels should we be adding to our mix to avoid a serious mismatch?
    For your purposes common refers to low level.

    Developers have stated that clans trying to recruit a few very low level players into their clan to reduce their opponent levels are "shooting themselves in the foot." This implies two things, first they are likely referring to a geometric mean code line in matchmaking (extreme outliers hold little weight) second that therefore your one very strong player weighs little as well. In my opinion this is an extreme advantage to your clan in war.

    In order to explain what kind of TH levels you should look for, I would like to break down the geometric mean coding that I suspect SC is using in matchmaking. I will assign an abstract value to "player strength" where a developed th9 is stronger than a midrange th9 which is stronger than a fresh th9.

    Player Strength TH Level
    10 Developed TH10
    9 Midrange TH10
    8 Fresh TH10
    7 Developed TH9
    6 Midrange TH9
    5 Fresh TH9
    4 Developed TH8
    3 Midrange TH8
    2 Fresh TH8
    1 TH7

    Analysis- You said 1 Developed th10, 4 developed th9, 4 midrange th8, 1 th7. Mathematically this reads: geometric mean = (10*7*7*7*7*3*3*3*3*1)^(1/10)=4.3 ( Slightly above Developed TH8)

    I interpret this to mean that when your war match is calculated you are searching for a clan whom are also slightly above developed th8 when averaged (this could be a clan with a wide spread of th levels like yours, or a clan of 10 fresh th9 or maxxed th8). Recruiting strong th8 and 7 will thus bring your strength down, resulting in matches with more common (low level) clans and vice versa.

    Note- The matching code uses (probably) an iterative algorithm along with geometric mean. If the search runs longer than 5-10 minutes you will likely be paired with a significantly stronger or weaker clan. This is explained in the OP. To prevent this, restart the search after 5-10 minutes.

    Note2- Hearty congratulations if you read and understood any of this.

    Update: Several clans have reported very unbalanced matches from very short search times, this is why.
    It is important to understand that a maxxed th8 can have the same strength as a premature th10, and a clan with 50% th10 and 50% th8 may have the same strength as a clan of 100% th9.
    Quote Originally Posted by Greentangent View Post
    Clans are matched based on STRENGTH. This is calculated using a geometric mean of the sum of members structure/troop/spell levels. A geometric mean is different from a numeric mean in that extreme outliers (very strong or very weak) numbers weigh less/little. Refer to the geometric mean solution on page 7 of this thread with these figures for proof.

    If your clan has 35% very strong members (e.g. th10) and 65% very weak members (th4) or vice versa, your clan strength is somewhere in between and you will likely be matched with a well balanced clan near that strength, but this could vary widely as there is no clear middle strength. In the posters' case, I surmise that he has some very strong players and very weak players. This could lead to a match with a clan of 100% moderately strong players.

    Examples of well balanced clan levels: 120, 115, 110, 105, 100, 95, 90, 85, 80, 75
    Or: 100, 100, 100, 100, 100, 100, 100, 100, 100, 100

    Example of poorly balanced clan levels: 120, 115, 110, 105, 50, 45, 40, 35, 30, 25
    Update: Proof of concept of geometric mean; that adding low levels to find weak opponents is "shooting yourself in the foot."
    Quote Originally Posted by SuperSteve{SuperCell}
    Also keep in mind that clan matchmaking is based on clan composition, and not average strength of the entire clan. As such, adding lower level member to your clan will not help you find easier matches, and will backfire in the form of providing more 3 star wins for the opposing clan against the low level members.
    Quote Originally Posted by Greentangent View Post
    It really seems like CW is going to pot lately.

    Obviously clans are matched on strength and therefore I can say that there are multiple ranges of clan strengths. I see patterns emerging in various ranges. Some range of strengths will be full of clans that have no clue what to do (lower level clans). The real problem is the upper strength ranges (eg at least 15 th10 in clan). I have found that likely most of the clans in this range are shameless TOS violating fluffybunnies and rule-abiding clans will forfeit against these players. See IIB and ITD war logs in this forum, they never have a good war that requires any skill, all of their opponents immediately forfeit.

    I am experimenting with different clan compositions to avoid these ranges in pursuit of good wars, supposedly what SC intended....

    Convo with leaders-
    "That corresponds to 7-8pm Beijing time. Very odd that they are not finding asian clans during asian primetime. I think our current method of starting at 4am Beijing time will work to avoid them.

    It's utterly disheartening that fluffybunnies are becoming prolific and you are correct that even if we are the best players in the world we are no match for fluffybunnyers. The only thing that we can do is avoid them; fortunately I think we will be able to do that by using very specific th composition. Many think that it is counter-intuitive how I reject th9/10 and recruit th7/8 but this is how we will avoid fluffybunnies.

    I totally agree that the realm of top war clans are likely nothing but fluffybunnies, but fluffybunnying takes a lot of effort and low levels are much less likely to be this invested. If we can maintain half of our clan as skilled low levels then we will be matched with similar clans who are also less likely to be fluffybunnying. Sadly we are basically barred from becoming a full th10 trophy clan if we want to war fairly. If we do encounter a clan like this ill no longer support humoring them; we will use all gobs in war cc, gob attacks etc.

    Metadata is the game; we will make some strange compromises and continue moving forward."

    Some random speculation:
    Quote Originally Posted by Greentangent View Post
    I have not speculated on other aspects of the algorithm because I lack enough evidence, however I suspect that another line of mathematical code may try to match number of thX to number of thX. See example in OP of "well balanced clan levels" e.g. a clan with a range of th10-th8 will not be matched with a clan of exclusive th9 even if they have similar average strengths. Or perhaps the algorithm does something like match quarters e.g. algorithm looks for one clan with similar strength of your top 25%, similar strength in second, third and fourth quarters uniquely.

    Bear in mind that "composition" is a description and not a mathematical value, which is what SC uses to find a match. Aside from developers' access to code, all we have is theory about what this could be. Some theories are pretty good though (gravity).

    Update 11/12 In regards to potential fixes in search algorithm:
    Quote Originally Posted by Greentangent View Post
    2. Amazingly I think this may be correct; after 2-3 hours on the short cycle recently we have decided to try 20 minute search times and have in fact found good matches in both low and high level clans. It is likely that there would be no announcement for this sort of change other than already having said "we are constantly working to improve matchmaking" so this can happen quietly at any time. It would be reasonable for SC to put a minimum time on the search to prevent what I once called "abuse or short cycle" and expand the time iteration. This would both improve balance in matchmaking and prevent/alleviate the need to reset after 5 minutes to find a balanced match.

    Another search after my quote has resulted in a 15 minute match that is fairly balanced (+-4 th10, th9) which is well within what I would consider tolerable and balanced, however a few weeks ago when 5 minute resets were working normally we would almost always have matches with identical number of th10, th9.

    The fact that even a few observing that something has changed with matchmaking indicates a very real possibility that the algorithm has been improved.
    Update 11/13 potential fixes in search algorithm:
    Quote Originally Posted by 2Big View Post
    Let's start off by saying that I am a defenseless player, in a defenseless war clan.We do non-stop wars, and have loads of fun. Or should I of said **Had**.We used to be able to find an opponent within 1-2 hours of searching. Most of the CW's were very fair, and each clan had an equal chance of winning.e were doing good, we had won 26 in a row, and had gotten 13 MAX stars in a row. We even got to 53 CW wins.Now though, we started searching for a CW. We started off at 50 members, and could not find a match in a day. So we figured we would kick a few peeps, and be down to 40/45. Well, we search for another 2 days, and still no CW. Now we are down to 30 members, and we still have no CW after 10 days of non-stop searching. I think that this is caused by a change in the CW system, by SC. Please change this back to its old ways, because not having a CW in 10 days is very upsetting, and kind of ruins the game.
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    Last edited by Greentangent; November 14th, 2014 at 03:56 AM.

  2. #2
    Millennial Club Jietoh's Avatar
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    While I agree with most of what you've said, Supercell has not confirmed any of it in any official post. The closest we've gotten is a quote from Super Steve that mismatches are preferable to no match or very long searches.

    The problem with your solution is that prep day has to start at the same time for each clan so there's a high probability that the two clans that were matched in your 12 hour window started their searches at different times so would have different prep day starts.

    I have proposed a solution which I think will truly work. I posted it in the ideas and feature request forum.

    Here's a link. Look it over and let me know what you think...
    Jietoh - Noob level Clash Royal...

  3. #3
    Centennial Club Greentangent's Avatar
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    Correct; it is only the best possible explanation/observation without seeing the game coding.

    Quote Originally Posted by Jietoh View Post
    a quote from Super Steve that mismatches are preferable to no match or very long searches
    This is one of the main reasons I believe SC uses an iterative search algorithm.
    Last edited by Greentangent; October 3rd, 2014 at 01:48 PM.

  4. #4
    Forum Hero rwelshjr's Avatar
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    Wow!! Thanks for putting this much effort into it. This is a fantastic piece of analysis. it does gibe with my own observations so whether or not it is 'official' I do think it is accurate.

    In our case I just restart the search every few minutes. I don't think that is unfair or c'h'e'a't'ing (it sensors the word). it is my preference to do that a bunch. But others may have other preferences, some might prefer just eating the unbalanced matches, they consider the 'gift' ones their repayment for the times they are someone else's gift.

    For me I think a 12 hour wait would make me crazy. it certainly would be tough on the personal scheduling for myself and my clan mates. But maybe others might prefer that.

    I agree there are real problems with the matchmaking, but it is not bad work by SC but rather a bad situation (shortage of available opponents) that they have to make the process work with. I think implementing any of these solutions is just trading one persons preference for another. Since there are no right or wrong answers for preferences they can do something or not do something and it will make no difference that someone will be happy and someone else unhappy.

    Actually I think posting the analysis you did is more helpful than anything SC can do because it helps the rest of us understand the issue so to deal with it. (and my own opinion is that us all dealing with it is the solution)
    Last edited by rwelshjr; September 8th, 2014 at 02:19 PM.

  5. #5
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    i dont see any difference, it wasnt balanced to begin with in mt opinion and isnt balanced now.

    Correlation does not imply causation.

  6. #6
    Centennial Club Greentangent's Avatar
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    Quote Originally Posted by VincentVegas View Post
    i dont see any difference, it wasnt balanced to begin with in mt opinion and isnt balanced now.

    Correlation does not imply causation.
    Sorry for the lack of clarification. OP was quotes from my discussion with leaders. "Balance" was referring to my own clans' wars over the course of a one month study. Our member level composition changed and we went from fast search well balanced matches to 30min+ unbalanced matches (e.g. Current war is 40 th10s vs my 13 th10s). There is a possible direct correlation to clan composition and match balance as shown in the last diagram.

  7. #7
    Forum Superstar Anarchos's Avatar
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    Quote Originally Posted by Greentangent View Post
    One simple way to abuse this algorithm is to cancel the search after 5-10 minutes and just try again later."
    I wouldn't call that abusing the algorithm. My clan has 25 members and 20+ are TH8. The vast majority are close to having maxed TH8(including walls and troops), however they're still TH8. The fact their defenses, troops, and walls are so high for TH8 our clan regularly has clan war searches that end with us facing off against a clan of 10 or so low range TH8, 10 or so low range TH9(near TH8 max def, +X Bows but low walls), and a handful if strong TH10. The system routinely gives us bad matches that are stacked in our opponents favor.

    I've found that if we cancel the search every 5-8 minutes and restart the search, when a match is finally found it tends to be a lot closer match. I wouldn't categorize that as abusing the system.
    Last edited by Anarchos; September 8th, 2014 at 05:00 PM.
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  8. #8
    Centennial Club Greentangent's Avatar
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    Quote Originally Posted by Anarchos View Post
    I wouldn't categorize that as abusing the system.
    Didn't mean to offend or put any negative connotations on anyone's strategy.

    If you feel like you are often drawing the short straw in clan wars then this is merely an equalizer to game mechanics which I personally feel are still in "early phases" of development.

  9. #9
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    I'm just curious, but why would cancelling the search do anything? Don't you just get matched up with the first clan that matches your match criteria?

    Unless the match criteria change based on how long your search has been open, restarting wouldn't do anything... You will still get matched up with the closest match...

  10. #10
    Centennial Club Greentangent's Avatar
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    Quote Originally Posted by herranton View Post
    Unless the match criteria change based on how long your search has been open, restarting wouldn't do anything...
    There you have it. See my second diagram; the criteria does change per the time searching. Currently the iterative algorithm used by supercell is designed to provide a match as fast as possible. Instead of waiting potentially hours for a balanced match, you get a "mismatch" so your clan does not have to wait (except for 24 long hours of waiting for prep day).

    Quote Originally Posted by Jietoh View Post
    The closest we've gotten is a quote from Super Steve that mismatches are preferable to no match or very long searches.
    Last edited by Greentangent; September 8th, 2014 at 06:47 PM.

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