posted by kautzy,
Ever since Valve converted MMR into ranks last year, the next change had been lurking in the shadows. All-new MMR has now finally gone live with the start of the new season. Watch out though, you might be in for a surprise after your calibration games. MMR has been changed and predictably, complaints on reddit and elsewhere are running wild. Valve seems to have altered the way that MMR is calculated throughout your calibration games. Single calibration games apparently carry more weight now, as a large number of players are reporting suprisingly large variance in their MMR.

Many users are speculating about the exact mechanism and values of the new MMR-System. This seems to be the consensus so far:

  • Wins and losses are the only thing that counts and individual performance is not a factor (confirmed by Valve).
  • The difficulty of the calibration matches is a result of the previous match. If you lose your match, you get placed in an "easier game" with a team that has less average MMR than the previous one. If you win your match, you will get placed in a "harder match", meaning teams with higher average MMR than the previous one.
  • The numerical value of the MMR difference from game to game seems to be somewhere around 200 points.

As of now, this is all just speculation though, since only Valve actually knows what the new MMR system really looks like under the hood. Nevertheless, the criticism seems to have at least some merit. Everybody's favortie player/caster-hybrid, Troels 'syndereN' Nielsen, has outlined a problematic scenario in a TwitLonger post:

10 games is an extremely little sample size. Let's say players A and B start on the same MMR (6000). Player A goes 2-8 and player B goes 8-2. Is B a much better than A based on those results? B could have had a few games where an opponent abandoned or where the enemy team picked worse heroes against the lineup B was playing in. Over the course of 10 games, it doesn't seem that improbable that this could happen a few times, _even if_ B's games get increasingly more difficult with each win compared to A's, all it takes is for a guy in the enemy team to abandon (from connection or... other issues) or an excellent last pick that can win the game alone (mind you, this hero may not even be played by B but by one of his team mates, so he may not even have contributed much to the victory but still win regardless), or a significant outdraft, which happens frequently in all brackets. Also, remember that loads of players are calibrating at the same time, so the uncertainty among the team mates is also really high. B may, even on his win streak, end up getting strong team mates who just had a bad start in calibration (lost a few of their first games, maybe they are 1-4 or something). Dota 2 is a game with way too many variables to even remotely accurately calibrate people based on 10 games. Such a low amount of games might produce accurate results in single-player games, though, where there are way less variables.

Based on the information gathered from various people's posts, A's end MMR could be roughly 5200, while B's may end up on 6800 (these numbers can be less or more extreme based on which games were won or lost - the games you were supposed to be favored in or the ones in which you weren't, from what I understood). The 3 extra games B won and A lost therefore amount to a total of 1600 MMR, or 64 straight wins.

As of now, it remains to be seen what impact the new system truly has on your MMR and whether things will revert back to "normal" over time. Whether this takes a long time or won't happen at all, some players might be in for a long grind that's completely out of their skill range. Or worse: they might be stuck in the infamous "ELO hell".

What has your experience with the new MMR been so far?