Posted 12 April 2013 - 11:13 AM

It's been two months since our last major update to matchmaking, where we introduced our first pass at Elo and saw a tremendous improvement in the quality of matches being kicked off. With the next patch we're bringing in a new round of changes, and we've got two big ones lined up: Weight Class Matching and Elo Rating Adjustment.

WEIGHT CLASS MATCHING

We're adding the ability for us, the developers, to adjust our weight matching tolerances on the fly. This is giving us a controlled way to tighten up the weight imbalance between teams that players are experiencing.

Fun fact: About 74% of games kicked off are within what we consider tolerable weight matching limits (the difference between a heavy vs. assault Mech on the opposing team). Of the remaining 26% of matches, about 7% are what we would call "horrendously bad" (i.e., they carry the weight difference of one or two full assault Mechs between teams).

When we tighten up the Weight Matching, we're going to drop our weight tolerance to 0 and see what happens. Teams will be almost equally built in terms of weight class, though they will draw from a wider skill range of players to compensate. We'll be keeping an eye on the system while doing this and will continue to tune it until we're happy with the match quality and wait times.

ELO RATING ADJUSTMENT

We discovered a bug that was causing player Elo values to become inflated. Players that would win a game against a weaker opponent were being rewarded as though they were the underdog in that match. This caused Elo values to increase by a lot when they should have increased by only a little, skewing the player Elo distribution so that it became top-heavy.

What we've done (beyond correcting the bug) is a complete re-simulation of Elo ratings for every player in the game. Using match history we've been logging since February 5th, we determined what every players Elo rating would have been if we were using the corrected algorithm. The difference we noticed is huge, and the new player Elo distributions look healthy. We're going to push these ratings to the servers when we patch on April 16th.

So, how will this affect things? Well, without going into the details of how Elo works, this significantly improves our ability to match similarly skilled players. The old algorithm had an unintended (although interesting) bias towards people who had played more games, whereas the new rating measures only how you're playing. The bottom line is that we can kick off more close matches.

ROLLOUT PLAN

So when will we get to see this stuff? You won't have to wait long; this goes live with the April 16th patch. Other fixes, such as better detection of disconnected players while matching are also going in at this time as well. However, we'll be staging the release of the Weight Matching tweaks to be sure the system is working correctly (and to give us time to collect a bit of data on the new operating conditions).

Here's the plan:

On Tuesday, April 16th, we'll patch as normal and will put in the adjusted Elo values.

On Thursday, April 18th (tentative date), we'll drop the weight matching tolerance to zero. This won't require a patch or an interruption of service.

We're excited to bring the next round of changes live and look forward to matching up with you. See you on the Battlefield!