map balance - CIG 2016
Map balance is hard.
Only about 5 competition maps have stats showing balance within a few percent of equal for all matchups. Seriously! That’s less than 2% of maps ever used in pro play! (Though to be fair, the total includes maps without enough games for us to know the balance.) The closest are the popular Fighting Spirit, Circuit Breaker, and Tau Cross, and the less-popular Arcadia 2 and Neo Aztec. If you want a balanced map pool beyond these 5 maps, you have to balance the maps against each other: “This one is T>P by 10%, so the rest should add up to P>T by 10%.” Of course those are human stats, and bot balance should be different, so you might want to balance using bot data.
The AIIDE and CIG rules both say that maps will be chosen at random from a larger pool. SSCAIT says its maps are selected from popular recent pro maps, and doesn’t mention balance. So I decided to look into it.
For today I calculated the balance of the CIG 2016 map pool, 5 maps randomly selected from a larger collection. Think of this as a first check to see how balance may come out when you’re not paying attention.
- (2)RideofValkyries1.0
- (3)Alchemist1.0
- (3)TauCross1.1
- (4)LunaTheFinal2.3
- (4)Python1.3
I used balance numbers from the TLPD map database, which gives statistics for pro games played from 1999 to 2012. It’s not a definitive current pro balance, but it should be pretty good and it was complete and easy to use. Alchemist is not often played (presumably because it is grossly Z>P; also, according to Liquipedia “Alchemist is mostly noted for being a poor attempt at an asymmetrical three-player map”) and its stats are based on only 53 games. The % number in each cell is the winning rate for the first race in the matchup over each column.
| map | TvZ | ZvP | PvT |
|---|---|---|---|
| Ride of Valkyries | 48.5% | 67.1% | 54.4% |
| Alchemist | 55.6% | 80% | 62.5% |
| Tau Cross | 50% | 50% | 52% |
| Luna the Final | 53.2% | 60.2% | 60% |
| Python | 55.2% | 53.9% | 45.8% |
| overall | 52.5% | 62.2% | 54.9% |
I’d say that’s a substantial Z>P imbalance.
The numbers from TLPD are raw outcomes, with no attempt to adjust for the strength of the players. That’s likely good enough; it should average out over the large number of games played on most of these maps. But if we want to compare the pro balance with the bot balance after the tournament is over, we may want to do some normalization of both data sets. I’m predicting that this tournament will be dominated by terran bots. A comparison might give the impression that the maps are T>P and T>Z for bots, when in fact the terran bots were playing better.
Tomorrow: AIIDE 2015 map balance.
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