AIIDE 2020 - McRave’s strategy representation
McRave lists its strategy choices with three names, such as “PoolLair,9Pool,1HatchMuta.” In trying to understand what McRave learned, I myself learned more about what the 3 names mean: They are chosen from a small structured set of composable elements which are strung together into full strategies. Here is the scheme:
1. HatchPool
1.1.1 12Hatch
1.2.1 2HatchMuta
1.2.2 2HatchSpeedling
2. PoolHatch
2.1.1 4Pool
2.1.2 9Pool
2.1.3 Overpool
2.1.4 12Pool
2.2.1 2HatchMuta
2.2.2 2HatchSpeedling
2.2.3 3HatchSpeedling
3. PoolLair
3.1.1 9Pool
3.2.1 1HatchMuta
I made up the numbering to depict how the elements fit together, as I understand it: First you pick a top-level category of builds, 1 2 or 3. Say you pick 2, spawning pool then hatchery. Under that, you pick a concrete build order that implements the top-level category, 2.1.x, from the list of ways that McRave knows to make a spawning pool first. After that—not under it—you pick a followup strategy, 2.2.x, from the strategies that are reachable via that category of builds. Notice that 9Pool appears under both PoolHatch and PoolLair (both are pool first), and that 2HatchMuta appears under both HatchPool and PoolHatch (all you need are 2 hatcheries). I count 15 different possible strategies in this scheme, 2 under HatchPool, 12 under PoolHatch, and 1 under PoolLair.
In principle, combinatorial schemes like this can represent a huge number of strategies with a small number of building blocks. Adding the one new item of 2.2.4 2HatchLurker would add 4 new strategies, though they might not all make sense in games. Having separate elements could also give a learning algorithm clues about how to generalize its findings.
In practice, McRave does not play all the strategies it can represent. It appears to have tight restrictions based on matchup. This list is based on the strategies that are mentioned in the learning files, not on code analysis, so it might be incomplete or misleading.
• ZvT: HatchPool-12Hatch or PoolHatch-Overpool or PoolHatch-12Pool, then for any of those, 2HatchMuta or 2HatchSpeedling.
• ZvP: PoolHatch-Overpool or PoolHatch-12Pool, then 2HatchMuta or (rarely) 2HatchSpeedling.
• ZvZ: PoolHatch-12Pool then 2HatchMuta or 2HatchSpeedling, or PoolLair-9Pool-1HatchMuta.
• ZvR: PoolHatch-Overpool or PoolHatch-12Pool, then 2HatchMuta or 2HatchSpeedling.
Next: Tables showing what strategy choices McRave learned.
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