No decompiling, just observing the game with a timer. I used a lot of community wiki/forum information as well. There has been some really amazing research done by the community [1][2], to figure out optimal resource harvesting strategies, and I used quite a bit of data from that.

[1] http://wiki.teamliquid.net/starcraft2/Mining_Minerals

[2] http://www.teamliquid.net/forum/sc2-strategy/140055-scientif...