[math-fun] Nice measure for Life patterns?

I'd like to compute the first bits of the "halting probability" of Conway's life; since CAs don't halt, I'd like to compute the probability that it evolves to a state that's easily detectable by Golly, like all empty or a still life or cyclic. (Also, I know the number is uncomputable, but that doesn't preclude a finite computable prefix.) Since any translation or reflection of a pattern has the same outcome as the original, I'd like to choose a measure on the set of cells such that computing the measure of all the translations and reflections of a pattern is easy. Any suggestions? -- Mike Stay - metaweta@gmail.com http://www.cs.auckland.ac.nz/~mike http://reperiendi.wordpress.com