[computer-go] Pattern Matching Methods

[Jason House]

Given the recent focus on pattern matching, I figured I'd try to catalog 
pattern matching methods that I've seen discussed.

1. Create a hash key of patterns/board position for comparison
    Run once for every board position, and fixed pattern size
2. DFA with a fixed search pattern (AKA Gnu Go's spiral pattern)
    Run once for every board position
3. DFA with a state-based search pattern
    (Next position to examine based on current DFA state)
    Run once for every board position
4. Recursively doubling pattern size
    (Look at 4 results from previous match)
    I personally don't know of anyone doing this...

Did I miss anything?  Any additional detail anyone would like to add? 
(such as the discussion within the rotate the dog or the tail thread)