corpus: 589,025 words, 588,286 distinct 8-grams

arm                     gens  hit-rate  mean-longest   max
------------------------------------------------------------
base                     240      0.02           0.1    10
ckpt450                  240      0.13           1.1    11
ckpt900                  240      0.23           2.0    11

positive control (corpus slice vs corpus): longest = 160 (must be large, else the detector is blind)