Measure the performance cost of volatile synchronization of mutable state in stateful transducers, cf CLJ-2146.
fast-transducers.core defines unsynchronized versions of clojure.core's transducers relying on volatile!. The volatile container is replaced with a clojure.lang.Box, the rest of the code is the same.
Run the benchmark with clojure -Aperf. Numbers are relative performance improvements of unsynchronized versions w.r.t their respective volatile-synchronized counterparts.