Those numbers a re bit small to get a full view of the way the pypy jit works: user=> (time (reduce1 + (range 100000))) Elapsed time: 903.011083603 msecs

Those numbers a re bit small to get a full view of the way the pypy jit works: user=> (time (reduce1 + (range 100000))) Elapsed time: 903.011083603 msecs 4999950000 user=> (time (reduce1 + (range 1000000))) Elapsed time: 777.748823166 msecs 499999500000 user=> (time (reduce1 + (range 10000000))) Elapsed time: 8764.57095146 msecs 49999995000000 user=> Clojure via hotspot: user=> (time (reduce + (range 100000))) "Elapsed time: 174.768593 msecs" 4999950000 user=> (time (reduce + (range 1000000))) "Elapsed time: 267.60421 msecs" 499999500000 user=> (time (reduce + (range 10000000))) "Elapsed time: 1131.77367 msecs" 49999995000000 user=> But yes, we still have some room for improvement.