Clojerl & Clojure Benchmarks

Benchmarks can be run in Clojerl and Clojure alike:

# Running on Clojure
lein run -m benchmarks -- 1
# Running on Clojerl
rebar3 clojerl run -m benchmarks -- 1

Measuring time on the BEAM

Issue on Mac OS X reporting nanosecond accuracy
- bencheeorg/benchee#313
- Bug report in https://bugs.erlang.org/browse/ERL-1067. "Fixed" in Erlang/OTP 22.2, but the problem is that Mac OS X system call provides only microsecond resolution (even though it reports nanosecond precision).