OTP22 vs OTP21 Benchmarking

test.erl

%% @doc Benchmark functions over lists.
%%      Use it like: c(test), test:bench({test, rec}, 250, 5000, 2000).
-module test.

-export [
    bench/4,
    bench_tc/2,
    rec/1,
    lrec/1
].

bench(Function, Tests, ListCount, Length) ->
    Lists = lists:duplicate(ListCount, lists:seq(1, Length)),
    %% Drop 2 outliers
    [_|TimesPlusOne] = lists:sort([bench_tc(Function, Lists) || _ <- lists:seq(1, Tests + 2)]),
    [_|Times] = lists:reverse(TimesPlusOne),
    %% Compute the Average
    lists:sum(Times) / Tests.

-spec bench_tc(flatmap | {module(), function()}, [[any()]]) -> number().
bench_tc({Module, Function}, Lists) ->
    element(1, timer:tc(Module, Function, [Lists]));
bench_tc(flatmap, Lists) ->
    element(1, timer:tc(lists, flatmap, [fun(X) -> X end, Lists])).


rec([Hd|Tail]) -> Hd ++ rec(Tail);
rec([]) -> [].

lrec([Hd|Tail]) -> length(Hd) + lrec(Tail);
lrec([]) -> 0.