beam_benchmarks

%% From https://github.com/madnight/benchmarksgame/blob/9f5a20ba09e668a20bb0f9765b33071fa9bb3f1d/LICENSE
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%% Copyright © 2004-2008 Brent Fulgham, 2005-2017 Isaac Gouy
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% The Computer Language Benchmarks Game
% http://benchmarksgame.alioth.debian.org/
%
% contributed by Isaac Gouy (Erlang novice)
% reset

-module(binarytrees).
-export([main/1]).

-define(Min,4).

main(N) ->
   Max = lists:max([?Min+2,N]),

   Stretch = Max + 1,
   StretchCheck = itemCheck(bottomUp(Stretch)),
   % io:fwrite("stretch tree of depth ~w\t check: ~w~n", [ Stretch, StretchCheck ]),

   LongLivedTree = bottomUp(Max),
   depthLoop(?Min,Max),

   DepthCheck = itemCheck(LongLivedTree),
   %io:fwrite("long lived tree of depth ~w\t check: ~w~n", [ Max, DepthCheck ]),

   {StretchCheck, DepthCheck}.

depthLoop(D,M) when D > M -> ok;
depthLoop(D,M) ->
   N = 1 bsl (M-D + ?Min),
   _Check = sumLoop(N,D,0),
   % io:fwrite("~w\t trees of depth ~w\t check: ~w~n", [ N, D, Check ]),
   depthLoop (D+2,M).

sumLoop(0,_,Sum) -> Sum;
sumLoop(N,D,Sum) ->
   sumLoop(N-1,D, Sum + itemCheck(bottomUp(D))).

bottomUp(0) -> {nil, nil};
bottomUp(D) -> {bottomUp(D-1), bottomUp(D-1)}.

itemCheck(nil) -> 0;
itemCheck({Left,Right}) ->
   1 + itemCheck(Left) + itemCheck(Right).