%% ---
%%  Excerpted from "Programming Erlang",
%%  published by The Pragmatic Bookshelf.
%%  Copyrights apply to this code. It may not be used to create training material, 
%%  courses, books, articles, and the like. Contact us if you are in doubt.
%%  We make no guarantees that this code is fit for any purpose. 
%%  Visit http://www.pragmaticprogrammer.com/titles/jaerlang for more book information.
%%---
-module(ptests).
-export([runtests/2,tests/1, fib/1]).
-import(lists, [map/2]).
-import(pmap, [pmap/2]).

tests([N]) ->
    Nsched = list_to_integer(atom_to_list(N)),
    run_tests(1, Nsched).

run_tests(N, Nsched) ->
    case test(N) of
	stop ->
	    init:stop();
	Val ->
	    io:format("~p.~n",[{Nsched, Val}]),
	    run_tests(N+1, Nsched)
    end.

test(1) ->
    %% Make 100 lists 
    %%   Each list contains 1000 random integers
    seed(),
    S = lists:seq(1,100),
    L = map(fun(_) -> mkList(1000) end, S),
    {Time1, S1} = timer:tc(lists,    map,  [fun lists:sort/1, L]),
    {Time2, S2} = timer:tc(pmap, pmap, [fun lists:sort/1, L]),
    {sort, Time1, Time2, equal(S1, S2)};
test(2) ->
    %% L = [27,27,27,..] 100 times
    L = lists:duplicate(100, 27), 
    {Time1, S1} = timer:tc(lists,    map,  [fun ptests:fib/1, L]),
    {Time2, S2} = timer:tc(pmap, pmap, [fun ptests:fib/1, L]),
    {fib, Time1, Time2, equal(S1, S2)};
test(3) ->
    stop.

%% Equal is used to test that map and pmap compute the same thing
equal(S,S)   -> true;
equal(S1,S2) ->  {differ, S1, S2}.
 
%% recursive (inefficent) fibonacci
fib(0) -> 1;
fib(1) -> 1;
fib(N) -> fib(N-1) + fib(N-2).

%% Reset the random number generator. This is so we
%% get the same sequence of random numbers each time we run
%% the program

seed() -> random:seed(44,55,66).

%% Make a list of K random numbers
%%    Each random number in the range 1..1000000
mkList(K) -> mkList(K, []).

mkList(0, L) -> L;
mkList(N, L) -> mkList(N-1, [random:uniform(1000000)|L]).