/* 

  Elevator benchmark in Picat.

  From https://swi-prolog.discourse.group/t/vm-code-refactor-thoughts/3845/54


  This model was created by Hakan Kjellerstrand, hakank@gmail.com
  See also my Picat page: http://www.hakank.org/picat/

*/

% import v3_utils.
% import util.
% import cp.


main => go.

/*
   Picat: 
     elevator: 1.766s.
     elevator1: 1.081s
     elevator2: 0.954s
     elevator3: 1.758s
     elevator4: 1.105s


   SWI-Prolog version 8.3.22:
   ?- time((between(1,10000,_), elevator(10000,_), fail; true)).
   % 100,030,002 inferences, 3.002 CPU in 3.002 seconds (100% CPU, 33318585 Lips)
   true.

   B-Prolog: CPU time 36.158 seconds. !

   GProlog: Don't work!

   Trealla: > 5minutes

   YAP: 0.754 CPU in 0.754 seconds (100% CPU)

   BinProlog, #12.01: > 4min?

   SICStus: don't have time/1 or between/3
       ?- [elevator2].
       ?- ensure_loaded(library(between)).
       ?- call_time((between(1,10000,_), elevator(10000,_), fail; true),Time).
       Time = 230 ? 

   ECLiPSe CLP: 
     [eclipse 12]: use_module(util).
     [eclipse 13]: between(1,10000,_), elevator(10000,_), fail; true.
     Yes (1.44s cpu)
     [eclipse 14]: between(1,10000,_), elevator(10000,_), fail; true.
     Yes (1.41s cpu)

   SICStus is the fastest so far: 0.230s!

*/

% elevator/2
go ?=>
  time((between(1,10000,_), elevator(10000,_), fail; true)),
  nl.
go => true.

% elevator1/2
go1 ?=>
  time((between(1,10000,_), elevator1(10000,_), fail; true)),
  nl.
go1 => true.

% elevator2/2
go2 ?=>
  time((between(1,10000,_), elevator2(10000,_), fail; true)),
  
  nl.
go2 => true.

% elevator3/1
go3 ?=>
  time((between(1,10000,_), _=elevator3(10000), fail; true)),
  nl.
go3 => true.

% elevator4/1
go4 ?=>
  time((between(1,10000,_), _=elevator4(10000), fail; true)),
  nl.
go4 => true.


% From
% https://swi-prolog.discourse.group/t/vm-code-refactor-thoughts/3845/54

% elevator/2
elevator(N,M) :-
   elevator(N, 0, M).
elevator(0, N, N) :- !.
elevator(N, X, Y) :-
    M is N-1,
    H is X+1,
    elevator(M, H, Y).

% elevator1/2
% Without is/2 assignements
elevator1(N,M) :-
   elevator1(N, 0, M).
elevator1(0, N, N) :- !.
elevator1(N, X, Y) :-
  elevator1(N-1, X+1, Y).


% elevator2/2.
% Picat style: Slightly faster
elevator2(N,M) =>
  elevator2(N, 0, M).
elevator2(0, N1, N2) => N1 = N2.
elevator2(N, X, Y) =>
  elevator2(N-1, X+1, Y).

% elevator3/1
% Functional version
% (inspired by Jan Burse's recursive Java code )
elevator3(N) = elevator3(N,0).
elevator3(N,M) = Res =>
  if N == 0 then
     Res = M
  else
     Res = elevator3(N-1,M+1)
  end.

% elevator4/1: same as elevator3/1-2 without if/1
elevator4(N) = elevator4(N,0).
elevator4(0,M) = M => true.
elevator4(N,M) = elevator4(N-1,M+1) => true.