/* 

  Benchmark fib in Picat v3.

  From bench/fib.pl  
  https://github.com/SWI-Prolog/bench.git

  Changes:
  - changed abolish_all_tables to initialize_table
  - changed table fib/2 to table
  - added println/1

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

*/


main => go.

go ?=>
  initialize_table,
  fib(1000,N),
  println(N),
  fail, 
  nl.

go => true.


% Tabling is also important for the memoisation it offers.
% The standard example is calculating Fibonacci numbers.
%
% As an example, this benchmark calculates the N-th Fibonacci number without tabling.
% You can compare its execution time to the version with tabling in fib-no-tabling-hprolog.pl
%
% This is also interesting for a paper (Marko, Tom).

top :- % abolish_all_tables,
       initialize_table,
       fib(1000,_),
       fail,
       nl.
top.

% :-table fib/2.
table
fib(0, 1) :- !.
fib(1, 1) :- !.
fib(N,F):-N>1,N1 is N-1, N2 is N-2,fib(N1,F1),fib(N2,F2),F is F1+F2.