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% Benchmark prime number generation using the sieve of Eratosthenes
% algorithm with assert/retract. This benchmark tests assert/retract and
% JIT index generation and destruction.
%
% Auther: Jan Wielemaker
% Copyright: Public domain.
top :- clean, primes(10000), fail.
top.
:- if(\+current_predicate(forall/2)).
forall(Cond,Act) :- \+ ( Cond, \+ Act ).
:- endif.
:- if(\+current_predicate(ignore/1)).
ignore(Goal) :- (Goal->true;true).
:- endif.
:- if(\+current_predicate(between/3)).
:- use_module(library(between)).
:- endif.
:- dynamic prime/1, candidate/1.
clean :-
retractall(prime(_)),
retractall(candidate(_)).
primes(N) :-
forall(between(2, N, I), assertz(candidate(I))),
sieve(N).
sieve(Max) :-
retract(candidate(First)),
!,
assertz(prime(First)),
First < Max,
sieve(First, 2, Max),
sieve(Max).
sieve(_).
sieve(N, Mul, Max) :-
I is N*Mul,
I =< Max,
!,
ignore(retract(candidate(I))),
Mul2 is Mul+1,
sieve(N, Mul2, Max).
sieve(_, _, _).
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