#!/usr/bin/env perl
use strict;
use warnings;
use threads;
use threads::shared;
# Overkill, but let's try to select a good bigint module.
my $bigint_class;
if (eval { require Math::GMPz; 1; }) {
$bigint_class = "Math::GMPz";
} elsif (eval { require Math::GMP; 1; }) {
$bigint_class = "Math::GMP";
} else {
require Math::BigInt;
Math::BigInt->import(try=>"GMP,Pari");
$bigint_class = "Math::BigInt";
}
use Math::Prime::Util ':all';
use Time::HiRes qw(gettimeofday tv_interval);
$| = 1;
# Find Fibonacci primes in parallel, using Math::Prime::Util and Perl threads.
#
# Dana Jacobsen, 2012.
#
# This will fully utilize however many cores you choose (using the $nthreads
# variable). It spreads the numbers across threads, where each one runs a
# BPSW test. A separate thread handles the in-order display. I have tested
# it on machines with 2, 4, 8, 12, 24, 32, and 64 cores.
#
# You will want Math::Prime::Util::GMP installed for performance.
#
# Also see the MCE example.
#
# On my 12-core computer:
# 24 5387 0.51088
# 25 9311 2.74327
# 26 9677 3.56398
# 27 14431 11.46177
# 28 25561 76.52618
# 29 30757 130.26143
# 30 35999 262.94690
# 31 37511 306.67707
# 32 50833 746.35491
#
# Though not as pretty as the Haskell solution on haskell.org, it is a
# different way of solving the problem that is faster and more scalable.
my $time_start = [gettimeofday];
my $nthreads = 12;
prime_precalc(10_000_000);
my @found :shared; # push the primes found here
my @karray : shared; # array of min k for each thread
my @threads;
push @threads, threads->create('fibprime', $_) for 1 .. $nthreads;
# Let the threads work for a little before starting the display loop
sleep 2;
my $n = 0;
lock(@karray);
while (1) {
cond_wait(@karray);
{
lock(@found);
next if @found == 0;
# Someone has found a result. Discover min k processed so far.
my $mink = $karray[1] || 0;
for my $t (2..$nthreads) {
my $progress = $karray[$t] || 0;
$mink = $progress if $progress < $mink;
}
next unless $mink > 0; # someone hasn't even started
@found = sort { (split(/ /, $a))[0] <=> (split(/ /, $b))[0] } @found;
while ( @found > 0 && (split(/ /, $found[0]))[0] <= $mink ) {
my($k, $time_int) = split(/ /, shift @found);
printf "%3d %7d %20.5f\n", ++$n, $k, $time_int;
}
}
}
$_->join() for (@threads);
sub fib_n {
my ($n, $fibstate) = @_;
@$fibstate = (1, $bigint_class->new(0), $bigint_class->new(1))
unless defined $fibstate->[0];
my ($curn, $a, $b) = @$fibstate;
die "fib_n only increases" if $n < $curn;
do { ($a, $b) = ($b, $a+$b); } for (1 .. $n-$curn);
@$fibstate = ($n, $a, $b);
$b;
}
sub fibprime {
my $tnum = shift;
my @fibstate;
my $nth = $tnum;
while (1) {
# Exploit knowledge that excepting k=4, all prime F_k have a prime k.
my $k = ($nth <= 2) ? 2 + $nth : nth_prime($nth);
$nth += $nthreads;
my $Fk = fib_n($k, \@fibstate);
if (is_prob_prime($Fk)) {
lock(@found);
push @found, $k . " " . tv_interval($time_start);
}
{
lock(@karray);
$karray[$tnum] = $k;
cond_signal(@karray);
}
}
}