Viewing file:  primes.pl (2.57 KB) -rw-r--r--
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#!/usr/bin/perl -w
###############################################################################
## ##
## Copyright (c) 1995 - 2013 by Steffen Beyer. ##
## All rights reserved. ##
## ##
## This program is free software; you can redistribute it ##
## and/or modify it under the same terms as Perl itself. ##
## ##
###############################################################################
use strict;
use vars qw($limit $set $start $stop $min $max $norm $i $j);
use Bit::Vector;
print "\n***** Calculating Prime Numbers - The Sieve Of Erathostenes *****\n";
$limit = 0;
if (-t STDIN)
{
while ($limit < 16)
{
print "\nPlease enter an upper limit (>15): ";
$limit = <STDIN>;
if ($limit =~ /^\s*(\d+)\s*$/) { $limit = $1; } else { $limit = 0; }
}
print "\n";
}
else
{
$limit = 100;
print "\nRunning in batch mode - using $limit as upper limit.\n\n";
}
$set = Bit::Vector->new($limit+1);
print "Calculating the prime numbers in the range [2..$limit]...\n\n";
$start = time;
$set->Primes();
## Alternative (slower!):
#$set->Fill();
#$set->Bit_Off(0);
#$set->Bit_Off(1);
#for ( $j = 4; $j <= $limit; $j += 2 ) { $set->Bit_Off($j); }
#for ( $i = 3; ($j = $i * $i) <= $limit; $i += 2 )
#{
# for ( ; $j <= $limit; $j += $i ) { $set->Bit_Off($j); }
#}
$stop = time;
&print_elapsed_time;
$min = $set->Min();
$max = $set->Max();
$norm = $set->Norm();
print "Found $norm prime numbers in the range [2..$limit]:\n\n";
for ( $i = $min, $j = 0; $i <= $max; $i++ )
{
if ($set->contains($i)) { print "prime number #", ++$j, " = $i\n"; }
}
print "\n";
exit;
sub print_elapsed_time
{
my($flag) = 0;
my($sec,$min,$hour,$year,$yday) = (gmtime($stop - $start))[0,1,2,5,7];
$year -= 70;
print "Elapsed time: ";
if ($year > 0)
{
printf("%d year%s ", $year, ($year!=1)?"s":"");
$flag = 1;
}
if (($yday > 0) || $flag)
{
printf("%d day%s ", $yday, ($yday!=1)?"s":"");
$flag = 1;
}
if (($hour > 0) || $flag)
{
printf("%d hour%s ", $hour, ($hour!=1)?"s":"");
$flag = 1;
}
if (($min > 0) || $flag)
{
printf("%d minute%s ", $min, ($min!=1)?"s":"");
}
printf("%d second%s.\n\n", $sec, ($sec!=1)?"s":"");
}
__END__
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