#!/usr/bin/perl -w

use strict;

use v5.10;

use threads;

use threads::shared;

use Fcntl "SEEK_SET";

use Math::BigFloat qw();

$| = 1;

my $off = tell DATA;

my $a :shared;

my $b :shared;

while (<DATA>) {

s/[\r\n]//g;

($a, $b) = ($_, $_ + 1);

last if (eof DATA);

$off = tell DATA;

seek DATA, $off, SEEK_SET;

my $c = Math::BigFloat->new($a * $a + $b * $b)->bsqrt->dparts();

say "a: $a, b: $b, c: $c, Δ: " . (100 / $c) . "%";

}

say "resuming from a: $a, b: $b...";

close DATA;

sub progress () {

$SIG{TERM} = $SIG{INT} = sub { threads->exit(); };

for (;;) {

select '', '', '', 0.5;

print "a: $a, b: $b\e[K\r";

}

}

my $thread = async \&progress;

open my $data, '+<', $0;

$SIG{TERM} = $SIG{INT} = $SIG{__DIE__} = sub {

say "\nreaping progress reporting thread";

$thread->kill('INT');

$thread->join();

say "saving resume point $a";

$off = tell $data;

say $data "$a";

close $data;

say "goodbye.";

exit;

};

seek $data, $off, SEEK_SET if ($off);

for (;; $a++, $b++) {

my ($c, $frac) = Math::BigFloat->new($a * $a + $b * $b)->bsqrt()->dparts();

if ($frac eq "0") {

say "a: $a, b: $b, c: $c, Δ: " . (100 / $c) . "%\e[K";

say $data "$a";

}

}

$thread->kill('INT');

$thread->join();

__DATA__

3

20

119

696

4059

23660

137903

803760

4684659

27304196

159140519

163810330