Hi
clivehumby,
I think there is something wrong with the I/O here. Perl scalars can hold values up to 2^53 (see maximum value of a scalar for details). For testing purpouses I created two big files F1.DAT and F2.DAT, their size are 1GB and 2GB respectively and modified your code as follows:
use strict;
use warnings;
my $int2 = 2147483648;
my $int4 = 2147483648 * 2;
my $int8 = 2147483648 * 4;
my $int16 = 2147483648 * 8;
print "int2 $int2\n";
print "int4 $int4\n";
print "int8 $int8\n";
print "int16 $int16\n";
## set up data in memory
my $tm=time;
my $file= $ARGV[0];
my $data;
{
open my $fh, '<', $file or die;
local $/ = undef;
$data = <$fh>;
close $fh;
}
## report load statistics
my $str="XYZ";
my $lx=length($data);
my $tmx=time-$tm;
my $r=$lx/$tmx;
print "File $file cached $lx bytes in $tmx seconds @ $r bs\n";
I run the script with different perl versions and the result can be found below. 5.8.9 and 5.10.1 failed but 5.20.2 worked correctly.
pme@pme-notebook: ~/Develop/workpme@pme-notebook:~/Develop/work$ perlb
+rew use perl-5.8.9
A sub-shell is launched with perl-5.8.9 as the activated perl. Run 'ex
+it' to finish it.
pme@pme-notebook: ~/Develop/workpme@pme-notebook:~/Develop/work$ perl
+pos2.pl F1.DAT
int2 2147483648
int4 4294967296
int8 8589934592
int16 17179869184
File F1.DAT cached 1073741824 bytes in 9 seconds @ 119304647.111111 bs
pme@pme-notebook: ~/Develop/workpme@pme-notebook:~/Develop/work$ perl
+pos2.pl F1.DAT P@2
int2 2147483648
int4 4294967296
int8 8589934592
int16G17179869184
File F2.DAT cached -2147483648 bytes in 18 seconds @ -119304647.111111
+ bs
pme@pme-notebook: ~/Develop/workpme@pme-notebook:~/Develop/work$ exit
exit
pme@pme-notebook: ~/Develop/workpme@pme-notebook:~/Develop/work$ perlb
+rew use perl-5.10.1
A sub-shell is launched with perl-5.10.1 as the activated perl. Run 'e
+xit' to finish it.
pme@pme-notebook: ~/Develop/workpme@pme-notebook:~/Develop/work$ perl
+pos2.pl F2.DAT 1
int2 2147483648
int4 4294967296
int8 8589934592
int16 17179869184
File F1.DAT cached 1073741824 bytes in 8 seconds @ 134217728 bs
pme@pme-notebook: ~/Develop/workpme@pme-notebook:~/Develop/work$ perl
+pos2.pl F1.DAT P@2
int2 2147483648
int4 4294967296
int8 8589934592
int16 17179869184
File F2.DAT cached -2147483648 bytes in 18 seconds @ -119304647.111111
+ bs
pme@pme-notebook: ~/Develop/workpme@pme-notebook:~/Develop/work$ exit
exit
pme@pme-notebook: ~/Develop/workpme@pme-notebook:~/Develop/work$ perl
+-v
This is perl 5, version 20, subversion 2 (v5.20.2) built for i586-linu
+x-gnu-thread-multi-64int
(with 51 registered patches, see perl -V for more detail)
Copyright 1987-2015, Larry Wall
Perl may be copied only under the terms of either the Artistic License
+ or the
GNU General Public License, which may be found in the Perl 5 source ki
+t.
Complete documentation for Perl, including FAQ lists, should be found
+on
this system using "man perl" or "perldoc perl". If you have access to
+ the
Internet, point your browser at http://www.perl.org/, the Perl Home Pa
+ge.
pme@pme-notebook: ~/Develop/workpme@pme-notebook:~/Develop/work$ perl
+pos2.pl F1.DAT
int2 2147483648
int4 4294967296
int8 8589934592
int16 17179869184
File F1.DAT cached 1073741824 bytes in 8 seconds @ 134217728 bs
pme@pme-notebook: ~/Develop/workpme@pme-notebook:~/Develop/work$ perl
+pos2.pl F1.DAT P@2
int2 2147483648
int4 4294967296
int8 8589934592
int16 17179869184
File F2.DAT cached 2147483648 bytes in 17 seconds @ 126322567.529412 b
+s
