On 10/25/05, John W. Krahn <[EMAIL PROTECTED]> wrote:
> M. Lewis wrote:
> > I'm trying to create a file of a certain size. Specifically 15MB for
> > some testing purposes. I want this file to have random characters. I'm
> > sure it would be easier (faster) to use the same character. What I'm
> > finding is my code is terribly slow to create a 15MB file.
> >
> > Is there a better / more efficient way ?
> >
> > Thanks,
> > Mike
> >
> >
> > #!/usr/bin/perl
> >
> > use strict;
> > use warnings;
> >
> > #PURPOSE - Create a file of a certain size (random characters)
> >
> > my $file = './test.txt';
> > my $size = 15728640; # 15MB
> >
> > open (OUT,">$file") || die "Cannot open $file :$!";
> >
> > print OUT (map+chr(ord('a')+rand 26),1..$size);
> >
> > close OUT;
>
> Your program is really slow because you are creating a 15MB list in memory.
> This will be a lot faster:
>
> my $size = 1024;
>
> for ( 1 .. 15 * 1024 ) {
> print OUT map chr( ord( 'a' ) + rand 26 ), 1 .. $size;
> }
Why map at all? Just forget the list entirely and let the system
buffer the output however it wants; it's going to anyway:
print OUT chr( ord( 'a') + rand 26 ) for 1..(15*1024*1024);
This is about 30% faster than map, at least for me. YMMV, of course.
HTH,
-- jay
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