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From: C.DeRykus on 17 Mar 2010 09:05
On Mar 17, 3:00 am, Oliver 'ojo' Bedford <news...(a)web.de> wrote:
> Am Mon, 15 Mar 2010 16:00:42 +0000 schrieb bugbear:
>
> > Jürgen Exner wrote:
> >> Oliver 'ojo' Bedford <news...(a)web.de> wrote:
> >>> For testing purposes I would like to fill chunks of memory (say 20M)
> >>> with arbitrary data (say bytes with values 1,2,...255,1,...).
>
> >>> What would be the fastest method?
>
> >> The easiest method would probably be to define a string with say 256
> >> bytes and then use the x operator to repeat it. I would guess it would
> >> also be quite fast because it uses perl interna only and doesn't
> >> involve a user-level loop.
>
> > If speed is really important (it often isn't) you may be able to
> > repeatedly "double up" by copying the head of the 20Meg space to itself..
>
>   Thanks for the help. I'll try both methods.
>
>   Speed is not important in my case - it's just a matter of convenience
> (and impatience on my side).
>

You may want to reconsider speed on Win32
though if you've seen the recent thread
"Help on string to array":

http://groups.google.com/group/comp.lang.perl.misc/browse_thread/thread/ddc58df14fe6e965/9c713aab4e254fdf?hl=en&lnk=gst&q=malloc+Win32#

One speed-up possibility is to grow the string
by doubling:

$max = 20_000_000;
$str = pack "C*",0..255;
do {$str .= $str;} until length $str >= $max;
substr($str, $max-length($str)) = '');

--
Charles DeRykus
From: ccc31807 on 17 Mar 2010 10:00
On Mar 15, 5:22 am, Oliver 'ojo' Bedford <news...(a)web.de> wrote:
> Hi!
>
> For testing purposes I would like to fill chunks of memory (say 20M) with
> arbitrary data (say bytes with values 1,2,...255,1,...).
>
> What would be the fastest method?
>
> Oliver

Use the recursive Fibonacci function, not tail recursive. It calls
itself twice on each iteration, so clogs up memory even for small
values.

use strict;
use warnings;

sub fib
{
my $n = shift;
if ($n <= 1) { return 1; }
else { return (fib($n - 1) + fib($n - 2)); }
}

my $N = $ARGV[0];
my $f = fib($N);
print "$f\n";
exit(0);
From: Ted Zlatanov on 17 Mar 2010 14:47
On Wed, 17 Mar 2010 07:00:13 -0700 (PDT) ccc31807 <cartercc(a)gmail.com> wrote:

c> On Mar 15, 5:22�am, Oliver 'ojo' Bedford <news...(a)web.de> wrote:
>> For testing purposes I would like to fill chunks of memory (say 20M) with
>> arbitrary data (say bytes with values 1,2,...255,1,...).
>>
>> What would be the fastest method?

c> Use the recursive Fibonacci function, not tail recursive. It calls
c> itself twice on each iteration, so clogs up memory even for small
c> values.

Out of curiousity, did you come up with this method for filling memory
on your own? I haven't seen it in the literature. It could be
patentable.

Ted
From: ccc31807 on 17 Mar 2010 16:29
On Mar 17, 2:47 pm, Ted Zlatanov <t...(a)lifelogs.com> wrote:
> Out of curiousity, did you come up with this method for filling memory
> on your own?  I haven't seen it in the literature.  It could be
> patentable.
>
> Ted

This is the standard recursive definition of Fibonacci, and I can't
take the credit for it.

In Joe Armstrong's book on Erlang, he gives a multi threaded way of
filling memory using threads, which is very easy and interesting.

CC.

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