(sacked: rename vs /bin/mv) Re: Re: mp3 organizer

[sacked]

Thanks for the suggestion! I was curious as to whether rename would be faster, though, since it requires one call per mp3, whereas /bin/mv requires only one call per directory. After a quick scan of my collection, I made a conservative estimate of five mp3s per directory (meaning, of course, five times as many calls are required for rename as /bin/mv). The results of a benchmark, however, were enlightening. Here is the benchmarking code I used:

#!/usr/bin/perl -w
#
# system('/bin/mv') vs rename

use strict;
use Benchmark;

use vars qw($rename_cnt $system_cnt $mp3dir1 $mp3dir2 @files @f1 @f2 $
+i $flip);

# $flip switches once per @files runs of the rename sub,
# then switches every call to the /bin/mv sub
$flip = $i = 0;

# flip-flop between these two dirs for move operations
$mp3dir1 = '/opt/mp3/';
$mp3dir2 = '/opt/tmp/';

# get file list
opendir(DIR, $mp3dir2) or die "can't open $mp3dir2 for read: $!\n\n";
@files = grep { /\.[Mm][Pp]3$/ } readdir(DIR);
closedir(DIR) or warn "error closing $mp3dir2: $!\n\n";

@f1 = map { $mp3dir1 . $_ } @files;
@f2 = map { $mp3dir2 . $_ } @files;

# run the func a few times
$rename_cnt = $#files * 10;
$system_cnt = int($rename_cnt / 5);

my $t = timeit($rename_cnt, \&rename_move_files);
print "$rename_cnt loops of 'rename' took:",timestr($t),"\n";
$t    = timeit($system_cnt, \&system_move_files);
print "$system_cnt loops of 'system' took:",timestr($t),"\n";

exit;

sub system_move_files {
  my ($src,$dst) = ($flip % 2) ? (\@f1,$mp3dir2) : (\@f2,$mp3dir1);

  system('/bin/mv', @$src, qq{$dst}) == 0
    or die "system('/bin/mv'): $?\n\n";

  ++$flip;
}

sub rename_move_files {
  my ($src,$dst) = ($flip % 2) ? (\@f1,\@f2) : (\@f2,\@f1);

  # so we can run this more than @files times
  my $j = $i % $#files;

  rename qq{$src->[$j]}, qq{$dst->[$j]} or die "can't rename $src->[$j
+]: $!\n\n";

  ++$i;
  ++$flip if ($i % $#files == 0);
}

__END__
results ranged from:

1300 loops of 'rename' took: 0 wallclock secs ( 0.01 usr +  0.05 sys =
+  0.06 CPU) @ 21666.67/s (n=1300)
260 loops of 'system' took: 2 wallclock secs ( 0.08 usr  0.13 sys +  0
+.44 cusr  1.46 csys =  2.11 CPU) @ 1238.10/s (n=260)

to:

1300 loops of 'rename' took: 0 wallclock secs ( 0.02 usr +  0.04 sys =
+  0.06 CPU) @ 21666.67/s (n=1300)
260 loops of 'system' took: 2 wallclock secs ( 0.03 usr  0.04 sys +  0
+.38 cusr  1.67 csys =  2.12 CPU) @ 3714.29/s (n=260)

Looks like the rename function wins.
--
"All we gotta do is apply the final touches!" -Parappa

sacked