Re^2: About List::Util's pure Perl shuffle()

[blazar]

I suppose taking references might save memory, but it doesn't save any time over this (on small or large lists):
[snip]
I get about 16% better than the List::Util version (YMMV).

Indeed I was about to yell: "well, but then let's just adapt BrowserUk's version simply removing the referencing and dereferencing":

sub bzr (@) {
    my @a = @_;
    my $n;
    my $i = @_;
    map +($n=randi($i--), $a[$n], $a[$n]=$a[$i])[1], @_;
}

But that won't work any more! (So kids don't copy the code above, it's crap! ;-) OTOH if I compare your code (as 'run') with BrowserUk's, I get:

      Rate  run  buk
run 7467/s   -- -12%
buk 8454/s  13%   --

So that seems the best both speed and possibly memory wise.

[runrig]

That's strange, I compared mine against BrowserUK's and get that they are very nearly equal (mine ahead by a meaningless 1 to 4%), until the list gets large (around a million), then I'm ahead by ~10%. This is for lists containing data only a few characters long, but as ikegami points out, for larger data, BrowserUK's wins by a longshot.

[ikegami]

Ah, but the fix is easy. It's in my reply (which was posted and updated with the fix before you posted yours).

[BrowserUk]

Here's a non-aliasing version that does work, but it doesn't perform very well. Why it works is left as an exercise.

sub bukNoAlias (@) {
    my @a = @_;
    my( $n, $t );
    my $i = @_;
    map+( $t=$a[ $n=rand($i--) ], $a[ $n ]=$a[ $i ] )[ 0 ], @_;
}