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Re^3: mem usage

by BrowserUk (Pope)
on May 26, 2010 at 19:17 UTC ( #841792=note: print w/ replies, xml ) Need Help??

in reply to Re^2: mem usage
in thread mem usage

You can trim your shuffle a little by omitting the line:         next if $i==$j;.

Swapping an item with itself doesn't affect the algorithm's fairness, and doing it once costs less, than testing n times and avoiding it once.

And you save a little more by avoiding the list assignment:

my $tmp = $array[ $i ]; $array[ $i ] = $array[ $j ]; $array[ $j ] = $tmp;

Doesn't look as nice though.

Examine what is said, not who speaks -- Silence betokens consent -- Love the truth but pardon error.
"Science is about questioning the status quo. Questioning authority".
In the absence of evidence, opinion is indistinguishable from prejudice.
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Re^4: mem usage
by ikegami (Pope) on May 26, 2010 at 19:46 UTC
    Including cleaning up the counter,
    sub shuffle { my $array = shift; my $i = @$array; while ($i) { my $j = int rand($i--); my $t = $array->[$i]; $array->[$i] = $array->[$j]; $array->[$j] = $t; } }
Re^4: mem usage
by halfcountplus (Hermit) on May 26, 2010 at 19:36 UTC
    You can trim your shuffle a little by omitting the line: next if $i==$j;

    Good point!

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