in reply to Re^2: In-place sort with order assignment
in thread In-place sort with order assignment

BTW: If I ever manage to get the keys out of the hash and into an array without blowing memory, then I intend to use your Sort::Key to sort them in-place. But, there doesn't seem to be a an in-place version of keysort that doesn't take a callback?

It seems the interface is not very consistent... actually, the function exists, it is Sort::Key::_sort_inplace.

In any case, perl builtin sort will perform equally faster as @k = sort @k gets optimized by the interpreter into an inplace operation.

BTW, using the quicksort algorithm instead of the default merge sort will also help to reduce memory usage.

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Re^4: In-place sort with order assignment
by BrowserUk (Patriarch) on Sep 19, 2010 at 19:37 UTC
    @k = sort @k gets optimized by the interpreter into an inplace operation.

    When did that make it into the release? Cos everytime it comes up here, I try it out and it doesn't seem to work. (And my attempt to search for the release info fail.)

    For now, Sort::Key::_sort_inplace() will do me fine.

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      That optimization was introduced here in 2004. Probably, the first stable release to incorporate it was perl 5.10.

      update: the optimization is documented in perl5100delta.

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        Hm. Do you see anything wrong with this usage that would prevent the in-place optimisation from kicking in? 

        perl -E"my @a; $a[$_]=rand for 1..1e6; <>; @a = sort @a; <>"

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        Because after the array is populated, memory usage stands at 42mb. After the sort, it jumped to 150MB.

        Which admittedly is substantially better than: 

        perl -E"my @a; $a[$_]=rand for 1..1e6; <>; my @b = sort @a; <>"

        [download]

        Where it leaps from 42MB to 280MB. But it doesn't meet my idea of 'in-place'.

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