I still get a weird result when I reverse the $a and $b in the comparator. Now it's: 
-1 0 0 0 7

[download]
Oh well, I think I'll keep the comparison caller in a separate subroutine for simplicity and maintainability anyway.

A similar mechanism should work for the heap sort version.

Actually, I don't need to do the same thing for the heap. All I need to do is call makeHeap on the first N items. That's O(N); building up the heap item-by-item is O(NlogN).

I'm thinking that this is good enough to go ahead with. If I implement the four simple cases (maxN, minN, maxNstr, minNstr) as you suggested, and also a user-supplied comparator, that will be fine.

We've been giving perl's sort an unfair advantage against our homemade comparator. I tried a benchmark against a call it didn't know how to optimize, { ($a < $b) ? -1 : (($a > $b) ? 1:0) }, and our partial sorts do better in many cases (5 in 1000, 5 in 10,000 etc.).

In reply to Re^9: Using $a and $b from XS by tall_man
in thread Using $a and $b from XS by tall_man

Title:
Use:  <p> text here (a paragraph) </p>
and:  <code> code here </code>
to format your post, it's "PerlMonks-approved HTML":


  • Posts are HTML formatted. Put <p> </p> tags around your paragraphs. Put <code> </code> tags around your code and data!
  • Titles consisting of a single word are discouraged, and in most cases are disallowed outright.
  • Read Where should I post X? if you're not absolutely sure you're posting in the right place.
  • Please read these before you post! —
  • Posts may use any of the Perl Monks Approved HTML tags:
    a, abbr, b, big, blockquote, br, caption, center, col, colgroup, dd, del, details, div, dl, dt, em, font, h1, h2, h3, h4, h5, h6, hr, i, ins, li, ol, p, pre, readmore, small, span, spoiler, strike, strong, sub, summary, sup, table, tbody, td, tfoot, th, thead, tr, tt, u, ul, wbr
  • You may need to use entities for some characters, as follows. (Exception: Within code tags, you can put the characters literally.)
            For:     Use:
    & &amp;
    < &lt;
    > &gt;
    [ &#91;
    ] &#93;
  • Link using PerlMonks shortcuts! What shortcuts can I use for linking?
  • See Writeup Formatting Tips and other pages linked from there for more info.