Beefy Boxes and Bandwidth Generously Provided by pair Networks
Pathologically Eclectic Rubbish Lister
 
PerlMonks  

comment on

( #3333=superdoc: print w/replies, xml ) Need Help??
Still don't understand why just changing the one line... caused it to slow down SO much.
Just off the top of my head, I suspect it may be a bad interaction between the " *" and the " +" causing the regex engine to backtrack excessively because they're separated only by an optional element, so a string of multiple spaces can match in multiple ways (no spaces/5 spaces, 1 space/4 spaces, etc.) which then multiplies the number of potential matches for the full string, each of which needs to be evaluated until the engine is satisfied that it either found one that's good enough or that no match exists. The capturing parens on foo may also be contributing.

If you want to test this theory, you could try changing the regex to $allfile =~ s/^( *foo)? +$_\n//mn; (leaving the capturing parens intact) or $allfile =~ s/^(?: *foo)? +$_\n//mn; (non-capturing parens, since you're really only using them for grouping) and seeing if that restores the original performance.


In reply to Re^3: some efficiency, please by dsheroh
in thread some efficiency, please by Anonymous Monk

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, 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, 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.
  • Log In?
    Username:
    Password:

    What's my password?
    Create A New User
    Chatterbox?
    and the web crawler heard nothing...

    How do I use this? | Other CB clients
    Other Users?
    Others examining the Monastery: (3)
    As of 2020-07-08 02:51 GMT
    Sections?
    Information?
    Find Nodes?
    Leftovers?
      Voting Booth?

      No recent polls found

      Notices?