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.
-
Are you posting in the right place? Check out Where do I post X? to know for sure.
-
Posts may use any of the Perl Monks Approved HTML tags. Currently these include the following:
<code> <a> <b> <big>
<blockquote> <br /> <dd>
<dl> <dt> <em> <font>
<h1> <h2> <h3> <h4>
<h5> <h6> <hr /> <i>
<li> <nbsp> <ol> <p>
<small> <strike> <strong>
<sub> <sup> <table>
<td> <th> <tr> <tt>
<u> <ul>
-
Snippets of code should be wrapped in
<code> tags not
<pre> tags. In fact, <pre>
tags should generally be avoided. If they must
be used, extreme care should be
taken to ensure that their contents do not
have long lines (<70 chars), in order to prevent
horizontal scrolling (and possible janitor
intervention).
-
Want more info? How to link
or How to display code and escape characters
are good places to start.
|
