the regex $str =~ /foo/ devolves to something pretty much like Index $str, 'foo'

Yes exactly. Itll be a little slower than a index but only becuase there is a longer codepath from the regex-opcode to the actual FBM search than from the index-opcode.

The surprise is how fast using a character set with a common prefix match is. That result also goes a long way to validating the benchmark.

And it illustrates a new optimisation in 5.10: 

                      Rate using_alt_match using_or_nomatch using_alt_
+nomatch using_or_match
using_alt_match   412710/s              --             -29%           
+   -30%           -36%
using_or_nomatch  580306/s             41%               --           
+    -1%            -9%
using_alt_nomatch 585631/s             42%               1%           
+     --            -9%
using_or_match    640118/s             55%              10%           
+     9%             --
1631660

[download]

Basically 5.10 is smart enough to convert /baz|bar/ into something close to /ba[rz]/. Its not quite as fast when written as an alternation due to current implmentation details, but it is very close.

---
$world=~s/war/peace/g

In reply to Re^2: Benchmarking regex alternation by demerphq
in thread Benchmarking regex alternation by Tanktalus

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.