Beefy Boxes and Bandwidth Generously Provided by pair Networks
good chemistry is complicated,
and a little bit messy -LW

Comment on

( #3333=superdoc: print w/replies, xml ) Need Help??
Your benchmark is not very realistic. As $n doesn't vary, you are completely ignoring the effect of the CPU cache misses that the lookup table may introduce.

The version of my benchmark I posted was the one I use -- in conjunction with -N=1 and uncommenting the print "@_"; -- to check that the output from all the methods is correct.

For timing runs, I operate on the loop counter $_, which when -N=10e6, is enough to exercise the full range of the table 38 times.

And I still get 20%+ improvement from the AoAs lookup:


C:\test>1021064 Shift&and took: 0.000000606833 seconds Lookup took: 0.000000485629 seconds Lookup2 took: 0.000000669586 seconds (un)pack took: 0.000007564075 seconds

In general, I've found it very difficult to detect, much less measure any discernible effect from cpu caching in perl code on my machine. It shows up readily in tight loops in C code, but Perl's memory allocation is so cache unfriendly that it rarely seems to come into play.

I would be interested to see the output from the above on your machine if you have a coupe of minutes.

With the rise and rise of 'Social' network sites: 'Computers are making people easier to use everyday'
Examine what is said, not who speaks -- Silence betokens consent -- Love the truth but pardon error.
"Science is about questioning the status quo. Questioning authority".
In the absence of evidence, opinion is indistinguishable from prejudice.

In reply to Re^4: Efficient bit-twiddling in Perl. by BrowserUk
in thread Efficient bit-twiddling in Perl. by BrowserUk

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?

    What's my password?
    Create A New User
    and all is quiet...

    How do I use this? | Other CB clients
    Other Users?
    Others about the Monastery: (4)
    As of 2018-05-25 05:55 GMT
    Find Nodes?
      Voting Booth?