Benchmark: timing 1000000 iterations of Grep, Max, Ternary...
      Grep:  4 wallclock secs ( 3.02 usr +  0.00 sys =  3.02 CPU) @ 331125.83/s (n=1000000)
       Max:  7 wallclock secs ( 5.79 usr +  0.00 sys =  5.79 CPU) @ 172711.57/s (n=1000000)
   Ternary:  5 wallclock secs ( 5.72 usr +  0.00 sys =  5.72 CPU) @ 174825.17/s (n=1000000)

Which is very different than what I had before. To shed some light on this, let me first point out that the code above is almost but not quite the code I got my previous results from.

The only difference is, my code put each snippet to be benchmarked inside a sub, and then game Benchmark the function calls. I did this because I thought it more acurately reflected real-world max() usage, but this is certainly not true for all programs. Also different is that I changed my to our, so as not to change the function calls or add use vars. Would this make any difference speed difference? I know our is new to 5.6.0, and I am already loving it, but I don't know it's internals.

Now I'll take Russ's code given above and just make that one change. The function calls are SO expensive compared to the rest of the code, that I will turn down the iterations to 10_000, but we will see it take much, much longer. Here is the code:

#!/usr/bin/perl -w
use strict;
our $now = 8;
our %url = ( monday => { @{[map(($_,1), (1..1000))]} } );
use Benchmark;
timethese(10000, {
    Grep => q{
    Grep();
    },
    Ternary => q{
    Ternary();
    },
    Max => q{
    Max();
    }
});

sub Grep {
    $now = (sort grep {$_ <= $now} keys %{$url{'monday'}})[-1];
}

sub Ternary {
    $now = ($now < $_ && $_ < 8 ? $_ : $now) for keys %{$url{'monday'}
+};
}

sub Max {
    foreach ( keys %{$url{'monday'}} ) { $now = $_ if $_ > $now };
}

[download]

And the results:

Benchmark: timing 10000 iterations of Grep, Max, Ternary...
      Grep: 72 wallclock secs (68.98 usr +  0.00 sys = 68.98 CPU) @ 144.97/s (n=10000)
       Max: 64 wallclock secs (60.01 usr +  0.00 sys = 60.01 CPU) @ 166.64/s (n=10000)
   Ternary: 66 wallclock secs (63.24 usr +  0.01 sys = 63.25 CPU) @ 158.10/s (n=10000)

And so this is more consistant with my earlier resutls.

Platform is an AMD K6-II/400 128megs SDRAM, running linux 2.2.12 and perl 5.6.0.

I really don't understand these results. I understand that function calls are very, very expensive( the reason OO is often slow; accessor methods vs lookups ), but I don't understand why the proportions are different. Why doesn't the function call add the same amount of proc time for each call? Or is there something else?

Paris Sinclair    |    4a75737420416e6f74686572
pariss@efn.org    |    205065726c204861636b6572
I wear my Geek Code on my finger.

In reply to Re: Algorithm Efficiency vs. Specialized Hardware? by Aighearach
in thread Algorithm Efficiency vs. Specialized Hardware? by Russ

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.