in reply to Re^4: Creating flexible method accessor (no benchmark?)
in thread Creating flexible method accessor

Perhaps you need to look up the word "significant". "Can be detected by careful measurement against an isolated subset" doesn't reach the point of "likely to be noticed" which is a minimum requirement for "significant".

Making your whole program run 10% faster isn't really significant as most people won't notice that something took 0.9 seconds instead of a full second. But making one tiny subroutine 10% faster is going to have much less than 10% impact on the speed of any program. Which is why it is very clearly insignificant. To have significance it has to have a noticeable impact. And impact is only noticed in the run time of real code.

I note that your benchmark didn't even use the example code being discussed. I bet the benchmark numbers are even more obviously not significant in that case. How insignificant it looks in that case is just a fraction of how insignificant it will be in real code.

- tye        

  • Comment on Re^5: Creating flexible method accessor (noticeable)

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Re^6: Creating flexible method accessor (noticeable)
by BrowserUk (Patriarch) on Feb 03, 2014 at 00:20 UTC

    When I run tobyink's benchmark under 5.18, I get a 20% reduction in runtime:

    C:\test>\perl5.18\bin\perl.exe
use strict;
use warnings;
use Benchmark qw(cmpthese);

my $name = 'foo';
my $path = 'foobar';
my $sub1 = sub { $_[0]{$path}{$name} = $_[1] if @_ == 2; $_[0]{$path}{
+$name} };
my $sub2 = eval qq[ sub { \$_[0]{$path}{$name} = \$_[1] if \@_ == 2; \
+$_[0]{$path}{$name} } ]
        or die($@);

my $self = {};

cmpthese -1, {
        closure => sub {
                $self->$sub1(0);
                $self->$sub1( $self->$sub1 + $_ ) for 0..10_000;
        },
        stringy => sub {
                $self->$sub2(0);
                $self->$sub2( $self->$sub2 + $_ ) for 0..10_000;
        },
};
^Z
          Rate closure stringy
closure 65.7/s      --    -17%
stringy 79.1/s     20%      --

    [download]

    If you got a 20% rise, you'd consider it "significant".

    If you were offered a 20% reduction in the cost of your next car, you'd consider it "significant".

    If you were offered a 20% reduction in your likelihood of early mortality, you'd consider it "significant".

    If you were gifted a 20% reduction in your daily processing, such that it reduced it from 25 hours to 20, you'd consider it "significant".

    Stop being an ass.

    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.
[reply]
[d/l]

      I would notice getting paid 20% more. I would notice paying 20% less for a car. I might notice if a script ran 20% faster. That's about the minimum percentage reduction in run-time that I'm likely to notice.

      But, of course, this isn't even close to a 20% reduction in the run time of a script.

      A much more apt comparison would be if you got a 20% discount on... the ashtrays in your car (only after subtracting out "overhead" so you really only got a 10% discount on the actual price of the ashtrays).

      This reminds me of a cartoon from my college newspaper that showed a sign saying "50% off books! 50% off supplies! Total savings: 100%!!". You have to believe in magical math like that in order to find a 20% reduction in something that is a tiny part of your total run-time to be "significant".

      Take a useful script and have somebody run it once with and once without this optimization. They won't notice that it ran faster. "Not noticeable" is well below "significant".

      - tye        

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