Re^2: Unusual sorting requirements; comparing three implementations.

[afoken]

in reply to Re: Unusual sorting requirements; comparing three implementations.
in thread Unusual sorting requirements; comparing three implementations.

sub x {
    my @sorted = map $_->[1],
    sort{ $a->[0] cmp $b->[0] } map[
        $_->title eq 'Manager' ? 'A'.$_->name : 'B'.$_->name, $_
    ], @employees;
}

Faster, but not correct for the original problem. tobyink's Test::More script tested for ->title =~ /Manager/, not for ->title eq 'Manager', and so all those non-generic Manager employees, like the Sales Manager, the Finance Manager, and the Marketing Manager will be sorted as NON-Manager employees. tobyink's benchmark script wrongly reduces the possible titles to "Staff" and "Manager".

Alexander

[BrowserUk]

Correcting that makes barely any difference to the performance:

sub x {
    my @sorted = map $_->[1],
    sort{ $a->[0] cmp $b->[0] } map[
        $_->title =~ /Manager/ ? 'A'.$_->name : 'B'.$_->name, $_
    ], @employees;
}

 cmpthese( -1, {
     obvious    => \&obvious,
     subtle     => \&subtle,
     functional => \&functional,
     x          => \&x,
 });
C:\test>junk87
             Rate    obvious     subtle functional          x
obvious     183/s         --       -18%       -60%       -83%
subtle      224/s        22%         --       -51%       -79%
functional  458/s       150%       105%         --       -57%
x          1070/s       483%       378%       134%         --

[tobyink]

Not sure if your computer's architecture is radically different to mine or something, but for me, this technique is still slightly slower than the functional approach, and much slower than keysort.

Read more... (2 kB)

Results:

              Rate     obvious       subtle pure_schwarz  functional     sortkey
obvious      133/s          --         -28%         -60%        -65%        -80%
subtle       186/s         39%           --         -45%        -52%        -72%
pure_schwarz 337/s        153%          81%           --        -12%        -50%
functional   383/s        187%         107%          14%          --        -43%
sortkey      671/s        403%         262%          99%         75%          --

[BrowserUk]

Not sure if your computer's architecture is radically different to mine or something, ...

The first difference I notice is that your fastest iterating solution -- 671/s -- is only half as fast as my fastest iterating solution -- 1100/s.

I seriously doubt my 3 y/o Core2Quad Q6600 @2.4GHz is twice as fast as your hardware.

So the major difference probably comes down to the fact that I couldn't be bothered to install yet another slow-accessor constructor, so I manually code my Person Class:

package Person {
    sub new{ my $p = shift; bless { @_ }, $p }
    sub name{ $_[0]->{name } }
    sub title{ $_[0]->{title} }
}

After that, why your results should be relatively different to mine I have no idea:

<Reveal this spoiler or all in this thread>

But mine are consistent:

C:\test>date /t & time/t && junk87
24/10/2012
19:39
             Rate    obvious     subtle functional          x
obvious     189/s         --       -16%       -60%       -83%
subtle      226/s        19%         --       -52%       -80%
functional  471/s       149%       109%         --       -57%
x          1101/s       482%       388%       134%         --

[BrowserUk]

Just for fun, I installed salva's Sort::Key and added:

sub x2 {
    my @sorted = keysort {
        $_->title =~ /Manager/ ? 'A'.$_->name : 'B'.$_->name
    } @employees;
}

With these results:

C:\test>junk87
             Rate    obvious     subtle functional          x         
+x2
obvious     186/s         --       -20%       -61%       -83%       -8
+9%
subtle      232/s        24%         --       -51%       -79%       -8
+6%
functional  477/s       156%       106%         --       -56%       -7
+2%
x          1085/s       483%       368%       127%         --       -3
+7%
x2         1717/s       822%       641%       260%        58%         
+--