in reply to Faster Hash Slices

Switching from a hashref to a hash may slightly improve matters. Accesses to hash elements are slightly faster going direct. Better still would be to abandon the hash altogether and access @aa directly, because array accesses are faster than hash ones, but this change might not be as simple.

use Moops; class Cow :rw { has name => (default => 'Ermintrude') }; say Cow->new->name

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Re^2: Faster Hash Slices
by shmem (Chancellor) on Nov 28, 2013 at 13:38 UTC

    Sure? AFAIK lookups against a named hash are slower*, since they need a extra lookup against the symbol table or pad to locate its reference.

    * the speed penalty is close to zero

    perl -le'print map{pack c,($-++?1:13)+ord}split//,ESEL'
[reply]

      Seems to be the case that named hash lookups are (marginally, but consistently) quicker:

      { 
    my $ref = { 1 .. 1e6 }; 
    my %h = 1 .. 1e6; 
    cmpthese -5,{
        a => sub{ exists $ref->{$_} and 1 for 1 .. 1e6; },
        b => sub{ exists $h{$_}     and 1 for 1 .. 1e6; }
    }
};;
    Rate   a   b
a 1.24/s  -- -3%
b 1.28/s  3%  --

    Rate   a   b
a 1.36/s  -- -5%
b 1.43/s  5%  --

    Rate   a   b
a 1.24/s  -- -3%
b 1.28/s  3%  --

    Rate   a   b
a 1.23/s  -- -5%
b 1.29/s  5%  --

    Rate   a   b
a 1.27/s  -- -3%
b 1.30/s  3%  --

      [download]
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      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".
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[reply]
[d/l]

        The same seems to be true for package variables ( scalar holding hashref and hash in the symbol table), and my variable lookup seems to be faster: 

        our $ref = { 1 .. 1e6 }; 
our %h = 1 .. 1e6; 
{ 
    my $_ref = { 1 .. 1e6 }; 
    my %_h = 1 .. 1e6; 
    cmpthese -5,{
        a => sub{ exists $_ref->{$_} and 1 for 1 .. 1e6; },
        b => sub{ exists $_h{$_}     and 1 for 1 .. 1e6; },
        c => sub{ exists $ref->{$_} and 1 for 1 .. 1e6; },
        d => sub{ exists $h{$_}     and 1 for 1 .. 1e6; }
    }
};;
    Rate   a   c   d   b
a 3.31/s  -- -2% -3% -4%
c 3.38/s  2%  -- -0% -2%
d 3.39/s  3%  0%  -- -2%
b 3.45/s  4%  2%  2%  --

        [download]

        Thanks for measurement and correction.

        perl -le'print map{pack c,($-++?1:13)+ord}split//,ESEL'
[reply]
[d/l]
        Maybe the verification of the reference type explains the difference?
        لսႽ† ᥲᥒ⚪⟊Ⴙᘓᖇ Ꮅᘓᖇ⎱ Ⴙᥲ𝇋ƙᘓᖇ
[reply]

      The reference is a named variable though, so that also needs a lookup in the symbol table or pad, plus needs to then be dereferenced.

      use Moops; class Cow :rw { has name => (default => 'Ermintrude') }; say Cow->new->name
[reply]

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