Tom Allison wrote:
> John W. Krahn wrote:
>> Mike Blezien wrote:
>>
>>> what is the most effecient way to combine multiple array refs into one
>>> array ref, IE:
>>>
>>> my $arrayrefA = ['1',2','3'];
>>> my $arrayrefB = ['4','5','6'];
>>> my $arrayrefC = ['7','8','9'];
>>>
>>> my $allarrayref = (Combine $arrayrefA $arrayrefB $arrayrefC)
>>
>> So you just want to combine the contents of the anonymous arrays?
>>
>> my $allarrayref = [ @$arrayrefA, @$arrayrefB, @$arrayrefC ];
>
> You might want to Benchmark this.
> I know from the perl cookbook that joining two hashes can be done this
> way but it's also mentioned that it is very memory intensive. I don't
> know if the same applies here.
>
> My results show that this is not the best way to procede if you are
> interested in performance.
>
> use strict;
> use warnings;
>
> use Benchmark;
> use Time::HiRes;
>
> my $A = [1,2,3,4,5,6,7,8,9];
> my $B = [11,12,13,14,15,16,17,18,19];
>
> timethese(10000000,
> {
> 'plain' => 'my $array = [$A, $B];',
> 'loopy' => 'push @$A, $_ foreach @$B;'
> });
Those aren't equivalent. 'plain' is only assigning two scalars while 'loopy'
is pushing nine scalars.
'plain' => 'my $array = [EMAIL PROTECTED], @$B];',
'loopy' => 'push @$array, $_ foreach @$A, @$B;'
But you don't need a foreach loop with push():
'plain' => 'my $array = [EMAIL PROTECTED], @$B];',
'loopy' => 'push @$array, @$A, @$B;'
$ perl -e'
use Benchmark q/cmpthese/;
my $A = [ 1 .. 9 ];
my $B = [ 11 .. 19 ];
cmpthese ( 10_000_000, {
scalar_assign => q/my $array = [ @$A, @$B ]/,
array_assign => q/my $array; @$array = ( @$A, @$B )/,
map_assign => q/my $array; @$array = map @$_, $A, $B/,
push => q/my $array; push @$array, @$A, @$B/,
push_loop1 => q/my $array; push @$array, $_ for @$A, @$B/,
push_loop2 => q/my $array; push @$array, @$_ for $A, $B/,
} );
'
Rate push_loop2 push_loop1 map_assign scalar_assign
array_assign push
push_loop2 550358/s -- -32% -49% -60%
-69% -69%
push_loop1 812348/s 48% -- -25% -40%
-54% -55%
map_assign 1084599/s 97% 34% -- -20%
-38% -40%
scalar_assign 1360544/s 147% 67% 25% --
-23% -24%
array_assign 1757469/s 219% 116% 62% 29%
-- -2%
push 1795332/s 226% 121% 66% 32%
2% --
John
--
use Perl;
program
fulfillment
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