I found a test script from 20 years ago here Re: array pre-allocation trick (top of thread array pre-allocation trick) and tweaked it to add a version explicitly assigning to the last item (with "last" in the name). Machine is of course faster so the rate's much different, but the numbers are maybe similar.
#!/usr/bin/perl
use strict;
use warnings;
use Benchmark qw /cmpthese timethese/;
our $size = 100_000;
cmpthese timethese(
-10 => {
push => 'my @arr; push @arr => $_ for 0 .. $::size - 1',
assign => 'my @arr; $arr [$_] = $_ for 0 .. $::size - 1',
assignpre => 'my @arr; $#arr = $::size - 1;
$arr [$_] = $_ for 0 .. $::size - 1',
assignlast => 'my @arr; $arr[ $::size - 1 ] = undef;
$arr [$_] = $_ for 0 .. $::size - 1',
slice => 'my @arr; @arr [0 .. $::size - 1] = (0 .. $::siz
+e - +1)',
slicepre => 'my @arr; $#arr = $::size - 1;
@arr [0 .. $::size - 1] = (0 .. $::size -
++1)',
slicelast => 'my @arr; $arr[ $::size - 1 ] = undef;
@arr [0 .. $::size - 1] = (0 .. $::size -
++1)',
} => 'none'
);
__END__
Rate slicepre slice slicelast assignpre assign assignla
+st push
slicepre 124/s -- -10% -11% -21% -27% -2
+8% -35%
slice 138/s 11% -- -0% -12% -19% -2
+0% -28%
slicelast 138/s 12% 0% -- -11% -18% -2
+0% -28%
assignpre 156/s 26% 13% 13% -- -8% -
+9% -19%
assign 169/s 37% 23% 22% 8% -- -
+2% -12%
assignlast 172/s 39% 25% 24% 10% 2%
+-- -10%
push 192/s 55% 39% 39% 23% 13% 1
+1% --
## Same comparisons node 209382 on my machine (maybe bit more apples t
+o apples)
Rate slicepre slice assignpre assign push
slicepre 123/s -- -10% -21% -25% -36%
slice 137/s 11% -- -12% -17% -29%
assignpre 156/s 27% 14% -- -5% -19%
assign 165/s 34% 20% 6% -- -14%
push 192/s 56% 40% 23% 17% --
The cake is a lie.
The cake is a lie.
The cake is a lie.
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