comment on

The shifting of elements from the array makes it empty after first iteration.

Ugh, I seem to be extra stupid today. But hey, it's not that easy still:


my @s = '0001' .. '1000';

cmpthese -1,{
    d => q[ my @d = @s; ],
    c => q[ my @c = @s; $c[ $_ ] += 0 for 0 .. $#c; ],
    a => q[ my @a = @s; $_ += 0 for @a; ],
    b => q[ my @b = @s; my @new; push @new, $_ + 0 while defined( $_ =
+ shift @b ) ],
};
[download]

Yields:


       Rate    c    a    b    d
c  793688/s   -- -59% -59% -84%
a 1941807/s 145%   --  -0% -60%
b 1942492/s 145%   0%   -- -60%
d 4812084/s 506% 148% 148%   --
[download]

So what do we have, shifting and for (@list) are equally fast? Not so:

my @s = '0000001' .. '1000000';

cmpthese -1,{
    d => q[ my @d = @s; ],
    c => q[ my @c = @s; $c[ $_ ] += 0 for 0 .. $#c; ],
    a => q[ my @a = @s; $_ += 0 for @a; ],
    b => q[ my @b = @s; my @new; push @new, $_ + 0 while defined( $_ =
+ shift @b ) ],
};
[download]

Gives these results:

       Rate    c    b    a    d
c  764586/s   -- -58% -62% -85%
b 1803742/s 136%   -- -10% -65%
a 2007409/s 163%  11%   -- -61%
d 5119310/s 570% 184% 155%   --
[download]

Which is logical, at last. Scandal of the century is averted, I stand corrected - the only thing I have to find out is why my tests on actual data consistently show shifting to be faster than for (@list). Not several orders of magnitude faster as it was in that faulty benchmark but considerably so. I believe I have to look for an error...

Regards,
Alex.

In reply to Re^5: Unpacking and converting by dwalin
in thread Unpacking and converting by dwalin

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