Re^3: Convert string to array - performance challenge

Added one more test case

my %tests = (
   split    => q{ my @a = split //, $buf;             },
   regex    => q{ my @a = $buf =~ /./sg;              },
   unpack_C => q{ my @a = map chr, unpack 'C*', $buf; },
   unpack_a => q{ my @a = unpack '(a)*', $buf;        },
   rev_chop => q{ my @a = reverse map chop($buf), 1..length($buf); },
   chop => q{ my @a; $a[ $_ ] = chop $buffer for length($buffer) .. 0;
+ },
);
[download]

And result was

            Rate rev_chop unpack_C    split    regex unpack_a     chop
rev_chop  17.6/s       --      -6%     -13%     -20%     -30%    -100%
unpack_C  18.7/s       6%       --      -7%     -15%     -25%    -100%
split     20.2/s      15%       8%       --      -8%     -20%    -100%
regex     22.0/s      25%      17%       9%       --     -13%    -100%
unpack_a  25.1/s      43%      34%      24%      14%       --    -100%
chop     68478/s  388556%  365714%  339175%  311691%  272542%       --
[download]

However I am yet to read "Benchmark" so someone please explain this output. :) UPDATE: Sorry! That was a silly mistake. Thanks almut.

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Re^4: Convert string to array - performance challenge by almut (Canon) on Apr 08, 2010 at 06:55 UTC
`my @a; $a[ $_ ] = chop $buffer for length($buffer) .. 0;` Unfortunately, "reversed" ranges like `length($buffer) .. 0` don't work... `print for 1..3; # 123 print for 3..1; # no output` [download] However, this would work, and is actually pretty fast (about the same as `substr`): `my @a; for (my $i=length($buffer)-1; $i>=0; $i--) { $a[$i] = chop $buffer; } # or my @a; my $i = length($buffer); $a[--$i] = chop $buffer while $i>0;` [download]	[reply] [d/l] [select]
Re^4: Convert string to array - performance challenge by ikegami (Patriarch) on Apr 08, 2010 at 15:11 UTC
`my @a; $a[ $_ ] = chop $buffer for length($buffer) .. 0;` You have an off-by-one error. If you could do that, it should be `my @a; $a[ $_ ] = chop $buffer for length($buffer)-1 .. 0;` [download] A simple fix for the already-described problem is to use negative indexing: `my @a; $a[ -$_ ] = chop $buffer for 1..length($buffer);` [download]	[reply] [d/l] [select]