Re: Is foreach split Optimized?

[Marshall]

I am curious about your benchmark program.
With my $str = "\nFoo\n\nBar Quz\nBaz\nx" x 500000;
I get:

5.020002
            (warning: too few iterations for a reliable count)
            (warning: too few iterations for a reliable count)
            (warning: too few iterations for a reliable count)
      s/iter index regex split
index   26.5    --  -61%  -66%
regex   10.3  158%    --  -12%
split   9.05  193%   13%    --

which basically means that the results don't matter.

Code as with my $str = "\nFoo\n\nBar Quz\nBaz\nx" x 50000;
Your benchmark default.

5.020002
            (warning: too few iterations for a reliable count)
            (warning: too few iterations for a reliable count)
        Rate index regex split
index 1.16/s    --  -21%  -34%
regex 1.47/s   27%    --  -16%
split 1.74/s   51%   19%    --

I am not sure what this means if anything.

[haukex]

(warning: too few iterations for a reliable count)

You can get rid of those warnings by increasing the runtime by saying e.g. cmpthese(-5, .... I did fiddle with it quite a bit, adjusting the string length, runtime, etc. and the results were always consistent that split was fastest by a significant margin.

[Marshall]

Interesting:

5.020002
         Rate  index  regex  split split2
index  1.17/s     --   -23%   -35%   -43%
regex  1.51/s    29%     --   -16%   -26%
split  1.79/s    53%    18%     --   -12%
split2 2.03/s    74%    35%    14%     --

split2 uses tr/// instead of regex s///...
Read more... (3 kB)

[haukex]

I'm investigating the speed of iterating through the string, not how it gets processed afterwards, which is why the loop bodies are all the same. So to make the benchmark be fair again, you'd have to make the same change in all the loops. I just added that bit of s/// code to provide a somewhat realistic loop body (Update: or rather, a placeholder for the actual loop body, which manipulates the $line a whole lot more and whose output is much more complex than one line of output per line of input), and as a (likely misguided) attempt to prevent for my $line (@x) { push @lines, $line; } from being optimized to @lines = @x;.