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Re: "switch$ia" (Russ: Useless Benchmarking again)

by Russ (Deacon)
on Oct 10, 2001 at 21:16 UTC ( [id://118056]=note: print w/replies, xml ) Need Help??

in reply to "switch$ia" but don't interpolate trailing "a"

I have to assume someone has done this before, but I didn't see it, so...

Benchmarking interpolated strings vs. appended strings:

use Benchmark; timethese( 1000000, { interp => sub {my $R = 1; my $S = "Test${R}a"}, append => sub {my $R = 1; my $S = 'Test' . $R . 'a'} });
results in:
Benchmark: timing 1000000 iterations of interp, manual... interp: 4 wallclock secs ( 3.68 usr + 0.05 sys = 3.73 CPU) @ 2680 +96.51/s manual: 3 wallclock secs ( 3.79 usr + -0.13 sys = 3.66 CPU) @ 2732 +24.04/s
Slightly faster to append strings together than to interpolate them, but statistically, it's a wash...

Brainbench 'Most Valuable Professional' for Perl

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Re: Re: "switch$ia" (Russ: Useless Benchmarking again)
by echo (Pilgrim) on Oct 10, 2001 at 21:19 UTC
    Someone please correct me if I'm wrong, ISTR interpolated strings are converted to concatenation at compile time?

      You are correct, at least according to the B::Deparse documentation. Interpolation is just syntactic sugar for concatenation. You can see it for yourself:

      $ perl -MO=Deparse,-p,-q -e '$foo = "BAR"; $bar = "a${foo}c"; $baz="a" +.$foo."c"' ($foo = 'BAR'); ($bar = (('a' . $foo) . 'c')); ($baz = (('a' . $foo) . 'c'));

      Update: Added concatenation to the example for comparison. Also, the output using B::Terse to dump the opcode tree may be more convincing.

      <sheepish grin>
      hehehe You're probably right.

      So, in the spirit of further useless benchmarking:

      use Benchmark; timethese( 10000000, { 5 => sub {my $R = 5;}, 6 => sub {my $R = 6;} });
      results in:
      5: 6 wallclock secs ( 6.61 usr + -0.03 sys = 6.58 CPU) @ 1519756 +.84/s 6: 6 wallclock secs ( 5.89 usr + 0.08 sys = 5.97 CPU) @ 1675041 +.88/s
      As you can see, it is slightly faster to assign a 6 than a 5, so I will use 6's more often from now on... :-)
      </sheepish grin>

      Brainbench 'Most Valuable Professional' for Perl

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