Making Programs Faster

Simple Benchmarker

        substr($s, 0, 3) = "abc"

        $s =~ s/.../abc/s

Which is faster?

     my $N = shift || 1000000;
     my $s = shift || "The quick brown fox jumps over the lazy dog";

     my ($su, $ss) = times;
     for (1 .. $N) { substr($s, 0, 3) = "abc" }
     my ($eu, $es) = times;
     my ($tu, $ts) = ($eu - $su, $es - $ss);
     my $total = $tu + $ts;
     printf "%20s %5.2f %5.2f %6.2f\n", "substr", $tu, $ts, $total;

     my ($su, $ss) = times;
     for (1 .. $N) { $s =~ s/.../abc/s }
     my ($eu, $es) = times;
     my ($tu, $ts) = ($eu - $su, $es - $ss);
     my $total = $tu + $ts;
     printf "%20s %5.2f %5.2f %6.2f\n", "regex", $tu, $ts, $total;

The output:

              substr  5.04  0.01   5.05
               regex  5.71  0.00   5.71