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lib/Perlito5X/Benchmark.pm  view on Meta::CPAN

    # Wait for the user timer to tick.  This makes the error range more like
    # -0.01, +0.  If we don't wait, then it's more like -0.01, +0.01.  This
    # may not seem important, but it significantly reduces the chances of
    # getting a too low initial $n in the initial, 'find the minimum' loop
    # in &countit.  This, in turn, can reduce the number of calls to
    # &runloop a lot, and thus reduce additive errors.
    #
    # Note that its possible for the act of reading the system clock to
    # burn lots of system CPU while we burn very little user clock in the
    # busy loop, which can cause the loop to run for a very long wall time.
    # So gradually ramp up the duration of the loop. See RT #122003
    #
    my $tbase = Benchmark->new(0)->[1];
    my $limit = 1;
    while ( ( $t0 = Benchmark->new(0) )->[1] == $tbase ) {
        for (my $i=0; $i < $limit; $i++) { my $x = $i / 1.5 } # burn user CPU
        $limit *= 1.1;
    }
    $subref->();
    $t1 = Benchmark->new($n);