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

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# 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);