=item clearallcache ( )

Clear all cached times.

=item cmpthese ( COUNT, CODEHASHREF, [ STYLE ] )

=item cmpthese ( RESULTSHASHREF, [ STYLE ] )

Optionally calls timethese(), then outputs comparison chart.  This:

    cmpthese( -1, { a => "++\$i", b => "\$i *= 2" } ) ;

outputs a chart like:

           Rate    b    a
    b 2831802/s   -- -61%
    a 7208959/s 155%   --

This chart is sorted from slowest to fastest, and shows the percent speed
difference between each pair of tests.

c<cmpthese> can also be passed the data structure that timethese() returns:

    $results = timethese( -1, { a => "++\$i", b => "\$i *= 2" } ) ;
    cmpthese( $results );

in case you want to see both sets of results.

Returns a reference to an ARRAY of rows, each row is an ARRAY of cells from the
above chart, including labels. This:

    my $rows = cmpthese( -1, { a => '++$i', b => '$i *= 2' }, "none" );

returns a data structure like:

    [
        [ '',       'Rate',   'b',    'a' ],
        [ 'b', '2885232/s',  '--', '-59%' ],
        [ 'a', '7099126/s', '146%',  '--' ],
    ]

B<NOTE>: This result value differs from previous versions, which returned
the C<timethese()> result structure.  If you want that, just use the two
statement C<timethese>...C<cmpthese> idiom shown above.

Incidently, note the variance in the result values between the two examples;
this is typical of benchmarking.  If this were a real benchmark, you would
probably want to run a lot more iterations.

=item countit(TIME, CODE)

Arguments: TIME is the minimum length of time to run CODE for, and CODE is
the code to run.  CODE may be either a code reference or a string to
be eval'd; either way it will be run in the caller's package.

TIME is I<not> negative.  countit() will run the loop many times to
calculate the speed of CODE before running it for TIME.  The actual
time run for will usually be greater than TIME due to system clock
resolution, so it's best to look at the number of iterations divided
by the times that you are concerned with, not just the iterations.

Returns: a Benchmark object.

=item disablecache ( )

Disable caching of timings for the null loop. This will force Benchmark
to recalculate these timings for each new piece of code timed.

=item enablecache ( )

Enable caching of timings for the null loop. The time taken for COUNT
rounds of the null loop will be calculated only once for each
different COUNT used.

=item timesum ( T1, T2 )

Returns the sum of two Benchmark times as a Benchmark object suitable
for passing to timestr().

=back

=head2 :hireswallclock

If the Time::HiRes module has been installed, you can specify the
special tag C<:hireswallclock> for Benchmark (if Time::HiRes is not
available, the tag will be silently ignored).  This tag will cause the
wallclock time to be measured in microseconds, instead of integer
seconds.  Note though that the speed computations are still conducted
in CPU time, not wallclock time.

=head1 NOTES

The data is stored as a list of values from the time and times
functions:

      ($real, $user, $system, $children_user, $children_system, $iters)

in seconds for the whole loop (not divided by the number of rounds).

The timing is done using time(3) and times(3).