NAME

     dispatch_benchmark — Measures block execution time

SYNOPSIS

     #include <dispatch/dispatch.h>

     uint64_t
     dispatch_benchmark(size_t count, void (^block)(void));

     uint64_t
     dispatch_benchmark_f(size_t count, void *context, void (*function)(void *));

DESCRIPTION

     The dispatch_benchmark() function executes the given block multiple times according to the count variable
     and then returns the average number of nanoseconds per execution.  This function is for debugging and
     performance analysis work.  For the best results, pass a high count value to dispatch_benchmark().  When
     benchmarking concurrent code, please compare the serial version of the code against the concurrent version,
     and compare the concurrent version on different classes of hardware.  Please look for inflection points
     with various data sets and keep the following facts in mind:

           •   Code bound by computational bandwidth may be inferred by proportional changes in performance as
               concurrency is increased.
           •   Code bound by memory bandwidth may be inferred by negligible changes in performance as
               concurrency is increased.
           •   Code bound by critical sections may be inferred by retrograde changes in performance as
               concurrency is increased.
                     •   Intentional: locks, mutexes, and condition variables.
                     •   Accidental: unrelated and frequently modified data on the same cache-line.

RETURN VALUE

     The dispatch_benchmark() function returns the average number of nanoseconds the given block takes to
     execute.

SEE ALSO

     dispatch(3)