def time( event )
      sync {stats[event].mark}
      yield
    ensure
      sync {stats[event].tick}
    end
def time( event )
      sync {stats[event].mark}
      yield
    ensure
      sync {stats[event].tick}
    end
Time the execution of the given block and store the results in the
 named _event_ sampler. The sampler will be created if it does not
 exist.