anchor.diff:      (declare (ignore _))
       (max 0.0d0 (local-time:timestamp-difference t1 t0))))
   
  -(defvar *default-overhead* (benchmark nil :timeout 2.0 :overhead 0))
  +(defvar *default-overhead* (benchmark nil :timeout 2.0 :overhead 0.0))
  
positive.code:           until (or (local-time:timestamp>= (local-time:now) tmax)
                      (and (not (null max-samples))
                           (>= number-of-samples max-samples))))
      (- (/ (reduce #'+ samples) number-of-samples)
         overhead)))
  
  (defun sample-execution-time-of-thunk (thunk min-sample-time)
  
negative.code:    (bench nil) => 0.00 nanoseconds
     (bench (make-hash-table)) => 247.03 nanoseconds"
    (declare (ignore max-samples min-sample-time timeout overhead))
    `(progn (print-time (benchmark ,form ,@args) *trace-output*)
            (values)))
  
  (defmacro benchmark (form &rest args &key max-samples min-sample-time timeout overhead)
    "Execute BODY multiple times to accurately measure its execution time in
  