#lang racket

(define echoer
  (thread
   (lambda ()
     (let loop ()
       (define source (thread-receive))
       (thread-send source #t)
       (loop)))))

(define LIMIT 10000000)
(define start-time (current-inexact-milliseconds))
(let loop ((n 0))
  (when (< n LIMIT)
    (thread-send echoer (current-thread))
    (thread-receive)
    (loop (+ n 1))))
(define stop-time (current-inexact-milliseconds))
(define deltasec (/ (- stop-time start-time) 1000.0))
(define roundtrip-hz (/ LIMIT deltasec))
(printf "~v roundtrips/sec, i.e. ~v messages/sec\n"
	roundtrip-hz
	(* 2 roundtrip-hz))
(printf "That's a per-message latency of ~v\n" (/ (* 2 roundtrip-hz)))