Simple example of using Green Threads to dispatch work and collect results

green-threads-example.lisp

(ql:quickload :green-threads)

(cl-cont:defun/cc channel-squared (n h &key (threads 20))
  (let ((in (make-instance 'gt:channel))
        (out (make-instance 'gt:channel)))
    ;; Spawn workers
    (loop
      :repeat threads
      :do (gt:with-green-thread
            (loop
              :for input := (gt:recv/cc in)
              :until (eql input :done)
              :do (gt:send/cc out (cons input (* input input))))))
    ;; Load numbers
    (gt:with-green-thread
      (loop
        :for i :from 1 :to n
        :do (gt:send/cc in i))
      (loop
        :repeat threads
        :do (gt:send/cc in :done)))
    ;; Put them into H
    (loop
      :repeat n
      :for (i . ii) := (gt:recv/cc out)
      :do (setf (gethash i h) ii))))

(let ((h (make-hash-table :synchronized t)))
  (gt:with-green-thread
    (channel-squared 1000 h))
  h)