April 7, 8, 9

Ok. I've been on the road quite a bit the last two days. More emacs-learning (and a little more actual programming) happened, but I didn't manage to get a post up. Today is something along similar lines to the priority queue: a fair scheduler. Written with the help of Emacs ocaml mode.

Thanks to the use of the Unix module, this needs to be linked with unix.cma at compile time (or run in an interpreter which has unix.cma loaded).

type 'qtype taskqueue =
    {queue: 'qtype;
      dotask: unit -> unit;
    target: float;
    mutable error: float}
     
let itertask taskqlist =
  let starttime =
    Unix.gettimeofday()
  and nextq =
    List.fold_left
      (fun a b -> if a.error > b.error then a else b)
      (List.hd taskqlist)
      taskqlist
  in let  nextqerror = nextq.error
  in
  nextq.dotask();
  let tasktime =
    Unix.gettimeofday() -. starttime in
  List.iter
    (fun q -> if q = nextq then
      q.error <- q.error -. nextqerror +. (tasktime /. nextq.target) )
    taskqlist;;