Implements priority donation according to the Imperial Pintos Specification (based on thread niceness and recent cpu time), using Round Robin ordering of threads

b2.coffee

PRI_MAX         =  63
RUN_TIME        =  36/4
TIMER_INTERVAL  =   4
TICKS_PER_SEC   = 100

crrt = null
ticks = 0

create_thread = (name, nice, pri = PRI_MAX) ->
  { name: name, p: pri, n: nice, rcpu: 0 }

threads = [
  create_thread 'a', 0, 63
  create_thread 'b', 1, 61
  create_thread 'c', 2, 59
].sort (a,b) -> b.p - a.p

sorted_threads = ->
  threads[..].sort (a,b) ->
    if a.name < b.name then return -1
    else if a.name > b.name then return 1 else return 0

space = (str, length) ->
  str = str.toString().trim()
  length -= str.length
  str + (null for s in [0..length]).join ' '

print_key = (key, length) ->
  vals = []
  for t in do sorted_threads
    vals.push t[key]
  space vals.join('/'), length

calc_priority = (t) ->
  t.p = Math.floor (PRI_MAX - (t.rcpu / 4) - (t.n * 2))
calc_load_avg = -> (59/60)*load_avg + (1/60)*threads.length

tick_second = ->
  do calc_load_avg
  for t in threads
    t.rcpu = (2*load_avg)/(2*load_avg + 1)*t.rcpu + t.n
   
next_thread = ->
  found = false
  threads = [].concat threads.reduce(((a,c) ->
    a[2* +(c.p < crrt.p)].push c if c != crrt; a
  ), [[],crrt,[]])...
  for t in threads
    if t.p >= crrt.p then return t

tick = ->
  if ((ticks += TIMER_INTERVAL)/TIMER_INTERVAL % TICKS_PER_SEC) == 0
    do tick_second
  (crrt ?= threads[0]).rcpu += 4
  for t in threads
    calc_priority t
  crrt = do next_thread

print_row = (crrt_name) ->
  console.log " #{space ticks, 3}    | #{print_key 'rcpu', 10}    | " +
              "#{print_key 'p', 9}     | #{crrt_name.toUpperCase()}"


ticks = 0
console.log " Timer  | Rcpu          | Pri           | Thread\n" +
            '-------------------------------------------------'
for _ in [0..RUN_TIME]
  print_row crrt?.name || '-'
  do tick

gistfile1.txt

 Timer  | Rcpu          | Pri           | Thread
-------------------------------------------------
 0      | 0/0/0         | 63/61/59      | -
 4      | 4/0/0         | 62/61/59      | A
 8      | 8/0/0         | 61/61/59      | B
 12     | 8/4/0         | 61/60/59      | A
 16     | 12/4/0        | 60/60/59      | B
 20     | 12/8/0        | 60/59/59      | A
 24     | 16/8/0        | 59/59/59      | C
 28     | 16/8/4        | 59/59/58      | B
 32     | 16/12/4       | 59/58/58      | A
 36     | 20/12/4       | 58/58/58      | C