Data commit

Task/Metered-concurrency/Haskell/metered-concurrency-1.hs

@@ -0,0 +1,29 @@
+import Control.Concurrent
+    ( newQSem,
+      signalQSem,
+      waitQSem,
+      threadDelay,
+      forkIO,
+      newEmptyMVar,
+      putMVar,
+      takeMVar,
+      QSem,
+      MVar )
+import Control.Monad ( replicateM_ )
+
+worker :: QSem -> MVar String -> Int -> IO ()
+worker q m n = do
+  waitQSem q
+  putMVar m $ "Worker " <> show n <> " has acquired the lock."
+  threadDelay 2000000 -- microseconds!
+  signalQSem q
+  putMVar m $ "Worker " <> show n <> " has released the lock."
+
+main :: IO ()
+main = do
+  q <- newQSem 3
+  m <- newEmptyMVar
+  let workers = 5
+      prints = 2 * workers
+  mapM_ (forkIO . worker q m) [1 .. workers]
+  replicateM_ prints $ takeMVar m >>= putStrLn

Task/Metered-concurrency/Haskell/metered-concurrency-2.hs

@@ -0,0 +1,17 @@
+procedure main(A)
+    n := integer(A[1] | 3)    # Max. number of active tasks
+    m := integer(A[2] | 2)    # Number of visits by each task
+    k := integer(A[3] | 5)    # Number of tasks
+    sem := [: |mutex([])\n :]
+    every put(threads := [], (i := 1 to k, thread
+              every 1 to m do {
+                 write("unit ",i," ready")
+                 until flag := trylock(!sem)
+                 write("unit ",i," running")
+                 delay(2000)
+                 write("unit ",i," done")
+                 unlock(flag)
+                 }))
+
+    every wait(!threads)
+end