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 // |reftest| skip

 /* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */

 /*

  * Any copyright is dedicated to the Public Domain.

  * http://creativecommons.org/licenses/publicdomain/

  * Contributor: Jason Orendorff

  */

 //-----------------------------------------------------------------------------

 var summary = "Dekker's algorithm for mutual exclusion";

 // Adapted from pseudocode in Wikipedia:

 // http://en.wikipedia.org/wiki/Dekker%27s_algorithm

 printStatus (summary);

 var N = 500;  // number of iterations

 // the mutex mechanism

 var f = [false, false];

 var turn = 0;

 // resource being protected

 var counter = 0;

 function worker(me) {

   let him = 1 - me;

   for (let i = 0; i < N; i++) {

     // enter the mutex

     f[me] = true;

     while (f[him]) {

       if (turn != me) {

         f[me] = false;

         while (turn != me)

           ;  // busy wait

         f[me] = true;

       }

     }

     // critical section

     let x = counter;

     sleep(0.003);

     counter = x + 1;

     // leave the mutex

     turn = him;

     f[me] = false;

   }

   return 'ok';

 }

 var expect;

 var actual;

 if (typeof scatter == 'undefined' || typeof sleep == 'undefined') {

   print('Test skipped. scatter or sleep not defined.');

   expect = actual = 'Test skipped.';

 } else {

   var results = scatter([function () { return worker(0); },

                          function () { return worker(1); }]);

   expect = "Thread status: [ok,ok], counter: " + (2 * N);

   actual = "Thread status: [" + results + "], counter: " + counter;

 }

 reportCompare(expect, actual, summary);