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 // Copyright 2006-2008 the V8 project authors. All rights reserved.

 // Redistribution and use in source and binary forms, with or without

 // modification, are permitted provided that the following conditions are

 // met:

 //

 //     * Redistributions of source code must retain the above copyright

 //       notice, this list of conditions and the following disclaimer.

 //     * Redistributions in binary form must reproduce the above

 //       copyright notice, this list of conditions and the following

 //       disclaimer in the documentation and/or other materials provided

 //       with the distribution.

 //     * Neither the name of Google Inc. nor the names of its

 //       contributors may be used to endorse or promote products derived

 //       from this software without specific prior written permission.

 //

 // THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS

 // "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT

 // LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR

 // A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT

 // OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,

 // SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT

 // LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,

 // DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY

 // THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT

 // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE

 // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

 // This is a JavaScript implementation of the Richards

 // benchmark from:

 //

 //    http://www.cl.cam.ac.uk/~mr10/Bench.html

 //

 // The benchmark was originally implemented in BCPL by

 // Martin Richards.

 //var Richards = new BenchmarkSuite('Richards', 34886, [

 //  new Benchmark("Richards", runRichards)

 //]);

 /**

  * The Richards benchmark simulates the task dispatcher of an

  * operating system.

  **/

 function runRichards() {

   var scheduler = new Scheduler();

   scheduler.addIdleTask(ID_IDLE, 0, null, COUNT);

   var queue = new Packet(null, ID_WORKER, KIND_WORK);

   queue = new Packet(queue,  ID_WORKER, KIND_WORK);

   scheduler.addWorkerTask(ID_WORKER, 1000, queue);

   queue = new Packet(null, ID_DEVICE_A, KIND_DEVICE);

   queue = new Packet(queue,  ID_DEVICE_A, KIND_DEVICE);

   queue = new Packet(queue,  ID_DEVICE_A, KIND_DEVICE);

   scheduler.addHandlerTask(ID_HANDLER_A, 2000, queue);

   queue = new Packet(null, ID_DEVICE_B, KIND_DEVICE);

   queue = new Packet(queue,  ID_DEVICE_B, KIND_DEVICE);

   queue = new Packet(queue,  ID_DEVICE_B, KIND_DEVICE);

   scheduler.addHandlerTask(ID_HANDLER_B, 3000, queue);

   scheduler.addDeviceTask(ID_DEVICE_A, 4000, null);

   scheduler.addDeviceTask(ID_DEVICE_B, 5000, null);

   scheduler.schedule();

   assertEq(scheduler.queueCount, EXPECTED_QUEUE_COUNT);

   assertEq(scheduler.holdCount, EXPECTED_HOLD_COUNT);

 }

 var COUNT = 1000;

 /**

  * These two constants specify how many times a packet is queued and

  * how many times a task is put on hold in a correct run of richards.

  * They don't have any meaning a such but are characteristic of a

  * correct run so if the actual queue or hold count is different from

  * the expected there must be a bug in the implementation.

  **/

 var EXPECTED_QUEUE_COUNT = 2322;

 var EXPECTED_HOLD_COUNT = 928;

 /**

  * A scheduler can be used to schedule a set of tasks based on their relative

  * priorities.  Scheduling is done by maintaining a list of task control blocks

  * which holds tasks and the data queue they are processing.

  * @constructor

  */

 function Scheduler() {

   this.queueCount = 0;

   this.holdCount = 0;

   this.blocks = new Array(NUMBER_OF_IDS);

   this.list = null;

   this.currentTcb = null;

   this.currentId = null;

 }

 var ID_IDLE       = 0;

 var ID_WORKER     = 1;

 var ID_HANDLER_A  = 2;

 var ID_HANDLER_B  = 3;

 var ID_DEVICE_A   = 4;

 var ID_DEVICE_B   = 5;

 var NUMBER_OF_IDS = 6;

 var KIND_DEVICE   = 0;

 var KIND_WORK     = 1;

 /**

  * Add an idle task to this scheduler.

  * @param {int} id the identity of the task

  * @param {int} priority the task's priority

  * @param {Packet} queue the queue of work to be processed by the task

  * @param {int} count the number of times to schedule the task

  */

 Scheduler.prototype.addIdleTask = function (id, priority, queue, count) {

   this.addRunningTask(id, priority, queue, new IdleTask(this, 1, count));

 };

 /**

  * Add a work task to this scheduler.

  * @param {int} id the identity of the task

  * @param {int} priority the task's priority

  * @param {Packet} queue the queue of work to be processed by the task

  */

 Scheduler.prototype.addWorkerTask = function (id, priority, queue) {

   this.addTask(id, priority, queue, new WorkerTask(this, ID_HANDLER_A, 0));

 };

 /**

  * Add a handler task to this scheduler.

  * @param {int} id the identity of the task

  * @param {int} priority the task's priority

  * @param {Packet} queue the queue of work to be processed by the task

  */

 Scheduler.prototype.addHandlerTask = function (id, priority, queue) {

   this.addTask(id, priority, queue, new HandlerTask(this));

 };

 /**

  * Add a handler task to this scheduler.

  * @param {int} id the identity of the task

  * @param {int} priority the task's priority

  * @param {Packet} queue the queue of work to be processed by the task

  */

 Scheduler.prototype.addDeviceTask = function (id, priority, queue) {

   this.addTask(id, priority, queue, new DeviceTask(this))

 };

 /**

  * Add the specified task and mark it as running.

  * @param {int} id the identity of the task

  * @param {int} priority the task's priority

  * @param {Packet} queue the queue of work to be processed by the task

  * @param {Task} task the task to add

  */

 Scheduler.prototype.addRunningTask = function (id, priority, queue, task) {

   this.addTask(id, priority, queue, task);

   this.currentTcb.setRunning();

 };

 /**

  * Add the specified task to this scheduler.

  * @param {int} id the identity of the task

  * @param {int} priority the task's priority

  * @param {Packet} queue the queue of work to be processed by the task

  * @param {Task} task the task to add

  */

 Scheduler.prototype.addTask = function (id, priority, queue, task) {

   this.currentTcb = new TaskControlBlock(this.list, id, priority, queue, task);

   this.list = this.currentTcb;

   this.blocks[id] = this.currentTcb;

 };

 /**

  * Execute the tasks managed by this scheduler.

  */

 Scheduler.prototype.schedule = function () {

   this.currentTcb = this.list;

   while (this.currentTcb != null) {

     if (this.currentTcb.isHeldOrSuspended()) {

       this.currentTcb = this.currentTcb.link;

     } else {

       this.currentId = this.currentTcb.id;

       this.currentTcb = this.currentTcb.run();

     }

   }

 };

 /**

  * Release a task that is currently blocked and return the next block to run.

  * @param {int} id the id of the task to suspend

  */

 Scheduler.prototype.release = function (id) {

   var tcb = this.blocks[id];

   if (tcb == null) return tcb;

   tcb.markAsNotHeld();

   if (tcb.priority > this.currentTcb.priority) {

     return tcb;

   } else {

     return this.currentTcb;

   }

 };

 /**

  * Block the currently executing task and return the next task control block

  * to run.  The blocked task will not be made runnable until it is explicitly

  * released, even if new work is added to it.

  */

 Scheduler.prototype.holdCurrent = function () {

   this.holdCount++;

   this.currentTcb.markAsHeld();

   return this.currentTcb.link;

 };

 /**

  * Suspend the currently executing task and return the next task control block

  * to run.  If new work is added to the suspended task it will be made runnable.

  */

 Scheduler.prototype.suspendCurrent = function () {

   this.currentTcb.markAsSuspended();

   return this.currentTcb;

 };

 /**

  * Add the specified packet to the end of the worklist used by the task

  * associated with the packet and make the task runnable if it is currently

  * suspended.

  * @param {Packet} packet the packet to add

  */

 Scheduler.prototype.queue = function (packet) {

   var t = this.blocks[packet.id];

   if (t == null) return t;

   this.queueCount++;

   packet.link = null;

   packet.id = this.currentId;

   return t.checkPriorityAdd(this.currentTcb, packet);

 };

 /**

  * A task control block manages a task and the queue of work packages associated

  * with it.

  * @param {TaskControlBlock} link the preceding block in the linked block list

  * @param {int} id the id of this block

  * @param {int} priority the priority of this block

  * @param {Packet} queue the queue of packages to be processed by the task

  * @param {Task} task the task

  * @constructor

  */

 function TaskControlBlock(link, id, priority, queue, task) {

   this.link = link;

   this.id = id;

   this.priority = priority;

   this.queue = queue;

   this.task = task;

   if (queue == null) {

     this.state = STATE_SUSPENDED;

   } else {

     this.state = STATE_SUSPENDED_RUNNABLE;

   }

 }

 /**

  * The task is running and is currently scheduled.

  */

 var STATE_RUNNING = 0;

 /**

  * The task has packets left to process.

  */

 var STATE_RUNNABLE = 1;

 /**

  * The task is not currently running.  The task is not blocked as such and may

 * be started by the scheduler.

  */

 var STATE_SUSPENDED = 2;

 /**

  * The task is blocked and cannot be run until it is explicitly released.

  */

 var STATE_HELD = 4;

 var STATE_SUSPENDED_RUNNABLE = STATE_SUSPENDED | STATE_RUNNABLE;

 var STATE_NOT_HELD = ~STATE_HELD;

 TaskControlBlock.prototype.setRunning = function () {

   this.state = STATE_RUNNING;

 };

 TaskControlBlock.prototype.markAsNotHeld = function () {

   this.state = this.state & STATE_NOT_HELD;

 };

 TaskControlBlock.prototype.markAsHeld = function () {

   this.state = this.state | STATE_HELD;

 };

 TaskControlBlock.prototype.isHeldOrSuspended = function () {

   return (this.state & STATE_HELD) != 0 || (this.state == STATE_SUSPENDED);

 };

 TaskControlBlock.prototype.markAsSuspended = function () {

   this.state = this.state | STATE_SUSPENDED;

 };

 TaskControlBlock.prototype.markAsRunnable = function () {

   this.state = this.state | STATE_RUNNABLE;

 };

 /**

  * Runs this task, if it is ready to be run, and returns the next task to run.

  */

 TaskControlBlock.prototype.run = function () {

   var packet;

   if (this.state == STATE_SUSPENDED_RUNNABLE) {

     packet = this.queue;

     this.queue = packet.link;

     if (this.queue == null) {

       this.state = STATE_RUNNING;

     } else {

       this.state = STATE_RUNNABLE;

     }

   } else {

     packet = null;

   }

   return this.task.run(packet);

 };

 /**

  * Adds a packet to the worklist of this block's task, marks this as runnable if

  * necessary, and returns the next runnable object to run (the one

  * with the highest priority).

  */

 TaskControlBlock.prototype.checkPriorityAdd = function (task, packet) {

   if (this.queue == null) {

     this.queue = packet;

     this.markAsRunnable();

     if (this.priority > task.priority) return this;

   } else {

     this.queue = packet.addTo(this.queue);

   }

   return task;

 };

 TaskControlBlock.prototype.toString = function () {

   return "tcb { " + this.task + "@" + this.state + " }";

 };

 /**

  * An idle task doesn't do any work itself but cycles control between the two

  * device tasks.

  * @param {Scheduler} scheduler the scheduler that manages this task

  * @param {int} v1 a seed value that controls how the device tasks are scheduled

  * @param {int} count the number of times this task should be scheduled

  * @constructor

  */

 function IdleTask(scheduler, v1, count) {

   this.scheduler = scheduler;

   this.v1 = v1;

   this.count = count;

 }

 IdleTask.prototype.run = function (packet) {

   this.count--;

   if (this.count == 0) return this.scheduler.holdCurrent();

   if ((this.v1 & 1) == 0) {

     this.v1 = this.v1 >> 1;

     return this.scheduler.release(ID_DEVICE_A);

   } else {

     this.v1 = (this.v1 >> 1) ^ 0xD008;

     return this.scheduler.release(ID_DEVICE_B);

   }

 };

 IdleTask.prototype.toString = function () {

   return "IdleTask"

 };

 /**

  * A task that suspends itself after each time it has been run to simulate

  * waiting for data from an external device.

  * @param {Scheduler} scheduler the scheduler that manages this task

  * @constructor

  */

 function DeviceTask(scheduler) {

   this.scheduler = scheduler;

   this.v1 = null;

 }

 DeviceTask.prototype.run = function (packet) {

   if (packet == null) {

     if (this.v1 == null) return this.scheduler.suspendCurrent();

     var v = this.v1;

     this.v1 = null;

     return this.scheduler.queue(v);

   } else {

     this.v1 = packet;

     return this.scheduler.holdCurrent();

   }

 };

 DeviceTask.prototype.toString = function () {

   return "DeviceTask";

 };

 /**

  * A task that manipulates work packets.

  * @param {Scheduler} scheduler the scheduler that manages this task

  * @param {int} v1 a seed used to specify how work packets are manipulated

  * @param {int} v2 another seed used to specify how work packets are manipulated

  * @constructor

  */

 function WorkerTask(scheduler, v1, v2) {

   this.scheduler = scheduler;

   this.v1 = v1;

   this.v2 = v2;

 }

 WorkerTask.prototype.run = function (packet) {

   if (packet == null) {

     return this.scheduler.suspendCurrent();

   } else {

     if (this.v1 == ID_HANDLER_A) {

       this.v1 = ID_HANDLER_B;

     } else {

       this.v1 = ID_HANDLER_A;

     }

     packet.id = this.v1;

     packet.a1 = 0;

     for (var i = 0; i < DATA_SIZE; i++) {

       this.v2++;

       if (this.v2 > 26) this.v2 = 1;

       packet.a2[i] = this.v2;

     }

     return this.scheduler.queue(packet);

   }

 };

 WorkerTask.prototype.toString = function () {

   return "WorkerTask";

 };

 /**

  * A task that manipulates work packets and then suspends itself.

  * @param {Scheduler} scheduler the scheduler that manages this task

  * @constructor

  */

 function HandlerTask(scheduler) {

   this.scheduler = scheduler;

   this.v1 = null;

   this.v2 = null;

 }

 HandlerTask.prototype.run = function (packet) {

   if (packet != null) {

     if (packet.kind == KIND_WORK) {

       this.v1 = packet.addTo(this.v1);

     } else {

       this.v2 = packet.addTo(this.v2);

     }

   }

   if (this.v1 != null) {

     var count = this.v1.a1;

     var v;

     if (count < DATA_SIZE) {

       if (this.v2 != null) {

         v = this.v2;

         this.v2 = this.v2.link;

         v.a1 = this.v1.a2[count];

         this.v1.a1 = count + 1;

         return this.scheduler.queue(v);

       }

     } else {

       v = this.v1;

       this.v1 = this.v1.link;

       return this.scheduler.queue(v);

     }

   }

   return this.scheduler.suspendCurrent();

 };

 HandlerTask.prototype.toString = function () {

   return "HandlerTask";

 };

 /* --- *

  * P a c k e t

  * --- */

 var DATA_SIZE = 4;

 /**

  * A simple package of data that is manipulated by the tasks.  The exact layout

  * of the payload data carried by a packet is not importaint, and neither is the

  * nature of the work performed on packets by the tasks.

  *

  * Besides carrying data, packets form linked lists and are hence used both as

  * data and worklists.

  * @param {Packet} link the tail of the linked list of packets

  * @param {int} id an ID for this packet

  * @param {int} kind the type of this packet

  * @constructor

  */

 function Packet(link, id, kind) {

   this.link = link;

   this.id = id;

   this.kind = kind;

   this.a1 = 0;

   this.a2 = new Array(DATA_SIZE);

 }

 /**

  * Add this packet to the end of a worklist, and return the worklist.

  * @param {Packet} queue the worklist to add this packet to

  */

 Packet.prototype.addTo = function (queue) {

   this.link = null;

   if (queue == null) return this;

   var peek, next = queue;

   while ((peek = next.link) != null)

     next = peek;

   next.link = this;

   return queue;

 };

 Packet.prototype.toString = function () {

   return "Packet";

 };

 runRichards();