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check-richards.js (15631B)

---

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// 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();