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previous-exams/2021-midterm/m21/project/buildSettings.sbt deleted 100644 → 0
View file @ 759afc66
// Used for Coursera submission (StudentPlugin)
// libraryDependencies += "org.scalaj" %% "scalaj-http" % "2.4.2"
// libraryDependencies += "com.typesafe.play" %% "play-json" % "2.7.4"
// Used for Base64 (StudentPlugin)
libraryDependencies += "commons-codec" % "commons-codec" % "1.10"
previous-exams/2021-midterm/m21/project/plugins.sbt deleted 100644 → 0
View file @ 759afc66
// addSbtPlugin("org.scala-js" % "sbt-scalajs" % "0.6.28")
addSbtPlugin("ch.epfl.lamp" % "sbt-dotty" % "0.5.3")
previous-exams/2021-midterm/m21/src/main/scala/m21/MultiWriterSeqCount.scala deleted 100644 → 0
View file @ 759afc66
package m21
import instrumentation._
import scala.annotation.tailrec
/** Multi-writer, multi-reader data structure containing a pair of integers. */
class MultiWriterSeqCount extends Monitor:
/** Do not directly use this variable, use `generation`, `setGeneration` and
* `compareAndSetGeneration` instead.
*/
protected val myGeneration: AbstractAtomicVariable[Int] = new AtomicVariable(1)
protected def generation: Int = myGeneration.get
protected def setGeneration(newGeneration: Int): Unit =
myGeneration.set(newGeneration)
protected def compareAndSetGeneration(expected: Int, newValue: Int): Boolean =
myGeneration.compareAndSet(expected, newValue)
/** Do not directly use this variable, use `x` and `setX` instead. */
protected var myX: Int = 0
protected def x: Int = myX
protected def setX(newX: Int): Unit =
myX = newX
/** Do not directly use this variable, use `y` and `setY` instead. */
protected var myY: Int = 0
protected def y: Int = myY
protected def setY(newY: Int): Unit =
myY = newY
/** Write new values into this data structure.
* This method is always safe to call.
* The implementation of this method is not allowed to call `synchronized`.
*/
@tailrec
final def write(newX: Int, newY: Int): Unit =
val old = generation
if old % 2 != 1 then
write(newX, newY)
else
if !compareAndSetGeneration(old, old + 1) then
write(newX, newY)
else
setX(newX)
setY(newY)
setGeneration(old + 2)
/** Copy the values previously written into this data structure into a tuple.
* This method is always safe to call.
* The implementation of this method is not allowed to call `synchronized`.
*/
@tailrec
final def copy(): (Int, Int) =
val old = generation
if old % 2 != 1 then
copy()
else
val result = (x, y)
if generation != old then
copy()
else
result
end MultiWriterSeqCount
previous-exams/2021-midterm/m21/src/main/scala/m21/SeqCount.scala deleted 100644 → 0
View file @ 759afc66
package m21
import instrumentation._
import scala.annotation.tailrec
/** Single-writer, multi-reader data structure containing a pair of integers. */
class SeqCount extends Monitor:
/** Do not directly use this variable, use `generation` and `setGeneration` instead. */
@volatile protected var myGeneration: Int = 1
protected def generation: Int = myGeneration
protected def setGeneration(newGeneration: Int): Unit =
myGeneration = newGeneration
/** Do not directly use this variable, use `x` and `setX` instead. */
protected var myX: Int = 0
protected def x: Int = myX
protected def setX(newX: Int): Unit =
myX = newX
/** Do not directly use this variable, use `y` and `setY` instead. */
protected var myY: Int = 0
protected def y: Int = myY
protected def setY(newY: Int): Unit =
myY = newY
/** Write new values into this data structure.
* This method must only be called from one thread at a time.
*/
final def write(newX: Int, newY: Int): Unit =
setGeneration(generation + 1)
setX(newX)
setY(newY)
setGeneration(generation + 1)
/** Copy the values previously written into this data structure into a tuple.
* This method is always safe to call.
* The implementation of this method is not allowed to call `synchronized`.
*/
@tailrec
final def copy(): (Int, Int) =
val old = generation
if old % 2 != 1 then
copy()
else
val result = (x, y)
if generation != old then
copy()
else
result
end SeqCount
previous-exams/2021-midterm/m21/src/main/scala/m21/instrumentation/AtomicVariable.scala deleted 100644 → 0
View file @ 759afc66
package m21.instrumentation
import java.util.concurrent.atomic._
abstract class AbstractAtomicVariable[T] {
def get: T
def set(value: T): Unit
def compareAndSet(expect: T, newval: T) : Boolean
}
class AtomicVariable[T](initial: T) extends AbstractAtomicVariable[T] {
private val atomic = new AtomicReference[T](initial)
override def get: T = atomic.get()
override def set(value: T): Unit = atomic.set(value)
override def compareAndSet(expected: T, newValue: T): Boolean = {
val current = atomic.get
if (current == expected) {
atomic.compareAndSet(current, newValue)
}
else {
false
}
}
}
previous-exams/2021-midterm/m21/src/main/scala/m21/instrumentation/Monitor.scala deleted 100644 → 0
View file @ 759afc66
package m21.instrumentation
class Dummy
trait Monitor {
implicit val dummy: Dummy = new Dummy
def wait()(implicit i: Dummy) = waitDefault()
def synchronized[T](e: => T)(implicit i: Dummy) = synchronizedDefault(e)
def notify()(implicit i: Dummy) = notifyDefault()
def notifyAll()(implicit i: Dummy) = notifyAllDefault()
private val lock = new AnyRef
// Can be overriden.
def waitDefault(): Unit = lock.wait()
def synchronizedDefault[T](toExecute: =>T): T = lock.synchronized(toExecute)
def notifyDefault(): Unit = lock.notify()
def notifyAllDefault(): Unit = lock.notifyAll()
}
previous-exams/2021-midterm/m21/src/test/scala/m21/TestSuite.scala deleted 100644 → 0
View file @ 759afc66
package m21
import scala.concurrent._
import scala.concurrent.duration._
import scala.collection.mutable.HashMap
import scala.util.Random
import instrumentation._
import instrumentation.TestHelper._
import instrumentation.TestUtils._
enum ThreadResult:
case WriteError(error: String)
case WriteSuccess
case Read(result: (Int, Int))
import ThreadResult._
class M21Suite extends munit.FunSuite:
/** If at least one thread resulted in an error,
* return `(false, errorMessage)` otherwise return `(true, "")`.
*/
def processResults(results: List[ThreadResult]): (Boolean, String) =
val success = (true, "")
results.foldLeft(success) {
case (acc @ (false, _), _) =>
// Report the first error found
acc
case (_, WriteError(error)) =>
(false, error)
case (_, Read((x, y))) if x + 1 != y =>
(false, s"Read ($x, $y) but expected y to be ${x + 1}")
case (_, _: Read | WriteSuccess) =>
success
}
def randomList(length: Int): List[Int] =
List.fill(length)(Random.nextInt)
test("SeqCount: single-threaded write and copy (1 pts)") {
val sc = new SeqCount
randomList(100).lazyZip(randomList(100)).foreach { (x, y) =>
sc.write(x, y)
assertEquals(sc.copy(), (x, y))
}
}
test("SeqCount: one write thread, two copy threads (4 pts)") {
testManySchedules(3, sched =>
val sc = new SchedulableSeqCount(sched)
// Invariant in this test: y == x + 1
sc.write(0, 1)
val randomValues = randomList(length = 5)
def writeThread(): ThreadResult =
randomValues.foldLeft(WriteSuccess) {
case (res: WriteError, _) =>
// Report the first error found
res
case (_, i) =>
sc.write(i, i + 1)
val writtenValues = (i, i + 1)
val readBack = sc.copy()
if writtenValues != readBack then
WriteError(s"Wrote $writtenValues but read back $readBack")
else
WriteSuccess
}
def copyThread(): ThreadResult =
Read(sc.copy())
val threads = List(
() => writeThread(),
() => copyThread(),
() => copyThread()
)
(threads, results => processResults(results.asInstanceOf[List[ThreadResult]]))
)
}
test("MultiWriterSeqCount: single-threaded write and copy (1 pts)") {
val sc = new MultiWriterSeqCount
randomList(100).lazyZip(randomList(100)).foreach { (x, y) =>
sc.write(x, y)
assertEquals(sc.copy(), (x, y))
}
}
test("MultiWriterSeqCount: two write threads, two copy threads (4 pts)") {
testManySchedules(4, sched =>
val msc = new SchedulableMultiWriterSeqCount(sched)
// Invariant in this test: y == x + 1
msc.write(0, 1)
val randomValues = randomList(length = 5)
def writeThread(): ThreadResult =
randomValues.foreach(i => msc.write(i, i + 1))
// Unlke in the SeqCount test, we do not verify that we can read back
// the values we wrote, because the other writer thread might have
// overwritten them already.
WriteSuccess
def copyThread(): ThreadResult =
Read(msc.copy())
val threads = List(
() => writeThread(),
() => writeThread(),
() => copyThread(),
() => copyThread()
)
(threads, results => processResults(results.asInstanceOf[List[ThreadResult]]))
)
}
import scala.concurrent.duration._
override val munitTimeout = 200.seconds
end M21Suite
previous-exams/2021-midterm/m21/src/test/scala/m21/instrumentation/MockedMonitor.scala deleted 100644 → 0
View file @ 759afc66
package m21.instrumentation
trait MockedMonitor extends Monitor {
def scheduler: Scheduler
// Can be overriden.
override def waitDefault() = {
scheduler.log("wait")
scheduler updateThreadState Wait(this, scheduler.threadLocks.tail)
}
override def synchronizedDefault[T](toExecute: =>T): T = {
scheduler.log("synchronized check")
val prevLocks = scheduler.threadLocks
scheduler updateThreadState Sync(this, prevLocks) // If this belongs to prevLocks, should just continue.
scheduler.log("synchronized -> enter")
try {
toExecute
} finally {
scheduler updateThreadState Running(prevLocks)
scheduler.log("synchronized -> out")
}
}
override def notifyDefault() = {
scheduler mapOtherStates {
state => state match {
case Wait(lockToAquire, locks) if lockToAquire == this => SyncUnique(this, state.locks)
case e => e
}
}
scheduler.log("notify")
}
override def notifyAllDefault() = {
scheduler mapOtherStates {
state => state match {
case Wait(lockToAquire, locks) if lockToAquire == this => Sync(this, state.locks)
case SyncUnique(lockToAquire, locks) if lockToAquire == this => Sync(this, state.locks)
case e => e
}
}
scheduler.log("notifyAll")
}
}
trait LockFreeMonitor extends Monitor {
override def waitDefault() = {
throw new Exception("Please use lock-free structures and do not use wait()")
}
override def synchronizedDefault[T](toExecute: =>T): T = {
throw new Exception("Please use lock-free structures and do not use synchronized()")
}
override def notifyDefault() = {
throw new Exception("Please use lock-free structures and do not use notify()")
}
override def notifyAllDefault() = {
throw new Exception("Please use lock-free structures and do not use notifyAll()")
}
}
abstract class ThreadState {
def locks: Seq[AnyRef]
}
trait CanContinueIfAcquiresLock extends ThreadState {
def lockToAquire: AnyRef
}
case object Start extends ThreadState { def locks: Seq[AnyRef] = Seq.empty }
case object End extends ThreadState { def locks: Seq[AnyRef] = Seq.empty }
case class Wait(lockToAquire: AnyRef, locks: Seq[AnyRef]) extends ThreadState
case class SyncUnique(lockToAquire: AnyRef, locks: Seq[AnyRef]) extends ThreadState with CanContinueIfAcquiresLock
case class Sync(lockToAquire: AnyRef, locks: Seq[AnyRef]) extends ThreadState with CanContinueIfAcquiresLock
case class Running(locks: Seq[AnyRef]) extends ThreadState
case class VariableReadWrite(locks: Seq[AnyRef]) extends ThreadState
previous-exams/2021-midterm/m21/src/test/scala/m21/instrumentation/Scheduler.scala deleted 100644 → 0
View file @ 759afc66
package m21.instrumentation
import java.util.concurrent._;
import scala.concurrent.duration._
import scala.collection.mutable._
import Stats._
import java.util.concurrent.atomic.AtomicInteger
sealed abstract class Result
case class RetVal(rets: List[Any]) extends Result
case class Except(msg: String, stackTrace: Array[StackTraceElement]) extends Result
case class Timeout(msg: String) extends Result
/**
* A class that maintains schedule and a set of thread ids.
* The schedules are advanced after an operation of a SchedulableBuffer is performed.
* Note: the real schedule that is executed may deviate from the input schedule
* due to the adjustments that had to be made for locks
*/
class Scheduler(sched: List[Int]) {
val maxOps = 500 // a limit on the maximum number of operations the code is allowed to perform
private var schedule = sched
private var numThreads = 0
private val realToFakeThreadId = Map[Long, Int]()
private val opLog = ListBuffer[String]() // a mutable list (used for efficient concat)
private val threadStates = Map[Int, ThreadState]()
/**
* Runs a set of operations in parallel as per the schedule.
* Each operation may consist of many primitive operations like reads or writes
* to shared data structure each of which should be executed using the function `exec`.
* @timeout in milliseconds
* @return true - all threads completed on time, false -some tests timed out.
*/
def runInParallel(timeout: Long, ops: List[() => Any]): Result = {
numThreads = ops.length
val threadRes = Array.fill(numThreads) { None: Any }
var exception: Option[Except] = None
val syncObject = new Object()
var completed = new AtomicInteger(0)
// create threads
val threads = ops.zipWithIndex.map {
case (op, i) =>
new Thread(new Runnable() {
def run(): Unit = {
val fakeId = i + 1
setThreadId(fakeId)
try {
updateThreadState(Start)
val res = op()
updateThreadState(End)
threadRes(i) = res
// notify the master thread if all threads have completed
if (completed.incrementAndGet() == ops.length) {
syncObject.synchronized { syncObject.notifyAll() }
}
} catch {
case e: Throwable if exception != None => // do nothing here and silently fail
case e: Throwable =>
log(s"throw ${e.toString}")
exception = Some(Except(s"Thread $fakeId crashed on the following schedule: \n" + opLog.mkString("\n"),
e.getStackTrace))
syncObject.synchronized { syncObject.notifyAll() }
//println(s"$fakeId: ${e.toString}")
//Runtime.getRuntime().halt(0) //exit the JVM and all running threads (no other way to kill other threads)
}
}
})
}
// start all threads
threads.foreach(_.start())
// wait for all threads to complete, or for an exception to be thrown, or for the time out to expire
var remTime = timeout
syncObject.synchronized {
timed { if(completed.get() != ops.length) syncObject.wait(timeout) } { time => remTime -= time }
}
if (exception.isDefined) {
exception.get
} else if (remTime <= 1) { // timeout ? using 1 instead of zero to allow for some errors
Timeout(opLog.mkString("\n"))
} else {
// every thing executed normally
RetVal(threadRes.toList)
}
}
// Updates the state of the current thread
def updateThreadState(state: ThreadState): Unit = {
val tid = threadId
synchronized {
threadStates(tid) = state
}
state match {
case Sync(lockToAquire, locks) =>
if (locks.indexOf(lockToAquire) < 0) waitForTurn else {
// Re-aqcuiring the same lock
updateThreadState(Running(lockToAquire +: locks))
}
case Start => waitStart()
case End => removeFromSchedule(tid)
case Running(_) =>
case _ => waitForTurn // Wait, SyncUnique, VariableReadWrite
}
}
def waitStart(): Unit = {
//while (threadStates.size < numThreads) {
//Thread.sleep(1)
//}
synchronized {
if (threadStates.size < numThreads) {
wait()
} else {
notifyAll()
}
}
}
def threadLocks = {
synchronized {
threadStates(threadId).locks
}
}
def threadState = {
synchronized {
threadStates(threadId)
}
}
def mapOtherStates(f: ThreadState => ThreadState) = {
val exception = threadId
synchronized {
for (k <- threadStates.keys if k != exception) {
threadStates(k) = f(threadStates(k))
}
}
}
def log(str: String) = {
if((realToFakeThreadId contains Thread.currentThread().getId())) {
val space = (" " * ((threadId - 1) * 2))
val s = space + threadId + ":" + "\n".r.replaceAllIn(str, "\n" + space + " ")
opLog += s
}
}
/**
* Executes a read or write operation to a global data structure as per the given schedule
* @param msg a message corresponding to the operation that will be logged
*/
def exec[T](primop: => T)(msg: => String, postMsg: => Option[T => String] = None): T = {
if(! (realToFakeThreadId contains Thread.currentThread().getId())) {
primop
} else {
updateThreadState(VariableReadWrite(threadLocks))
val m = msg
if(m != "") log(m)
if (opLog.size > maxOps)
throw new Exception(s"Total number of reads/writes performed by threads exceed $maxOps. A possible deadlock!")
val res = primop
postMsg match {
case Some(m) => log(m(res))
case None =>
}
res
}
}
private def setThreadId(fakeId: Int) = synchronized {
realToFakeThreadId(Thread.currentThread.getId) = fakeId
}
def threadId =
try {
realToFakeThreadId(Thread.currentThread().getId())
} catch {
case e: NoSuchElementException =>
throw new Exception("You are accessing shared variables in the constructor. This is not allowed. The variables are already initialized!")
}
private def isTurn(tid: Int) = synchronized {
(!schedule.isEmpty && schedule.head != tid)
}
def canProceed(): Boolean = {
val tid = threadId
canContinue match {
case Some((i, state)) if i == tid =>
//println(s"$tid: Runs ! Was in state $state")
canContinue = None
state match {
case Sync(lockToAquire, locks) => updateThreadState(Running(lockToAquire +: locks))
case SyncUnique(lockToAquire, locks) =>
mapOtherStates {
_ match {
case SyncUnique(lockToAquire2, locks2) if lockToAquire2 == lockToAquire => Wait(lockToAquire2, locks2)
case e => e
}
}
updateThreadState(Running(lockToAquire +: locks))
case VariableReadWrite(locks) => updateThreadState(Running(locks))
}
true
case Some((i, state)) =>
//println(s"$tid: not my turn but $i !")
false
case None =>
false
}
}
var threadPreference = 0 // In the case the schedule is over, which thread should have the preference to execute.
/** returns true if the thread can continue to execute, and false otherwise */
def decide(): Option[(Int, ThreadState)] = {
if (!threadStates.isEmpty) { // The last thread who enters the decision loop takes the decision.
//println(s"$threadId: I'm taking a decision")
if (threadStates.values.forall { case e: Wait => true case _ => false }) {
val waiting = threadStates.keys.map(_.toString).mkString(", ")
val s = if (threadStates.size > 1) "s" else ""
val are = if (threadStates.size > 1) "are" else "is"
throw new Exception(s"Deadlock: Thread$s $waiting $are waiting but all others have ended and cannot notify them.")
} else {
// Threads can be in Wait, Sync, SyncUnique, and VariableReadWrite mode.
// Let's determine which ones can continue.
val notFree = threadStates.collect { case (id, state) => state.locks }.flatten.toSet
val threadsNotBlocked = threadStates.toSeq.filter {
case (id, v: VariableReadWrite) => true
case (id, v: CanContinueIfAcquiresLock) => !notFree(v.lockToAquire) || (v.locks contains v.lockToAquire)
case _ => false
}
if (threadsNotBlocked.isEmpty) {
val waiting = threadStates.keys.map(_.toString).mkString(", ")
val s = if (threadStates.size > 1) "s" else ""
val are = if (threadStates.size > 1) "are" else "is"
val whoHasLock = threadStates.toSeq.flatMap { case (id, state) => state.locks.map(lock => (lock, id)) }.toMap
val reason = threadStates.collect {
case (id, state: CanContinueIfAcquiresLock) if !notFree(state.lockToAquire) =>
s"Thread $id is waiting on lock ${state.lockToAquire} held by thread ${whoHasLock(state.lockToAquire)}"
}.mkString("\n")
throw new Exception(s"Deadlock: Thread$s $waiting are interlocked. Indeed:\n$reason")
} else if (threadsNotBlocked.size == 1) { // Do not consume the schedule if only one thread can execute.
Some(threadsNotBlocked(0))
} else {
val next = schedule.indexWhere(t => threadsNotBlocked.exists { case (id, state) => id == t })
if (next != -1) {
//println(s"$threadId: schedule is $schedule, next chosen is ${schedule(next)}")
val chosenOne = schedule(next) // TODO: Make schedule a mutable list.
schedule = schedule.take(next) ++ schedule.drop(next + 1)
Some((chosenOne, threadStates(chosenOne)))
} else {
threadPreference = (threadPreference + 1) % threadsNotBlocked.size
val chosenOne = threadsNotBlocked(threadPreference) // Maybe another strategy
Some(chosenOne)
//threadsNotBlocked.indexOf(threadId) >= 0
/*
val tnb = threadsNotBlocked.map(_._1).mkString(",")
val s = if (schedule.isEmpty) "empty" else schedule.mkString(",")
val only = if (schedule.isEmpty) "" else " only"
throw new Exception(s"The schedule is $s but$only threads ${tnb} can continue")*/
}
}
}
} else canContinue
}
/**
* This will be called before a schedulable operation begins.
* This should not use synchronized
*/
var numThreadsWaiting = new AtomicInteger(0)
//var waitingForDecision = Map[Int, Option[Int]]() // Mapping from thread ids to a number indicating who is going to make the choice.
var canContinue: Option[(Int, ThreadState)] = None // The result of the decision thread Id of the thread authorized to continue.
private def waitForTurn = {
synchronized {
if (numThreadsWaiting.incrementAndGet() == threadStates.size) {
canContinue = decide()
notifyAll()
}
//waitingForDecision(threadId) = Some(numThreadsWaiting)
//println(s"$threadId Entering waiting with ticket number $numThreadsWaiting/${waitingForDecision.size}")
while (!canProceed()) wait()
}
numThreadsWaiting.decrementAndGet()
}
/**
* To be invoked when a thread is about to complete
*/
private def removeFromSchedule(fakeid: Int) = synchronized {
//println(s"$fakeid: I'm taking a decision because I finished")
schedule = schedule.filterNot(_ == fakeid)
threadStates -= fakeid
if (numThreadsWaiting.get() == threadStates.size) {
canContinue = decide()
notifyAll()
}
}
def getOperationLog() = opLog
}
previous-exams/2021-midterm/m21/src/test/scala/m21/instrumentation/Stats.scala deleted 100644 → 0
View file @ 759afc66
/* Copyright 2009-2015 EPFL, Lausanne */
package m21.instrumentation
import java.lang.management._
/**
* A collection of methods that can be used to collect run-time statistics about Leon programs.
* This is mostly used to test the resources properties of Leon programs
*/
object Stats {
def timed[T](code: => T)(cont: Long => Unit): T = {
var t1 = System.currentTimeMillis()
val r = code
cont((System.currentTimeMillis() - t1))
r
}
def withTime[T](code: => T): (T, Long) = {
var t1 = System.currentTimeMillis()
val r = code
(r, (System.currentTimeMillis() - t1))
}
}
previous-exams/2021-midterm/m21/src/test/scala/m21/instrumentation/TestHelper.scala deleted 100644 → 0
View file @ 759afc66
package m21.instrumentation
import scala.util.Random
import scala.collection.mutable.{Map => MutableMap}
import Stats._
object TestHelper {
val noOfSchedules = 10000 // set this to 100k during deployment
val readWritesPerThread = 20 // maximum number of read/writes possible in one thread
val contextSwitchBound = 10
val testTimeout = 150 // the total time out for a test in seconds
val schedTimeout = 15 // the total time out for execution of a schedule in secs
// Helpers
/*def testManySchedules(op1: => Any): Unit = testManySchedules(List(() => op1))
def testManySchedules(op1: => Any, op2: => Any): Unit = testManySchedules(List(() => op1, () => op2))
def testManySchedules(op1: => Any, op2: => Any, op3: => Any): Unit = testManySchedules(List(() => op1, () => op2, () => op3))
def testManySchedules(op1: => Any, op2: => Any, op3: => Any, op4: => Any): Unit = testManySchedules(List(() => op1, () => op2, () => op3, () => op4))*/
def testSequential[T](ops: Scheduler => Any)(assertions: T => (Boolean, String)) =
testManySchedules(1,
(sched: Scheduler) => {
(List(() => ops(sched)),
(res: List[Any]) => assertions(res.head.asInstanceOf[T]))
})
/**
* @numThreads number of threads
* @ops operations to be executed, one per thread
* @assertion as condition that will executed after all threads have completed (without exceptions)
* the arguments are the results of the threads
*/
def testManySchedules(numThreads: Int,
ops: Scheduler =>
(List[() => Any], // Threads
List[Any] => (Boolean, String)) // Assertion
) = {
var timeout = testTimeout * 1000L
val threadIds = (1 to numThreads)
//(1 to scheduleLength).flatMap(_ => threadIds).toList.permutations.take(noOfSchedules).foreach {
val schedules = (new ScheduleGenerator(numThreads)).schedules()
var schedsExplored = 0
schedules.takeWhile(_ => schedsExplored <= noOfSchedules && timeout > 0).foreach {
//case _ if timeout <= 0 => // break
case schedule =>
schedsExplored += 1
val schedr = new Scheduler(schedule)
//println("Exploring Sched: "+schedule)
val (threadOps, assertion) = ops(schedr)
if (threadOps.size != numThreads)
throw new IllegalStateException(s"Number of threads: $numThreads, do not match operations of threads: $threadOps")
timed { schedr.runInParallel(schedTimeout * 1000, threadOps) } { t => timeout -= t } match {
case Timeout(msg) =>
throw new java.lang.AssertionError("assertion failed\n"+"The schedule took too long to complete. A possible deadlock! \n"+msg)
case Except(msg, stkTrace) =>
val traceStr = "Thread Stack trace: \n"+stkTrace.map(" at "+_.toString).mkString("\n")
throw new java.lang.AssertionError("assertion failed\n"+msg+"\n"+traceStr)
case RetVal(threadRes) =>
// check the assertion
val (success, custom_msg) = assertion(threadRes)
if (!success) {
val msg = "The following schedule resulted in wrong results: \n" + custom_msg + "\n" + schedr.getOperationLog().mkString("\n")
throw new java.lang.AssertionError("Assertion failed: "+msg)
}
}
}
if (timeout <= 0) {
throw new java.lang.AssertionError("Test took too long to complete! Cannot check all schedules as your code is too slow!")
}
}
/**
* A schedule generator that is based on the context bound
*/
class ScheduleGenerator(numThreads: Int) {
val scheduleLength = readWritesPerThread * numThreads
val rands = (1 to scheduleLength).map(i => new Random(0xcafe * i)) // random numbers for choosing a thread at each position
def schedules(): LazyList[List[Int]] = {
var contextSwitches = 0
var contexts = List[Int]() // a stack of thread ids in the order of context-switches
val remainingOps = MutableMap[Int, Int]()
remainingOps ++= (1 to numThreads).map(i => (i, readWritesPerThread)) // num ops remaining in each thread
val liveThreads = (1 to numThreads).toSeq.toBuffer
/**
* Updates remainingOps and liveThreads once a thread is chosen for a position in the schedule
*/
def updateState(tid: Int): Unit = {
val remOps = remainingOps(tid)
if (remOps == 0) {
liveThreads -= tid
} else {
remainingOps += (tid -> (remOps - 1))
}
}
val schedule = rands.foldLeft(List[Int]()) {
case (acc, r) if contextSwitches < contextSwitchBound =>
val tid = liveThreads(r.nextInt(liveThreads.size))
contexts match {
case prev :: tail if prev != tid => // we have a new context switch here
contexts +:= tid
contextSwitches += 1
case prev :: tail =>
case _ => // init case
contexts +:= tid
}
updateState(tid)
acc :+ tid
case (acc, _) => // here context-bound has been reached so complete the schedule without any more context switches
if (!contexts.isEmpty) {
contexts = contexts.dropWhile(remainingOps(_) == 0)
}
val tid = contexts match {
case top :: tail => top
case _ => liveThreads(0) // here, there has to be threads that have not even started
}
updateState(tid)
acc :+ tid
}
schedule #:: schedules()
}
}
}
previous-exams/2021-midterm/m21/src/test/scala/m21/instrumentation/TestUtils.scala deleted 100644 → 0
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package m21.instrumentation
import scala.concurrent._
import scala.concurrent.duration._
import scala.concurrent.ExecutionContext.Implicits.global
object TestUtils {
def failsOrTimesOut[T](action: => T): Boolean = {
val asyncAction = Future {
action
}
try {
Await.result(asyncAction, 2000.millisecond)
} catch {
case _: Throwable => return true
}
return false
}
}
previous-exams/2021-midterm/m21/src/test/scala/m21/overrides.scala deleted 100644 → 0
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package m21
import instrumentation._
import scala.annotation.tailrec
import java.util.concurrent.atomic._
class SchedulableAtomicVariable[T](initial: T, scheduler: Scheduler, name: String) extends AbstractAtomicVariable[T]:
private val proxied: AtomicVariable[T] = new AtomicVariable[T](initial)
override def get: T = scheduler.exec {
proxied.get
} (s"", Some(res => s"$name: get $res"))
override def set(value: T): Unit = scheduler.exec {
proxied.set(value)
} (s"$name: set $value", None)
override def compareAndSet(expected: T, newValue: T): Boolean = {
scheduler.exec {
proxied.compareAndSet(expected, newValue)
} (s"$name: compareAndSet(expected = $expected, newValue = $newValue)", Some(res => s"$name: Did it set? $res") )
}
end SchedulableAtomicVariable
class SchedulableSeqCount(val scheduler: Scheduler) extends SeqCount with LockFreeMonitor:
override def generation: Int = scheduler.exec {
super.generation
} ("", Some(res => s"generation is $res"))
override def setGeneration(newGeneration: Int): Unit = scheduler.exec {
super.setGeneration(newGeneration)
} ( s"setGeneration($newGeneration)", None )
override def x: Int = scheduler.exec {
super.x
} ("", Some(res => s"x is $res"))
override def setX(newX: Int): Unit = scheduler.exec {
super.setX(newX)
} (s"setX($newX)", None)
override def y: Int = scheduler.exec {
super.y
} ("", Some(res => s"y is $res"))
override def setY(newY: Int): Unit = scheduler.exec {
super.setY(newY)
} (s"setY($newY)", None)
end SchedulableSeqCount
class SchedulableMultiWriterSeqCount(val scheduler: Scheduler) extends MultiWriterSeqCount with LockFreeMonitor:
override protected val myGeneration: AbstractAtomicVariable[Int] = new SchedulableAtomicVariable(1, scheduler, "myGeneration")
override def x: Int = scheduler.exec {
super.x
} ("", Some(res => s"x is $res"))
override def setX(newX: Int): Unit = scheduler.exec {
super.setX(newX)
} (s"setX($newX)", None)
override def y: Int = scheduler.exec {
super.y
} ("", Some(res => s"y is $res"))
override def setY(newY: Int): Unit = scheduler.exec {
super.setY(newY)
} (s"setY($newY)", None)
end SchedulableMultiWriterSeqCount
previous-exams/2021-midterm/m3.md deleted 100644 → 0
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Use the following commands to make a fresh clone of your repository:
```
git clone -b m3 git@gitlab.epfl.ch:lamp/student-repositories-s21/cs206-GASPAR.git m3
```
## Useful links
* [A guide to the Scala parallel collections](https://docs.scala-lang.org/overviews/parallel-collections/overview.html)
* [The API documentation of the Scala parallel collections](https://www.javadoc.io/doc/org.scala-lang.modules/scala-parallel-collections_2.13/latest/scala/collection/index.html)
* [The API documentation of the Scala standard library](https://www.scala-lang.org/files/archive/api/2.13.4)
* [The API documentation of the Java standard library](https://docs.oracle.com/en/java/javase/15/docs/api/index.html)
**If you have issues with the IDE, try [reimporting the
build](https://gitlab.epfl.ch/lamp/cs206/-/blob/master/labs/example-lab.md#ide-features-like-type-on-hover-or-go-to-definition-do-not-work),
if you still have problems, use `compile` in sbt instead.**
## Exercise
Given the following sequential implementation of a function that computes the sequence of rolling windowed averages, your task will be to complete and optimize a parallel version of this code.
```scala
/** Compute the rolling windowed mean of an array.
*
* For an array `arr = Arr(x1, x2, x3, ..., x_n)` the result is
* `Arr(x1, (x1+x2)/2, (x1+x2+x3)/3, (x2+x3+x4)/3, ..., (x_{n-2}, x_{n-1}, x_n)/n)`
*/
def rollingWinMeanParallel(arr: Arr[Int]): Arr[Double] = {
// Transform all numbers to averages of window of size 1
val arr1 = arr.map(x => AvgWin(x :: Nil))
// Compute the rolling windowed average by combining the windows together
val arr2 = arr1.scan(AvgWin(Nil))((acc, x) => acc.pushAll(x))
// Transform the windowed averages to Doubles
arr2.map(win => win.toDouble)
// Drop the extra initial element that was added by the scan
arr3.tail
```
This implementation has some issues:
- It does not use parallelism
- Creates two intermediate arrays by calling `map`
- Creates an extra intermediate arrays by calling `tail`
- Scan returns an extra element we do not need
We want to parallelize and avoid the creation of the extra arrays.
As we are calling a `scan` the natural operations we need are `upsweep` and `downsweep`.
It is possible specialize those operations for our problem by letting those operations do the mapping.
It is also possible to change those operations to not generate the first element.
We give you a version of `rollingWinMeanSequential` that partially implements the parallelization using `upsweep` and `downsweep`.
Your tasks in the exercise will be to:
- TASK 1: Implement the parallelization of `upsweep` and `downsweep`
- TASK 2: Remove the calls to the `map`
- TASK 3: Remove the call to `tail`
You can get partial points for solving part of the tasks.
The order of the tasks is a suggestion, you may do them in any order if that is simpler for you.
Look at the `Lib` trait to find the definitions of functions and classes you can use (or already used).
In this question we use a `Arr` array class instead of the normal `Array`. You may assume that this class has the same performance characteristics as the normal array. `Arr` provides only a limited set of operations.
previous-exams/2021-midterm/m3/.gitignore deleted 100644 → 0
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# General
*.DS_Store
*.swp
*~
# Dotty
*.class
*.tasty
*.hasTasty
# sbt
target/
# IDE
.bsp
.bloop
.metals
.vscode
# datasets
stackoverflow-grading.csv
wikipedia-grading.dat
previous-exams/2021-midterm/m3/assignment.sbt deleted 100644 → 0
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// Student tasks (i.e. submit, packageSubmission)
enablePlugins(StudentTasks)
previous-exams/2021-midterm/m3/build.sbt deleted 100644 → 0
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course := "midterm"
assignment := "m3"
scalaVersion := "3.0.0-RC1"
scalacOptions ++= Seq("-language:implicitConversions", "-deprecation")
libraryDependencies += "org.scalameta" %% "munit" % "0.7.22"
val MUnitFramework = new TestFramework("munit.Framework")
testFrameworks += MUnitFramework
// Decode Scala names
testOptions += Tests.Argument(MUnitFramework, "-s")
testSuite := "m3.M3Suite"
previous-exams/2021-midterm/m3/grading-tests.jar deleted 100644 → 0
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File deleted
previous-exams/2021-midterm/m3/project/FilteringReporterPlugin.scala deleted 100644 → 0
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package sbt // To access the private[sbt] compilerReporter key
package filteringReporterPlugin
import Keys._
import ch.epfl.lamp._
object FilteringReporterPlugin extends AutoPlugin {
override lazy val projectSettings = Seq(
// Turn off warning coming from scalameter that we cannot fix without changing scalameter
compilerReporter in (Compile, compile) ~= { reporter => new FilteringReporter(reporter) }
)
}
class FilteringReporter(reporter: xsbti.Reporter) extends xsbti.Reporter {
def reset(): Unit = reporter.reset()
def hasErrors: Boolean = reporter.hasErrors
def hasWarnings: Boolean = reporter.hasWarnings
def printSummary(): Unit = reporter.printSummary()
def problems: Array[xsbti.Problem] = reporter.problems
def log(problem: xsbti.Problem): Unit = {
if (!problem.message.contains("An existential type that came from a Scala-2 classfile cannot be"))
reporter.log(problem)
}
def comment(pos: xsbti.Position, msg: String): Unit =
reporter.comment(pos, msg)
override def toString = s"CollectingReporter($reporter)"
}
previous-exams/2021-midterm/m3/project/MOOCSettings.scala deleted 100644 → 0
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package ch.epfl.lamp
import sbt._
import sbt.Keys._
/**
* Coursera uses two versions of each assignment. They both have the same assignment key and part id but have
* different item ids.
*
* @param key Assignment key
* @param partId Assignment partId
* @param itemId Item id of the non premium version
* @param premiumItemId Item id of the premium version (`None` if the assignment is optional)
*/
case class CourseraId(key: String, partId: String, itemId: String, premiumItemId: Option[String])
/**
* Settings shared by all assignments, reused in various tasks.
*/
object MOOCSettings extends AutoPlugin {
override def requires = super.requires && filteringReporterPlugin.FilteringReporterPlugin
object autoImport {
val course = SettingKey[String]("course")
val assignment = SettingKey[String]("assignment")
val options = SettingKey[Map[String, Map[String, String]]]("options")
val courseraId = settingKey[CourseraId]("Coursera-specific information identifying the assignment")
val testSuite = settingKey[String]("Fully qualified name of the test suite of this assignment")
.withRank(KeyRanks.Invisible)
// Convenient alias
type CourseraId = ch.epfl.lamp.CourseraId
val CourseraId = ch.epfl.lamp.CourseraId
}
import autoImport._
override val globalSettings: Seq[Def.Setting[_]] = Seq(
// supershell is verbose, buggy and useless.
useSuperShell := false
)
override val projectSettings: Seq[Def.Setting[_]] = Seq(
parallelExecution in Test := false,
// Report test result after each test instead of waiting for every test to finish
logBuffered in Test := false,
name := s"${course.value}-${assignment.value}"
)
}