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InformationINF2440Spring2018writtenexamDateandtime:June11th,2018at09:00.Duration:4hoursMaterialallowed:Allwrittenmaterialisallowed.Noelectronicaidisallowed.ThelectureslidesareattachedasaPDF.

1 Question1.1:JavaThreadCreationInaJavaprogram,theprogrammermustcreateandstarteverythreadthattheprogramuses.Isthisright?Selectanalternative:

Yes,theprogrammustcreateandstartallthreads.

Yes,theprogrammustcreateandstartallthreadsinmain().

No,thefirstthreadiscreatedautomaticallyandisautomaticallystartedandsettoexecutethemain()method.Theremainingthreadsmustbecreatedandstartedbyoneoftheotherthreadsintheprogram.

No,theprogrammermustmerelyprovidethecodeforthethreads.Thecompilerwillthenautomaticallygeneratethethreadsatcompiletimeandensurethattheyarestartedwhentheprogramruns.

No,allthreadsarestartedautomatically.

Maximummarks:4

2 Question1.2:JavaThreadsFeaturesWhichofthefollowingstatementsaretrueforJavaThreadsthatarecreatedinthesameprogram?(Morethanoneanswerispossible.)Selectoneormorealternatives:

Javathreadscanexecuteinparallelindependentlyofoneanotheronmulti-coremachines.

Iftherearemorethreadsthanavailablecores,theprogramcannotberun.

Javathreadsexecuteatthesamespeedbecauseeachthreadisassignedtoitsowncore.

Javathreadscanaccessthelocalvariableofoneanother.

Javathreadsresideinacommonpartofmemoryandcanaccessstaticvariablesdeclaredintheclasscontainingthethreads.

Javathreadsalwaysexecuteoneatatime.

Maximummarks:6

3 Question1.3:JavaSynchronizedCanweensurethatonlyonethreadatatimeisexecutingamethodbyprefixingthemethodwiththe

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synchronizedkeyword.Selectanalternative:

Yes,ifmorethanonethreadcallsthemethod,theJavasystemensuresthatonlyonethreadisexecutingthemethodatatime.

Yes,exceptfortheinitialthreadrunningmain()--itisalwaysallowedtoexecutethemethodevenifanotherthreadisrunningthemethodatthesametime.

No,insidethemethod,wemustaddasynchronizationofsomekind,e.g.,CyclicBarrier.

Onlyifthemethodreturntypeisvoid.

Maximummarks:5

4 Question1.4:PerformanceofJavaThreadsWhichofthefollowingstatementsisclosesttoreality?Selectanalternative:

Javathreadscanbecreatedandrunsoquicklythatevenifwearejustdoingtwoorthreeintegeradditions,itisworthdoingtheminaseparatethreadbecausethethreadwillexecutequicklyonanothercore.

Javathreadstakealotoftimetocreateandtosynchronizesoingeneralathreadshouldnotbecreatedunlessitcandoalotofwork,e.g.,atleastmanythousandsofadditions.

JavaThreadsarecheaptocreateaslongastherearelessthreadsthancoresonthemachine.

Javathreadsareexpensivetocreatebutitbecomescheaperandcheapertocreatethreadsthemorethreadsaprogramcreates.

Maximummarks:5

Question2:CyclicBarriersInthisquestion,youshouldconsidertheprogramProblem.javaattachedasaPDF-document.

5 Question2.1:CyclicBarrier-terminationwithtwothreadsWhentheprogramiscalledwiththeparameters"20",willtheprogramalwaysterminate?Explainyouranswer.

Fillinyouranswerhere

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Fillinyouranswerhere

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Maximummarks:10

6 Question2.2:CyclicBarrier-outputwithtwothreadsWhentheprogramiscalledwiththeparameters"20",willtheprogramalwaysprintthesametext?Explainyouranswer.Fillinyouranswerhere

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Maximummarks:10

7 Question2.3CyclicBarrier:TerminationwithfourthreadsWhentheprogramiscalledwiththeparameters"22",willtheprogramalwaysterminate?Explainyouranswer.

Fillinyouranswerhere

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Fillinyouranswerhere

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Maximummarks:12

8 Question2.4:CyclicBarrier:OutputwithfourthreadsWhentheprogramiscalledwiththeparamters"22",willtheprogramalwaysprintthesametext?Ifso,showtheoutput.Ifnot,givetwodifferentexamplesofwhattheprogramprints.Fillinyouranswerhere

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Maximummarks:12

Question3:FindingPrimeDesertsThisquestionisbasedonErathostenesSievethatfindsprimenumbersuptoagivennumberN.YoushouldalreadybequitefamiliarwiththesieveasyouhaveimplementeditinOblig3(attachedasPDF).Thisquestionisaboutfindingso-calledPrimeDeserts.APrimeDesertisaninterval[A,B]whereA<B,AandB

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areprimenumbers,andthereisnoprimebetweenAandB.Examplesofsuchdesertsare[2,3],[7,11],[23,29],and[337,347].ThesizeofaPrimeDesertisdefinedasB-A-1,i.e.,thenumberofintegersstrictlybetweenAandB.AiscalledthestartpointofthePrimeDesertandBiscalledtheendpoint.YouaretowriteaJavaprogramthatgeneratesalistofPrimeDeserts.Thelistshouldbesortedsothattheintervalscomeinascendingorder,i.e.,thestartspointsareinascendingorder.ThefirstPrimeDesertis[2,3]andthereafter,thenextPrimeDesertshouldbelargerthanthepreviousonethroughoutthelist.Furthermore,youshouldfindallPrimeDesertswheretheendpointnogreaterthanN,butyoushouldexcludefromthelistanyPrimeDesertwhosesizeisnotgreaterthanthesizeofthepreviousPrimeDesertinthelist.Forexample,thatmeansthatthestartofthelistis:[2,3],[3,5],[7,11],[23,29],[89,97],...i.e.,[5,7],[11,13],[13,17],[17,19]andmoreareleftoutbecausetheirsizeisnotgreaterthanthepreviousPrimeDesertinthelist.Tobesure,youmaynotleaveoutaPrimeDesert,ifitislargerthanthepreviousinthelistandsmallerthanthenextone;forexample,youcannothavealistthatstartswith[2,3]followedby[23,29].YouneednotwritetheentireprogramasyoucanassumethatyoualreadyhavethecodethatyouwroteforOblig3.YouarewelcometobaseyourcodeonModell2fromthelecturesinWeek5(uke5).

9 Question3.1:SequentialProgramforfindingPrimeDesertsWriteasequentialJavaprogramthatfindsthelistofPrimeDesertsspecifiedintheintroductiontoQuestion3.Fillinyouranswerhere

Maximummarks:20

10 Question3.2:ParallelProgramtofindPrimeDesertsWriteaparallelJavaprogramthatfindsthelistofPrimeDesertsspecifiedintheintroductiontoQuestion3.Strivetoachieveaspeedupoverthesequentialversion.

Fillinyouranswerhere

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Fillinyouranswerhere

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Question4:BubblesortBubblesortisasortingalgorithmthatsorts,e.g.,anintegerarrayA,bycomparingtwoneighboringelementsandexchaningthem,ifthefirstoneisgreaterthanthesecond.Thesortingconsistsofanumberofpasses.Eachpassgoesthruthearrayoneelementatatimeandperformstheexchange,ifnecessary.Attheendofpassk,thek'thlargestnumberisinplaceatthetopofthearray,sothenextpassneednotconsiderthetopkelementsofthearray.AsequentialbubblesortofanintegerarrayisgivenasaPDFfile.

11 Question4.1ParallelizingBubblesortHowcanBubblesortbeparallelized?Describethedesignofasolution.

Fillinyouranswerhere

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Fillinyouranswerhere

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Maximummarks:20

12 Question4.2:ParallelBubblesortWriteaJavaprogramimplementingyourdesignofaparallelversionofBubblesortfromQuestion4.1.Strivetohaveaspeedupoverthesequentialversion.Putanyaddedexplanationthatyouhaveascommentsinthecode.Fillinyouranswerhere

Maximummarks:40

13 Question5.1:RecursionandParallelismTherearemanywaysofparallelizingarecurvisealgorithm.Ofthefollowingstatements,whichofthemisagoodidea(youmayselectmorethanone):

Selectoneormorealternatives:

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Selectoneormorealternatives:

Whentherecursivecallsformatreestructure,itisagoodideatospawnandusethreadsatthebottomofthetreeonly.

Asimplewaytoparallelizearecursiveprogramistohaveonethreadperrecursivecall.Thisalmostalwaysleadstoachievingagoodspeedup.

Itisimportanttolimitthenumberofthreads.

Whentherecursivecallsformatreestructure,itisagoodideatospawnnewthreadatthetopofthetreeandlimitthenumberofthreadsatthebottomofthetree.

Recursivecallsarerelativelyexpensivecomparedtocreatingandrunningathread.

Recursivecallsareseveralordersofmagnitudecheaperthancreatingandrunningathread.

Whentherecursivecallsformatreestructure,itisagoodideatoreplacebranchesatthelowerlevelsofthetreewithsimplesequentialsolutionsoftheproblem.

Itisimportanttobalancethenumberofthreadsandtheamountofworkdonebyeachthread.

Maximummarks:16

Question 12Attached

static void bubbleSort(int[] arr) { int n = arr.length; int temp; for (int i=0; i < n; i++){ for (int j=1; j < (n-i); j++){ if(arr[j-1] > arr[j]){ //swap elements temp = arr[j-1]; arr[j-1] = arr[j]; arr[j] = temp; } } } }

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Question 12Attached

static void bubbleSort(int[] arr) { int n = arr.length; int temp; for (int i=0; i < n; i++){ for (int j=1; j < (n-i); j++){ if(arr[j-1] > arr[j]){ //swap elements temp = arr[j-1]; arr[j-1] = arr[j]; arr[j] = temp; } } } }

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Question 5Attached

Problem-javaimport java.util.concurrent.*; class Problem { // felles data og metoder A static int num = 2; static int extra = 2; static CyclicBarrier b;

public static void main(String [] args) { Problem p = new Problem(); num = Integer.parseInt(args[0]); extra = Integer.parseInt(args[1]); b = new CyclicBarrier(num); p.utfoer(num+extra); // extra threads System.out.println(" Main TERMINATED"); } // end main

void utfoer (int antT) { Thread [] t = new Thread [antT]; for (int i =0; i< antT; i++) ( t[i] = new Thread(new Arbeider(i))).start(); try { for (int i =0; i< antT; i++) t[i].join(); } catch(Exception e) {} } // end utfoer

class Arbeider implements Runnable { // lokale data og metoder B int ind;

void sync() { try{ b.await(); } catch (Exception e) { return;} }

public Arbeider (int in) {ind = in;};

public void run() { sync(); System.out.println("A"+ind); sync(); System.out.println("B"+ind); } // end run } // end indre klasse Arbeider } // end class Problem

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Question 5Attached

Problem-javaimport java.util.concurrent.*; class Problem { // felles data og metoder A static int num = 2; static int extra = 2; static CyclicBarrier b;

public static void main(String [] args) { Problem p = new Problem(); num = Integer.parseInt(args[0]); extra = Integer.parseInt(args[1]); b = new CyclicBarrier(num); p.utfoer(num+extra); // extra threads System.out.println(" Main TERMINATED"); } // end main

void utfoer (int antT) { Thread [] t = new Thread [antT]; for (int i =0; i< antT; i++) ( t[i] = new Thread(new Arbeider(i))).start(); try { for (int i =0; i< antT; i++) t[i].join(); } catch(Exception e) {} } // end utfoer

class Arbeider implements Runnable { // lokale data og metoder B int ind;

void sync() { try{ b.await(); } catch (Exception e) { return;} }

public Arbeider (int in) {ind = in;};

public void run() { sync(); System.out.println("A"+ind); sync(); System.out.println("B"+ind); } // end run } // end indre klasse Arbeider } // end class Problem

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Question 6Attached

Problem-javaimport java.util.concurrent.*; class Problem { // felles data og metoder A static int num = 2; static int extra = 2; static CyclicBarrier b;

public static void main(String [] args) { Problem p = new Problem(); num = Integer.parseInt(args[0]); extra = Integer.parseInt(args[1]); b = new CyclicBarrier(num); p.utfoer(num+extra); // extra threads System.out.println(" Main TERMINATED"); } // end main

void utfoer (int antT) { Thread [] t = new Thread [antT]; for (int i =0; i< antT; i++) ( t[i] = new Thread(new Arbeider(i))).start(); try { for (int i =0; i< antT; i++) t[i].join(); } catch(Exception e) {} } // end utfoer

class Arbeider implements Runnable { // lokale data og metoder B int ind;

void sync() { try{ b.await(); } catch (Exception e) { return;} }

public Arbeider (int in) {ind = in;};

public void run() { sync(); System.out.println("A"+ind); sync(); System.out.println("B"+ind); } // end run } // end indre klasse Arbeider } // end class Problem

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Question 6Attached

Problem-javaimport java.util.concurrent.*; class Problem { // felles data og metoder A static int num = 2; static int extra = 2; static CyclicBarrier b;

public static void main(String [] args) { Problem p = new Problem(); num = Integer.parseInt(args[0]); extra = Integer.parseInt(args[1]); b = new CyclicBarrier(num); p.utfoer(num+extra); // extra threads System.out.println(" Main TERMINATED"); } // end main

void utfoer (int antT) { Thread [] t = new Thread [antT]; for (int i =0; i< antT; i++) ( t[i] = new Thread(new Arbeider(i))).start(); try { for (int i =0; i< antT; i++) t[i].join(); } catch(Exception e) {} } // end utfoer

class Arbeider implements Runnable { // lokale data og metoder B int ind;

void sync() { try{ b.await(); } catch (Exception e) { return;} }

public Arbeider (int in) {ind = in;};

public void run() { sync(); System.out.println("A"+ind); sync(); System.out.println("B"+ind); } // end run } // end indre klasse Arbeider } // end class Problem

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Question 7Attached

Problem-javaimport java.util.concurrent.*; class Problem { // felles data og metoder A static int num = 2; static int extra = 2; static CyclicBarrier b;

public static void main(String [] args) { Problem p = new Problem(); num = Integer.parseInt(args[0]); extra = Integer.parseInt(args[1]); b = new CyclicBarrier(num); p.utfoer(num+extra); // extra threads System.out.println(" Main TERMINATED"); } // end main

void utfoer (int antT) { Thread [] t = new Thread [antT]; for (int i =0; i< antT; i++) ( t[i] = new Thread(new Arbeider(i))).start(); try { for (int i =0; i< antT; i++) t[i].join(); } catch(Exception e) {} } // end utfoer

class Arbeider implements Runnable { // lokale data og metoder B int ind;

void sync() { try{ b.await(); } catch (Exception e) { return;} }

public Arbeider (int in) {ind = in;};

public void run() { sync(); System.out.println("A"+ind); sync(); System.out.println("B"+ind); } // end run } // end indre klasse Arbeider } // end class Problem

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Question 7Attached

Problem-javaimport java.util.concurrent.*; class Problem { // felles data og metoder A static int num = 2; static int extra = 2; static CyclicBarrier b;

public static void main(String [] args) { Problem p = new Problem(); num = Integer.parseInt(args[0]); extra = Integer.parseInt(args[1]); b = new CyclicBarrier(num); p.utfoer(num+extra); // extra threads System.out.println(" Main TERMINATED"); } // end main

void utfoer (int antT) { Thread [] t = new Thread [antT]; for (int i =0; i< antT; i++) ( t[i] = new Thread(new Arbeider(i))).start(); try { for (int i =0; i< antT; i++) t[i].join(); } catch(Exception e) {} } // end utfoer

class Arbeider implements Runnable { // lokale data og metoder B int ind;

void sync() { try{ b.await(); } catch (Exception e) { return;} }

public Arbeider (int in) {ind = in;};

public void run() { sync(); System.out.println("A"+ind); sync(); System.out.println("B"+ind); } // end run } // end indre klasse Arbeider } // end class Problem

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Question 8Attached

Problem-javaimport java.util.concurrent.*; class Problem { // felles data og metoder A static int num = 2; static int extra = 2; static CyclicBarrier b;

public static void main(String [] args) { Problem p = new Problem(); num = Integer.parseInt(args[0]); extra = Integer.parseInt(args[1]); b = new CyclicBarrier(num); p.utfoer(num+extra); // extra threads System.out.println(" Main TERMINATED"); } // end main

void utfoer (int antT) { Thread [] t = new Thread [antT]; for (int i =0; i< antT; i++) ( t[i] = new Thread(new Arbeider(i))).start(); try { for (int i =0; i< antT; i++) t[i].join(); } catch(Exception e) {} } // end utfoer

class Arbeider implements Runnable { // lokale data og metoder B int ind;

void sync() { try{ b.await(); } catch (Exception e) { return;} }

public Arbeider (int in) {ind = in;};

public void run() { sync(); System.out.println("A"+ind); sync(); System.out.println("B"+ind); } // end run } // end indre klasse Arbeider } // end class Problem

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Question 8Attached

Problem-javaimport java.util.concurrent.*; class Problem { // felles data og metoder A static int num = 2; static int extra = 2; static CyclicBarrier b;

public static void main(String [] args) { Problem p = new Problem(); num = Integer.parseInt(args[0]); extra = Integer.parseInt(args[1]); b = new CyclicBarrier(num); p.utfoer(num+extra); // extra threads System.out.println(" Main TERMINATED"); } // end main

void utfoer (int antT) { Thread [] t = new Thread [antT]; for (int i =0; i< antT; i++) ( t[i] = new Thread(new Arbeider(i))).start(); try { for (int i =0; i< antT; i++) t[i].join(); } catch(Exception e) {} } // end utfoer

class Arbeider implements Runnable { // lokale data og metoder B int ind;

void sync() { try{ b.await(); } catch (Exception e) { return;} }

public Arbeider (int in) {ind = in;};

public void run() { sync(); System.out.println("A"+ind); sync(); System.out.println("B"+ind); } // end run } // end indre klasse Arbeider } // end class Problem

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