public class SimplePerfectNumberUtil implements PerfectNumberUtil{ @Override public boolean isPerfect(int aNumber) { return sumOfFactors(aNumber)==2*aNumber; } private int sumOfFactors(int aNumber){ int sum = 0; for (int i=1;i<=aNumber;i++){ if (aNumber%i==0){ sum+=i; } } return sum; } }

Programming Scala book provides a sample scala actor implementation for this by breaking up the task of determining whether a large number is a perfect number by breaking up the large number into a range of smaller numbers - eg. a number like 3000 can be split up into say 0-1000, 1001-2000, 2001-3000, with a task responsible for summing up the factors in each of these ranges and summing up the result.

A slightly modified implementation based on the Programming Scala book is the following:

class PerfectUtilScala { def isPerfect(candidate: Int) = { val RANGE = 10000000 val numberOfPartitions = (candidate.toDouble / RANGE).ceil.toInt val caller = self val sumoffactorsActor = actor{ loop { react { case msg:FactorsRangeForCandidate => caller ! sumOfFactorsInRange(msg.lower, msg.upper, msg.candidate) } } } for (i <- 0 until numberOfPartitions) { val lower = i * RANGE + 1; val upper = candidate min (i + 1) * RANGE sumoffactorsActor ! new FactorsRangeForCandidate(lower, upper, candidate) } val sum = (0 /: (0 until numberOfPartitions)) { (partialSum, i) => receive { case sumInRange: Int => partialSum + sumInRange } } 2 * candidate == sum } private def sumOfFactorsInRange(lower: Int, upper: Int, number: Int) = { (0 /: (lower to upper)) { (sum, i) => if (number % i == 0) sum + i else sum } } } class FactorsRangeForCandidate(val lower:Int, val upper:Int, val candidate:Int)A Java Executors based implementation is the following:

public class ThreadPoolPerfectNumberUtil implements PerfectNumberUtil{ private ExecutorService threadpool = Executors.newFixedThreadPool(3); @SuppressWarnings("unchecked") public boolean isPerfect(int aNumber) { int RANGE = Constants.RANGE; int numberOfPartitions = new Double(Math.ceil(aNumber * 1.0 / RANGE)).intValue(); FutureAnd a Kilim based actor implementation:[] sumOfFactors = new Future[numberOfPartitions]; for (int i=0;i { private final int lower; private final int upper; private final int anumber; public SumOfFactorsTask(int lower, int upper, int anumber){ this.lower = lower; this.upper = upper; this.anumber = anumber; } @Override public Integer call() { int sum=0; for (int i=lower;i<=upper;i++){ if (anumber%i==0){ sum+=i; } } return sum; } }

public class ActorsPerfectNumberUtil extends Task implements PerfectNumberUtil { private MailboxThe codebase along with the Spring Integration based implementation is available at this Git location:mailbox; private Mailbox resultmailbox; private SumOfFactorsActor sumOfFactors; public ActorsPerfectNumberUtil() { mailbox = new Mailbox (); resultmailbox = new Mailbox (); sumOfFactors = new SumOfFactorsActor(mailbox, resultmailbox); sumOfFactors.start(); } public boolean isPerfect(int aNumber) { int RANGE = Constants.RANGE; int numberOfPartitions = new Double(Math.ceil(aNumber * 1.0 / RANGE)).intValue(); for (int i = 0; i < numberOfPartitions; i++) { int lower = i * RANGE + 1; int upper = (i + 1) * RANGE; if (aNumber < upper) upper = aNumber; mailbox.putnb(new FactorsRange(lower, upper, aNumber)); } int sum = 0; for (int i = 0; i < numberOfPartitions; i++) { sum += resultmailbox.getb(); } if (sum == 2*aNumber) return true; return false; } }

git://github.com/bijukunjummen/Perfect-Number.git

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