A Simple non-threaded (and non-optimized) java implementation for figuring out if a number is a perfect number is the following:
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 | 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;
}
}
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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:
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 | 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)
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1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 | 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();
Future<integer>[] sumOfFactors = new Future[numberOfPartitions];
for (int i=0;i<numberofpartitions;i++) (anumber="" *="" +="" 1;="" if="" int="" lower="i" range;="" range="" upper="(i+1)*" {=""><upper) (exception="" (int="" (sum="=2*aNumber)" +="sumOfFactors[i].get();" callable="" catch="" class="" e)="" false;="" for="" i="0;i<numberOfPartitions;i++)" if="" implements="" int="" new="" return="" runtimeexception(e);="" sum="0;" sumoffactors[i]="threadpool.submit(new" sumoffactorstask(lower,upper,anumber));="" sumoffactorstask="" throw="" true;="" try="" upper="aNumber;" {="" }=""><integer>{
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;
}
}
</integer></upper)></numberofpartitions;i++)></integer>
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1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 | public class ActorsPerfectNumberUtil extends Task implements PerfectNumberUtil {
private Mailbox<factorsrange> mailbox;
private Mailbox<integer> resultmailbox;
private SumOfFactorsActor sumOfFactors;
public ActorsPerfectNumberUtil() {
mailbox = new Mailbox<factorsrange>();
resultmailbox = new Mailbox<integer>();
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;
}
}
</integer></factorsrange></integer></factorsrange>
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The codebase along with the Spring Integration based implementation is available at this Git location:
git://github.com/bijukunjummen/Perfect-Number.git
