PrimeCalculator.java - CPU Intensive Process

JVM Tutorials - Herong's Tutorial Examples

∟CPU Impact of Multi-Thread Applications

∟PrimeCalculator.java - CPU Intensive Process

This section describes a thread productivity testing programs, PrimeCalculator.java, that repeats a work unit of finding all prime numbers in a given integer range. It is a good example of CPU intensive process.

Many Java applications are using the multithreading technology to run multiple processes of the same type concurrently instead of running them sequentially. Designers of those applications believe that multithreading will help to get more work done within the same time period.

In order to understand the impact on overall productivity of multithreading technology, let's start with a sample called PrimeCalculator.java to perform a series of work in a process. The unit of work is defined as find all prime numbers with a given integer range. Here is the source code of PrimeCalculator.java:

/* PrimeCalculator.java
 * Copyright (c) 2014, HerongYang.com, All Rights Reserved.
 */
public class PrimeCalculator extends Thread {
   public long longMax; // The maximum integer range to seach
   public long primeMax; // The maximum prime found
   public long primeCount; // The number of primes found
   public long jobCount; // The number of jobs done so far
   public static void main(String[] a) {
      long max = 1000; // Default integer range to search
      long interval = 1; // Default monitoring interval in seconds
      if (a.length>0) max = Long.parseLong(a[0]);
      if (a.length>1) interval = Long.parseLong(a[1]);
      System.out.println("Integer range to search: "+max);

      PrimeCalculator t = new PrimeCalculator(max);
      t.start();
      int i = 0;
      long startTime = System.currentTimeMillis();
      System.out.println(
         "Time, Count, Productivity, PrimeCount, PrimeMax");
      while (true) {
         try {
            sleep(interval*1000);
         } catch (InterruptedException e) {
            System.out.println("Monitor interrupted.");
         }
         long curTime = System.currentTimeMillis();
         long duration = (curTime - startTime)/1000;
         long productivity = t.jobCount/duration;
         System.out.println(duration+", "+t.jobCount
            +", "+productivity+", "+t.primeCount+", "+t.primeMax);
      }
   }
   public PrimeCalculator(long max) {
      longMax = max;
      primeCount = 0;
      primeMax = 0;
   }
   public void run() {
      jobCount = 0;
      while (true) {
      	 long count = 0;
      	 long max = 0;
         for (long i=3; i<=longMax; i++) {
            boolean isPrime = true;
            for (long j=2; j<=i/2 && isPrime; j++) {
               isPrime = i % j > 0;
            }
            if (isPrime) {
               count++;
               max = i;
            }
         }
      	 primeCount = count;
      	 primeMax = max;
         jobCount++;
      }
   }
}

Some notes on PrimeCalculator.java:

PrimeCalculator.java is designed as a Thread class, so it can be invoked as multithreading processes by a controlling program.
The run() method is designed to perform the work unit repeatedly in the endless while loop.
Work unit is to find all prime numbers in the given integer range, which uses CPU time only. No much memory is needed. No disk I/O operations and no database operations.
The main() method is designed to run the process as a single thread to verify the correctness of the process.

PrimeCalculator.java seems to be working correctly, as you can see from the following test results:

C:\>"\Program Files\java\jdk1.7.0_45\bin\javac" PrimeCalculator.java

C:\>"\Program Files\Java\jdk1.7.0_45\bin\java" PrimeCalculator 10
Integer range to search: 10
Time, Count, Productivity, PrimeCount, PrimeMax
1, 2157548, 2157151, 3, 7
2, 4424402, 2211945, 3, 7
3, 6682344, 2227439, 3, 7
4, 8939961, 2234982, 3, 7
5, 11208084, 2241519, 3, 7
...

C:\>"\Program Files\Java\jdk1.7.0_45\bin\java" PrimeCalculator 100
Integer range to search: 100
Time, Count, Productivity, PrimeCount, PrimeMax
1, 47040, 47039, 24, 97
2, 94461, 47229, 24, 97
3, 142121, 47373, 24, 97
4, 190369, 47592, 24, 97
5, 238784, 47756, 24, 97
...

C:\>"\Program Files\Java\jdk1.7.0_45\bin\java" PrimeCalculator 1000
Integer range to search: 1000
Time, Count, Productivity, PrimeCount, PrimeMax
1, 768, 768, 167, 997
2, 1602, 801, 167, 997
3, 2435, 811, 167, 997
4, 3266, 816, 167, 997
5, 4090, 818, 167, 997
6, 4922, 820, 167, 997
7, 5758, 822, 167, 997
8, 6588, 823, 167, 997
9, 7421, 824, 167, 997
10, 8254, 825, 167, 997
...

Last update: 2014.

Table of Contents

About This Book

Downloading and Installing JDK 1.8.0 on Windows

Downloading and Installing JDK 1.7.0 on Windows

java.lang.Runtime Class - The JVM Instance

java.lang.System Class - The Operating System

ClassLoader Class - Class Loaders

Class Class - Class Reflections

Sun's JVM - Java HotSpot VM

JRockit JVM 28.2.7 by Oracle Corporation

JVM Runtime Data Areas