Strange double calculation result with JDK 1.4.2

Question

Hi,
I've written a small benchmark to test the power of a Sharp Zaurus PDA. Wanting to compare it with my workstation, I ran it on the PC with JDK1.4.2 Beta and was really surprised to discover that the double calculation of Pi gave a non-correct result: Pi = 3.1413934230804443!!!
I've tried to isolate the bug without success at the moment. It only happens when run from the Zjb program in JDK1.4.2, either from the command line or from Eclipse.
The result is correct when run with JDK1.4.1, JDK1.4.1_01, JDK1.1.8 that are also setup on the PC. I extracted the faulty loop and executed the sniplet, but the result is OK. I added the previous lines (running the Ackerman function to test recursivity and stack management): still OK, from Eclipse and command line.
I think the problem must be a configuration one on my computer: a 2xPII 350, Win2K SP3. Perhaps the 1.4.2 JVM is using an old library... I can't imagine that the Beta JVM would have such problem.
Or there is a bug in the program which make the stack or the FPU registers break, but I can't find where: all other platforms I tested gave correct results.
Could someone with a JDK1.4.2 installation test my program and post what were the results for the Pi calculation?
The 10KB source is available on http://www.alterna.tv/zjb/Zjb.java
Thanks.

Answer 1

Yes, it was the Pentium, at the time when 100MHz was top speed...
My CPUs are supposed not to suffer from that old disease.
But if it were the case, new JVM can't drop software patches like this. Today, Intel started again the release of the new P4 at 3GHz, after adding a software patch for the hardware defect they had detected...
I post the code for my small program here as my Web site is frequently down this week:
import java.awt.BorderLayout;
import java.awt.Button;
import java.awt.Color;
import java.awt.Dialog;
import java.awt.Dimension;
import java.awt.FlowLayout;
import java.awt.Frame;
import java.awt.Graphics;
import java.awt.GridLayout;
import java.awt.Label;
import java.awt.List;
import java.awt.Panel;
import java.awt.TextField;
import java.awt.Toolkit;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.WindowAdapter;
import java.awt.event.WindowEvent;
import java.io.BufferedInputStream;
import java.io.BufferedOutputStream;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.math.BigInteger;
* Zjb: Zaurus Java Bechmark
* @author GenePi
class Zjb
     extends Frame
     static Zjb _mainWindow;
      * Number of benchmark runs.
     private final TextField _runs;
      * Results list
     private final List _results;
      * Wait, program is thinking...
     private final Label _wait;
      * Start button
     private final Button _start;
      * Benchmark running
     private volatile boolean _running = false;
      * Layout the main window.
     Zjb()
          super("Zaurus java benchmark 1.0");
          setLayout(new BorderLayout());
          // Input fields
          Panel top = new Panel(new GridLayout(1, 0));
          top.add(new Label("Number of runs"));
          _runs = new TextField("1");
          top.add(_runs);
          add(top, BorderLayout.NORTH);
          // Results list
          _results = new List();
          add(_results, BorderLayout.CENTER);
          // Start button
          final Panel bottom = new Panel(new FlowLayout(FlowLayout.RIGHT));
          _wait = new Label();
          bottom.add(_wait);
          _start = new Button("Start");
          _start.addActionListener(new ActionListener()
               public void actionPerformed(final ActionEvent evt)
                    if (!_running)
                         // Clear previous results and start benchmark.
                         _results.clear();
                         _start.setLabel("Stop");
                         _wait.setText("Running...          ");
                         bottom.validate();
                         _running = true;
                    else
                         _start.setLabel("Start");
                         _wait.setText("");
                         _running = false;
          bottom.add(_start);
          // Quit button
          final Button quit = new Button("Quit");
          quit.addActionListener(new ActionListener()
               public void actionPerformed(final ActionEvent evt)
                    System.exit(0);
          bottom.add(quit);
          add(bottom, BorderLayout.SOUTH);
          // Exit when main window closes
          addWindowListener(new WindowAdapter()
               public void windowClosing(final WindowEvent evt)
                    System.exit(0);
          Dimension dim = Toolkit.getDefaultToolkit().getScreenSize();
          setSize(dim);
          validate();
      * The benchmarks
      * @param runs Number of runs
     private static void runBenchmarks(final int runs)
          long start;
          long end;
          long totalStart;
          long totalEnd;
          // Integer arithmetic
          start = System.currentTimeMillis();
          totalStart = start;
          int resultInt = 0;
          for (int i = 0; i < runs; i++)
               resultInt = ackerman(3, 9);
               // resultInt = ackerman(3, 7);
          end = System.currentTimeMillis();
          _mainWindow._results.add("Integer arithmetic: " + ((end - start) / 1000.0) + " s [Ack(3,9)=" + resultInt + "]");
          if (!_mainWindow._running)
               return;
          // Float and double
          start = System.currentTimeMillis();
          double resultDouble = 0.0;
          for (int i = 0; i < runs; i++)
               resultDouble = 0.0;
               for (int j = 1; j < 1000000; j++)
                    resultDouble += 1.0 / ((double) j * (double) j);
               System.out.println("resultDouble=" + resultDouble);
               resultDouble = Math.sqrt(resultDouble * 6.0);
          end = System.currentTimeMillis();
          _mainWindow._results.add("Double arithmetic: " + ((end - start) / 1000.0) + " s [Pi=" + resultDouble + "]");
          if (!_mainWindow._running)
               return;
          // Big operations
          start = System.currentTimeMillis();
          BigInteger resultBig = new BigInteger("1");
          for (int i = 0; i < runs; i++)
               resultBig = fact(3000);
          end = System.currentTimeMillis();
          _mainWindow._results.add("Infinite arithmetic: " + ((end - start) / 1000.0) + " s [3000!=" + resultBig.toString().substring(1, 20) + "...]");
          if (!_mainWindow._running)
               return;
          // Strings
          start = System.currentTimeMillis();
          String resultString = null;
          for (int i = 0; i < runs; i++)
               final String alphabet = " qwertyuioplkjhgfdsazxcvbnm0789456123./*";
               StringBuffer buf = new StringBuffer();
               for (int j = 0; j < 100000; j++)
                    int pos = j % alphabet.length();
                    buf.append(alphabet.substring(pos, pos + 1));
               resultString = buf.toString();
          end = System.currentTimeMillis();
          _mainWindow._results.add("Strings: " + ((end - start) / 1000.0) + " s [" + resultString.substring(1, 20) + "...]");
          if (!_mainWindow._running)
               return;
          // Drawing
          start = System.currentTimeMillis();
          for (int i = 0; i < runs; i++)
               final int size = 200;
               Dialog dialog = new Dialog(_mainWindow, "Drawing...", true);
               dialog.add(new TestPanel(dialog));
               dialog.setSize(size, size);
               dialog.show();
          end = System.currentTimeMillis();
          _mainWindow._results.add("Drawing: " + ((end - start) / 1000.0) + " s");
          if (!_mainWindow._running)
               return;
          // File copy
          start = System.currentTimeMillis();
          String resultIO = "OK";
          loopIO:
          for (int i = 0; i < runs; i++)
               final String tempName = "/tmp/Zjb.tmp";
               try
                    BufferedOutputStream out = new BufferedOutputStream(new FileOutputStream(tempName));
                    for (int j = 0; j < 1000000; j++)
                         out.write((byte) j);
                    out.close();
                    BufferedInputStream in = new BufferedInputStream(new FileInputStream(tempName));
                    for (int j = 0; j < 1000000; j++)
                         int r = in.read();
                         if ((byte) r != (byte) j)
                              resultIO = "Failed";
                              System.err.println("Content mismatch at " + j);
                              break loopIO;
                    in.close();
                    new File(tempName).delete();
               catch(IOException ioe)
                    resultIO = "Failed";
                    System.err.println(ioe);
                    break loopIO;
          end = System.currentTimeMillis();
          _mainWindow._results.add("Files I/O: " + ((end - start) / 1000.0) + " s [1MB written/read/deleted: " + resultIO + "]");
          totalEnd = end;
          _mainWindow._results.add("");
          _mainWindow._results.add("Total: " + ((totalEnd - totalStart) / 1000.0) + " s");
      * Utility functions: Ackerman function
      * @param m
      * @param n
     private static int ackerman(final int m, final int n)
          if (m == 0)
               return (n + 1);
          else if (n == 0)
               return (ackerman(m - 1, 1));
          else
               return ackerman(m - 1, ackerman(m, (n - 1)));
      * Factorial of big numbers.
      * @param n
      * @return
     private static BigInteger fact(final int n)
          final BigInteger one = new BigInteger("1");
          BigInteger num = new BigInteger("1");
          BigInteger fact = new BigInteger("1");
          for (int i = 2; i <= n; i++)
               num = num.add(one);
               fact = fact.multiply(num);
          return fact;
      * Benchmark entry point.
      * @param args Command line arguments
     public static void main(String[] args)
          _mainWindow = new Zjb();
          _mainWindow.show();
          synchronized (Zjb.class)
               while (true)
                    try
                         Zjb.class.wait(500L);
                    catch (InterruptedException ie)
                         // Wake
                    if (_mainWindow._running)
                         try
                              runBenchmarks(Integer.parseInt(_mainWindow._runs.getText()));
                         catch (NumberFormatException nfe)
                              _mainWindow._runs.setText("1");
                              runBenchmarks(1);
                         _mainWindow._running = false;
                         _mainWindow._start.setLabel("Start");
                         _mainWindow._wait.setText("");
class TestPanel
     extends Panel
      * The dialog containing the panel.
     private final Dialog _dialog;
     TestPanel(final Dialog dialog)
          _dialog = dialog;
     public void paint(final Graphics g)
          Dimension dim = getSize();
          g.setColor(Color.white);
          g.fillRect(0, 0, dim.width, dim.height);
          for (int i = 0; i < 1000; i++)
               Color color = new Color((int) (Math.random() * Integer.MAX_VALUE));
               int x = (int) (Math.random() * dim.width);
               int y = (int) (Math.random() * dim.height);
               int width = (int) (Math.random() * dim.width);
               int height = (int) (Math.random() * dim.height);
               g.setColor(color);
               g.fillRect(x, y, width, height);
          g.setColor(Color.white);
          g.fillRect(0, 0, dim.width, dim.height);
          for (int i = 0; i < 1000; i++)
               Color color = new Color((int) (Math.random() * Integer.MAX_VALUE));
               int x = (int) (Math.random() * dim.width);
               int y = (int) (Math.random() * dim.height);
               int width = (int) (Math.random() * dim.width);
               int height = (int) (Math.random() * dim.height);
               g.setColor(color);
               g.fillOval(x, y, width, height);
          // Hide dialog when finished
          _dialog.hide();
}