Java example source code file (Test.java)

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divisor, exception, net, network, runnable, test, throwable, urlclassloader, verbose

The Test.java Java example source code

/*
 * Copyright (c) 2010, Oracle and/or its affiliates. All rights reserved.
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 only, as
 * published by the Free Software Foundation.
 *
 * This code is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 *
 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
 * or visit www.oracle.com if you need additional information or have any
 * questions.
 */

/**
 * @test
 * @bug 6603011
 * @summary long/int division by constant
 *
 * @run main/othervm -Xcomp -Xbatch -XX:-Inline Test
 */

//
// -XX:-Inline is essential to this test so that verification functions
//   divi, modi, divl and modl generate "plain" divides.
// -Xcomp -Xbatch are also useful to ensure the full range of
//   dividend and divisor combinations are tested
//

import java.net.*;

class s {
  static int  divi(int  dividend, int  divisor) { return dividend / divisor; }
  static int  modi(int  dividend, int  divisor) { return dividend % divisor; }
  static long divl(long dividend, long divisor) { return dividend / divisor; }
  static long modl(long dividend, long divisor) { return dividend % divisor; }
}

public class Test implements Runnable {
  // Report verbose messages on failure; turn off to suppress
  // too much output with gross numbers of failures.
  static final boolean VERBOSE = true;

  // Initailize DIVISOR so that it is final in this class.
  static final int DIVISOR;
  static {
    int value = 0;
    try {
      value = Integer.decode(System.getProperty("divisor"));
    } catch (Throwable e) {
    }
    DIVISOR = value;
  }

  // The methods of interest. We want the JIT to compile these
  // and convert the divide into a multiply.
  public int divbyI (int dividend)   { return dividend / DIVISOR; }
  public int modbyI (int dividend)   { return dividend % DIVISOR; }
  public long divbyL (long dividend) { return dividend / DIVISOR; }
  public long modbyL (long dividend) { return dividend % DIVISOR; }

  public int divisor() { return DIVISOR; }

  public boolean checkI (int dividend) {
    int quo = divbyI(dividend);
    int rem = modbyI(dividend);
    int quo0 = s.divi(dividend, divisor());
    int rem0 = s.modi(dividend, divisor());

    if (quo != quo0 || rem != rem0) {
      if (VERBOSE) {
        System.out.println("Computed: " + dividend + " / " + divisor() + " = " +
                           quo  + ", " + dividend + " % " + divisor() + " = " + rem );
        System.out.println("expected: " + dividend + " / " + divisor() + " = " +
                           quo0 + ", " + dividend + " % " + divisor() + " = " + rem0);
        // Report sign of rem failure
        if (rem != 0 && (rem ^ dividend) < 0) {
          System.out.println("  rem & dividend have different signs");
        }
        // Report range of rem failure
        if (java.lang.Math.abs(rem) >= java.lang.Math.abs(divisor())) {
          System.out.println("  remainder out of range");
        }
        // Report quo/rem identity relationship failure
        if ((quo * divisor()) + rem != dividend) {
          System.out.println("  quotien/remainder invariant broken");
        }
      }
      return false;
    }
    return true;
  }

  public boolean checkL (long dividend) {
    long quo = divbyL(dividend);
    long rem = modbyL(dividend);
    long quo0 = s.divl(dividend, divisor());
    long rem0 = s.modl(dividend, divisor());

    if (quo != quo0 || rem != rem0) {
      if (VERBOSE) {
        System.out.println("Computed: " + dividend + " / " + divisor() + " = " +
                           quo  + ", " + dividend + " % " + divisor() + " = " + rem );
        System.out.println("expected: " + dividend + " / " + divisor() + " = " +
                           quo0 + ", " + dividend + " % " + divisor() + " = " + rem0);
        // Report sign of rem failure
        if (rem != 0 && (rem ^ dividend) < 0) {
          System.out.println("  rem & dividend have different signs");
        }
        // Report range of rem failure
        if (java.lang.Math.abs(rem) >= java.lang.Math.abs(divisor())) {
          System.out.println("  remainder out of range");
        }
        // Report quo/rem identity relationship failure
        if ((quo * divisor()) + rem != dividend) {
          System.out.println(" (" + quo + " * " + divisor() + ") + " + rem + " != "
                             + dividend);
        }
      }
      return false;
    }
    return true;
  }

  public void run() {
    // Don't try to divide by zero
    if (divisor() == 0) return;

    // Range of dividends to check. Try dividends from start to end
    // inclusive, as well as variations on those values as shifted
    // left.
    int start = -1024;
    int end = 1024;

    // Test int division using a variety of dividends.
    int wrong = 0;
    int total = 0;

    outerloop:
    for (int i = start; i <= end; i++) {
      for (int s = 0; s < 32; s += 4) {
        total++;
        int dividend = i << s;
        if (!checkI(dividend)) {
          wrong++;
          // Stop on the first failure
          // break outerloop;
        }
      }
    }
    if (wrong > 0) {
      System.out.println("divisor " + divisor() + ": " +
                         wrong + "/" + total + " wrong int divisions");
    }

    // Test long division using a variety of dividends.
    wrong = 0;
    total = 0;

    outerloop:
    for (int i = start; i <= end; i++) {
      for (int s = 0; s < 64; s += 4) {
        total++;
        long dividend = ((long)i) << s;
        if (!checkL(dividend)) {
          wrong++;
          // Stop on the first failure
          // break outerloop;
        }
      }
    }
    if (wrong > 0) {
      System.out.println("divisor " + divisor() + ": " +
                         wrong + "/" + total + " wrong long divisions");
    }

  }

  // Reload this class with the "divisor" property set to the input parameter.
  // This allows the JIT to see q.DIVISOR as a final constant, and change
  // any divisions or mod operations into multiplies.
  public static void test_divisor(int divisor,
                                  URLClassLoader apploader) throws Exception {
    System.setProperty("divisor", "" + divisor);
    ClassLoader loader = new URLClassLoader(apploader.getURLs(),
                                            apploader.getParent());
    Class c = loader.loadClass("Test");
    Runnable r = (Runnable)c.newInstance();
    r.run();
  }

  public static void main(String[] args) throws Exception {
    Class cl = Class.forName("Test");
    URLClassLoader apploader = (URLClassLoader)cl.getClassLoader();


    // Test every divisor between -100 and 100.
    for (int i = -100; i <= 100; i++) {
      test_divisor(i, apploader);
    }

    // Try a few divisors outside the typical range.
    // The values below have been observed in rt.jar.
    test_divisor(101, apploader);
    test_divisor(400, apploader);
    test_divisor(1000, apploader);
    test_divisor(3600, apploader);
    test_divisor(9973, apploader);
    test_divisor(86400, apploader);
    test_divisor(1000000, apploader);
  }

}