/*

 * Copyright (c) 2018, Google 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.

 */

package MyPackage;

/**

 * @test

 * @build Frame HeapMonitor

 * @compile HeapMonitorStatArrayCorrectnessTest.java

 * @run main/othervm/native -agentlib:HeapMonitorTest MyPackage.HeapMonitorStatArrayCorrectnessTest

 */

public class HeapMonitorStatArrayCorrectnessTest {

  // Do 100000 iterations and expect maxIteration / multiplier samples.

  private static final int maxIteration = 100000;

  private static int array[];

  private static void allocate(int size) {

    for (int j = 0; j < maxIteration; j++) {

      array = new int[size];

    }

  }

  public static void main(String[] args) {

    int sizes[] = {1000, 10000, 100000};

    for (int currentSize : sizes) {

      System.out.println("Testing size " + currentSize);

      HeapMonitor.resetEventStorage();

      if (!HeapMonitor.eventStorageIsEmpty()) {

        throw new RuntimeException("Should not have any events stored yet.");

      }

      HeapMonitor.enableSamplingEvents();

      // 111 is as good a number as any.

      final int samplingMultiplier = 111;

      allocate(currentSize);

      HeapMonitor.disableSamplingEvents();

      // For simplifications, we ignore the array memory usage for array internals (with the array

      // sizes requested, it should be a negligible oversight).

      //

      // That means that with maxIterations, the loop in the method allocate requests:

      //    maxIterations * currentSize * 4 bytes (4 for integers)

      //

      // Via the enable sampling, the code requests a sample every samplingMultiplier * currentSize bytes.

      //

      // Therefore, the expected sample number is:

      //   (maxIterations * currentSize * 4) / (samplingMultiplier * currentSize);

      double expected = maxIteration;

      expected *= 4;

      expected /= samplingMultiplier;

      // 10% error ensures a sanity test without becoming flaky.

      // unlucky and not achieve the mean average fast enough for the test case.

      if (!HeapMonitor.statsHaveExpectedNumberSamples((int) expected, 10)) {

        throw new RuntimeException("Statistics should show about " + expected + " samples.");

      }

    }

  }

}