/*

 * 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

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 */

/*

 * This file is available under and governed by the GNU General Public

 * License version 2 only, as published by the Free Software Foundation.

 * However, the following notice accompanied the original version of this

 * file:

 *

 * Written by Doug Lea with assistance from members of JCP JSR-166

 * Expert Group and released to the public domain, as explained at

 * http://creativecommons.org/publicdomain/zero/1.0/

 */

import java.util.concurrent.Executors;

import java.util.concurrent.ExecutorService;

import java.util.concurrent.Phaser;

import java.util.concurrent.ThreadLocalRandom;

import java.util.concurrent.atomic.DoubleAccumulator;

import junit.framework.Test;

import junit.framework.TestSuite;

public class DoubleAccumulatorTest extends JSR166TestCase {

    public static void main(String[] args) {

        main(suite(), args);

    }

    public static Test suite() {

        return new TestSuite(DoubleAccumulatorTest.class);

    }

    /**

     * new instance initialized to supplied identity

     */

    public void testConstructor() {

        for (double identity : new double[] {

                 Double.NEGATIVE_INFINITY,

                 Double.POSITIVE_INFINITY,

                 Double.MIN_VALUE,

                 Double.MAX_VALUE,

                 0.0,

             })

            assertEquals(identity,

                         new DoubleAccumulator(Double::max, identity).get());

    }

    /**

     * accumulate accumulates given value to current, and get returns current value

     */

    public void testAccumulateAndGet() {

        DoubleAccumulator acc = new DoubleAccumulator(Double::max, 0.0);

        acc.accumulate(2.0);

        assertEquals(2.0, acc.get());

        acc.accumulate(-4.0);

        assertEquals(2.0, acc.get());

        acc.accumulate(4.0);

        assertEquals(4.0, acc.get());

    }

    /**

     * reset() causes subsequent get() to return zero

     */

    public void testReset() {

        DoubleAccumulator acc = new DoubleAccumulator(Double::max, 0.0);

        acc.accumulate(2.0);

        assertEquals(2.0, acc.get());

        acc.reset();

        assertEquals(0.0, acc.get());

    }

    /**

     * getThenReset() returns current value; subsequent get() returns zero

     */

    public void testGetThenReset() {

        DoubleAccumulator acc = new DoubleAccumulator(Double::max, 0.0);

        acc.accumulate(2.0);

        assertEquals(2.0, acc.get());

        assertEquals(2.0, acc.getThenReset());

        assertEquals(0.0, acc.get());

    }

    /**

     * toString returns current value.

     */

    public void testToString() {

        DoubleAccumulator acc = new DoubleAccumulator(Double::max, 0.0);

        assertEquals("0.0", acc.toString());

        acc.accumulate(1.0);

        assertEquals(Double.toString(1.0), acc.toString());

    }

    /**

     * intValue returns current value.

     */

    public void testIntValue() {

        DoubleAccumulator acc = new DoubleAccumulator(Double::max, 0.0);

        assertEquals(0, acc.intValue());

        acc.accumulate(1.0);

        assertEquals(1, acc.intValue());

    }

    /**

     * longValue returns current value.

     */

    public void testLongValue() {

        DoubleAccumulator acc = new DoubleAccumulator(Double::max, 0.0);

        assertEquals(0, acc.longValue());

        acc.accumulate(1.0);

        assertEquals(1, acc.longValue());

    }

    /**

     * floatValue returns current value.

     */

    public void testFloatValue() {

        DoubleAccumulator acc = new DoubleAccumulator(Double::max, 0.0);

        assertEquals(0.0f, acc.floatValue());

        acc.accumulate(1.0);

        assertEquals(1.0f, acc.floatValue());

    }

    /**

     * doubleValue returns current value.

     */

    public void testDoubleValue() {

        DoubleAccumulator acc = new DoubleAccumulator(Double::max, 0.0);

        assertEquals(0.0, acc.doubleValue());

        acc.accumulate(1.0);

        assertEquals(1.0, acc.doubleValue());

    }

    /**

     * accumulates by multiple threads produce correct result

     */

    public void testAccumulateAndGetMT() {

        final DoubleAccumulator acc

            = new DoubleAccumulator((x, y) -> x + y, 0.0);

        final int nThreads = ThreadLocalRandom.current().nextInt(1, 5);

        final Phaser phaser = new Phaser(nThreads + 1);

        final double total = nThreads * incs/2.0 * (incs - 1); // Gauss

        final Runnable task = () -> {

            phaser.arriveAndAwaitAdvance();

            for (int i = 0; i < incs; i++) {

                acc.accumulate((double) i);

                assertTrue(acc.get() <= total);

            }

            phaser.arrive();

        };

        final ExecutorService p = Executors.newCachedThreadPool();

        try (PoolCleaner cleaner = cleaner(p)) {

            for (int i = nThreads; i-->0; )

                p.execute(task);

            phaser.arriveAndAwaitAdvance();

            phaser.arriveAndAwaitAdvance();

            assertEquals(total, acc.get());

        }

    }

}