/*

 * Copyright (c) 2007, 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

 * @summary micro-benchmark correctness mode

 * @run main IteratorMicroBenchmark iterations=1 size=8 warmup=0

 */

import static java.util.stream.Collectors.toList;

import java.lang.ref.WeakReference;

import java.util.ArrayDeque;

import java.util.ArrayList;

import java.util.Arrays;

import java.util.Enumeration;

import java.util.Iterator;

import java.util.List;

import java.util.ListIterator;

import java.util.Map;

import java.util.Spliterator;

import java.util.Vector;

import java.util.concurrent.ConcurrentSkipListMap;

import java.util.concurrent.CountDownLatch;

import java.util.concurrent.ThreadLocalRandom;

import java.util.concurrent.TimeUnit;

import java.util.regex.Pattern;

/**

 * Usage: [iterations=N] [size=N] [filter=REGEXP] [warmup=SECONDS]

 *

 * To run this in micro-benchmark mode, simply run as a normal java program.

 * Be patient; this program runs for a very long time.

 * For faster runs, restrict execution using command line args.

 *

 * @author Martin Buchholz

 */

public class IteratorMicroBenchmark {

    abstract static class Job {

        private final String name;

        public Job(String name) { this.name = name; }

        public String name() { return name; }

        public abstract void work() throws Throwable;

    }

    static double warmupSeconds;

    static long warmupNanos;

    // --------------- GC finalization infrastructure ---------------

    /** No guarantees, but effective in practice. */

    static void forceFullGc() {

        CountDownLatch finalizeDone = new CountDownLatch(1);

        WeakReference<?> ref = new WeakReference<Object>(new Object() {

            protected void finalize() { finalizeDone.countDown(); }});

        try {

            for (int i = 0; i < 10; i++) {

                System.gc();

                if (finalizeDone.await(1L, TimeUnit.SECONDS) && ref.get() == null) {

                    System.runFinalization(); // try to pick up stragglers

                    return;

                }

            }

        } catch (InterruptedException unexpected) {

            throw new AssertionError("unexpected InterruptedException");

        }

        throw new AssertionError("failed to do a \"full\" gc");

    }

    /**

     * Runs each job for long enough that all the runtime compilers

     * have had plenty of time to warm up, i.e. get around to

     * compiling everything worth compiling.

     * Returns array of average times per job per run.

     */

    private static long[] time0(Job ... jobs) throws Throwable {

        long[] nanoss = new long[jobs.length];

        for (int i = 0; i < jobs.length; i++) {

            if (warmupNanos > 0) forceFullGc();

            Job job = jobs[i];

            long totalTime;

            int runs = 0;

            long startTime = System.nanoTime();

            do { job.work(); runs++; }

            while ((totalTime = System.nanoTime() - startTime) < warmupNanos);

            nanoss[i] = totalTime/runs;

        }

        return nanoss;

    }

    private static void time(Job ... jobs) throws Throwable {

        if (warmupSeconds > 0.0) time0(jobs); // Warm up run

        long[] nanoss = time0(jobs); // Real timing run

        long[] milliss = new long[jobs.length];

        double[] ratios = new double[jobs.length];

        final String nameHeader   = "Method";

        final String millisHeader = "Millis";

        final String ratioHeader  = "Ratio";

        int nameWidth   = nameHeader.length();

        int millisWidth = millisHeader.length();

        int ratioWidth  = ratioHeader.length();

        for (int i = 0; i < jobs.length; i++) {

            nameWidth = Math.max(nameWidth, jobs[i].name().length());

            milliss[i] = nanoss[i]/(1000L * 1000L);

            millisWidth = Math.max(millisWidth,

                                   String.format("%d", milliss[i]).length());

            ratios[i] = (double) nanoss[i] / (double) nanoss[0];

            ratioWidth = Math.max(ratioWidth,

                                  String.format("%.3f", ratios[i]).length());

        }

        String format = String.format("%%-%ds %%%dd %%%d.3f%%n",

                                      nameWidth, millisWidth, ratioWidth);

        String headerFormat = String.format("%%-%ds %%%ds %%%ds%%n",

                                            nameWidth, millisWidth, ratioWidth);

        System.out.printf(headerFormat, "Method", "Millis", "Ratio");

        // Print out absolute and relative times, calibrated against first job

        for (int i = 0; i < jobs.length; i++)

            System.out.printf(format, jobs[i].name(), milliss[i], ratios[i]);

    }

    private static String keywordValue(String[] args, String keyword) {

        for (String arg : args)

            if (arg.startsWith(keyword))

                return arg.substring(keyword.length() + 1);

        return null;

    }

    private static int intArg(String[] args, String keyword, int defaultValue) {

        String val = keywordValue(args, keyword);

        return (val == null) ? defaultValue : Integer.parseInt(val);

    }

    private static double doubleArg(String[] args, String keyword, double defaultValue) {

        String val = keywordValue(args, keyword);

        return (val == null) ? defaultValue : Double.parseDouble(val);

    }

    private static Pattern patternArg(String[] args, String keyword) {

        String val = keywordValue(args, keyword);

        return (val == null) ? null : Pattern.compile(val);

    }

    private static Job[] filter(Pattern filter, Job[] jobs) {

        return (filter == null) ? jobs

            : Arrays.stream(jobs)

            .filter(job -> filter.matcher(job.name()).find())

            .collect(toList())

            .toArray(new Job[0]);

    }

    private static void deoptimize(int sum) {

        if (sum == 42)

            System.out.println("the answer");

    }

    private static <T> List<T> asSubList(List<T> list) {

        return list.subList(0, list.size());

    }

    private static <T> Iterable<T> backwards(final List<T> list) {

        return new Iterable<T>() {

            public Iterator<T> iterator() {

                return new Iterator<T>() {

                    final ListIterator<T> it = list.listIterator(list.size());

                    public boolean hasNext() { return it.hasPrevious(); }

                    public T next()          { return it.previous(); }

                    public void remove()     {        it.remove(); }};}};

    }

    public static void main(String[] args) throws Throwable {

        final int iterations = intArg(args, "iterations", 100_000);

        final int size       = intArg(args, "size", 1000);

        warmupSeconds        = doubleArg(args, "warmup", 7.0);

        final Pattern filter = patternArg(args, "filter");

        warmupNanos = (long) (warmupSeconds * (1000L * 1000L * 1000L));

//         System.out.printf(

//             "iterations=%d size=%d, warmup=%1g, filter=\"%s\"%n",

//             iterations, size, warmupSeconds, filter);

        final ConcurrentSkipListMap<Integer,Integer> m

            = new ConcurrentSkipListMap<>();

        final ArrayList<Integer> al = new ArrayList<>(size);

        // Populate collections with random data

        final ThreadLocalRandom rnd = ThreadLocalRandom.current();

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

            m.put(rnd.nextInt(size), rnd.nextInt(size));

            al.add(rnd.nextInt(size));

        }

        final Vector<Integer> v = new Vector<>(al);

        final ArrayDeque<Integer> ad = new ArrayDeque<>(al);

        // shuffle ArrayDeque elements so they wrap

        for (int i = 0, n = rnd.nextInt(size); i < n; i++)

            ad.addLast(ad.removeFirst());

        // Also test "short" collections

        final int shortSize = 5;

        final Vector<Integer> sv = new Vector<>(v.subList(0, shortSize));

        final ArrayList<Integer> sal = new ArrayList<>(sv);

        // Checks for correctness *and* prevents loop optimizations

        class Check {

            private int sum;

            public void sum(int sum) {

                if (this.sum == 0)

                    this.sum = sum;

                if (this.sum != sum)

                    throw new AssertionError("Sum mismatch");

            }

        }

        final Check check      = new Check();

        final Check shortCheck = new Check();

        Job[] jobs = {

//          new Job("Vector iterate desugared") {

//              public void work() throws Throwable {

//                  for (int i = 0; i < iterations; i++) {

//                      int sum = 0;

//                      for (Iterator<Integer> it = v.iterator(); it.hasNext();)

//                          sum += it.next();

//                      check.sum(sum);}}},

            new Job("array loop") {

                public void work() throws Throwable {

                    Integer[] a = al.toArray(new Integer[0]);

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

                        int sum = 0;

                        int size = a.length;

                        for (int j = 0; j < size; ++j)

                            sum += a[j];

                        check.sum(sum);}}},

            new Job("descending array loop") {

                public void work() throws Throwable {

                    Integer[] a = al.toArray(new Integer[0]);

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

                        int sum = 0;

                        int size = a.length;

                        for (int j = size - 1; j >= 0; j--)

                            sum += a[j];

                        check.sum(sum);}}},

            new Job("Vector get loop") {

                public void work() throws Throwable {

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

                        int sum = 0;

                        int size = v.size();

                        for (int j = 0; j < size; ++j)

                            sum += v.get(j);

                        check.sum(sum);}}},

            new Job("Vector iterate for loop") {

                public void work() throws Throwable {

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

                        int sum = 0;

                        for (Integer n : v)

                            sum += n;

                        check.sum(sum);}}},

            new Job("Vector descending listIterator loop") {

                public void work() throws Throwable {

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

                        int sum = 0;

                        ListIterator<Integer> it = v.listIterator(al.size());

                        while (it.hasPrevious())

                            sum += it.previous();

                        check.sum(sum);}}},

            new Job("Vector Enumeration loop") {

                public void work() throws Throwable {

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

                        int sum = 0;

                        Enumeration<Integer> it = v.elements();

                        while (it.hasMoreElements())

                            sum += it.nextElement();

                        check.sum(sum);}}},

            new Job("Vector subList iterate for loop") {

                public void work() throws Throwable {

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

                        int sum = 0;

                        for (Integer n : asSubList(v))

                            sum += n;

                        check.sum(sum);}}},

            new Job("Vector subList subList subList iterate for loop") {

                public void work() throws Throwable {

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

                        int sum = 0;

                        for (Integer n : asSubList(asSubList(asSubList(v))))

                            sum += n;

                        check.sum(sum);}}},

            new Job("Vector backwards wrapper ListIterator for loop") {

                public void work() throws Throwable {

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

                        int sum = 0;

                        for (Integer n : backwards(v))

                            sum += n;

                        check.sum(sum);}}},

            new Job("Vector backwards wrapper subList ListIterator for loop") {

                public void work() throws Throwable {

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

                        int sum = 0;

                        for (Integer n : backwards(asSubList(v)))

                            sum += n;

                        check.sum(sum);}}},

//          new Job("Vector iterate for loop invokeinterface") {

//              public void work() throws Throwable {

//                  final List<Integer> l = v;

//                  for (int i = 0; i < iterations; i++) {

//                      int sum = 0;

//                      for (Integer n : l)

//                          sum += n;

//                      check.sum(sum);}}},

//          new Job("Vector subList iterate for loop invokeinterface") {

//              public void work() throws Throwable {

//                  final List<Integer> l = v;

//                  for (int i = 0; i < iterations; i++) {

//                      int sum = 0;

//                      for (Integer n : asSubList(l))

//                          sum += n;

//                      check.sum(sum);}}},

            new Job("Short Vector get loop") {

                public void work() throws Throwable {

                    for (int i = 0; i < (iterations * size / shortSize); i++) {

                        int sum = 0;

                        int size = sv.size();

                        for (int j = 0; j < size; ++j)

                            sum += sv.get(j);

                        shortCheck.sum(sum);}}},

            new Job("Short Vector iterate for loop") {

                public void work() throws Throwable {

                    for (int i = 0; i < (iterations * size / shortSize); i++) {

                        int sum = 0;

                        for (Integer n : sv)

                            sum += n;

                        shortCheck.sum(sum);}}},

            new Job("Short Vector sublist iterate for loop") {

                public void work() throws Throwable {

                    for (int i = 0; i < (iterations * size / shortSize); i++) {

                        int sum = 0;

                        for (Integer n : asSubList(sv))

                            sum += n;

                        shortCheck.sum(sum);}}},

            new Job("ArrayList get loop") {

                public void work() throws Throwable {

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

                        int sum = 0;

                        int size = al.size();

                        for (int j = 0; j < size; ++j)

                            sum += al.get(j);

                        check.sum(sum);}}},

            new Job("ArrayList iterate for loop") {

                public void work() throws Throwable {

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

                        int sum = 0;

                        for (Integer n : al)

                            sum += n;

                        check.sum(sum);}}},

            new Job("ArrayDeque iterate for loop") {

                public void work() throws Throwable {

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

                        int sum = 0;

                        for (Integer n : ad)

                            sum += n;

                        check.sum(sum);}}},

            new Job("ArrayList descending listIterator loop") {

                public void work() throws Throwable {

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

                        int sum = 0;

                        ListIterator<Integer> it = al.listIterator(al.size());

                        while (it.hasPrevious())

                            sum += it.previous();

                        check.sum(sum);}}},

            new Job("ArrayList listIterator loop") {

                public void work() throws Throwable {

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

                        int sum = 0;

                        ListIterator<Integer> it = al.listIterator();

                        while (it.hasNext())

                            sum += it.next();

                        check.sum(sum);}}},

            new Job("ArrayDeque.descendingIterator() loop") {

                public void work() throws Throwable {

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

                        int sum = 0;

                        Iterator<Integer> it = ad.descendingIterator();

                        while (it.hasNext())

                            sum += it.next();

                        check.sum(sum);}}},

            new Job("ArrayList.forEach") {

                public void work() throws Throwable {

                    int[] sum = new int[1];

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

                        sum[0] = 0;

                        al.forEach(n -> sum[0] += n);

                        check.sum(sum[0]);}}},

            new Job("ArrayDeque.forEach") {

                public void work() throws Throwable {

                    int[] sum = new int[1];

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

                        sum[0] = 0;

                        ad.forEach(n -> sum[0] += n);

                        check.sum(sum[0]);}}},

            new Job("Vector.forEach") {

                public void work() throws Throwable {

                    int[] sum = new int[1];

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

                        sum[0] = 0;

                        v.forEach(n -> sum[0] += n);

                        check.sum(sum[0]);}}},

            new Job("ArrayList.iterator().forEachRemaining()") {

                public void work() throws Throwable {

                    int[] sum = new int[1];

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

                        sum[0] = 0;

                        al.iterator().forEachRemaining(n -> sum[0] += n);

                        check.sum(sum[0]);}}},

            new Job("ArrayDeque.descendingIterator().forEachRemaining()") {

                public void work() throws Throwable {

                    int[] sum = new int[1];

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

                        sum[0] = 0;

                        ad.descendingIterator().forEachRemaining(n -> sum[0] += n);

                        check.sum(sum[0]);}}},

            new Job("ArrayDeque.iterator().forEachRemaining()") {

                public void work() throws Throwable {

                    int[] sum = new int[1];

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

                        sum[0] = 0;

                        ad.iterator().forEachRemaining(n -> sum[0] += n);

                        check.sum(sum[0]);}}},

            new Job("Vector.iterator().forEachRemaining()") {

                public void work() throws Throwable {

                    int[] sum = new int[1];

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

                        sum[0] = 0;

                        v.iterator().forEachRemaining(n -> sum[0] += n);

                        check.sum(sum[0]);}}},

            new Job("ArrayList.spliterator().forEachRemaining()") {

                public void work() throws Throwable {

                    int[] sum = new int[1];

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

                        sum[0] = 0;

                        al.spliterator().forEachRemaining(n -> sum[0] += n);

                        check.sum(sum[0]);}}},

            new Job("ArrayDeque.spliterator().forEachRemaining()") {

                public void work() throws Throwable {

                    int[] sum = new int[1];

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

                        sum[0] = 0;

                        ad.spliterator().forEachRemaining(n -> sum[0] += n);

                        check.sum(sum[0]);}}},

            new Job("Vector.spliterator().forEachRemaining()") {

                public void work() throws Throwable {

                    int[] sum = new int[1];

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

                        sum[0] = 0;

                        v.spliterator().forEachRemaining(n -> sum[0] += n);

                        check.sum(sum[0]);}}},

            new Job("ArrayList.spliterator().tryAdvance()") {

                public void work() throws Throwable {

                    int[] sum = new int[1];

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

                        sum[0] = 0;

                        Spliterator<Integer> spliterator = al.spliterator();

                        do {} while (spliterator.tryAdvance(n -> sum[0] += n));

                        check.sum(sum[0]);}}},

            new Job("ArrayDeque.spliterator().tryAdvance()") {

                public void work() throws Throwable {

                    int[] sum = new int[1];

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

                        sum[0] = 0;

                        Spliterator<Integer> spliterator = ad.spliterator();

                        do {} while (spliterator.tryAdvance(n -> sum[0] += n));

                        check.sum(sum[0]);}}},

            new Job("Vector.spliterator().tryAdvance()") {

                public void work() throws Throwable {

                    int[] sum = new int[1];

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

                        sum[0] = 0;

                        Spliterator<Integer> spliterator = v.spliterator();

                        do {} while (spliterator.tryAdvance(n -> sum[0] += n));

                        check.sum(sum[0]);}}},

            new Job("ArrayList.removeIf") {

                public void work() throws Throwable {

                    int[] sum = new int[1];

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

                        sum[0] = 0;

                        al.removeIf(n -> { sum[0] += n; return false; });