/*

 * 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.concurrent.TimeUnit.MILLISECONDS;

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

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

import java.lang.ref.ReferenceQueue;

import java.lang.ref.WeakReference;

import java.util.ArrayDeque;

import java.util.Arrays;

import java.util.ArrayList;

import java.util.Collection;

import java.util.Collections;

import java.util.Deque;

import java.util.HashMap;

import java.util.Iterator;

import java.util.LinkedList;

import java.util.List;

import java.util.ListIterator;

import java.util.PriorityQueue;

import java.util.Spliterator;

import java.util.Vector;

import java.util.concurrent.ArrayBlockingQueue;

import java.util.concurrent.ConcurrentLinkedDeque;

import java.util.concurrent.ConcurrentLinkedQueue;

import java.util.concurrent.CopyOnWriteArrayList;

import java.util.concurrent.LinkedBlockingDeque;

import java.util.concurrent.LinkedBlockingQueue;

import java.util.concurrent.LinkedTransferQueue;

import java.util.concurrent.PriorityBlockingQueue;

import java.util.concurrent.CountDownLatch;

import java.util.concurrent.ThreadLocalRandom;

import java.util.concurrent.atomic.LongAdder;

import java.util.function.UnaryOperator;

import java.util.regex.Pattern;

import java.util.stream.Stream;

/**

 * 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;

        public void run() {

            try { work(); }

            catch (Throwable ex) {

                // current job cannot always be deduced from stacktrace.

                throw new RuntimeException("Job failed: " + name(), ex);

            }

        }

    }

    final int iterations;

    final int size;             // number of elements in collections

    final double warmupSeconds;

    final long warmupNanos;

    final Pattern nameFilter;   // select subset of Jobs to run

    final boolean reverse;      // reverse order of Jobs

    final boolean shuffle;      // randomize order of Jobs

    IteratorMicroBenchmark(String[] args) {

        iterations    = intArg(args, "iterations", 10_000);

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

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

        nameFilter    = patternArg(args, "filter");

        reverse       = booleanArg(args, "reverse");

        shuffle       = booleanArg(args, "shuffle");

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

    }

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

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

    static void forceFullGc() {

        long timeoutMillis = 1000L;

        CountDownLatch finalized = new CountDownLatch(1);

        ReferenceQueue<Object> queue = new ReferenceQueue<>();

        WeakReference<Object> ref = new WeakReference<>(

            new Object() {

                @SuppressWarnings("deprecation")

                protected void finalize() { finalized.countDown(); }},

            queue);

        try {

            for (int tries = 3; tries--> 0; ) {

                System.gc();

                if (finalized.await(timeoutMillis, MILLISECONDS)

                    && queue.remove(timeoutMillis) != null

                    && ref.get() == null) {

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

                    return;

                }

                timeoutMillis *= 4;

            }

        } 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.

     */

    long[] time0(List<Job> jobs) {

        final int size = jobs.size();

        long[] nanoss = new long[size];

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

            if (warmupNanos > 0) forceFullGc();

            Job job = jobs.get(i);

            long totalTime;

            int runs = 0;

            long startTime = System.nanoTime();

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

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

            nanoss[i] = totalTime/runs;

        }

        return nanoss;

    }

    void time(List<Job> jobs) throws Throwable {

        if (warmupNanos > 0) time0(jobs); // Warm up run

        final int size = jobs.size();

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

        final long[] milliss = new long[size];

        final double[] ratios = new double[size];

        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 < size; i++) {

            nameWidth = Math.max(nameWidth, jobs.get(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 < size; i++)

            System.out.printf(format, jobs.get(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 boolean booleanArg(String[] args, String keyword) {

        String val = keywordValue(args, keyword);

        if (val == null || val.equals("false")) return false;

        if (val.equals("true")) return true;

        throw new IllegalArgumentException(val);

    }

    private static void deoptimize(int sum) {

        if (sum == 42)

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

    }

    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(); }};}};

    }

    // Checks for correctness *and* prevents loop optimizations

    static 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");

        }

    }

    volatile Check check = new Check();

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

        new IteratorMicroBenchmark(args).run();

    }

    HashMap<Class<?>, String> goodClassName = new HashMap<>();

    String goodClassName(Class<?> klazz) {

        return goodClassName.computeIfAbsent(

            klazz,

            k -> {

                String simple = k.getSimpleName();

                return (simple.equals("SubList")) // too simple!

                    ? k.getName().replaceFirst(".*\\.", "")

                    : simple;

            });

    }

    String goodClassName(Object x) {

        return goodClassName(x.getClass());

    }

    static List<Integer> makeSubList(

        List<Integer> elements,

        UnaryOperator<List<Integer>> copyConstructor) {

        final ArrayList<Integer> padded = new ArrayList<>();

        final ThreadLocalRandom rnd = ThreadLocalRandom.current();

        final int frontPorch = rnd.nextInt(3);

        final int backPorch = rnd.nextInt(3);

        for (int n = frontPorch; n--> 0; ) padded.add(rnd.nextInt());

        padded.addAll(elements);

        for (int n = backPorch; n--> 0; ) padded.add(rnd.nextInt());

        return copyConstructor.apply(padded)

            .subList(frontPorch, frontPorch + elements.size());

    }

    void run() throws Throwable {

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

        // Populate collections with random data

        final ThreadLocalRandom rnd = ThreadLocalRandom.current();

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

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

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

        final ArrayBlockingQueue<Integer> abq = new ArrayBlockingQueue<>(al.size());

        abq.addAll(al);

        // shuffle circular array elements so they wrap

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

            ad.addLast(ad.removeFirst());

            abq.add(abq.remove());

        }

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

        final List<Integer> immutableSubList

            = makeSubList(al, x -> List.of(x.toArray(new Integer[0])));

        Stream<Collection<Integer>> collections = concatStreams(

            Stream.of(

                // Lists and their subLists

                al,

                makeSubList(al, ArrayList::new),

                new Vector<>(al),

                makeSubList(al, Vector::new),

                new LinkedList<>(al),

                makeSubList(al, LinkedList::new),

                new CopyOnWriteArrayList<>(al),

                makeSubList(al, CopyOnWriteArrayList::new),

                ad,

                new PriorityQueue<>(al),

                new ConcurrentLinkedQueue<>(al),

                new ConcurrentLinkedDeque<>(al),

                // Blocking Queues

                abq,

                new LinkedBlockingQueue<>(al),

                new LinkedBlockingDeque<>(al),

                new LinkedTransferQueue<>(al),

                new PriorityBlockingQueue<>(al),

                List.of(al.toArray(new Integer[0]))),

            // avoid UnsupportedOperationException in jdk9 and jdk10

            (goodClassName(immutableSubList).equals("RandomAccessSubList"))

            ? Stream.empty()

            : Stream.of(immutableSubList));

        ArrayList<Job> jobs = collections

            .flatMap(x -> jobs(x))

            .filter(job ->

                nameFilter == null || nameFilter.matcher(job.name()).find())

            .collect(toCollection(ArrayList::new));

        if (reverse) Collections.reverse(jobs);

        if (shuffle) Collections.shuffle(jobs);

        time(jobs);

    }

    @SafeVarargs @SuppressWarnings("varargs")

    private static <T> Stream<T> concatStreams(Stream<T> ... streams) {

        return Stream.of(streams).flatMap(s -> s);

    }

    boolean isMutable(Collection<Integer> x) {

        return !(x.getClass().getName().contains("ImmutableCollections$"));

    }

    Stream<Job> jobs(Collection<Integer> x) {

        final String klazz = goodClassName(x);

        return concatStreams(

            collectionJobs(x),

            (isMutable(x))

            ? mutableCollectionJobs(x)

            : Stream.empty(),

            (x instanceof Deque)

            ? dequeJobs((Deque<Integer>)x)

            : Stream.empty(),

            (x instanceof List)

            ? listJobs((List<Integer>)x)

            : Stream.empty(),

            (x instanceof List && isMutable(x))

            ? mutableListJobs((List<Integer>)x)

            : Stream.empty());

    }

    Object sneakyAdder(int[] sneakySum) {

        return new Object() {

            public int hashCode() { throw new AssertionError(); }

            public boolean equals(Object z) {

                sneakySum[0] += (int) z; return false; }};

    }

    Stream<Job> collectionJobs(Collection<Integer> x) {

        final String klazz = goodClassName(x);

        return Stream.of(

            new Job(klazz + " iterate for loop") {

                public void work() throws Throwable {

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

                        int sum = 0;

                        for (Integer n : x)

                            sum += n;

                        check.sum(sum);}}},

            new Job(klazz + " iterator().forEachRemaining()") {

                public void work() throws Throwable {

                    int[] sum = new int[1];

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

                        sum[0] = 0;

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

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

            new Job(klazz + " 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 = x.spliterator();

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

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

            new Job(klazz + " spliterator().forEachRemaining()") {

                public void work() throws Throwable {

                    int[] sum = new int[1];

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

                        sum[0] = 0;

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

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

            new Job(klazz + " contains") {

                public void work() throws Throwable {

                    int[] sum = new int[1];

                    Object sneakyAdder = sneakyAdder(sum);

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

                        sum[0] = 0;

                        if (x.contains(sneakyAdder)) throw new AssertionError();

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

            new Job(klazz + " containsAll") {

                public void work() throws Throwable {

                    int[] sum = new int[1];

                    Collection<Object> sneakyAdderCollection =

                        Collections.singleton(sneakyAdder(sum));

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

                        sum[0] = 0;

                        if (x.containsAll(sneakyAdderCollection))

                            throw new AssertionError();

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

            new Job(klazz + " forEach") {

                public void work() throws Throwable {

                    int[] sum = new int[1];

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

                        sum[0] = 0;

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

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

            new Job(klazz + " toArray()") {

                public void work() throws Throwable {

                    int[] sum = new int[1];

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

                        sum[0] = 0;

                        for (Object o : x.toArray())

                            sum[0] += (Integer) o;

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

            new Job(klazz + " toArray(a)") {

                public void work() throws Throwable {

                    Integer[] a = new Integer[x.size()];

                    int[] sum = new int[1];

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

                        sum[0] = 0;

                        x.toArray(a);

                        for (Object o : a)

                            sum[0] += (Integer) o;

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

            new Job(klazz + " toArray(empty)") {

                public void work() throws Throwable {

                    Integer[] empty = new Integer[0];

                    int[] sum = new int[1];

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

                        sum[0] = 0;

                        for (Integer o : x.toArray(empty))

                            sum[0] += o;

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

            new Job(klazz + " stream().forEach") {

                public void work() throws Throwable {

                    int[] sum = new int[1];

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

                        sum[0] = 0;

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

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

            new Job(klazz + " stream().mapToInt") {

                public void work() throws Throwable {

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

                        check.sum(x.stream().mapToInt(e -> e).sum());}}},

            new Job(klazz + " stream().collect") {

                public void work() throws Throwable {

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

                        check.sum(x.stream()

                                  .collect(summingInt(e -> e)));}}},

            new Job(klazz + " stream()::iterator") {

                public void work() throws Throwable {

                    int[] sum = new int[1];

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

                        sum[0] = 0;

                        for (Integer o : (Iterable<Integer>) x.stream()::iterator)

                            sum[0] += o;

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

            new Job(klazz + " parallelStream().forEach") {

                public void work() throws Throwable {

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

                        LongAdder sum = new LongAdder();

                        x.parallelStream().forEach(n -> sum.add(n));

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

            new Job(klazz + " parallelStream().mapToInt") {

                public void work() throws Throwable {

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

                        check.sum(x.parallelStream().mapToInt(e -> e).sum());}}},

            new Job(klazz + " parallelStream().collect") {