/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.apache.commons.math4.userguide.rng;

import java.util.List;
import java.util.ArrayList;
import java.util.Random;

import org.apache.commons.rng.simple.RandomSource;
import org.apache.commons.rng.UniformRandomProvider;

import org.apache.commons.math4.random.RandomGenerator;
import org.apache.commons.math4.PerfTestUtils;

/**
 * Benchmark of the RNGs.
 */
public class RandomNumberGeneratorBenchmark {
    /** Number of loops over the operations to be benchmarked. */
    private static final int NUM_CALLS = 1_000_000;
    /** Number of runs for computing the statistics. */
    private static final int NUM_STATS = 500;
    /** Report formatting. */
    private static final int MAX_NAME_WIDTH = 45;

    /**
     * Program's entry point.
     *
     * @param args List of {@link RandomSource RNG indentifiers}.
     */
    public static void main(String[] args) throws Exception {
        final RandomNumberGeneratorBenchmark app = new RandomNumberGeneratorBenchmark();

        printEnv();

        final List<UniformRandomProvider> rngList = new ArrayList<>();
        for (int i = 0; i < args.length; i++) {
            rngList.add(RandomSource.create(RandomSource.valueOf(args[i])));
        }

        app.benchmark(rngList);
    }

    /**
     * Test all generators.
     * The reference is JDK's "Random".
     *
     * @param list List of generators to benchmark.
     */
    public void benchmark(List<UniformRandomProvider> rngList) {
        // Reference is JDK's "Random".
        final Random jdk = new Random();

        // List of benchmarked codes.
        final PerfTestUtils.RunTest[] candidates = new PerfTestUtils.RunTest[rngList.size() + 1];

        // "nextInt()" benchmark.

        candidates[0] = new PerfTestUtils.RunTest(jdk.toString()) {
                @Override
                    public Double call() throws Exception {
                    return (double) jdk.nextInt();
                }
            };
        for (int i = 0; i < rngList.size(); i++) {
            final UniformRandomProvider rng = rngList.get(i);

            candidates[i + 1] = new PerfTestUtils.RunTest(rng.toString()) {
                    @Override
                    public Double call() throws Exception {
                        return (double) rng.nextInt();
                    }
                };
        }

        PerfTestUtils.timeAndReport("nextInt()",
                                    MAX_NAME_WIDTH,
                                    NUM_CALLS,
                                    NUM_STATS,
                                    false,
                                    candidates);

        // "nextDouble()" benchmark.

        candidates[0] = new PerfTestUtils.RunTest(jdk.toString()) {
                @Override
                    public Double call() throws Exception {
                    return (double) jdk.nextDouble();
                }
            };
        for (int i = 0; i < rngList.size(); i++) {
            final UniformRandomProvider rng = rngList.get(i);

            candidates[i + 1] = new PerfTestUtils.RunTest(rng.toString()) {
                    @Override
                    public Double call() throws Exception {
                       return rng.nextDouble();
                    }
                };
        }

        PerfTestUtils.timeAndReport("nextDouble()",
                                    MAX_NAME_WIDTH,
                                    NUM_CALLS,
                                    NUM_STATS,
                                    false,
                                    candidates);

        // "nextLong()" benchmark.

        candidates[0] = new PerfTestUtils.RunTest(jdk.toString()) {
                @Override
                    public Double call() throws Exception {
                    return (double) jdk.nextLong();
                }
            };
        for (int i = 0; i < rngList.size(); i++) {
            final UniformRandomProvider rng = rngList.get(i);

            candidates[i + 1] = new PerfTestUtils.RunTest(rng.toString()) {
                    @Override
                    public Double call() throws Exception {
                        return (double) rng.nextLong();
                    }
                };
        }

        PerfTestUtils.timeAndReport("nextLong()",
                                    MAX_NAME_WIDTH,
                                    NUM_CALLS,
                                    NUM_STATS,
                                    false,
                                    candidates);
    }

    /**
     * Print environment.
     */
    private static void printEnv() {
        final String sep = " ";
        System.out.println("Java" + sep + System.getProperty("java.version"));
        System.out.println("Runtime" + sep + System.getProperty("java.runtime.version", "?"));
        System.out.println("JVM" + sep + System.getProperty("java.vm.name") +
                           sep + System.getProperty("java.vm.version"));
    }
}