content: /*
   * 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 accord.utils;
  
  import java.util.concurrent.atomic.AtomicLong;
  
  /**
   * Utility class for creating seeds.  This class mostly matches the semantics of {@link java.util.Random} but makes the logic work
   * for any random source.  This class should be used in replacement of most seed methods, and should always replace {@link java.util.concurrent.ThreadLocalRandom}
   * as that randomness will have a bias twords the same seed after a restart (if you rerun randomized tests by restarting
   * the JVM you will run with the same seed over and over again).
   */
  public class SeedProvider
  {
      public static final SeedProvider instance = new SeedProvider();
      private final AtomicLong seedUniquifier = new AtomicLong(8682522807148012L);
  
      private long seedUniquifier()
      {
          // L'Ecuyer, "Tables of Linear Congruential Generators of
          // Different Sizes and Good Lattice Structure", 1999
          for (; ; )
          {
              long current = seedUniquifier.get();
              long next = current * 1181783497276652981L;
              if (seedUniquifier.compareAndSet(current, next))
                  return next;
          }
      }
  
      public long nextSeed()
      {
          return seedUniquifier() ^ System.nanoTime();
      }
  }
  