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1   /*
2    * Licensed to the Apache Software Foundation (ASF) under one or more
3    * contributor license agreements.  See the NOTICE file distributed with
4    * this work for additional information regarding copyright ownership.
5    * The ASF licenses this file to You under the Apache License, Version 2.0
6    * (the "License"); you may not use this file except in compliance with
7    * the License.  You may obtain a copy of the License at
8    *
9    *      http://www.apache.org/licenses/LICENSE-2.0
10   *
11   * Unless required by applicable law or agreed to in writing, software
12   * distributed under the License is distributed on an "AS IS" BASIS,
13   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
14   * See the License for the specific language governing permissions and
15   * limitations under the License.
16   */
17  package org.apache.commons.rng;
18  
19  import java.util.stream.Stream;
20  
21  /**
22   * Applies to generators that can be advanced a large number of
23   * steps of the output sequence in a single operation.
24   *
25   * @since 1.3
26   */
27  public interface JumpableUniformRandomProvider extends UniformRandomProvider {
28      /**
29       * Creates a copy of the UniformRandomProvider and then advances the
30       * state of the current instance. The copy is returned.
31       *
32       * <p>The current state will be advanced in a single operation by the equivalent of a
33       * number of sequential calls to a method that updates the state of the provider. The
34       * size of the jump is implementation dependent.</p>
35       *
36       * <p>Repeat invocations of this method will create a series of generators
37       * that are uniformly spaced at intervals of the output sequence. Each generator provides
38       * non-overlapping output for the length of the jump for use in parallel computations.</p>
39       *
40       * @return A copy of the current state.
41       */
42      UniformRandomProvider jump();
43  
44      /**
45       * Returns an effectively unlimited stream of new random generators, each of which
46       * implements the {@link UniformRandomProvider} interface.
47       *
48       * @return a stream of random generators.
49       * @since 1.5
50       */
51      default Stream<UniformRandomProvider> jumps() {
52          return Stream.generate(this::jump).sequential();
53      }
54  
55      /**
56       * Returns a stream producing the given {@code streamSize} number of new random
57       * generators, each of which implements the {@link UniformRandomProvider}
58       * interface.
59       *
60       * @param streamSize Number of objects to generate.
61       * @return a stream of random generators; the stream is limited to the given
62       * {@code streamSize}.
63       * @throws IllegalArgumentException if {@code streamSize} is negative.
64       * @since 1.5
65       */
66      default Stream<UniformRandomProvider> jumps(long streamSize) {
67          UniformRandomProviderSupport.validateStreamSize(streamSize);
68          return jumps().limit(streamSize);
69      }
70  }