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 very large number of
23 * steps of the output sequence in a single operation.
24 *
25 * @since 1.3
26 */
27 public interface LongJumpableUniformRandomProvider extends JumpableUniformRandomProvider {
28 /**
29 * Creates a copy of the JumpableUniformRandomProvider 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 long 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 long jump for use in parallel computations.</p>
39 *
40 * <p>The returned copy may be jumped {@code m / n} times before overlap with the current
41 * instance where {@code m} is the long jump length and {@code n}
42 * is the jump length of the {@link #jump()} method.
43 *
44 * @return A copy of the current state.
45 */
46 JumpableUniformRandomProvider longJump();
47
48 /**
49 * Returns an effectively unlimited stream of new random generators, each of which
50 * implements the {@link JumpableUniformRandomProvider} interface.
51 *
52 * @return a stream of random generators.
53 * @since 1.5
54 */
55 default Stream<JumpableUniformRandomProvider> longJumps() {
56 return Stream.generate(this::longJump).sequential();
57 }
58
59 /**
60 * Returns a stream producing the given {@code streamSize} number of new random
61 * generators, each of which implements the {@link JumpableUniformRandomProvider}
62 * interface.
63 *
64 * @param streamSize Number of objects to generate.
65 * @return a stream of random generators; the stream is limited to the given
66 * {@code streamSize}.
67 * @throws IllegalArgumentException if {@code streamSize} is negative.
68 * @since 1.5
69 */
70 default Stream<JumpableUniformRandomProvider> longJumps(long streamSize) {
71 UniformRandomProviderSupport.validateStreamSize(streamSize);
72 return longJumps().limit(streamSize);
73 }
74 }