1 /*
2 * License : The MIT License
3 * Copyright(c) 2022 olyutorskii
4 */
5
6 package io.github.olyutorskii.aletojio.rng.lcg;
7
8 import io.github.olyutorskii.aletojio.rng.RndInt31;
9
10 /**
11 * Implementation of 31bit output Linear congruential generator(LCG).
12 *
13 * <p>LCG is a commonly used random number generator in the past.
14 *
15 * <p>* LCG implementations on CPU without 64-bit remainders
16 * often output only 31-bit random numbers.
17 *
18 * <p>Recurrence relation sequences : {@code X(n+1) = (X(n) * Mul + Inc) mod Mod}
19 *
20 * <ul>
21 * <li>Mul : Multiplier
22 * <li>Inc : Increment
23 * <li>Mod : Modulus
24 * </ul>
25 *
26 * @see <a href="https://en.wikipedia.org/wiki/Linear_congruential_generator">
27 * Linear congruential generator (Wikipedia)
28 * </a>
29 */
30 public class LcgRndInt31 extends AbstractLcg implements RndInt31 {
31
32 /**
33 * Constructor.
34 *
35 * <ul>
36 * <li>Multiplier must be 1 or greatrer.
37 * <li>Increment must be 0 or greatrer.
38 * <li>Modulus must be 2 or greater.
39 * </ul>
40 *
41 * @param mulArg multiplier
42 * @param incArg increment
43 * @param modArg modulus
44 * @throws IllegalArgumentException illegal argument
45 */
46 public LcgRndInt31(long mulArg, long incArg, long modArg)
47 throws IllegalArgumentException {
48 super(mulArg, incArg, modArg);
49 return;
50 }
51
52 /**
53 * {@inheritDoc}
54 *
55 * <p>result(31bit) reflects seed[0:30]
56 *
57 * @return {@inheritDoc}
58 */
59 @Override
60 protected int seedToResult() {
61 long lVal = getSeed() & MASK_B31;
62 int result = (int) lVal;
63 return result;
64 }
65
66 /**
67 * {@inheritDoc}
68 *
69 * @return {@inheritDoc}
70 */
71 @Override
72 public int nextInt31() {
73 int result = nextIntImpl();
74 return result;
75 }
76
77 }