01 /*
02 * Java Genetic Algorithm Library (jenetics-1.6.0).
03 * Copyright (c) 2007-2014 Franz Wilhelmstötter
04 *
05 * Licensed under the Apache License, Version 2.0 (the "License");
06 * you may not use this file except in compliance with the License.
07 * You may obtain a copy of the License at
08 *
09 * 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 * Author:
18 * Franz Wilhelmstötter (franz.wilhelmstoetter@gmx.at)
19 */
20 package org.jenetics.internal.math;
21
22 import static org.jenetics.util.math.pow;
23
24 import org.jenetics.util.StaticObject;
25
26 /**
27 * Mathematical functions regarding probabilities.
28 *
29 * @author <a href="mailto:franz.wilhelmstoetter@gmx.at">Franz Wilhelmstötter</a>
30 * @since 1.4
31 * @version 1.4 — <em>$Date: 2013-09-01 $</em>
32 */
33 public final class probability extends StaticObject {
34 private probability() {}
35
36 private static final long INT_RANGE = pow(2, 32) - 1;
37
38 /**
39 * Maps the probability, given in the range {@code [0, 1]}, to an
40 * integer in the range {@code [Integer.MIN_VALUE, Integer.MAX_VALUE]}.
41 *
42 * @see {@link #toInt(double)}
43 * @see {@link #toFloat(int)}
44 *
45 * @param probability the probability to widen.
46 * @return the widened probability.
47 */
48 public static int toInt(final float probability) {
49 return Math.round(INT_RANGE*probability + Integer.MIN_VALUE);
50 }
51
52 /**
53 * Maps the probability, given in the range {@code [0, 1]}, to an
54 * integer in the range {@code [Integer.MIN_VALUE, Integer.MAX_VALUE]}.
55 *
56 * @see {@link #toInt(float)}
57 * @see {@link #toFloat(int)}
58 *
59 * @param probability the probability to widen.
60 * @return the widened probability.
61 */
62 public static int toInt(final double probability) {
63 return (int)(Math.round(INT_RANGE*probability) + Integer.MIN_VALUE);
64 }
65
66 /**
67 * Maps the <i>integer</i> probability, within the range
68 * {@code [Integer.MIN_VALUE, Integer.MAX_VALUE]} back to a float
69 * probability within the range {@code [0, 1]}.
70 *
71 * @see {@link #toInt(float)}
72 * @see {@link #toInt(double)}
73 *
74 * @param probability the <i>integer</i> probability to map.
75 * @return the mapped probability within the range {@code [0, 1]}.
76 */
77 public static float toFloat(final int probability) {
78 final long value = (long)probability + Integer.MAX_VALUE;
79 return (float)(value/(double)INT_RANGE);
80 }
81 }
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