1 // ******************************************************************************
2 //
3 // Title: Force Field X.
4 // Description: Force Field X - Software for Molecular Biophysics.
5 // Copyright: Copyright (c) Michael J. Schnieders 2001-2024.
6 //
7 // This file is part of Force Field X.
8 //
9 // Force Field X is free software; you can redistribute it and/or modify it
10 // under the terms of the GNU General Public License version 3 as published by
11 // the Free Software Foundation.
12 //
13 // Force Field X is distributed in the hope that it will be useful, but WITHOUT
14 // ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
15 // FOR A PARTICULAR PURPOSE. See the GNU General Public License for more
16 // details.
17 //
18 // You should have received a copy of the GNU General Public License along with
19 // Force Field X; if not, write to the Free Software Foundation, Inc., 59 Temple
20 // Place, Suite 330, Boston, MA 02111-1307 USA
21 //
22 // Linking this library statically or dynamically with other modules is making a
23 // combined work based on this library. Thus, the terms and conditions of the
24 // GNU General Public License cover the whole combination.
25 //
26 // As a special exception, the copyright holders of this library give you
27 // permission to link this library with independent modules to produce an
28 // executable, regardless of the license terms of these independent modules, and
29 // to copy and distribute the resulting executable under terms of your choice,
30 // provided that you also meet, for each linked independent module, the terms
31 // and conditions of the license of that module. An independent module is a
32 // module which is not derived from or based on this library. If you modify this
33 // library, you may extend this exception to your version of the library, but
34 // you are not obligated to do so. If you do not wish to do so, delete this
35 // exception statement from your version.
36 //
37 // ******************************************************************************
38 package ffx.algorithms.optimize.anneal;
39
40 import org.apache.commons.math3.util.FastMath;
41
42 /**
43 * Exponential temperature schedule for simulated annealing
44 *
45 * @author Jacob M. Litman
46 * @author Michael J. Schnieders
47 * @since 1.0
48 */
49 public class ExpAnnealSchedule implements AnnealingSchedule {
50
51 private final int nWindows;
52 private final double tHigh;
53 private final double tLow;
54 private final double gamma;
55 private final String description;
56
57 /**
58 * Creates an exponential annealing schedule that decays as
59 * tHigh*((tLow/tHigh)^(1/(nWindows-1)))^(n-1). Caution: high values of nWindows could cause
60 * numeric instability.
61 *
62 * @param nWindows Number of windows.
63 * @param tLow Low temperature bound.
64 * @param tHigh High temperature bound.
65 */
66 public ExpAnnealSchedule(int nWindows, double tLow, double tHigh) {
67 assert nWindows > 1;
68 assert tLow < tHigh;
69 assert tLow >= 0;
70 assert Double.isFinite(tHigh);
71
72 this.nWindows = nWindows;
73 this.tHigh = tHigh;
74 this.tLow = tLow;
75 this.gamma = StrictMath.pow((tLow / tHigh), (1.0 / (nWindows - 1)));
76
77 description = String.format("Exponential annealing schedule with %d windows, "
78 + "initial temperature %12.7g K, final temperature %12.7g K, gamma %12.7g", nWindows, tHigh,
79 tLow, gamma);
80 }
81
82 @Override
83 public double getHighTemp() {
84 return tHigh;
85 }
86
87 @Override
88 public double getLowTemp() {
89 return tLow;
90 }
91
92 @Override
93 public int getNumWindows() {
94 return nWindows;
95 }
96
97 @Override
98 public double getTemperature(int i) {
99 assert i >= 0 && i < nWindows;
100 return tHigh * FastMath.pow(gamma, i);
101 }
102
103 @Override
104 public double[] getTemperatures() {
105 double[] temps = new double[nWindows];
106 for (int i = 0; i < nWindows; i++) {
107 temps[i] = getTemperature(i);
108 }
109 return temps;
110 }
111
112 @Override
113 public double maxWindowLength() {
114 return 1.0;
115 }
116
117 @Override
118 public double minWindowLength() {
119 return 1.0;
120 }
121
122 @Override
123 public String toString() {
124 return description;
125 }
126
127 @Override
128 public double totalWindowLength() {
129 return nWindows;
130 }
131
132 @Override
133 public double windowLength(int window) {
134 return 1.0;
135 }
136 }