1 // ******************************************************************************
2 //
3 // Title: Force Field X.
4 // Description: Force Field X - Software for Molecular Biophysics.
5 // Copyright: Copyright (c) Michael J. Schnieders 2001-2025.
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.openmm;
39
40 import static edu.uiowa.jopenmm.OpenMMLibrary.OpenMM_Boolean.OpenMM_False;
41 import static edu.uiowa.jopenmm.OpenMMLibrary.OpenMM_CMMotionRemover_create;
42 import static edu.uiowa.jopenmm.OpenMMLibrary.OpenMM_CMMotionRemover_destroy;
43 import static edu.uiowa.jopenmm.OpenMMLibrary.OpenMM_CMMotionRemover_getFrequency;
44 import static edu.uiowa.jopenmm.OpenMMLibrary.OpenMM_CMMotionRemover_setFrequency;
45 import static edu.uiowa.jopenmm.OpenMMLibrary.OpenMM_CMMotionRemover_usesPeriodicBoundaryConditions;
46
47 /**
48 * This class prevents the center of mass of a System from drifting. At each time step, it calculates the
49 * center of mass momentum, then adjusts the individual particle velocities to make it zero.
50 */
51 public class CMMotionRemover extends Force {
52
53 /**
54 * Create a CMMotionRemover.
55 *
56 * @param frequency the frequency (in time steps) at which center of mass motion should be removed
57 */
58 public CMMotionRemover(int frequency) {
59 super(OpenMM_CMMotionRemover_create(frequency));
60 }
61
62 /**
63 * Get the frequency (in time steps) at which center of mass motion should be removed.
64 *
65 * @return the frequency (in time steps) at which center of mass motion should be removed
66 */
67 public int getFrequency() {
68 return OpenMM_CMMotionRemover_getFrequency(pointer);
69 }
70
71 /**
72 * Destroy the OpenMM CMMotionRemover.
73 */
74 @Override
75 public void destroy() {
76 if (pointer != null) {
77 OpenMM_CMMotionRemover_destroy(pointer);
78 pointer = null;
79 }
80 }
81
82 /**
83 * Set the frequency (in time steps) at which center of mass motion should be removed.
84 *
85 * @param freq the frequency (in time steps) at which center of mass motion should be removed
86 */
87 public void setFrequency(int freq) {
88 OpenMM_CMMotionRemover_setFrequency(pointer, freq);
89 }
90
91 /**
92 * Returns whether or not this force makes use of periodic boundary
93 * conditions.
94 *
95 * @return true if force uses PBC and false otherwise
96 */
97 @Override
98 public boolean usesPeriodicBoundaryConditions() {
99 int pbc = OpenMM_CMMotionRemover_usesPeriodicBoundaryConditions(pointer);
100 return pbc != OpenMM_False;
101 }
102 }