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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
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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
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36  //
37  // ******************************************************************************
38  package ffx.potential.openmm;
39  
40  import ffx.openmm.CustomCompoundBondForce;
41  import ffx.openmm.DoubleArray;
42  import ffx.openmm.Force;
43  import ffx.openmm.IntArray;
44  import ffx.potential.ForceFieldEnergy;
45  import ffx.potential.bonded.StretchBend;
46  import ffx.potential.terms.StretchBendPotentialEnergy;
47  
48  import java.util.logging.Logger;
49  
50  import static edu.uiowa.jopenmm.OpenMMAmoebaLibrary.OpenMM_KJPerKcal;
51  import static edu.uiowa.jopenmm.OpenMMAmoebaLibrary.OpenMM_NmPerAngstrom;
52  import static edu.uiowa.jopenmm.OpenMMAmoebaLibrary.OpenMM_RadiansPerDegree;
53  import static java.lang.String.format;
54  
55  /**
56   * OpenMM Stretch-Bend Force.
57   */
58  public class StretchBendForce extends CustomCompoundBondForce {
59  
60    private static final Logger logger = Logger.getLogger(StretchBendForce.class.getName());
61  
62    /**
63     * Create an OpenMM Stretch-Bend Force.
64     *
65     * @param stretchBendPotentialEnergy The StretchBendPotentialEnergy instance that contains the stretch-bends.
66     */
67    public StretchBendForce(StretchBendPotentialEnergy stretchBendPotentialEnergy) {
68      super(3, StretchBendPotentialEnergy.getStretchBendEnergyString());
69      StretchBend[] stretchBends = stretchBendPotentialEnergy.getStretchBendArray();
70      addPerBondParameter("r12");
71      addPerBondParameter("r23");
72      addPerBondParameter("theta0");
73      addPerBondParameter("k1");
74      addPerBondParameter("k2");
75      setName("AmoebaStretchBend");
76  
77      IntArray particles = new IntArray(0);
78      DoubleArray parameters = new DoubleArray(0);
79      for (StretchBend stretchBend : stretchBends) {
80        int i1 = stretchBend.getAtom(0).getArrayIndex();
81        int i2 = stretchBend.getAtom(1).getArrayIndex();
82        int i3 = stretchBend.getAtom(2).getArrayIndex();
83        double r12 = stretchBend.bond0Eq * OpenMM_NmPerAngstrom;
84        double r23 = stretchBend.bond1Eq * OpenMM_NmPerAngstrom;
85        double theta0 = stretchBend.angleEq * OpenMM_RadiansPerDegree;
86        double k1 = stretchBend.force0 * OpenMM_KJPerKcal / OpenMM_NmPerAngstrom;
87        double k2 = stretchBend.force1 * OpenMM_KJPerKcal / OpenMM_NmPerAngstrom;
88        particles.append(i1);
89        particles.append(i2);
90        particles.append(i3);
91        parameters.append(r12);
92        parameters.append(r23);
93        parameters.append(theta0);
94        parameters.append(k1);
95        parameters.append(k2);
96        addBond(particles, parameters);
97        particles.resize(0);
98        parameters.resize(0);
99      }
100     particles.destroy();
101     parameters.destroy();
102 
103     int forceGroup = stretchBendPotentialEnergy.getForceGroup();
104     setForceGroup(forceGroup);
105     logger.info(format("  Stretch-Bends:                     %10d", stretchBends.length));
106     logger.fine(format("   Force Group:                      %10d", forceGroup));
107   }
108 
109   /**
110    * Create an OpenMM Stretch-Bend Force for Dual Topology.
111    *
112    * @param stretchBendPotentialEnergy The StretchBendPotentialEnergy instance that contains the stretch-bends.
113    * @param topology                   The topology index for the OpenMM System.
114    * @param openMMDualTopologyEnergy   The OpenMMDualTopologyEnergy instance.
115    */
116   public StretchBendForce(StretchBendPotentialEnergy stretchBendPotentialEnergy,
117                           int topology, OpenMMDualTopologyEnergy openMMDualTopologyEnergy) {
118     super(3, StretchBendPotentialEnergy.getStretchBendEnergyString());
119     StretchBend[] stretchBends = stretchBendPotentialEnergy.getStretchBendArray();
120     addPerBondParameter("r12");
121     addPerBondParameter("r23");
122     addPerBondParameter("theta0");
123     addPerBondParameter("k1");
124     addPerBondParameter("k2");
125     setName("AmoebaStretchBend");
126 
127     double scale = openMMDualTopologyEnergy.getTopologyScale(topology);
128 
129     IntArray particles = new IntArray(0);
130     DoubleArray parameters = new DoubleArray(0);
131     for (StretchBend stretchBend : stretchBends) {
132       int i1 = stretchBend.getAtom(0).getArrayIndex();
133       int i2 = stretchBend.getAtom(1).getArrayIndex();
134       int i3 = stretchBend.getAtom(2).getArrayIndex();
135       double r12 = stretchBend.bond0Eq * OpenMM_NmPerAngstrom;
136       double r23 = stretchBend.bond1Eq * OpenMM_NmPerAngstrom;
137       double theta0 = stretchBend.angleEq * OpenMM_RadiansPerDegree;
138       double k1 = stretchBend.force0 * OpenMM_KJPerKcal / OpenMM_NmPerAngstrom;
139       double k2 = stretchBend.force1 * OpenMM_KJPerKcal / OpenMM_NmPerAngstrom;
140       // Don't apply lambda scale to alchemical stretch bend
141       if (!stretchBend.applyLambda()) {
142         k1 = k1 * scale;
143         k2 = k2 * scale;
144       }
145       i1 = openMMDualTopologyEnergy.mapToDualTopologyIndex(topology, i1);
146       i2 = openMMDualTopologyEnergy.mapToDualTopologyIndex(topology, i2);
147       i3 = openMMDualTopologyEnergy.mapToDualTopologyIndex(topology, i3);
148       particles.append(i1);
149       particles.append(i2);
150       particles.append(i3);
151       parameters.append(r12);
152       parameters.append(r23);
153       parameters.append(theta0);
154       parameters.append(k1);
155       parameters.append(k2);
156       addBond(particles, parameters);
157       particles.resize(0);
158       parameters.resize(0);
159     }
160     particles.destroy();
161     parameters.destroy();
162 
163     int forceGroup = stretchBendPotentialEnergy.getForceGroup();
164     setForceGroup(forceGroup);
165     logger.info(format("  Stretch-Bends:                     %10d", stretchBends.length));
166     logger.fine(format("   Force Group:                      %10d", forceGroup));
167   }
168 
169   /**
170    * Convenience method to construct an OpenMM Stretch-Bend Force.
171    *
172    * @param openMMEnergy The OpenMM Energy instance that contains the stretch-bends.
173    * @return An OpenMM Stretch-Bend Force, or null if there are no stretch-bends.
174    */
175   public static Force constructForce(OpenMMEnergy openMMEnergy) {
176     StretchBendPotentialEnergy stretchBendPotentialEnergy = openMMEnergy.getStretchBendPotentialEnergy();
177     if (stretchBendPotentialEnergy == null) {
178       return null;
179     }
180     return new StretchBendForce(stretchBendPotentialEnergy);
181   }
182 
183   /**
184    * Convenience method to construct a Dual-Topology OpenMM Stretch-Bend Force.
185    *
186    * @param topology                 The topology index for the OpenMM System.
187    * @param openMMDualTopologyEnergy The OpenMMDualTopologyEnergy instance.
188    * @return An OpenMM Stretch-Bend Force, or null if there are no stretch-bends.
189    */
190   public static Force constructForce(int topology, OpenMMDualTopologyEnergy openMMDualTopologyEnergy) {
191     ForceFieldEnergy forceFieldEnergy = openMMDualTopologyEnergy.getForceFieldEnergy(topology);
192     StretchBendPotentialEnergy stretchBendPotentialEnergy = forceFieldEnergy.getStretchBendPotentialEnergy();
193     if (stretchBendPotentialEnergy == null) {
194       return null;
195     }
196     return new StretchBendForce(stretchBendPotentialEnergy, topology, openMMDualTopologyEnergy);
197   }
198 
199   /**
200    * Update this Stretch-Bend Force.
201    *
202    * @param openMMEnergy The OpenMM Energy instance that contains the stretch-bends.
203    */
204   public void updateForce(OpenMMEnergy openMMEnergy) {
205     StretchBendPotentialEnergy stretchBendPotentialEnergy = openMMEnergy.getStretchBendPotentialEnergy();
206     if (stretchBendPotentialEnergy == null) {
207       return;
208     }
209     StretchBend[] stretchBends = stretchBendPotentialEnergy.getStretchBendArray();
210 
211     IntArray particles = new IntArray(0);
212     DoubleArray parameters = new DoubleArray(0);
213     int index = 0;
214     for (StretchBend stretchBend : stretchBends) {
215       int i1 = stretchBend.getAtom(0).getArrayIndex();
216       int i2 = stretchBend.getAtom(1).getArrayIndex();
217       int i3 = stretchBend.getAtom(2).getArrayIndex();
218       double r12 = stretchBend.bond0Eq * OpenMM_NmPerAngstrom;
219       double r23 = stretchBend.bond1Eq * OpenMM_NmPerAngstrom;
220       double theta0 = stretchBend.angleEq * OpenMM_RadiansPerDegree;
221       double k1 = stretchBend.force0 * OpenMM_KJPerKcal / OpenMM_NmPerAngstrom;
222       double k2 = stretchBend.force1 * OpenMM_KJPerKcal / OpenMM_NmPerAngstrom;
223       particles.append(i1);
224       particles.append(i2);
225       particles.append(i3);
226       parameters.append(r12);
227       parameters.append(r23);
228       parameters.append(theta0);
229       parameters.append(k1);
230       parameters.append(k2);
231       setBondParameters(index++, particles, parameters);
232       particles.resize(0);
233       parameters.resize(0);
234     }
235     particles.destroy();
236     parameters.destroy();
237 
238     updateParametersInContext(openMMEnergy.getContext());
239   }
240 
241   /**
242    * Update existing Stretch-Bend Force for the Dual-Topology OpenMM System.
243    *
244    * @param topology                 The topology index for the OpenMM System.
245    * @param openMMDualTopologyEnergy The OpenMMDualTopologyEnergy instance.
246    */
247   public void updateForce(int topology, OpenMMDualTopologyEnergy openMMDualTopologyEnergy) {
248     ForceFieldEnergy forceFieldEnergy = openMMDualTopologyEnergy.getForceFieldEnergy(topology);
249     StretchBendPotentialEnergy stretchBendPotentialEnergy = forceFieldEnergy.getStretchBendPotentialEnergy();
250     if (stretchBendPotentialEnergy == null) {
251       return;
252     }
253     StretchBend[] stretchBends = stretchBendPotentialEnergy.getStretchBendArray();
254 
255     double scale = openMMDualTopologyEnergy.getTopologyScale(topology);
256 
257     IntArray particles = new IntArray(0);
258     DoubleArray parameters = new DoubleArray(0);
259     int index = 0;
260     for (StretchBend stretchBend : stretchBends) {
261       int i1 = stretchBend.getAtom(0).getArrayIndex();
262       int i2 = stretchBend.getAtom(1).getArrayIndex();
263       int i3 = stretchBend.getAtom(2).getArrayIndex();
264       double r12 = stretchBend.bond0Eq * OpenMM_NmPerAngstrom;
265       double r23 = stretchBend.bond1Eq * OpenMM_NmPerAngstrom;
266       double theta0 = stretchBend.angleEq * OpenMM_RadiansPerDegree;
267       double k1 = stretchBend.force0 * OpenMM_KJPerKcal / OpenMM_NmPerAngstrom;
268       double k2 = stretchBend.force1 * OpenMM_KJPerKcal / OpenMM_NmPerAngstrom;
269       // Don't apply lambda scale to alchemical stretch bend
270       if (!stretchBend.applyLambda()) {
271         k1 = k1 * scale;
272         k2 = k2 * scale;
273       }
274       i1 = openMMDualTopologyEnergy.mapToDualTopologyIndex(topology, i1);
275       i2 = openMMDualTopologyEnergy.mapToDualTopologyIndex(topology, i2);
276       i3 = openMMDualTopologyEnergy.mapToDualTopologyIndex(topology, i3);
277       particles.append(i1);
278       particles.append(i2);
279       particles.append(i3);
280       parameters.append(r12);
281       parameters.append(r23);
282       parameters.append(theta0);
283       parameters.append(k1);
284       parameters.append(k2);
285       setBondParameters(index++, particles, parameters);
286       particles.resize(0);
287       parameters.resize(0);
288     }
289     particles.destroy();
290     parameters.destroy();
291 
292     updateParametersInContext(openMMDualTopologyEnergy.getContext());
293   }
294 }