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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
35  // exception statement from your version.
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.AngleTorsion;
46  import ffx.potential.bonded.Atom;
47  import ffx.potential.terms.AnglePotentialEnergy;
48  import ffx.potential.terms.AngleTorsionPotentialEnergy;
49  
50  import java.util.logging.Logger;
51  
52  import static edu.uiowa.jopenmm.OpenMMAmoebaLibrary.OpenMM_KJPerKcal;
53  import static edu.uiowa.jopenmm.OpenMMAmoebaLibrary.OpenMM_RadiansPerDegree;
54  import static java.lang.String.format;
55  
56  /**
57   * OpenMM Angle-Torsion Force.
58   */
59  public class AngleTorsionForce extends CustomCompoundBondForce {
60  
61    private static final Logger logger = Logger.getLogger(AngleTorsionForce.class.getName());
62  
63    /**
64     * Create an OpenMM Angle-Torsion Force.
65     *
66     * @param angleTorsionPotentialEnergy The AngleTorsionPotentialEnergy instance that contains the Angle-Torsions
67     */
68    public AngleTorsionForce(AngleTorsionPotentialEnergy angleTorsionPotentialEnergy) {
69      super(4, AngleTorsion.angleTorsionForm());
70      AngleTorsion[] angleTorsions = angleTorsionPotentialEnergy.getAngleTorsionArray();
71      addGlobalParameter("phi1", 0);
72      addGlobalParameter("phi2", Math.PI);
73      addGlobalParameter("phi3", 0);
74      for (int m = 1; m < 3; m++) {
75        for (int n = 1; n < 4; n++) {
76          addPerBondParameter(format("k%d%d", m, n));
77        }
78      }
79      for (int m = 1; m < 3; m++) {
80        addPerBondParameter(format("a%d", m));
81      }
82      for (AngleTorsion angleTorsion : angleTorsions) {
83        double[] constants = angleTorsion.getConstants();
84        DoubleArray parameters = new DoubleArray(0);
85        for (int m = 0; m < 2; m++) {
86          for (int n = 0; n < 3; n++) {
87            int index = (3 * m) + n;
88            parameters.append(constants[index] * OpenMM_KJPerKcal);
89          }
90        }
91        Atom[] atoms = angleTorsion.getAtomArray(true);
92        parameters.append(angleTorsion.angleType1.angle[0] * OpenMM_RadiansPerDegree);
93        parameters.append(angleTorsion.angleType2.angle[0] * OpenMM_RadiansPerDegree);
94  
95        IntArray particles = new IntArray(0);
96        for (int i = 0; i < 4; i++) {
97          particles.append(atoms[i].getArrayIndex());
98        }
99  
100       addBond(particles, parameters);
101       parameters.destroy();
102       particles.destroy();
103     }
104 
105     int forceGroup = angleTorsionPotentialEnergy.getForceGroup();
106     setForceGroup(forceGroup);
107     logger.info(format("  Angle-Torsions:                    %10d", angleTorsions.length));
108     logger.fine(format("   Force Group:                      %10d", forceGroup));
109   }
110 
111   /**
112    * Create a Dual Topology OpenMM Angle-Torsion Force.
113    *
114    * @param angleTorsionPotentialEnergy The AngleTorsionPotentialEnergy instance that contains the Angle-Torsions.
115    * @param topology                 The topology index for the OpenMM System.
116    * @param openMMDualTopologyEnergy The OpenMMDualTopologyEnergy instance.
117    */
118   public AngleTorsionForce(AngleTorsionPotentialEnergy angleTorsionPotentialEnergy,
119                            int topology, OpenMMDualTopologyEnergy openMMDualTopologyEnergy) {
120     super(4, AngleTorsion.angleTorsionForm());
121     AngleTorsion[] angleTorsions = angleTorsionPotentialEnergy.getAngleTorsionArray();
122     addGlobalParameter("phi1", 0);
123     addGlobalParameter("phi2", Math.PI);
124     addGlobalParameter("phi3", 0);
125     for (int m = 1; m < 3; m++) {
126       for (int n = 1; n < 4; n++) {
127         addPerBondParameter(format("k%d%d", m, n));
128       }
129     }
130     for (int m = 1; m < 3; m++) {
131       addPerBondParameter(format("a%d", m));
132     }
133 
134     double scaleDT = openMMDualTopologyEnergy.getTopologyScale(topology);
135 
136     for (AngleTorsion angleTorsion : angleTorsions) {
137       double scale = 1.0;
138       // Don't apply lambda scale to alchemical stretch-torsion
139       if (!angleTorsion.applyLambda()) {
140         scale = scaleDT;
141       }
142       double[] constants = angleTorsion.getConstants();
143       DoubleArray parameters = new DoubleArray(0);
144       for (int m = 0; m < 2; m++) {
145         for (int n = 0; n < 3; n++) {
146           int index = (3 * m) + n;
147           parameters.append(constants[index] * OpenMM_KJPerKcal * scale);
148         }
149       }
150       Atom[] atoms = angleTorsion.getAtomArray(true);
151       parameters.append(angleTorsion.angleType1.angle[0] * OpenMM_RadiansPerDegree);
152       parameters.append(angleTorsion.angleType2.angle[0] * OpenMM_RadiansPerDegree);
153 
154       IntArray particles = new IntArray(0);
155       for (int i = 0; i < 4; i++) {
156         int atomIndex = atoms[i].getArrayIndex();
157         atomIndex = openMMDualTopologyEnergy.mapToDualTopologyIndex(topology, atomIndex);
158         particles.append(atomIndex);
159       }
160 
161       addBond(particles, parameters);
162       parameters.destroy();
163       particles.destroy();
164     }
165 
166     int forceGroup = angleTorsionPotentialEnergy.getForceGroup();
167     setForceGroup(forceGroup);
168     logger.info(format("  Angle-Torsions:                    %10d", angleTorsions.length));
169     logger.fine(format("   Force Group:                      %10d", forceGroup));
170   }
171 
172   /**
173    * Convenience method to construct an OpenMM Angle-Torsion Force.
174    *
175    * @param openMMEnergy The OpenMM Energy instance that contains the angle-torsions.
176    * @return An OpenMM Stretch-Bend Force, or null if there are no angle-torsion.
177    */
178   public static Force constructForce(OpenMMEnergy openMMEnergy) {
179     AngleTorsionPotentialEnergy angleTorsionPotentialEnergy = openMMEnergy.getAngleTorsionPotentialEnergy();
180     if (angleTorsionPotentialEnergy == null) {
181       return null;
182     }
183     return new AngleTorsionForce(angleTorsionPotentialEnergy);
184   }
185 
186   /**
187    * Convenience method to construct a Dual Topology OpenMM Angle-Torsion Force.
188    *
189    * @param topology                 The topology index for the OpenMM System.
190    * @param openMMDualTopologyEnergy The OpenMMDualTopologyEnergy instance.
191    * @return An OpenMM Stretch-Bend Force, or null if there are no angle-torsion.
192    */
193   public static Force constructForce(int topology, OpenMMDualTopologyEnergy openMMDualTopologyEnergy) {
194     ForceFieldEnergy forceFieldEnergy = openMMDualTopologyEnergy.getForceFieldEnergy(topology);
195     AngleTorsionPotentialEnergy angleTorsionPotentialEnergy = forceFieldEnergy.getAngleTorsionPotentialEnergy();
196     if (angleTorsionPotentialEnergy == null) {
197       return null;
198     }
199     return new AngleTorsionForce(angleTorsionPotentialEnergy, topology, openMMDualTopologyEnergy);
200   }
201 
202   /**
203    * Update the Dual Topology Angle-Torsion Force.
204    *
205    * @param topology                 The topology index for the OpenMM System.
206    * @param openMMDualTopologyEnergy The OpenMMDualTopologyEnergy instance.
207    */
208   public void updateForce(int topology, OpenMMDualTopologyEnergy openMMDualTopologyEnergy) {
209     ForceFieldEnergy forceFieldEnergy = openMMDualTopologyEnergy.getForceFieldEnergy(topology);
210     AngleTorsionPotentialEnergy angleTorsionPotentialEnergy = forceFieldEnergy.getAngleTorsionPotentialEnergy();
211     // Check if this system has angle-torsions.
212     if (angleTorsionPotentialEnergy == null) {
213       return;
214     }
215     AngleTorsion[] angleTorsions = angleTorsionPotentialEnergy.getAngleTorsionArray();
216 
217     double scaleDT = openMMDualTopologyEnergy.getTopologyScale(topology);
218 
219     int atIndex = 0;
220     for (AngleTorsion angleTorsion : angleTorsions) {
221       double scale = 1.0;
222       // Don't apply lambda scale to alchemical stretch-torsion
223       if (!angleTorsion.applyLambda()) {
224         scale = scaleDT;
225       }
226       double[] constants = angleTorsion.getConstants();
227       DoubleArray parameters = new DoubleArray(0);
228       for (int m = 0; m < 2; m++) {
229         for (int n = 0; n < 3; n++) {
230           int index = (3 * m) + n;
231           parameters.append(constants[index] * OpenMM_KJPerKcal * scale);
232         }
233       }
234       Atom[] atoms = angleTorsion.getAtomArray(true);
235       parameters.append(angleTorsion.angleType1.angle[0] * OpenMM_RadiansPerDegree);
236       parameters.append(angleTorsion.angleType2.angle[0] * OpenMM_RadiansPerDegree);
237 
238       IntArray particles = new IntArray(0);
239       for (int i = 0; i < 4; i++) {
240         int atomIndex = atoms[i].getArrayIndex();
241         atomIndex = openMMDualTopologyEnergy.mapToDualTopologyIndex(topology, atomIndex);
242         particles.append(atomIndex);
243       }
244 
245       setBondParameters(atIndex++, particles, parameters);
246       parameters.destroy();
247       particles.destroy();
248     }
249 
250     updateParametersInContext(openMMDualTopologyEnergy.getContext());
251   }
252 }