Merge pull request #1467 from peastman/amoebaperiodic

Periodic boundary conditions for AMOEBA bonded forces

plugins/amoeba/platforms/reference/src/SimTKReference/AmoebaReferenceOutOfPlaneBendForce.h

 
-/* Portions copyright (c) 2006 Stanford University and Simbios.
+/* Portions copyright (c) 2006-2016 Stanford University and Simbios.
  * Contributors: Pande Group
  *
  * Permission is hereby granted, free of charge, to any person obtaining
@@ -40,7 +40,7 @@ public:
        
        --------------------------------------------------------------------------------------- */
  
-    AmoebaReferenceOutOfPlaneBendForce() {};
+    AmoebaReferenceOutOfPlaneBendForce() : usePeriodic(false) {};
  
     /**---------------------------------------------------------------------------------------
        
@@ -50,6 +50,16 @@ public:
  
     ~AmoebaReferenceOutOfPlaneBendForce() {};
  
+    /**---------------------------------------------------------------------------------------
+
+       Set the force to use periodic boundary conditions.
+      
+       @param vectors    the vectors defining the periodic box
+      
+       --------------------------------------------------------------------------------------- */
+      
+    void setPeriodic(OpenMM::RealVec* vectors);
+
     /**---------------------------------------------------------------------------------------
      
         Calculate Amoeba out-of-plane-bend angle (force and energy)
@@ -86,6 +96,9 @@ public:
 
 private:
 
+    bool usePeriodic;
+    RealVec boxVectors[3];
+
     /**---------------------------------------------------------------------------------------
     
        Calculate Amoeba Out-Of-Plane-Bend ixn (force and energy)

plugins/amoeba/platforms/reference/src/SimTKReference/AmoebaReferencePiTorsionForce.cpp

-
-/* Portions copyright (c) 2006 Stanford University and Simbios.
+/* Portions copyright (c) 2006-2016 Stanford University and Simbios.
  * Contributors: Pande Group
  *
  * Permission is hereby granted, free of charge, to any person obtaining
@@ -29,6 +28,13 @@
 using std::vector;
 using namespace OpenMM;
 
+void AmoebaReferencePiTorsionForce::setPeriodic(OpenMM::RealVec* vectors) {
+    usePeriodic = true;
+    boxVectors[0] = vectors[0];
+    boxVectors[1] = vectors[1];
+    boxVectors[2] = vectors[2];
+}
+
 /**---------------------------------------------------------------------------------------
 
    Calculate Amoeba pi-torsion ixn (force and energy)
@@ -67,10 +73,18 @@ RealOpenMM AmoebaReferencePiTorsionForce::calculatePiTorsionIxn(const RealVec& p
     for (unsigned int ii = 0; ii < LastDeltaIndex; ii++) {
         deltaR[ii].resize(3);
     }
+    if (usePeriodic) {
+        AmoebaReferenceForce::loadDeltaRPeriodic(positionAtomD, positionAtomA, deltaR[AD], boxVectors);
+        AmoebaReferenceForce::loadDeltaRPeriodic(positionAtomD, positionAtomB, deltaR[BD], boxVectors);
+        AmoebaReferenceForce::loadDeltaRPeriodic(positionAtomC, positionAtomE, deltaR[EC], boxVectors);
+        AmoebaReferenceForce::loadDeltaRPeriodic(positionAtomC, positionAtomF, deltaR[FC], boxVectors);
+    }
+    else {
         AmoebaReferenceForce::loadDeltaR(positionAtomD, positionAtomA, deltaR[AD]);
         AmoebaReferenceForce::loadDeltaR(positionAtomD, positionAtomB, deltaR[BD]);
         AmoebaReferenceForce::loadDeltaR(positionAtomC, positionAtomE, deltaR[EC]);
         AmoebaReferenceForce::loadDeltaR(positionAtomC, positionAtomF, deltaR[FC]);
+    }
 
     enum { A, B, C, D, E, F, LastAtomIndex };
     std::vector<RealOpenMM> d[LastAtomIndex];

plugins/amoeba/platforms/reference/src/SimTKReference/AmoebaReferencePiTorsionForce.h

 
-/* Portions copyright (c) 2006 Stanford University and Simbios.
+/* Portions copyright (c) 2006-2016 Stanford University and Simbios.
  * Contributors: Pande Group
  *
  * Permission is hereby granted, free of charge, to any person obtaining
@@ -40,7 +40,7 @@ public:
        
        --------------------------------------------------------------------------------------- */
  
-    AmoebaReferencePiTorsionForce() {};
+    AmoebaReferencePiTorsionForce() : usePeriodic(false) {};
  
     /**---------------------------------------------------------------------------------------
        
@@ -50,6 +50,16 @@ public:
  
     ~AmoebaReferencePiTorsionForce() {};
  
+    /**---------------------------------------------------------------------------------------
+
+       Set the force to use periodic boundary conditions.
+      
+       @param vectors    the vectors defining the periodic box
+      
+       --------------------------------------------------------------------------------------- */
+      
+    void setPeriodic(OpenMM::RealVec* vectors);
+
      /**---------------------------------------------------------------------------------------
      
         Calculate Amoeba torsion ixns (force and energy)
@@ -85,6 +95,9 @@ public:
 
 private:
 
+    bool usePeriodic;
+    RealVec boxVectors[3];
+
     /**---------------------------------------------------------------------------------------
     
        Calculate Amoeba pi-torsion ixn (force and energy)

plugins/amoeba/platforms/reference/src/SimTKReference/AmoebaReferenceStretchBendForce.cpp

 
-/* Portions copyright (c) 2006 Stanford University and Simbios.
+/* Portions copyright (c) 2006-2016 Stanford University and Simbios.
  * Contributors: Pande Group
  *
  * Permission is hereby granted, free of charge, to any person obtaining
@@ -29,6 +29,13 @@
 using std::vector;
 using namespace OpenMM;
 
+void AmoebaReferenceStretchBendForce::setPeriodic(OpenMM::RealVec* vectors) {
+    usePeriodic = true;
+    boxVectors[0] = vectors[0];
+    boxVectors[1] = vectors[1];
+    boxVectors[2] = vectors[2];
+}
+
 /**---------------------------------------------------------------------------------------
 
    Calculate Amoeba stretch bend angle ixn (force and energy)
@@ -76,8 +83,14 @@ RealOpenMM AmoebaReferenceStretchBendForce::calculateStretchBendIxn(const RealVe
     for (unsigned int ii = 0; ii < LastDeltaIndex; ii++) {
         deltaR[ii].resize(3);
     }
+    if (usePeriodic) {
+        AmoebaReferenceForce::loadDeltaRPeriodic(positionAtomB, positionAtomA, deltaR[AB], boxVectors);
+        AmoebaReferenceForce::loadDeltaRPeriodic(positionAtomB, positionAtomC, deltaR[CB], boxVectors);
+    }
+    else {
         AmoebaReferenceForce::loadDeltaR(positionAtomB, positionAtomA, deltaR[AB]);
         AmoebaReferenceForce::loadDeltaR(positionAtomB, positionAtomC, deltaR[CB]);
+    }
     RealOpenMM  rAB2 = AmoebaReferenceForce::getNormSquared3(deltaR[AB]);
     RealOpenMM  rAB  = SQRT(rAB2);
     RealOpenMM  rCB2 = AmoebaReferenceForce::getNormSquared3(deltaR[CB]);

plugins/amoeba/platforms/reference/src/SimTKReference/AmoebaReferenceStretchBendForce.h

 
-/* Portions copyright (c) 2006 Stanford University and Simbios.
+/* Portions copyright (c) 2006-2016 Stanford University and Simbios.
  * Contributors: Pande Group
  *
  * Permission is hereby granted, free of charge, to any person obtaining
@@ -40,7 +40,7 @@ public:
        
        --------------------------------------------------------------------------------------- */
  
-    AmoebaReferenceStretchBendForce() {};
+    AmoebaReferenceStretchBendForce() : usePeriodic(false) {};
  
     /**---------------------------------------------------------------------------------------
        
@@ -50,6 +50,16 @@ public:
  
     ~AmoebaReferenceStretchBendForce() {};
 
+    /**---------------------------------------------------------------------------------------
+
+       Set the force to use periodic boundary conditions.
+      
+       @param vectors    the vectors defining the periodic box
+      
+       --------------------------------------------------------------------------------------- */
+      
+    void setPeriodic(OpenMM::RealVec* vectors);
+
      /**---------------------------------------------------------------------------------------
      
         Calculate Amoeba stretch bend ixns (force and energy)
@@ -84,6 +94,9 @@ public:
 
 private:
 
+    bool usePeriodic;
+    RealVec boxVectors[3];
+
     /**---------------------------------------------------------------------------------------
     
        Calculate Amoeba stretch bend angle ixn (force and energy)

plugins/amoeba/platforms/reference/src/SimTKReference/AmoebaReferenceTorsionTorsionForce.cpp

-
-/* Portions copyright (c) 2006 Stanford University and Simbios.
+/* Portions copyright (c) 2006-2016 Stanford University and Simbios.
  * Contributors: Pande Group
  *
  * Permission is hereby granted, free of charge, to any person obtaining
@@ -28,6 +27,13 @@
 using std::vector;
 using namespace OpenMM;
 
+void AmoebaReferenceTorsionTorsionForce::setPeriodic(OpenMM::RealVec* vectors) {
+    usePeriodic = true;
+    boxVectors[0] = vectors[0];
+    boxVectors[1] = vectors[1];
+    boxVectors[2] = vectors[2];
+}
+
 /**---------------------------------------------------------------------------------------
 
    Load grid values from rectenclosing angles
@@ -294,9 +300,16 @@ int AmoebaReferenceTorsionTorsionForce::checkTorsionSign(
         deltaR[ii].resize(3);
     }   
 
+    if (usePeriodic) {
+        AmoebaReferenceForce::loadDeltaRPeriodic(positionAtomC, positionAtomA, deltaR[CA], boxVectors);
+        AmoebaReferenceForce::loadDeltaRPeriodic(positionAtomC, positionAtomB, deltaR[CB], boxVectors);
+        AmoebaReferenceForce::loadDeltaRPeriodic(positionAtomC, positionAtomD, deltaR[CD], boxVectors);
+    }
+    else {
         AmoebaReferenceForce::loadDeltaR(positionAtomC, positionAtomA, deltaR[CA]);
         AmoebaReferenceForce::loadDeltaR(positionAtomC, positionAtomB, deltaR[CB]);
         AmoebaReferenceForce::loadDeltaR(positionAtomC, positionAtomD, deltaR[CD]);
+    }
 
     RealOpenMM volume = deltaR[CA][0]*(deltaR[CB][1]*deltaR[CD][2] - deltaR[CB][2]*deltaR[CD][1]) +
                         deltaR[CB][0]*(deltaR[CD][1]*deltaR[CA][2] - deltaR[CD][2]*deltaR[CA][1]) +
@@ -351,6 +364,16 @@ RealOpenMM AmoebaReferenceTorsionTorsionForce::calculateTorsionTorsionIxn(const
         deltaR[ii].resize(3);
     }   
 
+    if (usePeriodic) {
+        AmoebaReferenceForce::loadDeltaRPeriodic(positionAtomA, positionAtomB, deltaR[BA], boxVectors);
+        AmoebaReferenceForce::loadDeltaRPeriodic(positionAtomB, positionAtomC, deltaR[CB], boxVectors);
+        AmoebaReferenceForce::loadDeltaRPeriodic(positionAtomC, positionAtomD, deltaR[DC], boxVectors);
+        AmoebaReferenceForce::loadDeltaRPeriodic(positionAtomD, positionAtomE, deltaR[ED], boxVectors);
+        AmoebaReferenceForce::loadDeltaRPeriodic(positionAtomA, positionAtomC, deltaR[CA], boxVectors);
+        AmoebaReferenceForce::loadDeltaRPeriodic(positionAtomB, positionAtomD, deltaR[DB], boxVectors);
+        AmoebaReferenceForce::loadDeltaRPeriodic(positionAtomC, positionAtomE, deltaR[EC], boxVectors);
+    }
+    else {
         AmoebaReferenceForce::loadDeltaR(positionAtomA, positionAtomB, deltaR[BA]);
         AmoebaReferenceForce::loadDeltaR(positionAtomB, positionAtomC, deltaR[CB]);
         AmoebaReferenceForce::loadDeltaR(positionAtomC, positionAtomD, deltaR[DC]);
@@ -358,6 +381,7 @@ RealOpenMM AmoebaReferenceTorsionTorsionForce::calculateTorsionTorsionIxn(const
         AmoebaReferenceForce::loadDeltaR(positionAtomA, positionAtomC, deltaR[CA]);
         AmoebaReferenceForce::loadDeltaR(positionAtomB, positionAtomD, deltaR[DB]);
         AmoebaReferenceForce::loadDeltaR(positionAtomC, positionAtomE, deltaR[EC]);
+    }
 
     std::vector<RealOpenMM> d[LastAtomIndex];
     for (unsigned int ii = 0; ii < LastAtomIndex; ii++) {

plugins/amoeba/platforms/reference/src/SimTKReference/AmoebaReferenceTorsionTorsionForce.h

 
-/* Portions copyright (c) 2006 Stanford University and Simbios.
+/* Portions copyright (c) 2006-2016 Stanford University and Simbios.
  * Contributors: Pande Group
  *
  * Permission is hereby granted, free of charge, to any person obtaining
@@ -40,7 +40,7 @@ public:
        
        --------------------------------------------------------------------------------------- */
  
-    AmoebaReferenceTorsionTorsionForce() {};
+    AmoebaReferenceTorsionTorsionForce() : usePeriodic(false) {};
  
     /**---------------------------------------------------------------------------------------
        
@@ -50,6 +50,16 @@ public:
  
     ~AmoebaReferenceTorsionTorsionForce() {};
 
+    /**---------------------------------------------------------------------------------------
+
+       Set the force to use periodic boundary conditions.
+      
+       @param vectors    the vectors defining the periodic box
+      
+       --------------------------------------------------------------------------------------- */
+      
+    void setPeriodic(OpenMM::RealVec* vectors);
+
      /**---------------------------------------------------------------------------------------
      
         Calculate Amoeba torsion-torsion ixns (force and energy)
@@ -84,6 +94,9 @@ public:
 
 private:
 
+    bool usePeriodic;
+    RealVec boxVectors[3];
+
     /**---------------------------------------------------------------------------------------
     
        Load grid values from rectangle enclosing angles

plugins/amoeba/platforms/reference/tests/TestReferenceAmoebaAngleForce.cpp

@@ -6,7 +6,7 @@
  * Biological Structures at Stanford, funded under the NIH Roadmap for        *
  * Medical Research, grant U54 GM072970. See https://simtk.org.               *
  *                                                                            *
- * Portions copyright (c) 2008 Stanford University and the Authors.           *
+ * Portions copyright (c) 2008-2016 Stanford University and the Authors.      *
  * Authors: Peter Eastman                                                     *
  * Contributors:                                                              *
  *                                                                            *
@@ -35,6 +35,7 @@
 
 #include "openmm/internal/AssertionUtilities.h"
 #include "openmm/Context.h"
+#include "openmm/CustomAngleForce.h"
 #include "OpenMMAmoeba.h"
 #include "openmm/System.h"
 #include "openmm/LangevinIntegrator.h"
@@ -274,12 +275,63 @@ void testOneAngle() {
     compareWithExpectedForceAndEnergy(context, *amoebaAngleForce, TOL, "testOneAngle");
 }
 
+void testPeriodic() {
+    // Create a force that uses periodic boundary conditions, then compare to an identical custom force.
+    
+    System system;
+    system.setDefaultPeriodicBoxVectors(Vec3(3, 0, 0), Vec3(0, 3, 0), Vec3(0, 0, 3));
+    int numParticles = 3;
+    for (int ii = 0; ii < numParticles; ii++)
+        system.addParticle(1.0);
+    LangevinIntegrator integrator(0.0, 0.1, 0.01);
+    AmoebaAngleForce* amoebaAngleForce = new AmoebaAngleForce();
+    double angle      = 100.0;
+    double quadraticK = 1.0;
+    double cubicK     = 1.0e-01;
+    double quarticK   = 1.0e-02;
+    double penticK    = 1.0e-03;
+    double sexticK    = 1.0e-04;
+    amoebaAngleForce->addAngle(0, 1, 2, angle, quadraticK);
+    amoebaAngleForce->setAmoebaGlobalAngleCubic(cubicK);
+    amoebaAngleForce->setAmoebaGlobalAngleQuartic(quarticK);
+    amoebaAngleForce->setAmoebaGlobalAnglePentic(penticK);
+    amoebaAngleForce->setAmoebaGlobalAngleSextic(sexticK);
+    amoebaAngleForce->setUsesPeriodicBoundaryConditions(true);
+    system.addForce(amoebaAngleForce);
+    CustomAngleForce* customForce = new CustomAngleForce("k2*delta^2 + k3*delta^3 + k4*delta^4 + k5*delta^5 + k6*delta^6; delta=theta-theta0");
+    customForce->addGlobalParameter("theta0", angle*M_PI/180);
+    customForce->addGlobalParameter("k2", quadraticK*pow(180/M_PI, 2.0));
+    customForce->addGlobalParameter("k3", cubicK*pow(180/M_PI, 3.0));
+    customForce->addGlobalParameter("k4", quarticK*pow(180/M_PI, 4.0));
+    customForce->addGlobalParameter("k5", penticK*pow(180/M_PI, 5.0));
+    customForce->addGlobalParameter("k6", sexticK*pow(180/M_PI, 6.0));
+    customForce->addAngle(0, 1, 2);
+    customForce->setUsesPeriodicBoundaryConditions(true);
+    customForce->setForceGroup(1);
+    system.addForce(customForce);
+    Context context(system, integrator, Platform::getPlatformByName("Reference"));
+
+    std::vector<Vec3> positions(numParticles);
+
+    positions[0] = Vec3(0, 1, 0);
+    positions[1] = Vec3(0, 0, 0);
+    positions[2] = Vec3(0, 0, 2);
+
+    context.setPositions(positions);
+    State s1 = context.getState(State::Forces | State::Energy, true, 1);
+    State s2 = context.getState(State::Forces | State::Energy, true, 2);
+    ASSERT_EQUAL_TOL(s2.getPotentialEnergy(), s1.getPotentialEnergy(), 1e-5);
+    for (int i = 0; i < numParticles; i++)
+        ASSERT_EQUAL_VEC(s2.getForces()[i], s1.getForces()[i], 1e-5);
+}
+
 int main(int numberOfArguments, char* argv[]) {
 
     try {
-        std::cout << "TestCudaAmoebaAngleForce running test..." << std::endl;
+        std::cout << "TestReferenceAmoebaAngleForce running test..." << std::endl;
         registerAmoebaReferenceKernelFactories();
         testOneAngle();
+        testPeriodic();
     }
     catch(const std::exception& e) {
         std::cout << "exception: " << e.what() << std::endl;

plugins/amoeba/platforms/reference/tests/TestReferenceAmoebaBondForce.cpp

@@ -6,7 +6,7 @@
  * Biological Structures at Stanford, funded under the NIH Roadmap for        *
  * Medical Research, grant U54 GM072970. See https://simtk.org.               *
  *                                                                            *
- * Portions copyright (c) 2008 Stanford University and the Authors.           *
+ * Portions copyright (c) 2008-2016 Stanford University and the Authors.      *
  * Authors: Peter Eastman                                                     *
  * Contributors:                                                              *
  *                                                                            *
@@ -35,6 +35,7 @@
 
 #include "openmm/internal/AssertionUtilities.h"
 #include "openmm/Context.h"
+#include "openmm/CustomBondForce.h"
 #include "OpenMMAmoeba.h"
 #include "openmm/System.h"
 #include "openmm/LangevinIntegrator.h"
@@ -201,6 +202,49 @@ void testTwoBond() {
     compareWithExpectedForceAndEnergy(context, *amoebaBondForce, TOL, "testTwoBond");
 }
 
+void testPeriodic() {
+    // Create a force that uses periodic boundary conditions, then compare to an identical custom force.
+    
+    System system;
+    system.setDefaultPeriodicBoxVectors(Vec3(3, 0, 0), Vec3(0, 3, 0), Vec3(0, 0, 3));
+    int numParticles = 2;
+    for (int ii = 0; ii < numParticles; ii++)
+        system.addParticle(1.0);
+    LangevinIntegrator integrator(0.0, 0.1, 0.01);
+    AmoebaBondForce* amoebaBondForce = new AmoebaBondForce();
+    double bondLength = 1.5;
+    double quadraticK = 1.0;
+    double cubicK     = 2.0;
+    double quarticK   = 3.0;
+    amoebaBondForce->setAmoebaGlobalBondCubic(cubicK);
+    amoebaBondForce->setAmoebaGlobalBondQuartic(quarticK);
+    amoebaBondForce->addBond(0, 1, bondLength, quadraticK);
+    amoebaBondForce->setUsesPeriodicBoundaryConditions(true);
+    system.addForce(amoebaBondForce);
+    CustomBondForce* customForce = new CustomBondForce("k2*delta^2 + k3*delta^3 + k4*delta^4; delta=r-r0");
+    customForce->addGlobalParameter("r0", bondLength);
+    customForce->addGlobalParameter("k2", quadraticK);
+    customForce->addGlobalParameter("k3", cubicK);
+    customForce->addGlobalParameter("k4", quarticK);
+    customForce->addBond(0, 1);
+    customForce->setUsesPeriodicBoundaryConditions(true);
+    customForce->setForceGroup(1);
+    system.addForce(customForce);
+    Context context(system, integrator, Platform::getPlatformByName("Reference"));
+
+    std::vector<Vec3> positions(numParticles);
+
+    positions[0] = Vec3(0, 2, 0);
+    positions[1] = Vec3(0, 0, 0);
+
+    context.setPositions(positions);
+    State s1 = context.getState(State::Forces | State::Energy, true, 1);
+    State s2 = context.getState(State::Forces | State::Energy, true, 2);
+    ASSERT_EQUAL_TOL(s2.getPotentialEnergy(), s1.getPotentialEnergy(), 1e-5);
+    for (int i = 0; i < numParticles; i++)
+        ASSERT_EQUAL_VEC(s2.getForces()[i], s1.getForces()[i], 1e-5);
+}
+
 int main(int numberOfArguments, char* argv[]) {
 
     try {
@@ -208,6 +252,7 @@ int main(int numberOfArguments, char* argv[]) {
         registerAmoebaReferenceKernelFactories();
         //testOneBond();
         testTwoBond();
+        testPeriodic();
     }
     catch(const std::exception& e) {
         std::cout << "exception: " << e.what() << std::endl;

plugins/amoeba/platforms/reference/tests/TestReferenceAmoebaInPlaneAngleForce.cpp

@@ -6,7 +6,7 @@
  * Biological Structures at Stanford, funded under the NIH Roadmap for        *
  * Medical Research, grant U54 GM072970. See https://simtk.org.               *
  *                                                                            *
- * Portions copyright (c) 2008 Stanford University and the Authors.           *
+ * Portions copyright (c) 2008-2016 Stanford University and the Authors.      *
  * Authors: Peter Eastman                                                     *
  * Contributors:                                                              *
  *                                                                            *
@@ -354,12 +354,57 @@ void testOneAngle() {
     compareWithExpectedForceAndEnergy(context, *amoebaInPlaneAngleForce, TOL, "testOneInPlaneAngle");
 }
 
+void testPeriodic() {
+    // Create a force that uses periodic boundary conditions.
+
+    System system;
+    system.setDefaultPeriodicBoxVectors(Vec3(3, 0, 0), Vec3(0, 3, 0), Vec3(0, 0, 3));
+    int numberOfParticles = 4;
+    for (int ii = 0; ii < numberOfParticles; ii++)
+        system.addParticle(1.0);
+    LangevinIntegrator integrator(0.0, 0.1, 0.01);
+    AmoebaInPlaneAngleForce* amoebaInPlaneAngleForce = new AmoebaInPlaneAngleForce();
+    double angle      = 65.0;
+    double quadraticK = 1.0;
+    double cubicK     = 0.0e-01;
+    double quarticK   = 0.0e-02;
+    double penticK    = 0.0e-03;
+    double sexticK    = 0.0e-04;
+    amoebaInPlaneAngleForce->addAngle(0, 1, 2, 3, angle, quadraticK);
+    amoebaInPlaneAngleForce->setAmoebaGlobalInPlaneAngleCubic(cubicK);
+    amoebaInPlaneAngleForce->setAmoebaGlobalInPlaneAngleQuartic(quarticK);
+    amoebaInPlaneAngleForce->setAmoebaGlobalInPlaneAnglePentic(penticK);
+    amoebaInPlaneAngleForce->setAmoebaGlobalInPlaneAngleSextic(sexticK);
+    amoebaInPlaneAngleForce->setUsesPeriodicBoundaryConditions(true);
+    system.addForce(amoebaInPlaneAngleForce);
+    Context context(system, integrator, Platform::getPlatformByName("Reference"));
+
+    std::vector<Vec3> positions(numberOfParticles);
+    positions[0] = Vec3(0, 1, 0);
+    positions[1] = Vec3(0, 0, 0);
+    positions[2] = Vec3(0, 0, 1);
+    positions[3] = Vec3(1, 1, 1);
+
+    context.setPositions(positions);
+    State s1 = context.getState(State::Forces | State::Energy);
+    
+    // Move one atom to a position that should give identical results.
+
+    positions[2] = Vec3(0, 0, -2);
+    context.setPositions(positions);
+    State s2 = context.getState(State::Forces | State::Energy);
+    ASSERT_EQUAL_TOL(s1.getPotentialEnergy(), s2.getPotentialEnergy(), 1e-5);
+    for (int i = 0; i < numberOfParticles; i++)
+        ASSERT_EQUAL_VEC(s1.getForces()[i], s2.getForces()[i], 1e-5);
+}
+
 int main(int numberOfArguments, char* argv[]) {
 
     try {
         std::cout << "TestReferenceAmoebaInPlaneAngleForce running test..." << std::endl;
         registerAmoebaReferenceKernelFactories();
         testOneAngle();
+        testPeriodic();
     }
     catch(const std::exception& e) {
         std::cout << "exception: " << e.what() << std::endl;

plugins/amoeba/platforms/reference/tests/TestReferenceAmoebaOutOfPlaneBendForce.cpp

@@ -6,7 +6,7 @@
  * Biological Structures at Stanford, funded under the NIH Roadmap for        *
  * Medical Research, grant U54 GM072970. See https://simtk.org.               *
  *                                                                            *
- * Portions copyright (c) 2008 Stanford University and the Authors.           *
+ * Portions copyright (c) 2008-2016 Stanford University and the Authors.      *
  * Authors: Peter Eastman                                                     *
  * Contributors:                                                              *
  *                                                                            *
@@ -461,12 +461,50 @@ void testOneOutOfPlaneBend2(int setId) {
     }
 }
 
+void testPeriodic() {
+    // Create a force that uses periodic boundary conditions.
+
+    System system;
+    system.setDefaultPeriodicBoxVectors(Vec3(3, 0, 0), Vec3(0, 3, 0), Vec3(0, 0, 3));
+    int numberOfParticles = 4;
+    for (int ii = 0; ii < numberOfParticles; ii++)
+        system.addParticle(1.0);
+    LangevinIntegrator integrator(0.0, 0.1, 0.01);
+    AmoebaOutOfPlaneBendForce* amoebaOutOfPlaneBendForce = new AmoebaOutOfPlaneBendForce();
+    amoebaOutOfPlaneBendForce->setAmoebaGlobalOutOfPlaneBendCubic( -0.1400000E-01);
+    amoebaOutOfPlaneBendForce->setAmoebaGlobalOutOfPlaneBendQuartic(0.5600000E-04);
+    amoebaOutOfPlaneBendForce->setAmoebaGlobalOutOfPlaneBendPentic(-0.7000000E-06);
+    amoebaOutOfPlaneBendForce->setAmoebaGlobalOutOfPlaneBendSextic( 0.2200000E-07);
+    double kOutOfPlaneBend = 0.328682196E-01;
+    amoebaOutOfPlaneBendForce->addOutOfPlaneBend(0, 1, 2, 3, kOutOfPlaneBend);
+    amoebaOutOfPlaneBendForce->setUsesPeriodicBoundaryConditions(true);
+    system.addForce(amoebaOutOfPlaneBendForce);
+    Context context(system, integrator, Platform::getPlatformByName("Reference"));
+    std::vector<Vec3> positions(numberOfParticles);
+    positions[0] = Vec3(0, 0, 0);
+    positions[1] = Vec3(1, 0, 0);
+    positions[2] = Vec3(0, 1, 0);
+    positions[3] = Vec3(0, 0, 1);
+    context.setPositions(positions);
+    State s1 = context.getState(State::Forces | State::Energy);
+    
+    // Move one atom to a position that should give identical results.
+
+    positions[3] = Vec3(0, 0, -2);
+    context.setPositions(positions);
+    State s2 = context.getState(State::Forces | State::Energy);
+    ASSERT_EQUAL_TOL(s1.getPotentialEnergy(), s2.getPotentialEnergy(), 1e-5);
+    for (int i = 0; i < numberOfParticles; i++)
+        ASSERT_EQUAL_VEC(s1.getForces()[i], s2.getForces()[i], 1e-5);
+}
+
 int main(int numberOfArguments, char* argv[]) {
 
     try {
         std::cout << "TestReferenceAmoebaOutOfPlaneBendForce running test..." << std::endl;
         registerAmoebaReferenceKernelFactories();
         testOneOutOfPlaneBend();
+        testPeriodic();
         //testOneOutOfPlaneBend2(atoi(argv[1]));
         //for (int ii = 1; ii <= 6; ii++) {
         //     testOneOutOfPlaneBend2(ii);

plugins/amoeba/platforms/reference/tests/TestReferenceAmoebaPiTorsionForce.cpp

@@ -6,7 +6,7 @@
  * Biological Structures at Stanford, funded under the NIH Roadmap for        *
  * Medical Research, grant U54 GM072970. See https://simtk.org.               *
  *                                                                            *
- * Portions copyright (c) 2008 Stanford University and the Authors.           *
+ * Portions copyright (c) 2008-2016 Stanford University and the Authors.      *
  * Authors: Peter Eastman                                                     *
  * Contributors:                                                              *
  *                                                                            *
@@ -290,12 +290,48 @@ void testOnePiTorsion() {
     compareWithExpectedForceAndEnergy(context, *amoebaPiTorsionForce, TOL, "testOnePiTorsion");
 }
 
+void testPeriodic() {
+    // Create a force that uses periodic boundary conditions.
+
+    System system;
+    system.setDefaultPeriodicBoxVectors(Vec3(3, 0, 0), Vec3(0, 3, 0), Vec3(0, 0, 3));
+    int numberOfParticles = 6;
+    for (int ii = 0; ii < numberOfParticles; ii++)
+        system.addParticle(1.0);
+    LangevinIntegrator integrator(0.0, 0.1, 0.01);
+    AmoebaPiTorsionForce* amoebaPiTorsionForce = new AmoebaPiTorsionForce();
+    double kTorsion = 6.85;
+    amoebaPiTorsionForce->addPiTorsion(0, 1, 2, 3, 4, 5, kTorsion);
+    amoebaPiTorsionForce->setUsesPeriodicBoundaryConditions(true);
+    system.addForce(amoebaPiTorsionForce);
+    Context context(system, integrator, Platform::getPlatformByName("Reference"));
+    std::vector<Vec3> positions(numberOfParticles);
+    positions[0] = Vec3(0, 1, 0);
+    positions[1] = Vec3(0, 0, 0);
+    positions[2] = Vec3(0, 0, 0.5);
+    positions[3] = Vec3(0.4, 0.4, 0.4);
+    positions[4] = Vec3(1, 0, 1);
+    positions[5] = Vec3(1, 1, 0);
+    context.setPositions(positions);
+    State s1 = context.getState(State::Forces | State::Energy);
+    
+    // Move one atom to a position that should give identical results.
+
+    positions[0] = Vec3(0, -2, 0);
+    context.setPositions(positions);
+    State s2 = context.getState(State::Forces | State::Energy);
+    ASSERT_EQUAL_TOL(s1.getPotentialEnergy(), s2.getPotentialEnergy(), 1e-5);
+    for (int i = 0; i < numberOfParticles; i++)
+        ASSERT_EQUAL_VEC(s1.getForces()[i], s2.getForces()[i], 1e-5);
+}
+
 int main(int numberOfArguments, char* argv[]) {
 
     try {
         std::cout << "TestReferenceAmoebaPiTorsionForce running test..." << std::endl;
         registerAmoebaReferenceKernelFactories();
         testOnePiTorsion();
+        testPeriodic();
     }
     catch(const std::exception& e) {
         std::cout << "exception: " << e.what() << std::endl;

plugins/amoeba/platforms/reference/tests/TestReferenceAmoebaStretchBendForce.cpp

@@ -6,7 +6,7 @@
  * Biological Structures at Stanford, funded under the NIH Roadmap for        *
  * Medical Research, grant U54 GM072970. See https://simtk.org.               *
  *                                                                            *
- * Portions copyright (c) 2008 Stanford University and the Authors.           *
+ * Portions copyright (c) 2008-2016 Stanford University and the Authors.      *
  * Authors: Peter Eastman                                                     *
  * Contributors:                                                              *
  *                                                                            *
@@ -270,12 +270,48 @@ void testOneStretchBend() {
     compareWithExpectedForceAndEnergy(context, *amoebaStretchBendForce, TOL, "testOneStretchBend");
 }
 
+void testPeriodic() {
+    // Create a force that uses periodic boundary conditions.
+
+    System system;
+    system.setDefaultPeriodicBoxVectors(Vec3(3, 0, 0), Vec3(0, 3, 0), Vec3(0, 0, 3));
+    int numberOfParticles = 3;
+    for (int ii = 0; ii < numberOfParticles; ii++)
+        system.addParticle(1.0);
+    LangevinIntegrator integrator(0.0, 0.1, 0.01);
+    AmoebaStretchBendForce* amoebaStretchBendForce = new AmoebaStretchBendForce();
+    double abLength         = 0.144800000E+01;
+    double cbLength         = 0.101500000E+01;
+    double angleStretchBend = 0.108500000E+03*DegreesToRadians;
+    double kStretchBend     = 1.0;
+    amoebaStretchBendForce->addStretchBend(0, 1, 2, abLength, cbLength, angleStretchBend, kStretchBend, kStretchBend);
+    amoebaStretchBendForce->setUsesPeriodicBoundaryConditions(true);
+    system.addForce(amoebaStretchBendForce);
+    Context context(system, integrator, Platform::getPlatformByName("Reference"));
+    std::vector<Vec3> positions(numberOfParticles);
+    positions[0] = Vec3(0, 1, 0);
+    positions[1] = Vec3(0, 0, 0);
+    positions[2] = Vec3(0, 0, 1);
+    context.setPositions(positions);
+    State s1 = context.getState(State::Forces | State::Energy);
+    
+    // Move one atom to a position that should give identical results.
+
+    positions[2] = Vec3(0, 0, -2);
+    context.setPositions(positions);
+    State s2 = context.getState(State::Forces | State::Energy);
+    ASSERT_EQUAL_TOL(s1.getPotentialEnergy(), s2.getPotentialEnergy(), 1e-5);
+    for (int i = 0; i < numberOfParticles; i++)
+        ASSERT_EQUAL_VEC(s1.getForces()[i], s2.getForces()[i], 1e-5);
+}
+
 int main(int numberOfArguments, char* argv[]) {
 
     try {
         std::cout << "TestReferenceAmoebaStretchBendForce running test..." << std::endl;
         registerAmoebaReferenceKernelFactories();
         testOneStretchBend();
+        testPeriodic();
     }
     catch(const std::exception& e) {
         std::cout << "exception: " << e.what() << std::endl;

plugins/amoeba/platforms/reference/tests/TestReferenceAmoebaTorsionTorsionForce.cpp

@@ -6,7 +6,7 @@
  * Biological Structures at Stanford, funded under the NIH Roadmap for        *
  * Medical Research, grant U54 GM072970. See https://simtk.org.               *
  *                                                                            *
- * Portions copyright (c) 2008 Stanford University and the Authors.           *
+ * Portions copyright (c) 2008-2016 Stanford University and the Authors.      *
  * Authors: Peter Eastman                                                     *
  * Contributors:                                                              *
  *                                                                            *
@@ -2669,6 +2669,44 @@ void testTorsionTorsion(int systemId, bool includeDerivs) {
     ASSERT_EQUAL_TOL(expectedEnergy, state.getPotentialEnergy(), tolerance);
 }
 
+void testPeriodic() {
+    // Create a force that uses periodic boundary conditions.
+
+    System system;
+    system.setDefaultPeriodicBoxVectors(Vec3(3, 0, 0), Vec3(0, 3, 0), Vec3(0, 0, 3));
+    int numberOfParticles = 6;
+    for (int ii = 0; ii < numberOfParticles; ii++)
+        system.addParticle(1.0);
+    LangevinIntegrator integrator(0.0, 0.1, 0.01);
+    AmoebaTorsionTorsionForce* amoebaTorsionTorsionForce = new AmoebaTorsionTorsionForce();
+    int chiralCheckAtomIndex;
+    int gridIndex;
+    chiralCheckAtomIndex  = 5;
+    gridIndex             = 2;
+    amoebaTorsionTorsionForce->addTorsionTorsion(0, 1, 2, 3, 4, chiralCheckAtomIndex, 0);
+    amoebaTorsionTorsionForce->setTorsionTorsionGrid(0, getTorsionGrid(gridIndex, false));
+    amoebaTorsionTorsionForce->setUsesPeriodicBoundaryConditions(true);
+    system.addForce(amoebaTorsionTorsionForce);
+    Context context(system, integrator, Platform::getPlatformByName("Reference"));
+    std::vector<Vec3> positions(numberOfParticles);
+    positions[0] = Vec3(0, 1, 0);
+    positions[1] = Vec3(0, 0, 0);
+    positions[2] = Vec3(0, 0, 0.5);
+    positions[3] = Vec3(0.4, 0.4, 0.4);
+    positions[4] = Vec3(1, 0, 1);
+    positions[5] = Vec3(1, 1, 0);
+    context.setPositions(positions);
+    State s1 = context.getState(State::Forces | State::Energy);
+    
+    // Move one atom to a position that should give identical results.
+
+    positions[0] = Vec3(0, -2, 0);
+    context.setPositions(positions);
+    State s2 = context.getState(State::Forces | State::Energy);
+    ASSERT_EQUAL_TOL(s1.getPotentialEnergy(), s2.getPotentialEnergy(), 1e-5);
+    for (int i = 0; i < numberOfParticles; i++)
+        ASSERT_EQUAL_VEC(s1.getForces()[i], s2.getForces()[i], 1e-5);
+}
 
 int main(int numberOfArguments, char* argv[]) {
 
@@ -2677,6 +2715,7 @@ int main(int numberOfArguments, char* argv[]) {
         registerAmoebaReferenceKernelFactories();
         testTorsionTorsion(1, true);
         testTorsionTorsion(1, false);
+        testPeriodic();
     }
     catch(const std::exception& e) {
         std::cout << "exception: " << e.what() << std::endl;

plugins/amoeba/serialization/src/AmoebaAngleForceProxy.cpp

@@ -42,11 +42,12 @@ AmoebaAngleForceProxy::AmoebaAngleForceProxy() : SerializationProxy("AmoebaAngle
 }
 
 void AmoebaAngleForceProxy::serialize(const void* object, SerializationNode& node) const {
-    node.setIntProperty("version", 2);
+    node.setIntProperty("version", 3);
 
     const AmoebaAngleForce& force = *reinterpret_cast<const AmoebaAngleForce*>(object);
 
     node.setIntProperty("forceGroup", force.getForceGroup());
+    node.setBoolProperty("usesPeriodic", force.usesPeriodicBoundaryConditions());
     node.setDoubleProperty("cubic",   force.getAmoebaGlobalAngleCubic());
     node.setDoubleProperty("quartic", force.getAmoebaGlobalAngleQuartic());
     node.setDoubleProperty("pentic",  force.getAmoebaGlobalAnglePentic());
@@ -63,12 +64,14 @@ void AmoebaAngleForceProxy::serialize(const void* object, SerializationNode& nod
 
 void* AmoebaAngleForceProxy::deserialize(const SerializationNode& node) const {
     int version = node.getIntProperty("version");
-    if (version < 1 || version > 2)
+    if (version < 1 || version > 3)
         throw OpenMMException("Unsupported version number");
     AmoebaAngleForce* force = new AmoebaAngleForce();
     try {
         if (version > 1)
             force->setForceGroup(node.getIntProperty("forceGroup", 0));
+        if (version > 2)
+            force->setUsesPeriodicBoundaryConditions(node.getBoolProperty("usesPeriodic"));
         force->setAmoebaGlobalAngleCubic(node.getDoubleProperty("cubic"));
         force->setAmoebaGlobalAngleQuartic(node.getDoubleProperty("quartic"));
         force->setAmoebaGlobalAnglePentic(node.getDoubleProperty("pentic"));

plugins/amoeba/serialization/src/AmoebaBondForceProxy.cpp

@@ -42,10 +42,11 @@ AmoebaBondForceProxy::AmoebaBondForceProxy() : SerializationProxy("AmoebaBondFor
 }
 
 void AmoebaBondForceProxy::serialize(const void* object, SerializationNode& node) const {
-    node.setIntProperty("version", 2);
+    node.setIntProperty("version", 3);
     const AmoebaBondForce& force = *reinterpret_cast<const AmoebaBondForce*>(object);
 
     node.setIntProperty("forceGroup", force.getForceGroup());
+    node.setBoolProperty("usesPeriodic", force.usesPeriodicBoundaryConditions());
     node.setDoubleProperty("cubic",   force.getAmoebaGlobalBondCubic());
     node.setDoubleProperty("quartic", force.getAmoebaGlobalBondQuartic());
 
@@ -60,12 +61,14 @@ void AmoebaBondForceProxy::serialize(const void* object, SerializationNode& node
 
 void* AmoebaBondForceProxy::deserialize(const SerializationNode& node) const {
     int version = node.getIntProperty("version");
-    if (version < 1 || version > 2)
+    if (version < 1 || version > 3)
         throw OpenMMException("Unsupported version number");
     AmoebaBondForce* force = new AmoebaBondForce();
     try {
         if (version > 1)
             force->setForceGroup(node.getIntProperty("forceGroup", 0));
+        if (version > 2)
+            force->setUsesPeriodicBoundaryConditions(node.getBoolProperty("usesPeriodic"));
         force->setAmoebaGlobalBondCubic(node.getDoubleProperty("cubic"));
         force->setAmoebaGlobalBondQuartic(node.getDoubleProperty("quartic"));
         const SerializationNode& bonds = node.getChildNode("Bonds");

plugins/amoeba/serialization/src/AmoebaInPlaneAngleForceProxy.cpp

@@ -43,10 +43,11 @@ AmoebaInPlaneAngleForceProxy::AmoebaInPlaneAngleForceProxy() : SerializationProx
 
 void AmoebaInPlaneAngleForceProxy::serialize(const void* object, SerializationNode& node) const {
 
-    node.setIntProperty("version", 2);
+    node.setIntProperty("version", 3);
     const AmoebaInPlaneAngleForce& force = *reinterpret_cast<const AmoebaInPlaneAngleForce*>(object);
 
     node.setIntProperty("forceGroup", force.getForceGroup());
+    node.setBoolProperty("usesPeriodic", force.usesPeriodicBoundaryConditions());
     node.setDoubleProperty("cubic",      force.getAmoebaGlobalInPlaneAngleCubic());
     node.setDoubleProperty("quartic",    force.getAmoebaGlobalInPlaneAngleQuartic());
     node.setDoubleProperty("pentic",     force.getAmoebaGlobalInPlaneAnglePentic());
@@ -63,12 +64,14 @@ void AmoebaInPlaneAngleForceProxy::serialize(const void* object, SerializationNo
 
 void* AmoebaInPlaneAngleForceProxy::deserialize(const SerializationNode& node) const {
     int version = node.getIntProperty("version");
-    if (version < 1 || version > 2)
+    if (version < 1 || version > 3)
         throw OpenMMException("Unsupported version number");
     AmoebaInPlaneAngleForce* force = new AmoebaInPlaneAngleForce();
     try {
         if (version > 1)
             force->setForceGroup(node.getIntProperty("forceGroup", 0));
+        if (version > 2)
+            force->setUsesPeriodicBoundaryConditions(node.getBoolProperty("usesPeriodic"));
         force->setAmoebaGlobalInPlaneAngleCubic( node.getDoubleProperty("cubic"));
         force->setAmoebaGlobalInPlaneAngleQuartic(node.getDoubleProperty("quartic"));
         force->setAmoebaGlobalInPlaneAnglePentic(node.getDoubleProperty("pentic"));

plugins/amoeba/serialization/src/AmoebaOutOfPlaneBendForceProxy.cpp

@@ -42,9 +42,10 @@ AmoebaOutOfPlaneBendForceProxy::AmoebaOutOfPlaneBendForceProxy() : Serialization
 }
 
 void AmoebaOutOfPlaneBendForceProxy::serialize(const void* object, SerializationNode& node) const {
-    node.setIntProperty("version", 2);
+    node.setIntProperty("version", 3);
     const AmoebaOutOfPlaneBendForce& force = *reinterpret_cast<const AmoebaOutOfPlaneBendForce*>(object);
     node.setIntProperty("forceGroup", force.getForceGroup());
+    node.setBoolProperty("usesPeriodic", force.usesPeriodicBoundaryConditions());
     node.setDoubleProperty("cubic",   force.getAmoebaGlobalOutOfPlaneBendCubic());
     node.setDoubleProperty("quartic", force.getAmoebaGlobalOutOfPlaneBendQuartic());
     node.setDoubleProperty("pentic",  force.getAmoebaGlobalOutOfPlaneBendPentic());
@@ -61,12 +62,14 @@ void AmoebaOutOfPlaneBendForceProxy::serialize(const void* object, Serialization
 
 void* AmoebaOutOfPlaneBendForceProxy::deserialize(const SerializationNode& node) const {
     int version = node.getIntProperty("version");
-    if (version < 1 || version > 2)
+    if (version < 1 || version > 3)
         throw OpenMMException("Unsupported version number");
     AmoebaOutOfPlaneBendForce* force = new AmoebaOutOfPlaneBendForce();
     try {
         if (version > 1)
             force->setForceGroup(node.getIntProperty("forceGroup", 0));
+        if (version > 2)
+            force->setUsesPeriodicBoundaryConditions(node.getBoolProperty("usesPeriodic"));
         force->setAmoebaGlobalOutOfPlaneBendCubic(node.getDoubleProperty("cubic"));
         force->setAmoebaGlobalOutOfPlaneBendQuartic(node.getDoubleProperty("quartic"));
         force->setAmoebaGlobalOutOfPlaneBendPentic(node.getDoubleProperty("pentic"));

plugins/amoeba/serialization/src/AmoebaPiTorsionForceProxy.cpp

@@ -42,9 +42,10 @@ AmoebaPiTorsionForceProxy::AmoebaPiTorsionForceProxy() : SerializationProxy("Amo
 }
 
 void AmoebaPiTorsionForceProxy::serialize(const void* object, SerializationNode& node) const {
-    node.setIntProperty("version", 2);
+    node.setIntProperty("version", 3);
     const AmoebaPiTorsionForce& force = *reinterpret_cast<const AmoebaPiTorsionForce*>(object);
     node.setIntProperty("forceGroup", force.getForceGroup());
+    node.setBoolProperty("usesPeriodic", force.usesPeriodicBoundaryConditions());
     SerializationNode& bonds = node.createChildNode("PiTorsion");
     for (unsigned int ii = 0; ii < static_cast<unsigned int>(force.getNumPiTorsions()); ii++) {
         int particle1, particle2, particle3, particle4, particle5, particle6;
@@ -56,12 +57,14 @@ void AmoebaPiTorsionForceProxy::serialize(const void* object, SerializationNode&
 
 void* AmoebaPiTorsionForceProxy::deserialize(const SerializationNode& node) const {
     int version = node.getIntProperty("version");
-    if (version < 1 || version > 2)
+    if (version < 1 || version > 3)
         throw OpenMMException("Unsupported version number");
     AmoebaPiTorsionForce* force = new AmoebaPiTorsionForce();
     try {
         if (version > 1)
             force->setForceGroup(node.getIntProperty("forceGroup", 0));
+        if (version > 2)
+            force->setUsesPeriodicBoundaryConditions(node.getBoolProperty("usesPeriodic"));
         const SerializationNode& bonds = node.getChildNode("PiTorsion");
         for (unsigned int ii = 0; ii < bonds.getChildren().size(); ii++) {
             const SerializationNode& bond = bonds.getChildren()[ii];

plugins/amoeba/serialization/src/AmoebaStretchBendForceProxy.cpp

@@ -42,9 +42,10 @@ AmoebaStretchBendForceProxy::AmoebaStretchBendForceProxy() : SerializationProxy(
 }
 
 void AmoebaStretchBendForceProxy::serialize(const void* object, SerializationNode& node) const {
-    node.setIntProperty("version", 3);
+    node.setIntProperty("version", 4);
     const AmoebaStretchBendForce& force = *reinterpret_cast<const AmoebaStretchBendForce*>(object);
     node.setIntProperty("forceGroup", force.getForceGroup());
+    node.setBoolProperty("usesPeriodic", force.usesPeriodicBoundaryConditions());
     SerializationNode& bonds = node.createChildNode("StretchBendAngles");
     for (unsigned int ii = 0; ii < static_cast<unsigned int>(force.getNumStretchBends()); ii++) {
         int particle1, particle2, particle3;
@@ -57,12 +58,14 @@ void AmoebaStretchBendForceProxy::serialize(const void* object, SerializationNod
 
 void* AmoebaStretchBendForceProxy::deserialize(const SerializationNode& node) const {
     int version = node.getIntProperty("version");
-    if (version < 1 || version > 3)
+    if (version < 1 || version > 4)
         throw OpenMMException("Unsupported version number");
     AmoebaStretchBendForce* force = new AmoebaStretchBendForce();
     try {
         if (version > 2)
             force->setForceGroup(node.getIntProperty("forceGroup", 0));
+        if (version > 3)
+            force->setUsesPeriodicBoundaryConditions(node.getBoolProperty("usesPeriodic"));
         const SerializationNode& bonds = node.getChildNode("StretchBendAngles");
         for (unsigned int ii = 0; ii < (int) bonds.getChildren().size(); ii++) {
             const SerializationNode& bond = bonds.getChildren()[ii];