Add

platforms/brook/tests/TestBrookAngleBondForce.cpp

+/* -------------------------------------------------------------------------- *
+ *                                   OpenMM                                   *
+ * -------------------------------------------------------------------------- *
+ * This is part of the OpenMM molecular simulation toolkit originating from   *
+ * Simbios, the NIH National Center for Physics-Based Simulation of           *
+ * 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.           *
+ * Authors: Mark Friedrichs                                                   *
+ * Contributors:                                                              *
+ *                                                                            *
+ * Permission is hereby granted, free of charge, to any person obtaining a    *
+ * copy of this software and associated documentation files (the "Software"), *
+ * to deal in the Software without restriction, including without limitation  *
+ * the rights to use, copy, modify, merge, publish, distribute, sublicense,   *
+ * and/or sell copies of the Software, and to permit persons to whom the      *
+ * Software is furnished to do so, subject to the following conditions:       *
+ *                                                                            *
+ * The above copyright notice and this permission notice shall be included in *
+ * all copies or substantial portions of the Software.                        *
+ *                                                                            *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR *
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,   *
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL    *
+ * THE AUTHORS, CONTRIBUTORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM,    *
+ * DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR      *
+ * OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE  *
+ * USE OR OTHER DEALINGS IN THE SOFTWARE.                                     *
+ * -------------------------------------------------------------------------- */
+
+/**
+ * This tests the Brook harmonic angle bond force/energy
+ */
+
+#include "../../../tests/AssertionUtilities.h"
+#include "BrookPlatform.h"
+#include "OpenMMContext.h"
+#include "HarmonicAngleForce.h"
+#include "System.h"
+#include "LangevinIntegrator.h"
+#include <vector>
+
+#define PI_M               3.141592653589
+
+using namespace OpenMM;
+using namespace std;
+
+const double TOL = 1e-5;
+
+void testBrookAngles( FILE* log ){
+
+// ---------------------------------------------------------------------------------------
+
+   static const std::string methodName      = "testBrookAngles";
+   static const int debug                   = 1;
+   
+   int PrintOn                              = 0; 
+   int numberOfParticles                    = 4;
+   double mass                              = 2.0;
+
+// ---------------------------------------------------------------------------------------
+
+   PrintOn = log ? PrintOn : 0;
+
+   if( PrintOn ){
+      (void) fprintf( log, "%s\n", methodName.c_str() ); (void) fflush( log );
+   }
+
+   BrookPlatform platform( 32, "cal", log );
+   System system( numberOfParticles, 0 ); 
+   LangevinIntegrator integrator( 0, 0.1, 0.01 );
+
+   // int numParticles, int numBonds, int numAngles, int numPeriodicTorsions, int numRBTorsions
+
+   HarmonicAngleForce* forceField = new HarmonicAngleForce(2);
+
+   // int index, int atom1, int atom2, int atom3, double angle, double k
+   forceField->setAngleParameters(0, 0, 1, 2, PI_M/3, 1.1);
+   forceField->setAngleParameters(1, 1, 2, 3, PI_M/2, 1.2);
+   system.addForce(forceField);
+
+   OpenMMContext context(system, integrator, platform);
+   vector<Vec3> positions(numberOfParticles);
+
+   positions[0] = Vec3(0, 1, 0);
+   positions[1] = Vec3(0, 0, 0);
+   positions[2] = Vec3(1, 0, 0);
+   positions[3] = Vec3(2, 1, 0);
+
+   context.setPositions(positions);
+
+   State state = context.getState( State::Forces | State::Energy );
+
+   const vector<Vec3>& forces = state.getForces();
+   if( PrintOn ){
+      (void) fprintf( log, "Angle bond forces\n");
+      for( int ii = 0; ii < numberOfParticles; ii++ ){
+         (void) fprintf( log, "%d [%.5e %.5e %.5e]\n", ii, forces[ii][0], forces[ii][1], forces[ii][2] );
+      }
+      (void) fflush( log );
+   }
+
+   double tolerance  = 1.0e-03;
+   double torque1    = 1.1*PI_M/6;
+   double torque2    = 1.2*PI_M/4;
+   ASSERT_EQUAL_VEC(Vec3(torque1, 0, 0), forces[0], tolerance);
+   ASSERT_EQUAL_VEC(Vec3(-0.5*torque2, 0.5*torque2, 0), forces[3], tolerance); // reduced by sqrt(2) due to the bond length, another sqrt(2) due to the angle
+   ASSERT_EQUAL_VEC(Vec3(forces[0][0]+forces[1][0]+forces[2][0]+forces[3][0],
+                         forces[0][1]+forces[1][1]+forces[2][1]+forces[3][1],
+                         forces[0][2]+forces[1][2]+forces[2][2]+forces[3][2]),
+                         Vec3(0, 0, 0), tolerance);
+
+   ASSERT_EQUAL_TOL(0.5*1.1*(PI_M/6)*(PI_M/6) + 0.5*1.2*(PI_M/4)*(PI_M/4), state.getPotentialEnergy(), tolerance);
+
+   if( PrintOn ){
+      (void) fprintf( log, "Angle bond forces ok tolerance=%.2e\n", tolerance ); (void) fflush( log );
+   }
+}
+
+int main( ){
+
+// ---------------------------------------------------------------------------------------
+
+   static const std::string methodName      = "testBrookAngles";
+   FILE* log                                = stdout;
+
+// ---------------------------------------------------------------------------------------
+
+   (void) fflush( stdout );
+   (void) fflush( stderr );
+   try {
+      testBrookAngles( log );
+    } catch( const exception& e ){
+      (void) fprintf( log, "Exception %s %.s\n", methodName.c_str(),  e.what() ); (void) fflush( log );
+      return 1;
+   }   
+   (void) fprintf( log, "\n%s done\n", methodName.c_str() ); (void) fflush( log );
+
+   return 0;
+}

platforms/brook/tests/TestBrookHarmonicBondForce.cpp

+/* -------------------------------------------------------------------------- *
+ *                                   OpenMM                                   *
+ * -------------------------------------------------------------------------- *
+ * This is part of the OpenMM molecular simulation toolkit originating from   *
+ * Simbios, the NIH National Center for Physics-Based Simulation of           *
+ * 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.           *
+ * Authors: Mark Friedrichs                                                   *
+ * Contributors:                                                              *
+ *                                                                            *
+ * Permission is hereby granted, free of charge, to any person obtaining a    *
+ * copy of this software and associated documentation files (the "Software"), *
+ * to deal in the Software without restriction, including without limitation  *
+ * the rights to use, copy, modify, merge, publish, distribute, sublicense,   *
+ * and/or sell copies of the Software, and to permit persons to whom the      *
+ * Software is furnished to do so, subject to the following conditions:       *
+ *                                                                            *
+ * The above copyright notice and this permission notice shall be included in *
+ * all copies or substantial portions of the Software.                        *
+ *                                                                            *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR *
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,   *
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL    *
+ * THE AUTHORS, CONTRIBUTORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM,    *
+ * DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR      *
+ * OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE  *
+ * USE OR OTHER DEALINGS IN THE SOFTWARE.                                     *
+ * -------------------------------------------------------------------------- */
+
+/**
+ * This tests the Brook Harmonic bond force/energy
+ */
+
+#include "../../../tests/AssertionUtilities.h"
+#include "BrookPlatform.h"
+#include "OpenMMContext.h"
+#include "HarmonicBondForce.h"
+#include "System.h"
+#include "LangevinIntegrator.h"
+#include <vector>
+
+using namespace OpenMM;
+using namespace std;
+
+const double TOL = 1e-5;
+
+void testBrookBonds( FILE* log ){
+
+// ---------------------------------------------------------------------------------------
+
+   static const std::string methodName      = "testBrookBonds";
+   int PrintOn                              = 0;
+   int numberOfParticles                    = 3;
+   double mass                              = 2.0;
+
+// ---------------------------------------------------------------------------------------
+
+   PrintOn = log ? PrintOn : 0;
+
+   if( PrintOn ){
+      (void) fprintf( log, "%s\n", methodName.c_str() ); (void) fflush( log );
+   }
+
+   BrookPlatform platform( 32, "cal", log );
+   System system( numberOfParticles, 0 ); 
+   LangevinIntegrator integrator(0, 0.1, 0.01);
+
+   // int numParticles, int numBonds, int numAngles, int numPeriodicTorsions, int numRBTorsions
+
+   HarmonicBondForce* forceField = new HarmonicBondForce( 2 ); 
+
+   // ( index, atom1, atom2, length, k )
+   forceField->setBondParameters(0, 0, 1, 1.5, 0.8);
+   forceField->setBondParameters(1, 1, 2, 1.2, 0.7);
+   system.addForce(forceField);
+
+   OpenMMContext context(system, integrator, platform);
+   vector<Vec3> positions(3);
+
+   positions[0] = Vec3(0, 2, 0); 
+   positions[1] = Vec3(0, 0, 0); 
+   positions[2] = Vec3(1, 0, 0); 
+
+   context.setPositions(positions);
+
+   //(void) fprintf( log, "testBrookBonds:Calling getState\n");
+   //(void) fflush( log );
+
+   State state = context.getState( State::Forces | State::Energy );
+
+   const vector<Vec3>& forces = state.getForces();
+   if( PrintOn ){
+      (void) fprintf( log, "Harmonic bond forces\n");
+      for( int ii = 0; ii < numberOfParticles; ii++ ){
+         (void) fprintf( log, "%d [%.5e %.5e %.5e]\n", ii, forces[ii][0], forces[ii][1], forces[ii][2] );
+      }
+      (void) fflush( log );
+   }
+
+   ASSERT_EQUAL_VEC(Vec3(0, -0.8*0.5, 0), forces[0], TOL);
+   ASSERT_EQUAL_VEC(Vec3(0.7*0.2, 0, 0), forces[2], TOL);
+   ASSERT_EQUAL_VEC(Vec3(-forces[0][0]-forces[2][0], -forces[0][1]-forces[2][1], -forces[0][2]-forces[2][2]), forces[1], TOL);
+
+   if( PrintOn ){
+      (void) fprintf( log, "Harmonic bond forces ok -- checking energy\n"); (void) fflush( log );
+   }
+
+   ASSERT_EQUAL_TOL( 0.5*0.8*0.5*0.5 + 0.5*0.7*0.2*0.2, state.getPotentialEnergy(), TOL);
+
+   if( PrintOn ){
+      (void) fprintf( log, "Harmonic bond energy ok\n"); (void) fflush( log );
+   }
+
+}
+
+int main( ){
+
+// ---------------------------------------------------------------------------------------
+
+   static const std::string methodName      = "testBrookBonds";
+   FILE* log                                = stdout;
+
+// ---------------------------------------------------------------------------------------
+
+   (void) fflush( stdout );
+   (void) fflush( stderr );
+   try {
+      testBrookBonds( log );
+    }  catch( const exception& e ){
+      (void) fprintf( log, "Exception %s %.s\n", methodName.c_str(), e.what() ); (void) fflush( log );
+      return 1;
+   }   
+   (void) fprintf( log, "\n%s done\n", methodName.c_str() ); (void) fflush( log );
+
+   return 0;
+}

platforms/brook/tests/TestBrookRBTorsionForce.cpp

+/* -------------------------------------------------------------------------- *
+ *                                   OpenMM                                   *
+ * -------------------------------------------------------------------------- *
+ * This is part of the OpenMM molecular simulation toolkit originating from   *
+ * Simbios, the NIH National Center for Physics-Based Simulation of           *
+ * 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.           *
+ * Authors: Mark Friedrichs                                                   *
+ * Contributors:                                                              *
+ *                                                                            *
+ * Permission is hereby granted, free of charge, to any person obtaining a    *
+ * copy of this software and associated documentation files (the "Software"), *
+ * to deal in the Software without restriction, including without limitation  *
+ * the rights to use, copy, modify, merge, publish, distribute, sublicense,   *
+ * and/or sell copies of the Software, and to permit persons to whom the      *
+ * Software is furnished to do so, subject to the following conditions:       *
+ *                                                                            *
+ * The above copyright notice and this permission notice shall be included in *
+ * all copies or substantial portions of the Software.                        *
+ *                                                                            *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR *
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,   *
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL    *
+ * THE AUTHORS, CONTRIBUTORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM,    *
+ * DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR      *
+ * OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE  *
+ * USE OR OTHER DEALINGS IN THE SOFTWARE.                                     *
+ * -------------------------------------------------------------------------- */
+
+/**
+ * This tests the Brook RB torsion bond force/energy
+ */
+
+#include "../../../tests/AssertionUtilities.h"
+#include "BrookPlatform.h"
+#include "ReferencePlatform.h"
+#include "OpenMMContext.h"
+#include "RBTorsionForce.h"
+#include "System.h"
+#include "LangevinIntegrator.h"
+#include <vector>
+
+#define PI_M               3.141592653589
+
+using namespace OpenMM;
+using namespace std;
+
+const double TOL = 1e-5;
+
+void testBrookRBTorsions( FILE* log ){
+
+// ---------------------------------------------------------------------------------------
+
+   static const std::string methodName      = "RBTorsions";
+   int PrintOn                              = 0;
+   
+   int numberOfParticles                    = 4;
+   double mass                              = 2.0;
+
+// ---------------------------------------------------------------------------------------
+
+   PrintOn = log ? PrintOn : 0;
+
+   if( PrintOn ){
+      (void) fprintf( log, "%s\n", methodName.c_str() ); (void) fflush( log );
+   }
+
+   BrookPlatform platform( 32, "cal", log );
+   //ReferencePlatform platform;
+   System system( numberOfParticles, 0 ); 
+   LangevinIntegrator integrator( 0, 0.1, 0.01 );
+
+   RBTorsionForce* forceField = new RBTorsionForce( 1 );
+   forceField->setTorsionParameters(0, 0, 1, 2, 3, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6);
+   system.addForce(forceField);
+
+   OpenMMContext context(system, integrator, platform);
+   vector<Vec3> positions(numberOfParticles);
+
+   positions[0] = Vec3(0, 1, 0);
+   positions[1] = Vec3(0, 0, 0);
+   positions[2] = Vec3(1, 0, 0);
+   positions[3] = Vec3(1, 1, 1);
+
+   context.setPositions(positions);
+
+   State state = context.getState( State::Forces | State::Energy );
+
+   const vector<Vec3>& forces = state.getForces();
+   if( PrintOn ){
+      (void) fprintf( log, "RB torsion bond forces\n");
+      for( int ii = 0; ii < numberOfParticles; ii++ ){
+         (void) fprintf( log, "%d [%.5e %.5e %.5e]\n", ii, forces[ii][0], forces[ii][1], forces[ii][2] );
+      }
+      (void) fflush( log );
+   }
+
+   double psi    = 0.25*PI_M - PI_M;
+   double torque = 0.0;
+   for (int i = 1; i < 6; ++i) {
+      double c  = 0.1*(i+1);
+      torque   += -c*i*std::pow(std::cos(psi), i-1)*std::sin(psi);
+   }
+
+   if( PrintOn ){
+      (void) fprintf( log, "RB torsion bond expected forces\n");
+      (void) fprintf( log, "0 [0.0 0.0 %.5e]\n", torque );
+      (void) fprintf( log, "3 [0.0 %.5e %.5e]\n", 0.5*torque, -0.5*torque );
+      (void) fflush( log );
+   }
+
+   double tolerance = 0.001;
+   ASSERT_EQUAL_VEC(Vec3(0, 0, torque), forces[0], tolerance );
+   ASSERT_EQUAL_VEC(Vec3(0, 0.5*torque, -0.5*torque), forces[3], tolerance );
+   ASSERT_EQUAL_VEC(Vec3(forces[0][0]+forces[1][0]+forces[2][0]+forces[3][0],
+                         forces[0][1]+forces[1][1]+forces[2][1]+forces[3][1],
+                         forces[0][2]+forces[1][2]+forces[2][2]+forces[3][2]),
+                         Vec3(0, 0, 0), tolerance);
+
+   double energy = 0.0;
+   for (int i = 0; i < 6; ++i) {
+       double c = 0.1*(i+1);
+       energy += c*std::pow(std::cos(psi), i);
+   }
+   ASSERT_EQUAL_TOL(energy, state.getPotentialEnergy(), tolerance );
+
+   if( PrintOn ){
+      (void) fprintf( log, "RB torsion bond forces ok tolerance=%.2e\n", tolerance); fflush( log );
+   }
+}
+
+int main( ){
+
+// ---------------------------------------------------------------------------------------
+
+   static const std::string methodName      = "testBrookRbTorsion";
+   FILE* log                                = stdout;
+
+// ---------------------------------------------------------------------------------------
+
+   (void) fflush( stdout );
+   (void) fflush( stderr );
+   try {
+      testBrookRBTorsions( log );
+    } catch( const exception& e ){
+      (void) fprintf( log, "Exception %s %.s\n", methodName.c_str(),  e.what() ); (void) fflush( log );
+      return 1;
+   }   
+   (void) fprintf( log, "\n%s done\n", methodName.c_str() ); (void) fflush( log );
+
+   return 0;
+}

platforms/brook/tests/testBrookPeriodicTorsionForce.cpp

+/* -------------------------------------------------------------------------- *
+ *                                   OpenMM                                   *
+ * -------------------------------------------------------------------------- *
+ * This is part of the OpenMM molecular simulation toolkit originating from   *
+ * Simbios, the NIH National Center for Physics-Based Simulation of           *
+ * 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.           *
+ * Authors: Mark Friedrichs                                                   *
+ * Contributors:                                                              *
+ *                                                                            *
+ * Permission is hereby granted, free of charge, to any person obtaining a    *
+ * copy of this software and associated documentation files (the "Software"), *
+ * to deal in the Software without restriction, including without limitation  *
+ * the rights to use, copy, modify, merge, publish, distribute, sublicense,   *
+ * and/or sell copies of the Software, and to permit persons to whom the      *
+ * Software is furnished to do so, subject to the following conditions:       *
+ *                                                                            *
+ * The above copyright notice and this permission notice shall be included in *
+ * all copies or substantial portions of the Software.                        *
+ *                                                                            *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR *
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,   *
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL    *
+ * THE AUTHORS, CONTRIBUTORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM,    *
+ * DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR      *
+ * OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE  *
+ * USE OR OTHER DEALINGS IN THE SOFTWARE.                                     *
+ * -------------------------------------------------------------------------- */
+
+/**
+ * This tests the Brook periodic torsion bond force/energy
+ */
+
+#include "../../../tests/AssertionUtilities.h"
+#include "BrookPlatform.h"
+#include "OpenMMContext.h"
+#include "PeriodicTorsionForce.h"
+#include "System.h"
+#include "LangevinIntegrator.h"
+#include <vector>
+
+#define PI_M               3.141592653589
+
+using namespace OpenMM;
+using namespace std;
+
+const double TOL = 1e-5;
+
+
+
+void testBrookPeriodicTorsions( FILE* log ){
+
+// ---------------------------------------------------------------------------------------
+
+   static const std::string methodName      = "PeriodicTorsions";
+   int PrintOn                              = 0;
+   int numberOfParticles                    = 4;
+   double mass                              = 2.0;
+
+// ---------------------------------------------------------------------------------------
+
+   PrintOn = log ? PrintOn : 0;
+
+   if( PrintOn ){
+      (void) fprintf( log, "%s\n", methodName.c_str() ); (void) fflush( log );
+   }   
+
+   BrookPlatform platform( 32, "cal", log );
+   System system( numberOfParticles, 0 ); 
+   LangevinIntegrator integrator( 0, 0.1, 0.01 );
+
+   // int numParticles, int numBonds, int numAngles, int numPeriodicTorsions, int numRBTorsions
+
+   PeriodicTorsionForce* forceField = new PeriodicTorsionForce( 1 ); 
+
+   // int index, int atom1, int atom2, int atom3, double angle, double k
+   forceField->setTorsionParameters(0, 0, 1, 2, 3, 2, PI_M/3, 1.1);
+   system.addForce(forceField);
+
+   OpenMMContext context(system, integrator, platform);
+   vector<Vec3> positions(numberOfParticles);
+
+   positions[0] = Vec3(0, 1, 0);
+   positions[1] = Vec3(0, 0, 0);
+   positions[2] = Vec3(1, 0, 0);
+   positions[3] = Vec3(1, 0, 2);
+
+   context.setPositions(positions);
+
+   State state = context.getState( State::Forces | State::Energy );
+
+   const vector<Vec3>& forces = state.getForces();
+   if( PrintOn ){
+      (void) fprintf( log, "Periodic torsion bond forces\n");
+      for( int ii = 0; ii < numberOfParticles; ii++ ){
+         (void) fprintf( log, "%d [%.5e %.5e %.5e]\n", ii, forces[ii][0], forces[ii][1], forces[ii][2] );
+      }
+      (void) fflush( log );
+   }
+
+   double torque    = -2*1.1*std::sin(2*PI_M/3);
+   double tolerance = 1.0e-03;
+   ASSERT_EQUAL_VEC(Vec3(0, 0, torque), forces[0], tolerance );
+   ASSERT_EQUAL_VEC(Vec3(0, 0.5*torque, 0), forces[3], tolerance );
+   ASSERT_EQUAL_VEC(Vec3(forces[0][0]+forces[1][0]+forces[2][0]+forces[3][0],
+                         forces[0][1]+forces[1][1]+forces[2][1]+forces[3][1],
+                         forces[0][2]+forces[1][2]+forces[2][2]+forces[3][2]),
+                         Vec3(0, 0, 0), tolerance );
+
+   ASSERT_EQUAL_TOL(1.1*(1+std::cos(2*PI_M/3)), state.getPotentialEnergy(), tolerance );
+   if( PrintOn ){
+      (void) fprintf( log, "Periodic torsion bond forces ok -- tolerance=%.2e\n", tolerance); (void) fflush( log );
+   }
+}
+
+int main( ){
+
+// ---------------------------------------------------------------------------------------
+
+   static const std::string methodName      = "testBrookPeriodicTorsions";
+   FILE* log                                = stdout;
+
+// ---------------------------------------------------------------------------------------
+
+   (void) fflush( stdout );
+   (void) fflush( stderr );
+   try {
+      testBrookPeriodicTorsions( log );
+    } catch( const exception& e ){
+      (void) fprintf( log, "Exception %s %.s\n", methodName.c_str(),  e.what() ); (void) fflush( log );
+      return 1;
+   }   
+   (void) fprintf( log, "\n%s done\n", methodName.c_str() ); (void) fflush( log );
+
+   return 0;
+}