Long range dispersion correction is enabled by default

openmmapi/src/NonbondedForce.cpp

@@ -46,7 +46,7 @@ using std::string;
 using std::stringstream;
 using std::vector;
 
-NonbondedForce::NonbondedForce() : nonbondedMethod(NoCutoff), cutoffDistance(1.0), rfDielectric(78.3), ewaldErrorTol(5e-4), useDispersionCorrection(false) {
+NonbondedForce::NonbondedForce() : nonbondedMethod(NoCutoff), cutoffDistance(1.0), rfDielectric(78.3), ewaldErrorTol(5e-4), useDispersionCorrection(true) {
 }
 
 NonbondedForce::NonbondedMethod NonbondedForce::getNonbondedMethod() const {

openmmapi/src/NonbondedForceImpl.cpp

@@ -95,10 +95,6 @@ void NonbondedForceImpl::initialize(ContextImpl& context) {
         if (cutoff > 0.5*boxVectors[0][0] || cutoff > 0.5*boxVectors[1][1] || cutoff > 0.5*boxVectors[2][2])
             throw OpenMMException("NonbondedForce: The cutoff distance cannot be greater than half the periodic box size.");
     }
-    else {
-        if (owner.getUseDispersionCorrection())
-            throw OpenMMException("NonbondedForce: Dispersion correction may only be used with periodic boundary conditions.");
-    }
     dynamic_cast<CalcNonbondedForceKernel&>(kernel.getImpl()).initialize(context.getSystem(), owner);
 }
 
@@ -176,6 +172,9 @@ int NonbondedForceImpl::findZero(const NonbondedForceImpl::ErrorFunction& f, int
 }
 
 double NonbondedForceImpl::calcDispersionCorrection(const System& system, const NonbondedForce& force) {
+    if (force.getNonbondedMethod() == NonbondedForce::NoCutoff || force.getNonbondedMethod() == NonbondedForce::CutoffNonPeriodic)
+        return 0.0;
+    
     // Identify all particle classes (defined by sigma and epsilon), and count the number of
     // particles in each class.
 

platforms/cuda/tests/TestCudaNonbondedForce.cpp

@@ -631,14 +631,14 @@ void testDispersionCorrection() {
     Context context(system, integrator, platform);
     context.setPositions(positions);
     double energy1 = context.getState(State::Energy).getPotentialEnergy();
-    nonbonded->setUseDispersionCorrection(true);
+    nonbonded->setUseDispersionCorrection(false);
     context.reinitialize();
     context.setPositions(positions);
     double energy2 = context.getState(State::Energy).getPotentialEnergy();
     double term1 = (0.5*pow(1.1, 12)/pow(cutoff, 9))/9;
     double term2 = (0.5*pow(1.1, 6)/pow(cutoff, 3))/3;
     double expected = 8*M_PI*numParticles*numParticles*(term1-term2)/(boxSize*boxSize*boxSize);
-    ASSERT_EQUAL_TOL(expected, energy2-energy1, 1e-4);
+    ASSERT_EQUAL_TOL(expected, energy1-energy2, 1e-4);
 
     // Now modify half the particles to be different, and see if it is still correct.
 
@@ -648,11 +648,11 @@ void testDispersionCorrection() {
         numType2++;
     }
     int numType1 = numParticles-numType2;
-    nonbonded->setUseDispersionCorrection(false);
+    nonbonded->setUseDispersionCorrection(true);
     context.reinitialize();
     context.setPositions(positions);
     energy1 = context.getState(State::Energy).getPotentialEnergy();
-    nonbonded->setUseDispersionCorrection(true);
+    nonbonded->setUseDispersionCorrection(false);
     context.reinitialize();
     context.setPositions(positions);
     energy2 = context.getState(State::Energy).getPotentialEnergy();
@@ -667,7 +667,7 @@ void testDispersionCorrection() {
     term1 /= (numParticles*(numParticles+1))/2;
     term2 /= (numParticles*(numParticles+1))/2;
     expected = 8*M_PI*numParticles*numParticles*(term1-term2)/(boxSize*boxSize*boxSize);
-    ASSERT_EQUAL_TOL(expected, energy2-energy1, 1e-4);
+    ASSERT_EQUAL_TOL(expected, energy1-energy2, 1e-4);
 }
 
 int main() {

platforms/opencl/tests/TestOpenCLNonbondedForce.cpp

@@ -636,14 +636,14 @@ void testDispersionCorrection() {
     Context context(system, integrator, platform);
     context.setPositions(positions);
     double energy1 = context.getState(State::Energy).getPotentialEnergy();
-    nonbonded->setUseDispersionCorrection(true);
+    nonbonded->setUseDispersionCorrection(false);
     context.reinitialize();
     context.setPositions(positions);
     double energy2 = context.getState(State::Energy).getPotentialEnergy();
     double term1 = (0.5*pow(1.1, 12)/pow(cutoff, 9))/9;
     double term2 = (0.5*pow(1.1, 6)/pow(cutoff, 3))/3;
     double expected = 8*M_PI*numParticles*numParticles*(term1-term2)/(boxSize*boxSize*boxSize);
-    ASSERT_EQUAL_TOL(expected, energy2-energy1, 1e-4);
+    ASSERT_EQUAL_TOL(expected, energy1-energy2, 1e-4);
 
     // Now modify half the particles to be different, and see if it is still correct.
 
@@ -653,11 +653,11 @@ void testDispersionCorrection() {
         numType2++;
     }
     int numType1 = numParticles-numType2;
-    nonbonded->setUseDispersionCorrection(false);
+    nonbonded->setUseDispersionCorrection(true);
     context.reinitialize();
     context.setPositions(positions);
     energy1 = context.getState(State::Energy).getPotentialEnergy();
-    nonbonded->setUseDispersionCorrection(true);
+    nonbonded->setUseDispersionCorrection(false);
     context.reinitialize();
     context.setPositions(positions);
     energy2 = context.getState(State::Energy).getPotentialEnergy();
@@ -672,7 +672,7 @@ void testDispersionCorrection() {
     term1 /= (numParticles*(numParticles+1))/2;
     term2 /= (numParticles*(numParticles+1))/2;
     expected = 8*M_PI*numParticles*numParticles*(term1-term2)/(boxSize*boxSize*boxSize);
-    ASSERT_EQUAL_TOL(expected, energy2-energy1, 1e-4);
+    ASSERT_EQUAL_TOL(expected, energy1-energy2, 1e-4);
 }
 
 int main() {

platforms/reference/tests/TestReferenceNonbondedForce.cpp

@@ -384,14 +384,14 @@ void testDispersionCorrection() {
     Context context(system, integrator, platform);
     context.setPositions(positions);
     double energy1 = context.getState(State::Energy).getPotentialEnergy();
-    nonbonded->setUseDispersionCorrection(true);
+    nonbonded->setUseDispersionCorrection(false);
     context.reinitialize();
     context.setPositions(positions);
     double energy2 = context.getState(State::Energy).getPotentialEnergy();
     double term1 = (0.5*pow(1.1, 12)/pow(cutoff, 9))/9;
     double term2 = (0.5*pow(1.1, 6)/pow(cutoff, 3))/3;
     double expected = 8*M_PI*numParticles*numParticles*(term1-term2)/(boxSize*boxSize*boxSize);
-    ASSERT_EQUAL_TOL(expected, energy2-energy1, 1e-4);
+    ASSERT_EQUAL_TOL(expected, energy1-energy2, 1e-4);
 
     // Now modify half the particles to be different, and see if it is still correct.
 
@@ -401,11 +401,11 @@ void testDispersionCorrection() {
         numType2++;
     }
     int numType1 = numParticles-numType2;
-    nonbonded->setUseDispersionCorrection(false);
+    nonbonded->setUseDispersionCorrection(true);
     context.reinitialize();
     context.setPositions(positions);
     energy1 = context.getState(State::Energy).getPotentialEnergy();
-    nonbonded->setUseDispersionCorrection(true);
+    nonbonded->setUseDispersionCorrection(false);
     context.reinitialize();
     context.setPositions(positions);
     energy2 = context.getState(State::Energy).getPotentialEnergy();
@@ -420,7 +420,7 @@ void testDispersionCorrection() {
     term1 /= (numParticles*(numParticles+1))/2;
     term2 /= (numParticles*(numParticles+1))/2;
     expected = 8*M_PI*numParticles*numParticles*(term1-term2)/(boxSize*boxSize*boxSize);
-    ASSERT_EQUAL_TOL(expected, energy2-energy1, 1e-4);
+    ASSERT_EQUAL_TOL(expected, energy1-energy2, 1e-4);
 }
 
 int main() {