void testCutoff14() {
System system;
VerletIntegrator integrator(0.01);
NonbondedForce* nonbonded = new NonbondedForce();
nonbonded->setNonbondedMethod(NonbondedForce::CutoffNonPeriodic);
for (int i = 0; i < 5; ++i) {
system.addParticle(1.0);
nonbonded->addParticle(0, 1.5, 0);
}
const double cutoff = 3.5;
nonbonded->setCutoffDistance(cutoff);
const double eps = 30.0;
nonbonded->setReactionFieldDielectric(eps);
vector<pair<int, int> > bonds;
bonds.push_back(pair<int, int>(0, 1));
bonds.push_back(pair<int, int>(1, 2));
bonds.push_back(pair<int, int>(2, 3));
bonds.push_back(pair<int, int>(3, 4));
nonbonded->createExceptionsFromBonds(bonds, 0.0, 0.0);
int first14, second14;
for (int i = 0; i < nonbonded->getNumExceptions(); i++) {
int particle1, particle2;
double chargeProd, sigma, epsilon;
nonbonded->getExceptionParameters(i, particle1, particle2, chargeProd, sigma, epsilon);
if ((particle1 == 0 && particle2 == 3) || (particle1 == 3 && particle2 == 0))
first14 = i;
if ((particle1 == 1 && particle2 == 4) || (particle1 == 4 && particle2 == 1))
second14 = i;
}
system.addForce(nonbonded);
Context context(system, integrator, platform);
vector<Vec3> positions(5);
positions[0] = Vec3(0, 0, 0);
positions[1] = Vec3(1, 0, 0);
positions[2] = Vec3(2, 0, 0);
positions[3] = Vec3(3, 0, 0);
positions[4] = Vec3(4, 0, 0);
for (int i = 1; i < 5; ++i) {
// Test LJ forces
nonbonded->setParticleParameters(0, 0, 1.5, 1);
for (int j = 1; j < 5; ++j)
nonbonded->setParticleParameters(j, 0, 1.5, 0);
nonbonded->setParticleParameters(i, 0, 1.5, 1);
nonbonded->setExceptionParameters(first14, 0, 3, 0, 1.5, i == 3 ? 0.5 : 0.0);
nonbonded->setExceptionParameters(second14, 1, 4, 0, 1.5, 0.0);
context.reinitialize();
context.setPositions(positions);
State state = context.getState(State::Forces | State::Energy);
const vector<Vec3>& forces = state.getForces();
double r = positions[i][0];
double x = 1.5/r;
double e = 1.0;
double force = 4.0*e*(12*std::pow(x, 12.0)-6*std::pow(x, 6.0))/r;
double energy = 4.0*e*(std::pow(x, 12.0)-std::pow(x, 6.0));
if (i == 3) {
force *= 0.5;
energy *= 0.5;
}
if (i < 3 || r > cutoff) {
force = 0;
energy = 0;
}
ASSERT_EQUAL_VEC(Vec3(-force, 0, 0), forces[0], TOL);
ASSERT_EQUAL_VEC(Vec3(force, 0, 0), forces[i], TOL);
ASSERT_EQUAL_TOL(energy, state.getPotentialEnergy(), TOL);
// Test Coulomb forces
const double q = 0.7;
nonbonded->setParticleParameters(0, q, 1.5, 0);
nonbonded->setParticleParameters(i, q, 1.5, 0);
nonbonded->setExceptionParameters(first14, 0, 3, i == 3 ? q*q/1.2 : 0, 1.5, 0);
nonbonded->setExceptionParameters(second14, 1, 4, 0, 1.5, 0);
context.reinitialize();
context.setPositions(positions);
state = context.getState(State::Forces | State::Energy);
const vector<Vec3>& forces2 = state.getForces();
force = ONE_4PI_EPS0*q*q/(r*r);
energy = ONE_4PI_EPS0*q*q/r;
if (i == 3) {
force /= 1.2;
energy /= 1.2;
}
if (i < 3 || r > cutoff) {
force = 0;
energy = 0;
}
ASSERT_EQUAL_VEC(Vec3(-force, 0, 0), forces2[0], TOL);
ASSERT_EQUAL_VEC(Vec3(force, 0, 0), forces2[i], TOL);
ASSERT_EQUAL_TOL(energy, state.getPotentialEnergy(), TOL);
}
}
void testExclusionsAnd14() {
System system;
NonbondedForce* nonbonded = new NonbondedForce();
for (int i = 0; i < 5; ++i) {
system.addParticle(1.0);
nonbonded->addParticle(0, 1.5, 0);
}
vector<pair<int, int> > bonds;
bonds.push_back(pair<int, int>(0, 1));
bonds.push_back(pair<int, int>(1, 2));
bonds.push_back(pair<int, int>(2, 3));
bonds.push_back(pair<int, int>(3, 4));
nonbonded->createExceptionsFromBonds(bonds, 0.0, 0.0);
int first14, second14;
for (int i = 0; i < nonbonded->getNumExceptions(); i++) {
int particle1, particle2;
double chargeProd, sigma, epsilon;
nonbonded->getExceptionParameters(i, particle1, particle2, chargeProd, sigma, epsilon);
if ((particle1 == 0 && particle2 == 3) || (particle1 == 3 && particle2 == 0))
first14 = i;
if ((particle1 == 1 && particle2 == 4) || (particle1 == 4 && particle2 == 1))
second14 = i;
}
system.addForce(nonbonded);
VerletIntegrator integrator(0.01);
Context context(system, integrator, platform);
for (int i = 1; i < 5; ++i) {
// Test LJ forces
vector<Vec3> positions(5);
const double r = 1.0;
for (int j = 0; j < 5; ++j) {
nonbonded->setParticleParameters(j, 0, 1.5, 0);
positions[j] = Vec3(0, j, 0);
}
nonbonded->setParticleParameters(0, 0, 1.5, 1);
nonbonded->setParticleParameters(i, 0, 1.5, 1);
nonbonded->setExceptionParameters(first14, 0, 3, 0, 1.5, i == 3 ? 0.5 : 0.0);
nonbonded->setExceptionParameters(second14, 1, 4, 0, 1.5, 0.0);
positions[i] = Vec3(r, 0, 0);
context.reinitialize();
context.setPositions(positions);
State state = context.getState(State::Forces | State::Energy);
const vector<Vec3>& forces = state.getForces();
double x = 1.5/r;
double eps = 1.0;
double force = 4.0*eps*(12*std::pow(x, 12.0)-6*std::pow(x, 6.0))/r;
double energy = 4.0*eps*(std::pow(x, 12.0)-std::pow(x, 6.0));
if (i == 3) {
force *= 0.5;
energy *= 0.5;
}
if (i < 3) {
force = 0;
energy = 0;
}
ASSERT_EQUAL_VEC(Vec3(-force, 0, 0), forces[0], TOL);
ASSERT_EQUAL_VEC(Vec3(force, 0, 0), forces[i], TOL);
ASSERT_EQUAL_TOL(energy, state.getPotentialEnergy(), TOL);
// Test Coulomb forces
nonbonded->setParticleParameters(0, 2, 1.5, 0);
nonbonded->setParticleParameters(i, 2, 1.5, 0);
nonbonded->setExceptionParameters(first14, 0, 3, i == 3 ? 4/1.2 : 0, 1.5, 0);
nonbonded->setExceptionParameters(second14, 1, 4, 0, 1.5, 0);
context.reinitialize();
context.setPositions(positions);
state = context.getState(State::Forces | State::Energy);
const vector<Vec3>& forces2 = state.getForces();
force = ONE_4PI_EPS0*4/(r*r);
energy = ONE_4PI_EPS0*4/r;
if (i == 3) {
force /= 1.2;
energy /= 1.2;
}
if (i < 3) {
force = 0;
energy = 0;
}
ASSERT_EQUAL_VEC(Vec3(-force, 0, 0), forces2[0], TOL);
ASSERT_EQUAL_VEC(Vec3(force, 0, 0), forces2[i], TOL);
ASSERT_EQUAL_TOL(energy, state.getPotentialEnergy(), TOL);
}
}
