void testWaterSystem() {
ReferencePlatform platform;
System system;
static int numParticles = 648;
const double boxSize = 1.86206;
for (int i = 0 ; i < numParticles ; i++)
{
system.addParticle(1.0);
}
VerletIntegrator integrator(0.01);
NonbondedForce* nonbonded = new NonbondedForce();
for (int i = 0 ; i < numParticles/3 ; i++)
{
nonbonded->addParticle(-0.82, 1, 0);
nonbonded->addParticle(0.41, 1, 0);
nonbonded->addParticle(0.41, 1, 0);
}
nonbonded->setNonbondedMethod(NonbondedForce::CutoffPeriodic);
const double cutoff = 0.8;
nonbonded->setCutoffDistance(cutoff);
system.setDefaultPeriodicBoxVectors(Vec3(boxSize, 0, 0), Vec3(0, boxSize, 0), Vec3(0, 0, boxSize));
nonbonded->setEwaldErrorTolerance(EWALD_TOL);
system.addForce(nonbonded);
Context context(system, integrator, platform);
vector<Vec3> positions(numParticles);
#include "water.dat"
context.setPositions(positions);
State state1 = context.getState(State::Forces | State::Energy);
const vector<Vec3>& forces = state1.getForces();
// Take a small step in the direction of the energy gradient.
double norm = 0.0;
for (int i = 0; i < numParticles; ++i) {
Vec3 f = state1.getForces()[i];
norm += f[0]*f[0] + f[1]*f[1] + f[2]*f[2];
}
norm = std::sqrt(norm);
const double delta = 1e-3;
double step = delta/norm;
for (int i = 0; i < numParticles; ++i) {
Vec3 p = positions[i];
Vec3 f = state1.getForces()[i];
positions[i] = Vec3(p[0]-f[0]*step, p[1]-f[1]*step, p[2]-f[2]*step);
}
context.setPositions(positions);
// See whether the potential energy changed by the expected amount.
nonbonded->setNonbondedMethod(NonbondedForce::Ewald);
State state2 = context.getState(State::Energy);
ASSERT_EQUAL_TOL(norm, (state2.getPotentialEnergy()-state1.getPotentialEnergy())/delta, 0.01)
}
void testCutoffAndPeriodic() {
ReferencePlatform platform;
System system;
system.addParticle(1.0);
system.addParticle(1.0);
LangevinIntegrator integrator(0, 0.1, 0.01);
GBSAOBCForce* gbsa = new GBSAOBCForce();
NonbondedForce* nonbonded = new NonbondedForce();
gbsa->addParticle(-1, 0.15, 1);
nonbonded->addParticle(-1, 1, 0);
gbsa->addParticle(1, 0.15, 1);
nonbonded->addParticle(1, 1, 0);
const double cutoffDistance = 3.0;
const double boxSize = 10.0;
nonbonded->setCutoffDistance(cutoffDistance);
gbsa->setCutoffDistance(cutoffDistance);
system.setDefaultPeriodicBoxVectors(Vec3(boxSize, 0, 0), Vec3(0, boxSize, 0), Vec3(0, 0, boxSize));
system.addForce(gbsa);
system.addForce(nonbonded);
vector<Vec3> positions(2);
positions[0] = Vec3(0, 0, 0);
positions[1] = Vec3(2, 0, 0);
// Calculate the forces for both cutoff and periodic with two different atom positions.
nonbonded->setNonbondedMethod(NonbondedForce::CutoffNonPeriodic);
gbsa->setNonbondedMethod(GBSAOBCForce::CutoffNonPeriodic);
Context context(system, integrator, platform);
context.setPositions(positions);
State state1 = context.getState(State::Forces);
nonbonded->setNonbondedMethod(NonbondedForce::CutoffPeriodic);
gbsa->setNonbondedMethod(GBSAOBCForce::CutoffPeriodic);
context.reinitialize();
context.setPositions(positions);
State state2 = context.getState(State::Forces);
positions[1][0]+= boxSize;
nonbonded->setNonbondedMethod(NonbondedForce::CutoffNonPeriodic);
gbsa->setNonbondedMethod(GBSAOBCForce::CutoffNonPeriodic);
context.reinitialize();
context.setPositions(positions);
State state3 = context.getState(State::Forces);
nonbonded->setNonbondedMethod(NonbondedForce::CutoffPeriodic);
gbsa->setNonbondedMethod(GBSAOBCForce::CutoffPeriodic);
context.reinitialize();
context.setPositions(positions);
State state4 = context.getState(State::Forces);
// All forces should be identical, exception state3 which should be zero.
ASSERT_EQUAL_VEC(state1.getForces()[0], state2.getForces()[0], 0.01);
ASSERT_EQUAL_VEC(state1.getForces()[1], state2.getForces()[1], 0.01);
ASSERT_EQUAL_VEC(state1.getForces()[0], state4.getForces()[0], 0.01);
ASSERT_EQUAL_VEC(state1.getForces()[1], state4.getForces()[1], 0.01);
ASSERT_EQUAL_VEC(state3.getForces()[0], Vec3(0, 0, 0), 0.01);
ASSERT_EQUAL_VEC(state3.getForces()[1], Vec3(0, 0, 0), 0.01);
}
void testPeriodic() {
System system;
system.addParticle(1.0);
system.addParticle(1.0);
system.addParticle(1.0);
VerletIntegrator integrator(0.01);
NonbondedForce* nonbonded = new NonbondedForce();
nonbonded->addParticle(1.0, 1, 0);
nonbonded->addParticle(1.0, 1, 0);
nonbonded->addParticle(1.0, 1, 0);
nonbonded->addException(0, 1, 0.0, 1.0, 0.0);
nonbonded->setNonbondedMethod(NonbondedForce::CutoffPeriodic);
const double cutoff = 2.0;
nonbonded->setCutoffDistance(cutoff);
system.setDefaultPeriodicBoxVectors(Vec3(4, 0, 0), Vec3(0, 4, 0), Vec3(0, 0, 4));
system.addForce(nonbonded);
Context context(system, integrator, platform);
vector<Vec3> positions(3);
positions[0] = Vec3(0, 0, 0);
positions[1] = Vec3(2, 0, 0);
positions[2] = Vec3(3, 0, 0);
context.setPositions(positions);
State state = context.getState(State::Forces | State::Energy);
const vector<Vec3>& forces = state.getForces();
const double eps = 78.3;
const double krf = (1.0/(cutoff*cutoff*cutoff))*(eps-1.0)/(2.0*eps+1.0);
const double crf = (1.0/cutoff)*(3.0*eps)/(2.0*eps+1.0);
const double force = ONE_4PI_EPS0*(1.0)*(1.0-2.0*krf*1.0);
ASSERT_EQUAL_VEC(Vec3(force, 0, 0), forces[0], TOL);
ASSERT_EQUAL_VEC(Vec3(-force, 0, 0), forces[1], TOL);
ASSERT_EQUAL_VEC(Vec3(0, 0, 0), forces[2], TOL);
ASSERT_EQUAL_TOL(2*ONE_4PI_EPS0*(1.0)*(1.0+krf*1.0-crf), state.getPotentialEnergy(), TOL);
}
void testCutoff() {
System system;
system.addParticle(1.0);
system.addParticle(1.0);
system.addParticle(1.0);
VerletIntegrator integrator(0.01);
NonbondedForce* forceField = new NonbondedForce();
forceField->addParticle(1.0, 1, 0);
forceField->addParticle(1.0, 1, 0);
forceField->addParticle(1.0, 1, 0);
forceField->setNonbondedMethod(NonbondedForce::CutoffNonPeriodic);
const double cutoff = 2.9;
forceField->setCutoffDistance(cutoff);
const double eps = 50.0;
forceField->setReactionFieldDielectric(eps);
system.addForce(forceField);
Context context(system, integrator, platform);
vector<Vec3> positions(3);
positions[0] = Vec3(0, 0, 0);
positions[1] = Vec3(0, 2, 0);
positions[2] = Vec3(0, 3, 0);
context.setPositions(positions);
State state = context.getState(State::Forces | State::Energy);
const vector<Vec3>& forces = state.getForces();
const double krf = (1.0/(cutoff*cutoff*cutoff))*(eps-1.0)/(2.0*eps+1.0);
const double crf = (1.0/cutoff)*(3.0*eps)/(2.0*eps+1.0);
const double force1 = ONE_4PI_EPS0*(1.0)*(0.25-2.0*krf*2.0);
const double force2 = ONE_4PI_EPS0*(1.0)*(1.0-2.0*krf*1.0);
ASSERT_EQUAL_VEC(Vec3(0, -force1, 0), forces[0], TOL);
ASSERT_EQUAL_VEC(Vec3(0, force1-force2, 0), forces[1], TOL);
ASSERT_EQUAL_VEC(Vec3(0, force2, 0), forces[2], TOL);
const double energy1 = ONE_4PI_EPS0*(1.0)*(0.5+krf*4.0-crf);
const double energy2 = ONE_4PI_EPS0*(1.0)*(1.0+krf*1.0-crf);
ASSERT_EQUAL_TOL(energy1+energy2, state.getPotentialEnergy(), TOL);
}
void testEwald2Ions() {
System system;
system.addParticle(1.0);
system.addParticle(1.0);
VerletIntegrator integrator(0.01);
NonbondedForce* nonbonded = new NonbondedForce();
nonbonded->addParticle(1.0, 1, 0);
nonbonded->addParticle(-1.0, 1, 0);
nonbonded->setNonbondedMethod(NonbondedForce::Ewald);
const double cutoff = 2.0;
nonbonded->setCutoffDistance(cutoff);
nonbonded->setEwaldErrorTolerance(TOL);
system.setDefaultPeriodicBoxVectors(Vec3(6, 0, 0), Vec3(0, 6, 0), Vec3(0, 0, 6));
system.addForce(nonbonded);
Context context(system, integrator, platform);
vector<Vec3> positions(2);
positions[0] = Vec3(3.048000,2.764000,3.156000);
positions[1] = Vec3(2.809000,2.888000,2.571000);
context.setPositions(positions);
State state = context.getState(State::Forces | State::Energy);
const vector<Vec3>& forces = state.getForces();
ASSERT_EQUAL_VEC(Vec3(-123.711, 64.1877, -302.716), forces[0], 10*TOL);
ASSERT_EQUAL_VEC(Vec3( 123.711, -64.1877, 302.716), forces[1], 10*TOL);
ASSERT_EQUAL_TOL(-217.276, state.getPotentialEnergy(), 0.01/*10*TOL*/);
}
void testForceEnergyConsistency() {
// Create a box of polarizable particles.
const int gridSize = 3;
const int numAtoms = gridSize*gridSize*gridSize;
const double spacing = 0.6;
const double boxSize = spacing*(gridSize+1);
const double temperature = 300.0;
const double temperatureDrude = 10.0;
System system;
vector<Vec3> positions;
NonbondedForce* nonbonded = new NonbondedForce();
DrudeForce* drude = new DrudeForce();
system.addForce(nonbonded);
system.addForce(drude);
system.setDefaultPeriodicBoxVectors(Vec3(boxSize, 0, 0), Vec3(0, boxSize, 0), Vec3(0, 0, boxSize));
nonbonded->setNonbondedMethod(NonbondedForce::PME);
nonbonded->setCutoffDistance(1.0);
nonbonded->setUseSwitchingFunction(true);
nonbonded->setSwitchingDistance(0.9);
nonbonded->setEwaldErrorTolerance(5e-5);
for (int i = 0; i < numAtoms; i++) {
int startIndex = system.getNumParticles();
system.addParticle(1.0);
system.addParticle(1.0);
nonbonded->addParticle(1.0, 0.3, 1.0);
nonbonded->addParticle(-1.0, 0.3, 1.0);
nonbonded->addException(startIndex, startIndex+1, 0, 1, 0);
drude->addParticle(startIndex+1, startIndex, -1, -1, -1, -1.0, 0.001, 1, 1);
}
for (int i = 0; i < gridSize; i++)
for (int j = 0; j < gridSize; j++)
for (int k = 0; k < gridSize; k++) {
Vec3 pos(i*spacing, j*spacing, k*spacing);
positions.push_back(pos);
positions.push_back(pos);
}
// Simulate it and check that force and energy remain consistent.
DrudeLangevinIntegrator integ(temperature, 50.0, temperatureDrude, 50.0, 0.001);
Platform& platform = Platform::getPlatformByName("Reference");
Context context(system, integ, platform);
context.setPositions(positions);
State prevState;
for (int i = 0; i < 100; i++) {
State state = context.getState(State::Energy | State::Forces | State::Positions);
if (i > 0) {
double expectedEnergyChange = 0;
for (int j = 0; j < system.getNumParticles(); j++) {
Vec3 delta = state.getPositions()[j]-prevState.getPositions()[j];
expectedEnergyChange -= 0.5*(state.getForces()[j]+prevState.getForces()[j]).dot(delta);
}
ASSERT_EQUAL_TOL(expectedEnergyChange, state.getPotentialEnergy()-prevState.getPotentialEnergy(), 0.05);
}
prevState = state;
integ.step(1);
}
}
void testParallelComputation(NonbondedForce::NonbondedMethod method) {
System system;
const int numParticles = 200;
for (int i = 0; i < numParticles; i++)
system.addParticle(1.0);
NonbondedForce* force = new NonbondedForce();
for (int i = 0; i < numParticles; i++)
force->addParticle(i%2-0.5, 0.5, 1.0);
force->setNonbondedMethod(method);
system.addForce(force);
system.setDefaultPeriodicBoxVectors(Vec3(5,0,0), Vec3(0,5,0), Vec3(0,0,5));
OpenMM_SFMT::SFMT sfmt;
init_gen_rand(0, sfmt);
vector<Vec3> positions(numParticles);
for (int i = 0; i < numParticles; i++)
positions[i] = Vec3(5*genrand_real2(sfmt), 5*genrand_real2(sfmt), 5*genrand_real2(sfmt));
for (int i = 0; i < numParticles; ++i)
for (int j = 0; j < i; ++j) {
Vec3 delta = positions[i]-positions[j];
if (delta.dot(delta) < 0.1)
force->addException(i, j, 0, 1, 0);
}
// Create two contexts, one with a single device and one with two devices.
VerletIntegrator integrator1(0.01);
Context context1(system, integrator1, platform);
context1.setPositions(positions);
State state1 = context1.getState(State::Forces | State::Energy);
VerletIntegrator integrator2(0.01);
string deviceIndex = platform.getPropertyValue(context1, CudaPlatform::CudaDeviceIndex());
map<string, string> props;
props[CudaPlatform::CudaDeviceIndex()] = deviceIndex+","+deviceIndex;
Context context2(system, integrator2, platform, props);
context2.setPositions(positions);
State state2 = context2.getState(State::Forces | State::Energy);
// See if they agree.
ASSERT_EQUAL_TOL(state1.getPotentialEnergy(), state2.getPotentialEnergy(), 1e-5);
for (int i = 0; i < numParticles; i++)
ASSERT_EQUAL_VEC(state1.getForces()[i], state2.getForces()[i], 1e-5);
// Modify some particle parameters and see if they still agree.
for (int i = 0; i < numParticles; i += 5) {
double charge, sigma, epsilon;
force->getParticleParameters(i, charge, sigma, epsilon);
force->setParticleParameters(i, 0.9*charge, sigma, epsilon);
}
force->updateParametersInContext(context1);
force->updateParametersInContext(context2);
state1 = context1.getState(State::Forces | State::Energy);
state2 = context2.getState(State::Forces | State::Energy);
ASSERT_EQUAL_TOL(state1.getPotentialEnergy(), state2.getPotentialEnergy(), 1e-5);
for (int i = 0; i < numParticles; i++)
ASSERT_EQUAL_VEC(state1.getForces()[i], state2.getForces()[i], 1e-5);
}
void testLargeSystem() {
const int numMolecules = 50;
const int numParticles = numMolecules*2;
const double cutoff = 2.0;
const double boxSize = 5.0;
const double tolerance = 5;
System system;
system.setDefaultPeriodicBoxVectors(Vec3(boxSize, 0, 0), Vec3(0, boxSize, 0), Vec3(0, 0, boxSize));
NonbondedForce* nonbonded = new NonbondedForce();
nonbonded->setCutoffDistance(cutoff);
nonbonded->setNonbondedMethod(NonbondedForce::CutoffPeriodic);
system.addForce(nonbonded);
// Create a cloud of molecules.
OpenMM_SFMT::SFMT sfmt;
init_gen_rand(0, sfmt);
vector<Vec3> positions(numParticles);
for (int i = 0; i < numMolecules; i++) {
system.addParticle(1.0);
system.addParticle(1.0);
nonbonded->addParticle(-1.0, 0.2, 0.2);
nonbonded->addParticle(1.0, 0.2, 0.2);
positions[2*i] = Vec3(boxSize*genrand_real2(sfmt), boxSize*genrand_real2(sfmt), boxSize*genrand_real2(sfmt));
positions[2*i+1] = Vec3(positions[2*i][0]+1.0, positions[2*i][1], positions[2*i][2]);
system.addConstraint(2*i, 2*i+1, 1.0);
}
// Minimize it and verify that the energy has decreased.
ReferencePlatform platform;
VerletIntegrator integrator(0.01);
Context context(system, integrator, platform);
context.setPositions(positions);
State initialState = context.getState(State::Forces | State::Energy);
LocalEnergyMinimizer::minimize(context, tolerance);
State finalState = context.getState(State::Forces | State::Energy | State::Positions);
ASSERT(finalState.getPotentialEnergy() < initialState.getPotentialEnergy());
// Compute the force magnitude, subtracting off any component parallel to a constraint, and
// check that it satisfies the requested tolerance.
double forceNorm = 0.0;
for (int i = 0; i < numParticles; i += 2) {
Vec3 dir = finalState.getPositions()[i+1]-finalState.getPositions()[i];
double distance = sqrt(dir.dot(dir));
dir *= 1.0/distance;
Vec3 f = finalState.getForces()[i];
f -= dir*dir.dot(f);
forceNorm += f.dot(f);
f = finalState.getForces()[i+1];
f -= dir*dir.dot(f);
forceNorm += f.dot(f);
}
forceNorm = sqrt(forceNorm/(4*numMolecules));
ASSERT(forceNorm < 3*tolerance);
}
void testArgonBox() {
const int gridSize = 8;
const double mass = 40.0; // Ar atomic mass
const double temp = 120.0; // K
const double epsilon = BOLTZ * temp; // L-J well depth for Ar
const double sigma = 0.34; // L-J size for Ar in nm
const double density = 0.8; // atoms / sigma^3
double cellSize = sigma / pow(density, 0.333);
double boxSize = gridSize * cellSize;
double cutoff = 2.0 * sigma;
// Create a box of argon atoms.
System system;
NonbondedForce* nonbonded = new NonbondedForce();
vector<Vec3> positions;
OpenMM_SFMT::SFMT sfmt;
init_gen_rand(0, sfmt);
const Vec3 half(0.5, 0.5, 0.5);
for (int i = 0; i < gridSize; i++) {
for (int j = 0; j < gridSize; j++) {
for (int k = 0; k < gridSize; k++) {
system.addParticle(mass);
nonbonded->addParticle(0, sigma, epsilon);
positions.push_back((Vec3(i, j, k) + half + Vec3(genrand_real2(sfmt), genrand_real2(sfmt), genrand_real2(sfmt))*0.1) * cellSize);
}
}
}
nonbonded->setNonbondedMethod(NonbondedForce::CutoffPeriodic);
nonbonded->setCutoffDistance(cutoff);
system.setDefaultPeriodicBoxVectors(Vec3(boxSize, 0, 0), Vec3(0, boxSize, 0), Vec3(0, 0, boxSize));
system.addForce(nonbonded);
VariableVerletIntegrator integrator(1e-5);
Context context(system, integrator, platform);
context.setPositions(positions);
context.setVelocitiesToTemperature(temp);
// Equilibrate.
integrator.stepTo(1.0);
// Simulate it and see whether energy remains constant.
State state0 = context.getState(State::Energy);
double initialEnergy = state0.getKineticEnergy() + state0.getPotentialEnergy();
for (int i = 0; i < 20; i++) {
double t = 1.0 + 0.05*(i+1);
integrator.stepTo(t);
State state = context.getState(State::Energy);
double energy = state.getKineticEnergy() + state.getPotentialEnergy();
ASSERT_EQUAL_TOL(initialEnergy, energy, 0.01);
}
}
void testSwitchingFunction(NonbondedForce::NonbondedMethod method) {
ReferencePlatform platform;
System system;
system.setDefaultPeriodicBoxVectors(Vec3(6, 0, 0), Vec3(0, 6, 0), Vec3(0, 0, 6));
system.addParticle(1.0);
system.addParticle(1.0);
VerletIntegrator integrator(0.01);
NonbondedForce* nonbonded = new NonbondedForce();
nonbonded->addParticle(0, 1.2, 1);
nonbonded->addParticle(0, 1.4, 2);
nonbonded->setNonbondedMethod(method);
nonbonded->setCutoffDistance(2.0);
nonbonded->setUseSwitchingFunction(true);
nonbonded->setSwitchingDistance(1.5);
nonbonded->setUseDispersionCorrection(false);
system.addForce(nonbonded);
Context context(system, integrator, platform);
vector<Vec3> positions(2);
positions[0] = Vec3(0, 0, 0);
double eps = SQRT_TWO;
// Compute the interaction at various distances.
for (double r = 1.0; r < 2.5; r += 0.1) {
positions[1] = Vec3(r, 0, 0);
context.setPositions(positions);
State state = context.getState(State::Forces | State::Energy);
// See if the energy is correct.
double x = 1.3/r;
double expectedEnergy = 4.0*eps*(std::pow(x, 12.0)-std::pow(x, 6.0));
double switchValue;
if (r <= 1.5)
switchValue = 1;
else if (r >= 2.0)
switchValue = 0;
else {
double t = (r-1.5)/0.5;
switchValue = 1+t*t*t*(-10+t*(15-t*6));
}
ASSERT_EQUAL_TOL(switchValue*expectedEnergy, state.getPotentialEnergy(), TOL);
// See if the force is the gradient of the energy.
double delta = 1e-3;
positions[1] = Vec3(r-delta, 0, 0);
context.setPositions(positions);
double e1 = context.getState(State::Energy).getPotentialEnergy();
positions[1] = Vec3(r+delta, 0, 0);
context.setPositions(positions);
double e2 = context.getState(State::Energy).getPotentialEnergy();
ASSERT_EQUAL_TOL((e2-e1)/(2*delta), state.getForces()[0][0], 1e-3);
}
}
void testSerialization() {
// Create a Force.
NonbondedForce force;
force.setNonbondedMethod(NonbondedForce::CutoffPeriodic);
force.setCutoffDistance(2.0);
force.setEwaldErrorTolerance(1e-3);
force.setReactionFieldDielectric(50.0);
force.setUseDispersionCorrection(false);
force.addParticle(1, 0.1, 0.01);
force.addParticle(0.5, 0.2, 0.02);
force.addParticle(-0.5, 0.3, 0.03);
force.addException(0, 1, 2, 0.5, 0.1);
force.addException(1, 2, 0.2, 0.4, 0.2);
// Serialize and then deserialize it.
stringstream buffer;
XmlSerializer::serialize<NonbondedForce>(&force, "Force", buffer);
NonbondedForce* copy = XmlSerializer::deserialize<NonbondedForce>(buffer);
// Compare the two forces to see if they are identical.
NonbondedForce& force2 = *copy;
ASSERT_EQUAL(force.getNonbondedMethod(), force2.getNonbondedMethod());
ASSERT_EQUAL(force.getCutoffDistance(), force2.getCutoffDistance());
ASSERT_EQUAL(force.getEwaldErrorTolerance(), force2.getEwaldErrorTolerance());
ASSERT_EQUAL(force.getReactionFieldDielectric(), force2.getReactionFieldDielectric());
ASSERT_EQUAL(force.getUseDispersionCorrection(), force2.getUseDispersionCorrection());
ASSERT_EQUAL(force.getNumParticles(), force2.getNumParticles());
for (int i = 0; i < force.getNumParticles(); i++) {
double charge1, sigma1, epsilon1;
double charge2, sigma2, epsilon2;
force.getParticleParameters(i, charge1, sigma1, epsilon1);
force2.getParticleParameters(i, charge2, sigma2, epsilon2);
ASSERT_EQUAL(charge1, charge2);
ASSERT_EQUAL(sigma1, sigma2);
ASSERT_EQUAL(epsilon1, epsilon2);
}
ASSERT_EQUAL(force.getNumExceptions(), force2.getNumExceptions());
for (int i = 0; i < force.getNumExceptions(); i++) {
int a1, a2, b1, b2;
double charge1, sigma1, epsilon1;
double charge2, sigma2, epsilon2;
force.getExceptionParameters(i, a1, b1, charge1, sigma1, epsilon1);
force2.getExceptionParameters(i, a2, b2, charge2, sigma2, epsilon2);
ASSERT_EQUAL(a1, a2);
ASSERT_EQUAL(b1, b2);
ASSERT_EQUAL(charge1, charge2);
ASSERT_EQUAL(sigma1, sigma2);
ASSERT_EQUAL(epsilon1, epsilon2);
}
}
/**
* Test getting and setting per-DOF variables.
*/
void testPerDofVariables() {
const int numParticles = 200;
const double boxSize = 10;
System system;
system.setDefaultPeriodicBoxVectors(Vec3(boxSize, 0, 0), Vec3(0, boxSize, 0), Vec3(0, 0, boxSize));
NonbondedForce* nb = new NonbondedForce();
system.addForce(nb);
nb->setNonbondedMethod(NonbondedForce::CutoffNonPeriodic);
vector<Vec3> positions(numParticles);
OpenMM_SFMT::SFMT sfmt;
init_gen_rand(0, sfmt);
for (int i = 0; i < numParticles; i++) {
system.addParticle(1.5);
nb->addParticle(i%2 == 0 ? 1 : -1, 0.1, 1);
bool close = true;
while (close) {
positions[i] = Vec3(boxSize*genrand_real2(sfmt), boxSize*genrand_real2(sfmt), boxSize*genrand_real2(sfmt));
close = false;
for (int j = 0; j < i; ++j) {
Vec3 delta = positions[i]-positions[j];
if (delta.dot(delta) < 0.1)
close = true;
}
}
}
CustomIntegrator integrator(0.01);
integrator.addPerDofVariable("temp", 0);
integrator.addPerDofVariable("pos", 0);
integrator.addComputePerDof("v", "v+dt*f/m");
integrator.addComputePerDof("x", "x+dt*v");
integrator.addComputePerDof("pos", "x");
Context context(system, integrator, platform);
context.setPositions(positions);
vector<Vec3> initialValues(numParticles);
for (int i = 0; i < numParticles; i++)
initialValues[i] = Vec3(i+0.1, i+0.2, i+0.3);
integrator.setPerDofVariable(0, initialValues);
// Run a simulation, then query per-DOF values and see if they are correct.
vector<Vec3> values;
context.getState(State::Forces); // Cause atom reordering to happen before the first step
for (int i = 0; i < 200; ++i) {
integrator.step(1);
State state = context.getState(State::Positions);
integrator.getPerDofVariable(0, values);
for (int j = 0; j < numParticles; j++)
ASSERT_EQUAL_VEC(initialValues[j], values[j], 1e-5);
integrator.getPerDofVariable(1, values);
for (int j = 0; j < numParticles; j++)
ASSERT_EQUAL_VEC(state.getPositions()[j], values[j], 1e-5);
}
}
/**
* Test a multiple time step r-RESPA integrator.
*/
void testRespa() {
const int numParticles = 8;
System system;
system.setDefaultPeriodicBoxVectors(Vec3(4, 0, 0), Vec3(0, 4, 0), Vec3(0, 0, 4));
CustomIntegrator integrator(0.002);
integrator.addComputePerDof("v", "v+0.5*dt*f1/m");
for (int i = 0; i < 2; i++) {
integrator.addComputePerDof("v", "v+0.5*(dt/2)*f0/m");
integrator.addComputePerDof("x", "x+(dt/2)*v");
integrator.addComputePerDof("v", "v+0.5*(dt/2)*f0/m");
}
integrator.addComputePerDof("v", "v+0.5*dt*f1/m");
HarmonicBondForce* bonds = new HarmonicBondForce();
for (int i = 0; i < numParticles-2; i++)
bonds->addBond(i, i+1, 1.0, 0.5);
system.addForce(bonds);
NonbondedForce* nb = new NonbondedForce();
nb->setCutoffDistance(2.0);
nb->setNonbondedMethod(NonbondedForce::Ewald);
for (int i = 0; i < numParticles; ++i) {
system.addParticle(i%2 == 0 ? 5.0 : 10.0);
nb->addParticle((i%2 == 0 ? 0.2 : -0.2), 0.5, 5.0);
}
nb->setForceGroup(1);
nb->setReciprocalSpaceForceGroup(0);
system.addForce(nb);
Context context(system, integrator, platform);
vector<Vec3> positions(numParticles);
vector<Vec3> velocities(numParticles);
OpenMM_SFMT::SFMT sfmt;
init_gen_rand(0, sfmt);
for (int i = 0; i < numParticles; ++i) {
positions[i] = Vec3(i/2, (i+1)/2, 0);
velocities[i] = Vec3(genrand_real2(sfmt)-0.5, genrand_real2(sfmt)-0.5, genrand_real2(sfmt)-0.5);
}
context.setPositions(positions);
context.setVelocities(velocities);
// Simulate it and monitor energy conservations.
double initialEnergy = 0.0;
for (int i = 0; i < 1000; ++i) {
State state = context.getState(State::Energy);
double energy = state.getKineticEnergy()+state.getPotentialEnergy();
if (i == 1)
initialEnergy = energy;
else if (i > 1)
ASSERT_EQUAL_TOL(initialEnergy, energy, 0.05);
integrator.step(2);
}
}
void testErrorTolerance(NonbondedForce::NonbondedMethod method) {
// Create a cloud of random point charges.
const int numParticles = 51;
const double boxWidth = 5.0;
System system;
system.setDefaultPeriodicBoxVectors(Vec3(boxWidth, 0, 0), Vec3(0, boxWidth, 0), Vec3(0, 0, boxWidth));
NonbondedForce* force = new NonbondedForce();
system.addForce(force);
vector<Vec3> positions(numParticles);
OpenMM_SFMT::SFMT sfmt;
init_gen_rand(0, sfmt);
for (int i = 0; i < numParticles; i++) {
system.addParticle(1.0);
force->addParticle(-1.0+i*2.0/(numParticles-1), 1.0, 0.0);
positions[i] = Vec3(boxWidth*genrand_real2(sfmt), boxWidth*genrand_real2(sfmt), boxWidth*genrand_real2(sfmt));
}
force->setNonbondedMethod(method);
ReferencePlatform platform;
// For various values of the cutoff and error tolerance, see if the actual error is reasonable.
for (double cutoff = 1.0; cutoff < boxWidth/2; cutoff *= 1.2) {
force->setCutoffDistance(cutoff);
vector<Vec3> refForces;
double norm = 0.0;
for (double tol = 5e-5; tol < 1e-3; tol *= 2.0) {
force->setEwaldErrorTolerance(tol);
VerletIntegrator integrator(0.01);
Context context(system, integrator, platform);
context.setPositions(positions);
State state = context.getState(State::Forces);
if (refForces.size() == 0) {
refForces = state.getForces();
for (int i = 0; i < numParticles; i++)
norm += refForces[i].dot(refForces[i]);
norm = sqrt(norm);
}
else {
double diff = 0.0;
for (int i = 0; i < numParticles; i++) {
Vec3 delta = refForces[i]-state.getForces()[i];
diff += delta.dot(delta);
}
diff = sqrt(diff)/norm;
ASSERT(diff < 2*tol);
}
}
}
}
void testTruncatedOctahedron() {
const int numMolecules = 50;
const int numParticles = numMolecules*2;
const float cutoff = 2.0;
Vec3 a(6.7929, 0, 0);
Vec3 b(-2.264163559406279, 6.404455775962287, 0);
Vec3 c(-2.264163559406279, -3.2019384603140684, 5.54658849047036);
System system;
system.setDefaultPeriodicBoxVectors(a, b, c);
NonbondedForce* force = new NonbondedForce();
OpenMM_SFMT::SFMT sfmt;
init_gen_rand(0, sfmt);
vector<Vec3> positions(numParticles);
force->setCutoffDistance(cutoff);
force->setNonbondedMethod(NonbondedForce::CutoffPeriodic);
for (int i = 0; i < numMolecules; i++) {
system.addParticle(1.0);
system.addParticle(1.0);
force->addParticle(-1, 0.2, 0.2);
force->addParticle(1, 0.2, 0.2);
positions[2*i] = a*(5*genrand_real2(sfmt)-2) + b*(5*genrand_real2(sfmt)-2) + c*(5*genrand_real2(sfmt)-2);
positions[2*i+1] = positions[2*i] + Vec3(1.0, 0.0, 0.0);
system.addConstraint(2*i, 2*i+1, 1.0);
}
system.addForce(force);
VerletIntegrator integrator(0.01);
Context context(system, integrator, Platform::getPlatformByName("Reference"));
context.setPositions(positions);
State initialState = context.getState(State::Positions | State::Energy, true);
for (int i = 0; i < numMolecules; i++) {
Vec3 center = (initialState.getPositions()[2*i]+initialState.getPositions()[2*i+1])*0.5;
ASSERT(center[0] >= 0.0);
ASSERT(center[1] >= 0.0);
ASSERT(center[2] >= 0.0);
ASSERT(center[0] <= a[0]);
ASSERT(center[1] <= b[1]);
ASSERT(center[2] <= c[2]);
}
double initialEnergy = initialState.getPotentialEnergy();
context.setState(initialState);
State finalState = context.getState(State::Positions | State::Energy, true);
double finalEnergy = finalState.getPotentialEnergy();
ASSERT_EQUAL_TOL(initialEnergy, finalEnergy, 1e-4);
}
void testEwaldExact() {
// Use a NaCl crystal to compare the calculated and Madelung energies
const int numParticles = 1000;
const double cutoff = 1.0;
const double boxSize = 2.82;
ReferencePlatform platform;
System system;
for (int i = 0; i < numParticles/2; i++)
system.addParticle(22.99);
for (int i = 0; i < numParticles/2; i++)
system.addParticle(35.45);
VerletIntegrator integrator(0.01);
NonbondedForce* nonbonded = new NonbondedForce();
for (int i = 0; i < numParticles/2; i++)
nonbonded->addParticle(1.0, 1.0,0.0);
for (int i = 0; i < numParticles/2; i++)
nonbonded->addParticle(-1.0, 1.0,0.0);
nonbonded->setNonbondedMethod(NonbondedForce::Ewald);
nonbonded->setCutoffDistance(cutoff);
system.setDefaultPeriodicBoxVectors(Vec3(boxSize, 0, 0), Vec3(0, boxSize, 0), Vec3(0, 0, boxSize));
nonbonded->setEwaldErrorTolerance(EWALD_TOL);
system.addForce(nonbonded);
Context context(system, integrator, platform);
vector<Vec3> positions(numParticles);
#include "nacl_crystal.dat"
context.setPositions(positions);
State state = context.getState(State::Forces | State::Energy);
const vector<Vec3>& forces = state.getForces();
// The potential energy of an ion in a crystal is
// E = - (M*e^2/ 4*pi*epsilon0*a0),
// where
// M : Madelung constant (dimensionless, for FCC cells such as NaCl it is 1.7476)
// e : 1.6022 × 10−19 C
// 4*pi*epsilon0: 1.112 × 10−10 C²/(J m)
// a0 : 0.282 x 10-9 m (perfect cell)
//
// E is then the energy per pair of ions, so for our case
// E has to be divided by 2 (per ion), multiplied by N(avogadro), multiplied by number of particles, and divided by 1000 for kJ
double exactEnergy = - (1.7476 * 1.6022e-19 * 1.6022e-19 * 6.02214e+23 * numParticles) / (1.112e-10 * 0.282e-9 * 2 * 1000);
//cout << "exact\t\t: " << exactEnergy << endl;
//cout << "calc\t\t: " << state.getPotentialEnergy() << endl;
ASSERT_EQUAL_TOL(exactEnergy, state.getPotentialEnergy(), 100*EWALD_TOL);
}
void testTriclinic() {
// Create a triclinic box containing eight particles.
System system;
system.setDefaultPeriodicBoxVectors(Vec3(2.5, 0, 0), Vec3(0.5, 3.0, 0), Vec3(0.7, 0.9, 3.5));
for (int i = 0; i < 8; i++)
system.addParticle(1.0);
NonbondedForce* force = new NonbondedForce();
system.addForce(force);
force->setNonbondedMethod(NonbondedForce::PME);
force->setCutoffDistance(1.0);
force->setPMEParameters(3.45891, 32, 40, 48);
for (int i = 0; i < 4; i++)
force->addParticle(-1, 0.440104, 0.4184); // Cl parameters
for (int i = 0; i < 4; i++)
force->addParticle(1, 0.332840, 0.0115897); // Na parameters
vector<Vec3> positions(8);
positions[0] = Vec3(1.744, 2.788, 3.162);
positions[1] = Vec3(1.048, 0.762, 2.340);
positions[2] = Vec3(2.489, 1.570, 2.817);
positions[3] = Vec3(1.027, 1.893, 3.271);
positions[4] = Vec3(0.937, 0.825, 0.009);
positions[5] = Vec3(2.290, 1.887, 3.352);
positions[6] = Vec3(1.266, 1.111, 2.894);
positions[7] = Vec3(0.933, 1.862, 3.490);
// Compute the forces and energy.
VerletIntegrator integ(0.001);
Context context(system, integ, platform);
context.setPositions(positions);
State state = context.getState(State::Forces | State::Energy);
// Compare them to values computed by Gromacs.
double expectedEnergy = -963.370;
vector<Vec3> expectedForce(8);
expectedForce[0] = Vec3(4.25253e+01, -1.23503e+02, 1.22139e+02);
expectedForce[1] = Vec3(9.74752e+01, 1.68213e+02, 1.93169e+02);
expectedForce[2] = Vec3(-1.50348e+02, 1.29165e+02, 3.70435e+02);
expectedForce[3] = Vec3(9.18644e+02, -3.52571e+00, -1.34772e+03);
expectedForce[4] = Vec3(-1.61193e+02, 9.01528e+01, -7.12904e+01);
expectedForce[5] = Vec3(2.82630e+02, 2.78029e+01, -3.72864e+02);
expectedForce[6] = Vec3(-1.47454e+02, -2.14448e+02, -3.55789e+02);
expectedForce[7] = Vec3(-8.82195e+02, -7.39132e+01, 1.46202e+03);
for (int i = 0; i < 8; i++) {
ASSERT_EQUAL_VEC(expectedForce[i], state.getForces()[i], 1e-4);
}
ASSERT_EQUAL_TOL(expectedEnergy, state.getPotentialEnergy(), 1e-4);
}
void testPMEParameters() {
// Create a cloud of random point charges.
const int numParticles = 51;
const double boxWidth = 4.7;
System system;
system.setDefaultPeriodicBoxVectors(Vec3(boxWidth, 0, 0), Vec3(0, boxWidth, 0), Vec3(0, 0, boxWidth));
NonbondedForce* force = new NonbondedForce();
system.addForce(force);
vector<Vec3> positions(numParticles);
OpenMM_SFMT::SFMT sfmt;
init_gen_rand(0, sfmt);
for (int i = 0; i < numParticles; i++) {
system.addParticle(1.0);
force->addParticle(-1.0+i*2.0/(numParticles-1), 1.0, 0.0);
positions[i] = Vec3(boxWidth*genrand_real2(sfmt), boxWidth*genrand_real2(sfmt), boxWidth*genrand_real2(sfmt));
}
force->setNonbondedMethod(NonbondedForce::PME);
ReferencePlatform platform;
// Compute the energy with an error tolerance of 1e-3.
force->setEwaldErrorTolerance(1e-3);
VerletIntegrator integrator1(0.01);
Context context1(system, integrator1, platform);
context1.setPositions(positions);
double energy1 = context1.getState(State::Energy).getPotentialEnergy();
// Try again with an error tolerance of 1e-4.
force->setEwaldErrorTolerance(1e-4);
VerletIntegrator integrator2(0.01);
Context context2(system, integrator2, platform);
context2.setPositions(positions);
double energy2 = context2.getState(State::Energy).getPotentialEnergy();
// Now explicitly set the parameters. These should match the values that were
// used for tolerance 1e-3.
force->setPMEParameters(2.49291157051793, 32, 32, 32);
VerletIntegrator integrator3(0.01);
Context context3(system, integrator3, platform);
context3.setPositions(positions);
double energy3 = context3.getState(State::Energy).getPotentialEnergy();
ASSERT_EQUAL_TOL(energy1, energy3, 1e-6);
ASSERT(fabs((energy1-energy2)/energy1) > 1e-5);
}
void testChangingBoxSize() {
ReferencePlatform platform;
System system;
system.setDefaultPeriodicBoxVectors(Vec3(4, 0, 0), Vec3(0, 5, 0), Vec3(0, 0, 6));
system.addParticle(1.0);
NonbondedForce* nb = new NonbondedForce();
nb->setNonbondedMethod(NonbondedForce::CutoffPeriodic);
nb->setCutoffDistance(2.0);
nb->addParticle(1, 0.5, 0.5);
system.addForce(nb);
LangevinIntegrator integrator(300.0, 1.0, 0.01);
Context context(system, integrator, platform);
vector<Vec3> positions;
positions.push_back(Vec3());
context.setPositions(positions);
Vec3 x, y, z;
context.getState(State::Forces).getPeriodicBoxVectors(x, y, z);
ASSERT_EQUAL_VEC(Vec3(4, 0, 0), x, 0);
ASSERT_EQUAL_VEC(Vec3(0, 5, 0), y, 0);
ASSERT_EQUAL_VEC(Vec3(0, 0, 6), z, 0);
context.setPeriodicBoxVectors(Vec3(7, 0, 0), Vec3(0, 8, 0), Vec3(0, 0, 9));
context.getState(State::Forces).getPeriodicBoxVectors(x, y, z);
ASSERT_EQUAL_VEC(Vec3(7, 0, 0), x, 0);
ASSERT_EQUAL_VEC(Vec3(0, 8, 0), y, 0);
ASSERT_EQUAL_VEC(Vec3(0, 0, 9), z, 0);
// Shrinking the box too small should produce an exception.
context.setPeriodicBoxVectors(Vec3(7, 0, 0), Vec3(0, 3.9, 0), Vec3(0, 0, 9));
bool ok = true;
try {
context.getState(State::Forces).getPeriodicBoxVectors(x, y, z);
ok = false;
}
catch (exception& ex) {
}
ASSERT(ok);
}
void testRandomSeed() {
const int numParticles = 8;
const double temp = 100.0;
const double pressure = 1.5;
ReferencePlatform platform;
System system;
system.setDefaultPeriodicBoxVectors(Vec3(8, 0, 0), Vec3(0, 8, 0), Vec3(0, 0, 8));
VerletIntegrator integrator(0.01);
NonbondedForce* forceField = new NonbondedForce();
forceField->setNonbondedMethod(NonbondedForce::CutoffPeriodic);
for (int i = 0; i < numParticles; ++i) {
system.addParticle(2.0);
forceField->addParticle((i%2 == 0 ? 1.0 : -1.0), 1.0, 5.0);
}
system.addForce(forceField);
MonteCarloBarostat* barostat = new MonteCarloBarostat(pressure, temp, 1);
system.addForce(barostat);
ASSERT(barostat->usesPeriodicBoundaryConditions());
ASSERT(system.usesPeriodicBoundaryConditions());
vector<Vec3> positions(numParticles);
vector<Vec3> velocities(numParticles);
for (int i = 0; i < numParticles; ++i) {
positions[i] = Vec3((i%2 == 0 ? 2 : -2), (i%4 < 2 ? 2 : -2), (i < 4 ? 2 : -2));
velocities[i] = Vec3(0, 0, 0);
}
// Try twice with the same random seed.
barostat->setRandomNumberSeed(5);
Context context(system, integrator, platform);
context.setPositions(positions);
context.setVelocities(velocities);
integrator.step(10);
State state1 = context.getState(State::Positions);
context.reinitialize();
context.setPositions(positions);
context.setVelocities(velocities);
integrator.step(10);
State state2 = context.getState(State::Positions);
// Try twice with a different random seed.
barostat->setRandomNumberSeed(10);
context.reinitialize();
context.setPositions(positions);
context.setVelocities(velocities);
integrator.step(10);
State state3 = context.getState(State::Positions);
context.reinitialize();
context.setPositions(positions);
context.setVelocities(velocities);
integrator.step(10);
State state4 = context.getState(State::Positions);
// Compare the results.
for (int i = 0; i < numParticles; i++) {
for (int j = 0; j < 3; j++) {
ASSERT(state1.getPositions()[i][j] == state2.getPositions()[i][j]);
ASSERT(state3.getPositions()[i][j] == state4.getPositions()[i][j]);
ASSERT(state1.getPositions()[i][j] != state3.getPositions()[i][j]);
}
}
}
/**
* Make sure that atom reordering respects virtual sites.
*/
void testReordering() {
const double cutoff = 2.0;
const double boxSize = 20.0;
System system;
NonbondedForce* nonbonded = new NonbondedForce();
system.addForce(nonbonded);
nonbonded->setNonbondedMethod(NonbondedForce::CutoffNonPeriodic);
nonbonded->setCutoffDistance(cutoff);
vector<Vec3> positions;
OpenMM_SFMT::SFMT sfmt;
init_gen_rand(0, sfmt);
// Create linear molecules with TwoParticleAverage virtual sites.
for (int i = 0; i < 50; i++) {
int start = system.getNumParticles();
system.addParticle(1.0);
system.addParticle(1.0);
system.addParticle(0.0);
system.setVirtualSite(start+2, new TwoParticleAverageSite(start, start+1, 0.4, 0.6));
system.addConstraint(start, start+1, 2.0);
for (int i = 0; i < 3; i++) {
nonbonded->addParticle(0, 0.2, 1);
for (int j = 0; j < i; j++)
nonbonded->addException(start+i, start+j, 0, 1, 0);
}
Vec3 pos(boxSize*genrand_real2(sfmt), boxSize*genrand_real2(sfmt), boxSize*genrand_real2(sfmt));
positions.push_back(pos);
positions.push_back(pos+Vec3(2, 0, 0));
positions.push_back(Vec3());
}
// Create planar molecules with ThreeParticleAverage virtual sites.
for (int i = 0; i < 50; i++) {
int start = system.getNumParticles();
system.addParticle(1.0);
system.addParticle(1.0);
system.addParticle(1.0);
system.addParticle(0.0);
system.setVirtualSite(start+3, new ThreeParticleAverageSite(start, start+1, start+2, 0.3, 0.5, 0.2));
system.addConstraint(start, start+1, 1.0);
system.addConstraint(start, start+2, 1.0);
system.addConstraint(start+1, start+2, sqrt(2.0));
for (int i = 0; i < 4; i++) {
nonbonded->addParticle(0, 0.2, 1);
for (int j = 0; j < i; j++)
nonbonded->addException(start+i, start+j, 0, 1, 0);
}
Vec3 pos(boxSize*genrand_real2(sfmt), boxSize*genrand_real2(sfmt), boxSize*genrand_real2(sfmt));
positions.push_back(pos);
positions.push_back(pos+Vec3(1, 0, 0));
positions.push_back(pos+Vec3(0, 1, 0));
positions.push_back(Vec3());
}
// Create tetrahedral molecules with OutOfPlane virtual sites.
for (int i = 0; i < 50; i++) {
int start = system.getNumParticles();
system.addParticle(1.0);
system.addParticle(1.0);
system.addParticle(1.0);
system.addParticle(0.0);
system.setVirtualSite(start+3, new OutOfPlaneSite(start, start+1, start+2, 0.3, 0.5, 0.2));
system.addConstraint(start, start+1, 1.0);
system.addConstraint(start, start+2, 1.0);
system.addConstraint(start+1, start+2, sqrt(2.0));
for (int i = 0; i < 4; i++) {
nonbonded->addParticle(0, 0.2, 1);
for (int j = 0; j < i; j++)
nonbonded->addException(start+i, start+j, 0, 1, 0);
}
Vec3 pos(boxSize*genrand_real2(sfmt), boxSize*genrand_real2(sfmt), boxSize*genrand_real2(sfmt));
positions.push_back(pos);
positions.push_back(pos+Vec3(1, 0, 0));
positions.push_back(pos+Vec3(0, 1, 0));
positions.push_back(Vec3());
}
// Simulate it and check conservation laws.
LangevinIntegrator integrator(300.0, 0.1, 0.002);
Context context(system, integrator, platform);
context.setPositions(positions);
context.applyConstraints(0.0001);
for (int i = 0; i < 1000; i++) {
State state = context.getState(State::Positions);
const vector<Vec3>& pos = state.getPositions();
for (int j = 0; j < 150; j += 3)
ASSERT_EQUAL_VEC(pos[j]*0.4+pos[j+1]*0.6, pos[j+2], 1e-5);
for (int j = 150; j < 350; j += 4)
ASSERT_EQUAL_VEC(pos[j]*0.3+pos[j+1]*0.5+pos[j+2]*0.2, pos[j+3], 1e-5);
for (int j = 350; j < 550; j += 4) {
Vec3 v12 = pos[j+1]-pos[j];
Vec3 v13 = pos[j+2]-pos[j];
Vec3 cross = v12.cross(v13);
ASSERT_EQUAL_VEC(pos[j]+v12*0.3+v13*0.5+cross*0.2, pos[j+3], 1e-5);
}
integrator.step(1);
}
}
void testLongRangeCorrection() {
// Create a box of particles.
int gridSize = 5;
int numParticles = gridSize*gridSize*gridSize;
double boxSize = gridSize*0.7;
double cutoff = boxSize/3;
System standardSystem;
System customSystem;
VerletIntegrator integrator1(0.01);
VerletIntegrator integrator2(0.01);
NonbondedForce* standardNonbonded = new NonbondedForce();
CustomNonbondedForce* customNonbonded = new CustomNonbondedForce("4*eps*((sigma/r)^12-(sigma/r)^6); sigma=0.5*(sigma1+sigma2); eps=sqrt(eps1*eps2)");
customNonbonded->addPerParticleParameter("sigma");
customNonbonded->addPerParticleParameter("eps");
vector<Vec3> positions(numParticles);
int index = 0;
vector<double> params1(2);
params1[0] = 1.1;
params1[1] = 0.5;
vector<double> params2(2);
params2[0] = 1;
params2[1] = 1;
for (int i = 0; i < gridSize; i++)
for (int j = 0; j < gridSize; j++)
for (int k = 0; k < gridSize; k++) {
standardSystem.addParticle(1.0);
customSystem.addParticle(1.0);
if (index%2 == 0) {
standardNonbonded->addParticle(0, params1[0], params1[1]);
customNonbonded->addParticle(params1);
}
else {
standardNonbonded->addParticle(0, params2[0], params2[1]);
customNonbonded->addParticle(params2);
}
positions[index] = Vec3(i*boxSize/gridSize, j*boxSize/gridSize, k*boxSize/gridSize);
index++;
}
standardNonbonded->setNonbondedMethod(NonbondedForce::CutoffPeriodic);
customNonbonded->setNonbondedMethod(CustomNonbondedForce::CutoffPeriodic);
standardNonbonded->setCutoffDistance(cutoff);
customNonbonded->setCutoffDistance(cutoff);
standardSystem.setDefaultPeriodicBoxVectors(Vec3(boxSize, 0, 0), Vec3(0, boxSize, 0), Vec3(0, 0, boxSize));
customSystem.setDefaultPeriodicBoxVectors(Vec3(boxSize, 0, 0), Vec3(0, boxSize, 0), Vec3(0, 0, boxSize));
standardNonbonded->setUseDispersionCorrection(true);
customNonbonded->setUseLongRangeCorrection(true);
standardNonbonded->setUseSwitchingFunction(true);
customNonbonded->setUseSwitchingFunction(true);
standardNonbonded->setSwitchingDistance(0.8*cutoff);
customNonbonded->setSwitchingDistance(0.8*cutoff);
standardSystem.addForce(standardNonbonded);
customSystem.addForce(customNonbonded);
// Compute the correction for the standard force.
Context context1(standardSystem, integrator1, platform);
context1.setPositions(positions);
double standardEnergy1 = context1.getState(State::Energy).getPotentialEnergy();
standardNonbonded->setUseDispersionCorrection(false);
context1.reinitialize();
context1.setPositions(positions);
double standardEnergy2 = context1.getState(State::Energy).getPotentialEnergy();
// Compute the correction for the custom force.
Context context2(customSystem, integrator2, platform);
context2.setPositions(positions);
double customEnergy1 = context2.getState(State::Energy).getPotentialEnergy();
customNonbonded->setUseLongRangeCorrection(false);
context2.reinitialize();
context2.setPositions(positions);
double customEnergy2 = context2.getState(State::Energy).getPotentialEnergy();
// See if they agree.
ASSERT_EQUAL_TOL(standardEnergy1-standardEnergy2, customEnergy1-customEnergy2, 1e-4);
}
void testWithBarostat() {
const int gridSize = 3;
const int numMolecules = gridSize*gridSize*gridSize;
const int numParticles = numMolecules*2;
const int numCopies = 5;
const double spacing = 2.0;
const double cutoff = 3.0;
const double boxSize = spacing*(gridSize+1);
const double temperature = 300.0;
System system;
system.setDefaultPeriodicBoxVectors(Vec3(boxSize, 0, 0), Vec3(0, boxSize, 0), Vec3(0, 0, boxSize));
HarmonicBondForce* bonds = new HarmonicBondForce();
system.addForce(bonds);
NonbondedForce* nonbonded = new NonbondedForce();
nonbonded->setCutoffDistance(cutoff);
nonbonded->setNonbondedMethod(NonbondedForce::PME);
nonbonded->setForceGroup(1);
nonbonded->setReciprocalSpaceForceGroup(2);
system.addForce(nonbonded);
system.addForce(new MonteCarloBarostat(0.5, temperature));
// Create a cloud of molecules.
OpenMM_SFMT::SFMT sfmt;
init_gen_rand(0, sfmt);
vector<Vec3> positions(numParticles);
for (int i = 0; i < numMolecules; i++) {
system.addParticle(1.0);
system.addParticle(1.0);
nonbonded->addParticle(-0.2, 0.2, 0.2);
nonbonded->addParticle(0.2, 0.2, 0.2);
nonbonded->addException(2*i, 2*i+1, 0, 1, 0);
bonds->addBond(2*i, 2*i+1, 1.0, 10000.0);
}
RPMDIntegrator integ(numCopies, temperature, 50.0, 0.001);
Platform& platform = Platform::getPlatformByName("Reference");
Context context(system, integ, platform);
for (int copy = 0; copy < numCopies; copy++) {
for (int i = 0; i < gridSize; i++)
for (int j = 0; j < gridSize; j++)
for (int k = 0; k < gridSize; k++) {
Vec3 pos = Vec3(spacing*(i+0.02*genrand_real2(sfmt)), spacing*(j+0.02*genrand_real2(sfmt)), spacing*(k+0.02*genrand_real2(sfmt)));
int index = k+gridSize*(j+gridSize*i);
positions[2*index] = pos;
positions[2*index+1] = Vec3(pos[0]+1.0, pos[1], pos[2]);
}
integ.setPositions(copy, positions);
}
// Check the temperature.
const int numSteps = 500;
integ.step(100);
vector<double> ke(numCopies, 0.0);
for (int i = 0; i < numSteps; i++) {
integ.step(1);
vector<State> state(numCopies);
for (int j = 0; j < numCopies; j++)
state[j] = integ.getState(j, State::Velocities, true);
for (int j = 0; j < numParticles; j++) {
for (int k = 0; k < numCopies; k++) {
Vec3 v = state[k].getVelocities()[j];
ke[k] += 0.5*system.getParticleMass(j)*v.dot(v);
}
}
}
double meanKE = 0.0;
for (int i = 0; i < numCopies; i++)
meanKE += ke[i];
meanKE /= numSteps*numCopies;
double expectedKE = 0.5*numCopies*numParticles*3*BOLTZ*temperature;
ASSERT_USUALLY_EQUAL_TOL(expectedKE, meanKE, 1e-2);
}
void testEnergyEthane(int applyBornRadiiScaling) {
ReferencePlatform platform;
const int numParticles = 8;
System system;
LangevinIntegrator integrator(0, 0.1, 0.01);
// harmonic bond
double C_HBondDistance = 0.1097;
double C_CBondDistance = 0.1504;
HarmonicBondForce* bonds = new HarmonicBondForce();
bonds->addBond(0, 1, C_HBondDistance, 0.0);
bonds->addBond(2, 1, C_HBondDistance, 0.0);
bonds->addBond(3, 1, C_HBondDistance, 0.0);
bonds->addBond(1, 4, C_CBondDistance, 0.0);
bonds->addBond(5, 4, C_HBondDistance, 0.0);
bonds->addBond(6, 4, C_HBondDistance, 0.0);
bonds->addBond(7, 4, C_HBondDistance, 0.0);
system.addForce(bonds);
double C_radius, C_gamma, C_charge, H_radius, H_gamma, H_charge;
int AM1_BCC = 1;
H_charge = -0.053;
C_charge = -3.0*H_charge;
if (AM1_BCC) {
C_radius = 0.180;
C_gamma = -0.2863;
H_radius = 0.125;
H_gamma = 0.2437;
}
else {
C_radius = 0.215;
C_gamma = -1.1087;
H_radius = 0.150;
H_gamma = 0.1237;
}
NonbondedForce* nonbonded = new NonbondedForce();
nonbonded->setNonbondedMethod(NonbondedForce::NoCutoff);
GBVIForce* forceField = new GBVIForce();
if (applyBornRadiiScaling) {
forceField->setBornRadiusScalingMethod(GBVIForce::QuinticSpline);
}
else {
forceField->setBornRadiusScalingMethod(GBVIForce::NoScaling);
}
for (int i = 0; i < numParticles; i++) {
system.addParticle(1.0);
forceField->addParticle(H_charge, H_radius, H_gamma);
nonbonded->addParticle( H_charge, H_radius, 0.0);
}
forceField->setParticleParameters(1, C_charge, C_radius, C_gamma);
forceField->setParticleParameters(4, C_charge, C_radius, C_gamma);
nonbonded->setParticleParameters( 1, C_charge, C_radius, 0.0);
nonbonded->setParticleParameters( 4, C_charge, C_radius, 0.0);
forceField->addBond(0, 1, C_HBondDistance);
forceField->addBond(2, 1, C_HBondDistance);
forceField->addBond(3, 1, C_HBondDistance);
forceField->addBond(1, 4, C_CBondDistance);
forceField->addBond(5, 4, C_HBondDistance);
forceField->addBond(6, 4, C_HBondDistance);
forceField->addBond(7, 4, C_HBondDistance);
std::vector<pair<int, int> > bondExceptions;
std::vector<double> bondDistances;
bondExceptions.push_back(pair<int, int>(0, 1));
bondDistances.push_back(C_HBondDistance);
bondExceptions.push_back(pair<int, int>(2, 1));
bondDistances.push_back(C_HBondDistance);
bondExceptions.push_back(pair<int, int>(3, 1));
bondDistances.push_back(C_HBondDistance);
bondExceptions.push_back(pair<int, int>(1, 4));
bondDistances.push_back(C_CBondDistance);
bondExceptions.push_back(pair<int, int>(5, 4));
bondDistances.push_back(C_HBondDistance);
bondExceptions.push_back(pair<int, int>(6, 4));
bondDistances.push_back(C_HBondDistance);
bondExceptions.push_back(pair<int, int>(7, 4));
bondDistances.push_back(C_HBondDistance);
nonbonded->createExceptionsFromBonds(bondExceptions, 0.0, 0.0);
system.addForce(forceField);
system.addForce(nonbonded);
Context context(system, integrator, platform);
vector<Vec3> positions(numParticles);
positions[0] = Vec3(0.5480, 1.7661, 0.0000);
positions[1] = Vec3(0.7286, 0.8978, 0.6468);
positions[2] = Vec3(0.4974, 0.0000, 0.0588);
positions[3] = Vec3(0.0000, 0.9459, 1.4666);
positions[4] = Vec3(2.1421, 0.8746, 1.1615);
positions[5] = Vec3(2.3239, 0.0050, 1.8065);
positions[6] = Vec3(2.8705, 0.8295, 0.3416);
positions[7] = Vec3(2.3722, 1.7711, 1.7518);
context.setPositions(positions);
State state = context.getState(State::Forces | State::Energy);
// Take a small step in the direction of the energy gradient.
double norm = 0.0;
double forceSum[3] = { 0.0, 0.0, 0.0 };
for (int i = 0; i < numParticles; ++i) {
Vec3 f = state.getForces()[i];
norm += f[0]*f[0] + f[1]*f[1] + f[2]*f[2];
forceSum[0] += f[0];
forceSum[1] += f[1];
forceSum[2] += f[2];
}
norm = std::sqrt(norm);
const double delta = 1e-4;
double step = delta/norm;
for (int i = 0; i < numParticles; ++i) {
Vec3 p = positions[i];
Vec3 f = state.getForces()[i];
positions[i] = Vec3(p[0]-f[0]*step, p[1]-f[1]*step, p[2]-f[2]*step);
}
context.setPositions(positions);
State state2 = context.getState(State::Energy);
// See whether the potential energy changed by the expected amount.
ASSERT_EQUAL_TOL(norm, (state2.getPotentialEnergy()-state.getPotentialEnergy())/delta, 0.01)
}
void testCoulombLennardJones() {
const int numMolecules = 300;
const int numParticles = numMolecules*2;
const double boxSize = 20.0;
// Create two systems: one with a NonbondedForce, and one using a CustomNonbondedForce to implement the same interaction.
System standardSystem;
System customSystem;
for (int i = 0; i < numParticles; i++) {
standardSystem.addParticle(1.0);
customSystem.addParticle(1.0);
}
NonbondedForce* standardNonbonded = new NonbondedForce();
CustomNonbondedForce* customNonbonded = new CustomNonbondedForce("4*eps*((sigma/r)^12-(sigma/r)^6)+138.935456*q/r; q=q1*q2; sigma=0.5*(sigma1+sigma2); eps=sqrt(eps1*eps2)");
customNonbonded->addPerParticleParameter("q");
customNonbonded->addPerParticleParameter("sigma");
customNonbonded->addPerParticleParameter("eps");
vector<Vec3> positions(numParticles);
vector<Vec3> velocities(numParticles);
OpenMM_SFMT::SFMT sfmt;
init_gen_rand(0, sfmt);
vector<double> params(3);
for (int i = 0; i < numMolecules; i++) {
if (i < numMolecules/2) {
standardNonbonded->addParticle(1.0, 0.2, 0.1);
params[0] = 1.0;
params[1] = 0.2;
params[2] = 0.1;
customNonbonded->addParticle(params);
standardNonbonded->addParticle(-1.0, 0.1, 0.1);
params[0] = -1.0;
params[1] = 0.1;
customNonbonded->addParticle(params);
}
else {
standardNonbonded->addParticle(1.0, 0.2, 0.2);
params[0] = 1.0;
params[1] = 0.2;
params[2] = 0.2;
customNonbonded->addParticle(params);
standardNonbonded->addParticle(-1.0, 0.1, 0.2);
params[0] = -1.0;
params[1] = 0.1;
customNonbonded->addParticle(params);
}
positions[2*i] = Vec3(boxSize*genrand_real2(sfmt), boxSize*genrand_real2(sfmt), boxSize*genrand_real2(sfmt));
positions[2*i+1] = Vec3(positions[2*i][0]+1.0, positions[2*i][1], positions[2*i][2]);
velocities[2*i] = Vec3(genrand_real2(sfmt), genrand_real2(sfmt), genrand_real2(sfmt));
velocities[2*i+1] = Vec3(genrand_real2(sfmt), genrand_real2(sfmt), genrand_real2(sfmt));
standardNonbonded->addException(2*i, 2*i+1, 0.0, 1.0, 0.0);
customNonbonded->addExclusion(2*i, 2*i+1);
}
standardNonbonded->setNonbondedMethod(NonbondedForce::NoCutoff);
customNonbonded->setNonbondedMethod(CustomNonbondedForce::NoCutoff);
standardSystem.addForce(standardNonbonded);
customSystem.addForce(customNonbonded);
VerletIntegrator integrator1(0.01);
VerletIntegrator integrator2(0.01);
Context context1(standardSystem, integrator1, platform);
Context context2(customSystem, integrator2, platform);
context1.setPositions(positions);
context2.setPositions(positions);
context1.setVelocities(velocities);
context2.setVelocities(velocities);
State state1 = context1.getState(State::Forces | State::Energy);
State state2 = context2.getState(State::Forces | State::Energy);
ASSERT_EQUAL_TOL(state1.getPotentialEnergy(), state2.getPotentialEnergy(), 1e-4);
for (int i = 0; i < numParticles; i++) {
ASSERT_EQUAL_VEC(state1.getForces()[i], state2.getForces()[i], 1e-4);
}
}
void testWater() {
// Create a box of SWM4-NDP water molecules. This involves constraints, virtual sites,
// and Drude particles.
const int gridSize = 3;
const int numMolecules = gridSize*gridSize*gridSize;
const double spacing = 0.6;
const double boxSize = spacing*(gridSize+1);
System system;
NonbondedForce* nonbonded = new NonbondedForce();
DrudeForce* drude = new DrudeForce();
system.addForce(nonbonded);
system.addForce(drude);
system.setDefaultPeriodicBoxVectors(Vec3(boxSize, 0, 0), Vec3(0, boxSize, 0), Vec3(0, 0, boxSize));
nonbonded->setNonbondedMethod(NonbondedForce::CutoffPeriodic);
nonbonded->setCutoffDistance(1.0);
for (int i = 0; i < numMolecules; i++) {
int startIndex = system.getNumParticles();
system.addParticle(15.6); // O
system.addParticle(0.4); // D
system.addParticle(1.0); // H1
system.addParticle(1.0); // H2
system.addParticle(0.0); // M
nonbonded->addParticle(1.71636, 0.318395, 0.21094*4.184);
nonbonded->addParticle(-1.71636, 1, 0);
nonbonded->addParticle(0.55733, 1, 0);
nonbonded->addParticle(0.55733, 1, 0);
nonbonded->addParticle(-1.11466, 1, 0);
for (int j = 0; j < 5; j++)
for (int k = 0; k < j; k++)
nonbonded->addException(startIndex+j, startIndex+k, 0, 1, 0);
system.addConstraint(startIndex, startIndex+2, 0.09572);
system.addConstraint(startIndex, startIndex+3, 0.09572);
system.addConstraint(startIndex+2, startIndex+3, 0.15139);
system.setVirtualSite(startIndex+4, new ThreeParticleAverageSite(startIndex, startIndex+2, startIndex+3, 0.786646558, 0.106676721, 0.106676721));
drude->addParticle(startIndex+1, startIndex, -1, -1, -1, -1.71636, ONE_4PI_EPS0*1.71636*1.71636/(100000*4.184), 1, 1);
}
vector<Vec3> positions;
for (int i = 0; i < gridSize; i++)
for (int j = 0; j < gridSize; j++)
for (int k = 0; k < gridSize; k++) {
Vec3 pos(i*spacing, j*spacing, k*spacing);
positions.push_back(pos);
positions.push_back(pos);
positions.push_back(pos+Vec3(0.09572, 0, 0));
positions.push_back(pos+Vec3(-0.023999, 0.092663, 0));
positions.push_back(pos);
}
// Simulate it and check energy conservation and the total force on the Drude particles.
DrudeSCFIntegrator integ(0.0005);
Platform& platform = Platform::getPlatformByName("Reference");
Context context(system, integ, platform);
context.setPositions(positions);
context.applyConstraints(1e-5);
context.setVelocitiesToTemperature(300.0);
State state = context.getState(State::Energy);
double initialEnergy;
int numSteps = 1000;
for (int i = 0; i < numSteps; i++) {
integ.step(1);
state = context.getState(State::Energy | State::Forces);
if (i == 0)
initialEnergy = state.getPotentialEnergy()+state.getKineticEnergy();
else
ASSERT_EQUAL_TOL(initialEnergy, state.getPotentialEnergy()+state.getKineticEnergy(), 0.01);
const vector<Vec3>& force = state.getForces();
double norm = 0.0;
for (int j = 1; j < (int) force.size(); j += 5)
norm += sqrt(force[j].dot(force[j]));
norm = (norm/numMolecules);
ASSERT(norm < 1.0);
}
}
/**
* Run a constant pressure simulation on an anisotropic Einstein crystal
* using isotropic and anisotropic barostats. There are a total of 15 simulations:
*
* 1) 3 pressures: 9.0, 10.0, 11.0 bar, for each of the following groups:
* 2) 3 groups of simulations that scale just one axis: x, y, z
* 3) 1 group of simulations that scales all three axes in the anisotropic barostat
* 4) 1 group of simulations that scales all three axes in the isotropic barostat
*
* Results that we will check:
*
* a) In each group of simulations, the volume should decrease with increasing pressure
* b) In the three simulation groups that scale just one axis, the compressibility (i.e. incremental volume change
* with increasing pressure) should go like kx > ky > kz (because the spring constant is largest in the z-direction)
* c) The anisotropic barostat should produce the same result as the isotropic barostat when all three axes are scaled
*/
void testEinsteinCrystal() {
const int numParticles = 64;
const int frequency = 2;
const int equil = 10000;
const int steps = 5000;
const double pressure = 10.0;
const double pressureInMD = pressure*(AVOGADRO*1e-25); // pressure in kJ/mol/nm^3
const double temp = 300.0; // Only test one temperature since we're looking at three pressures.
const double pres3[] = {2.0, 8.0, 15.0};
const double initialVolume = numParticles*BOLTZ*temp/pressureInMD;
const double initialLength = std::pow(initialVolume, 1.0/3.0);
vector<double> initialPositions(3);
vector<double> results;
// Run four groups of anisotropic simulations; scaling just x, y, z, then all three.
for (int a = 0; a < 4; a++) {
// Test barostat for three different pressures.
for (int p = 0; p < 3; p++) {
// Create a system of noninteracting particles attached by harmonic springs to their initial positions.
System system;
system.setDefaultPeriodicBoxVectors(Vec3(initialLength, 0, 0), Vec3(0, initialLength, 0), Vec3(0, 0, initialLength));
vector<Vec3> positions(numParticles);
OpenMM_SFMT::SFMT sfmt;
init_gen_rand(0, sfmt);
// Anisotropic force constants.
CustomExternalForce* force = new CustomExternalForce("0.005*(x-x0)^2 + 0.01*(y-y0)^2 + 0.02*(z-z0)^2");
force->addPerParticleParameter("x0");
force->addPerParticleParameter("y0");
force->addPerParticleParameter("z0");
NonbondedForce* nb = new NonbondedForce();
nb->setNonbondedMethod(NonbondedForce::CutoffPeriodic);
for (int i = 0; i < numParticles; ++i) {
system.addParticle(1.0);
positions[i] = Vec3(((i/16)%4+0.5)*initialLength/4, ((i/4)%4+0.5)*initialLength/4, (i%4+0.5)*initialLength/4);
initialPositions[0] = positions[i][0];
initialPositions[1] = positions[i][1];
initialPositions[2] = positions[i][2];
force->addParticle(i, initialPositions);
nb->addParticle(0, initialLength/6, 0.1);
}
system.addForce(force);
system.addForce(nb);
// Create the barostat.
MonteCarloAnisotropicBarostat* barostat = new MonteCarloAnisotropicBarostat(Vec3(pres3[p], pres3[p], pres3[p]), temp, (a==0||a==3), (a==1||a==3), (a==2||a==3), frequency);
system.addForce(barostat);
barostat->setTemperature(temp);
LangevinIntegrator integrator(temp, 0.1, 0.01);
Context context(system, integrator, platform);
context.setPositions(positions);
// Let it equilibrate.
integrator.step(equil);
// Now run it for a while and see if the volume is correct.
double volume = 0.0;
for (int j = 0; j < steps; ++j) {
Vec3 box[3];
context.getState(0).getPeriodicBoxVectors(box[0], box[1], box[2]);
volume += box[0][0]*box[1][1]*box[2][2];
integrator.step(frequency);
}
volume /= steps;
results.push_back(volume);
}
}
for (int p = 0; p < 3; p++) {
// Create a system of noninteracting particles attached by harmonic springs to their initial positions.
System system;
system.setDefaultPeriodicBoxVectors(Vec3(initialLength, 0, 0), Vec3(0, initialLength, 0), Vec3(0, 0, initialLength));
vector<Vec3> positions(numParticles);
OpenMM_SFMT::SFMT sfmt;
init_gen_rand(0, sfmt);
// Anisotropic force constants.
CustomExternalForce* force = new CustomExternalForce("0.005*(x-x0)^2 + 0.01*(y-y0)^2 + 0.02*(z-z0)^2");
force->addPerParticleParameter("x0");
force->addPerParticleParameter("y0");
force->addPerParticleParameter("z0");
NonbondedForce* nb = new NonbondedForce();
nb->setNonbondedMethod(NonbondedForce::CutoffPeriodic);
for (int i = 0; i < numParticles; ++i) {
system.addParticle(1.0);
positions[i] = Vec3(((i/16)%4+0.5)*initialLength/4, ((i/4)%4+0.5)*initialLength/4, (i%4+0.5)*initialLength/4);
initialPositions[0] = positions[i][0];
initialPositions[1] = positions[i][1];
initialPositions[2] = positions[i][2];
force->addParticle(i, initialPositions);
nb->addParticle(0, initialLength/6, 0.1);
}
system.addForce(force);
system.addForce(nb);
// Create the barostat.
MonteCarloBarostat* barostat = new MonteCarloBarostat(pres3[p], temp, frequency);
system.addForce(barostat);
barostat->setTemperature(temp);
LangevinIntegrator integrator(temp, 0.1, 0.001);
Context context(system, integrator, platform);
context.setPositions(positions);
// Let it equilibrate.
integrator.step(equil);
// Now run it for a while and see if the volume is correct.
double volume = 0.0;
for (int j = 0; j < steps; ++j) {
Vec3 box[3];
context.getState(0).getPeriodicBoxVectors(box[0], box[1], box[2]);
volume += box[0][0]*box[1][1]*box[2][2];
integrator.step(frequency);
}
volume /= steps;
results.push_back(volume);
}
// Check to see if volumes decrease with increasing pressure.
ASSERT_USUALLY_TRUE(results[0] > results[1]);
ASSERT_USUALLY_TRUE(results[1] > results[2]);
ASSERT_USUALLY_TRUE(results[3] > results[4]);
ASSERT_USUALLY_TRUE(results[4] > results[5]);
ASSERT_USUALLY_TRUE(results[6] > results[7]);
ASSERT_USUALLY_TRUE(results[7] > results[8]);
// Check to see if incremental volume changes with increasing pressure go like kx > ky > kz.
ASSERT_USUALLY_TRUE((results[0] - results[1]) > (results[3] - results[4]));
ASSERT_USUALLY_TRUE((results[1] - results[2]) > (results[4] - results[5]));
ASSERT_USUALLY_TRUE((results[3] - results[4]) > (results[6] - results[7]));
ASSERT_USUALLY_TRUE((results[4] - results[5]) > (results[7] - results[8]));
// Check to see if the volumes are equal for isotropic and anisotropic (all axis).
ASSERT_USUALLY_EQUAL_TOL(results[9], results[12], 3/std::sqrt((double) steps));
ASSERT_USUALLY_EQUAL_TOL(results[10], results[13], 3/std::sqrt((double) steps));
ASSERT_USUALLY_EQUAL_TOL(results[11], results[14], 3/std::sqrt((double) steps));
}
void testSerialization() {
// Create a Force.
NonbondedForce force;
force.setForceGroup(3);
force.setNonbondedMethod(NonbondedForce::CutoffPeriodic);
force.setSwitchingDistance(1.5);
force.setUseSwitchingFunction(true);
force.setCutoffDistance(2.0);
force.setEwaldErrorTolerance(1e-3);
force.setReactionFieldDielectric(50.0);
force.setUseDispersionCorrection(false);
double alpha = 0.5;
int nx = 3, ny = 5, nz = 7;
force.setPMEParameters(alpha, nx, ny, nz);
double dalpha = 0.8;
int dnx = 4, dny = 6, dnz = 7;
force.setLJPMEParameters(dalpha, dnx, dny, dnz);
force.addParticle(1, 0.1, 0.01);
force.addParticle(0.5, 0.2, 0.02);
force.addParticle(-0.5, 0.3, 0.03);
force.addException(0, 1, 2, 0.5, 0.1);
force.addException(1, 2, 0.2, 0.4, 0.2);
force.addGlobalParameter("scale1", 1.0);
force.addGlobalParameter("scale2", 2.0);
force.addParticleParameterOffset("scale1", 2, 1.5, 2.0, 2.5);
force.addExceptionParameterOffset("scale2", 1, -0.1, -0.2, -0.3);
// Serialize and then deserialize it.
stringstream buffer;
XmlSerializer::serialize<NonbondedForce>(&force, "Force", buffer);
NonbondedForce* copy = XmlSerializer::deserialize<NonbondedForce>(buffer);
// Compare the two forces to see if they are identical.
NonbondedForce& force2 = *copy;
ASSERT_EQUAL(force.getForceGroup(), force2.getForceGroup());
ASSERT_EQUAL(force.getNonbondedMethod(), force2.getNonbondedMethod());
ASSERT_EQUAL(force.getSwitchingDistance(), force2.getSwitchingDistance());
ASSERT_EQUAL(force.getUseSwitchingFunction(), force2.getUseSwitchingFunction());
ASSERT_EQUAL(force.getCutoffDistance(), force2.getCutoffDistance());
ASSERT_EQUAL(force.getEwaldErrorTolerance(), force2.getEwaldErrorTolerance());
ASSERT_EQUAL(force.getReactionFieldDielectric(), force2.getReactionFieldDielectric());
ASSERT_EQUAL(force.getUseDispersionCorrection(), force2.getUseDispersionCorrection());
ASSERT_EQUAL(force.getNumParticles(), force2.getNumParticles());
ASSERT_EQUAL(force.getNumExceptions(), force2.getNumExceptions());
ASSERT_EQUAL(force.getNumGlobalParameters(), force2.getNumGlobalParameters());
ASSERT_EQUAL(force.getNumParticleParameterOffsets(), force2.getNumParticleParameterOffsets());
ASSERT_EQUAL(force.getNumExceptionParameterOffsets(), force2.getNumExceptionParameterOffsets());
double alpha2;
int nx2, ny2, nz2;
force2.getPMEParameters(alpha2, nx2, ny2, nz2);
ASSERT_EQUAL(alpha, alpha2);
ASSERT_EQUAL(nx, nx2);
ASSERT_EQUAL(ny, ny2);
ASSERT_EQUAL(nz, nz2);
double dalpha2;
int dnx2, dny2, dnz2;
force2.getLJPMEParameters(dalpha2, dnx2, dny2, dnz2);
ASSERT_EQUAL(dalpha, dalpha2);
ASSERT_EQUAL(dnx, dnx2);
ASSERT_EQUAL(dny, dny2);
ASSERT_EQUAL(dnz, dnz2);
for (int i = 0; i < force.getNumGlobalParameters(); i++) {
ASSERT_EQUAL(force.getGlobalParameterName(i), force2.getGlobalParameterName(i));
ASSERT_EQUAL(force.getGlobalParameterDefaultValue(i), force2.getGlobalParameterDefaultValue(i));
}
for (int i = 0; i < force.getNumParticleParameterOffsets(); i++) {
int index1, index2;
string param1, param2;
double charge1, sigma1, epsilon1;
double charge2, sigma2, epsilon2;
force.getParticleParameterOffset(i, param1, index1, charge1, sigma1, epsilon1);
force2.getParticleParameterOffset(i, param2, index2, charge2, sigma2, epsilon2);
ASSERT_EQUAL(index1, index1);
ASSERT_EQUAL(param1, param2);
ASSERT_EQUAL(charge1, charge2);
ASSERT_EQUAL(sigma1, sigma2);
ASSERT_EQUAL(epsilon1, epsilon2);
}
for (int i = 0; i < force.getNumExceptionParameterOffsets(); i++) {
int index1, index2;
string param1, param2;
double charge1, sigma1, epsilon1;
double charge2, sigma2, epsilon2;
force.getExceptionParameterOffset(i, param1, index1, charge1, sigma1, epsilon1);
force2.getExceptionParameterOffset(i, param2, index2, charge2, sigma2, epsilon2);
ASSERT_EQUAL(index1, index1);
ASSERT_EQUAL(param1, param2);
ASSERT_EQUAL(charge1, charge2);
ASSERT_EQUAL(sigma1, sigma2);
ASSERT_EQUAL(epsilon1, epsilon2);
}
for (int i = 0; i < force.getNumParticles(); i++) {
double charge1, sigma1, epsilon1;
double charge2, sigma2, epsilon2;
force.getParticleParameters(i, charge1, sigma1, epsilon1);
force2.getParticleParameters(i, charge2, sigma2, epsilon2);
ASSERT_EQUAL(charge1, charge2);
ASSERT_EQUAL(sigma1, sigma2);
ASSERT_EQUAL(epsilon1, epsilon2);
}
ASSERT_EQUAL(force.getNumExceptions(), force2.getNumExceptions());
for (int i = 0; i < force.getNumExceptions(); i++) {
int a1, a2, b1, b2;
double charge1, sigma1, epsilon1;
double charge2, sigma2, epsilon2;
force.getExceptionParameters(i, a1, b1, charge1, sigma1, epsilon1);
force2.getExceptionParameters(i, a2, b2, charge2, sigma2, epsilon2);
ASSERT_EQUAL(a1, a2);
ASSERT_EQUAL(b1, b2);
ASSERT_EQUAL(charge1, charge2);
ASSERT_EQUAL(sigma1, sigma2);
ASSERT_EQUAL(epsilon1, epsilon2);
}
}
void testEwaldPME(bool includeExceptions) {
// Use amorphous NaCl system for the tests
const int numParticles = 894;
const double cutoff = 1.2;
const double boxSize = 3.00646;
double tol = 1e-5;
ReferencePlatform reference;
System system;
NonbondedForce* nonbonded = new NonbondedForce();
nonbonded->setNonbondedMethod(NonbondedForce::Ewald);
nonbonded->setCutoffDistance(cutoff);
nonbonded->setEwaldErrorTolerance(tol);
for (int i = 0; i < numParticles/2; i++)
system.addParticle(22.99);
for (int i = 0; i < numParticles/2; i++)
system.addParticle(35.45);
for (int i = 0; i < numParticles/2; i++)
nonbonded->addParticle(1.0, 1.0,0.0);
for (int i = 0; i < numParticles/2; i++)
nonbonded->addParticle(-1.0, 1.0,0.0);
system.setDefaultPeriodicBoxVectors(Vec3(boxSize, 0, 0), Vec3(0, boxSize, 0), Vec3(0, 0, boxSize));
system.addForce(nonbonded);
vector<Vec3> positions(numParticles);
#include "nacl_amorph.dat"
if (includeExceptions) {
// Add some exclusions.
for (int i = 0; i < numParticles-1; i++) {
Vec3 delta = positions[i]-positions[i+1];
if (sqrt(delta.dot(delta)) < 0.5*cutoff)
nonbonded->addException(i, i+1, i%2 == 0 ? 0.0 : 0.5, 1.0, 0.0);
}
}
// (1) Check whether the Reference and CPU platforms agree when using Ewald Method
VerletIntegrator integrator1(0.01);
VerletIntegrator integrator2(0.01);
Context cpuContext(system, integrator1, platform);
Context referenceContext(system, integrator2, reference);
cpuContext.setPositions(positions);
referenceContext.setPositions(positions);
State cpuState = cpuContext.getState(State::Forces | State::Energy);
State referenceState = referenceContext.getState(State::Forces | State::Energy);
tol = 1e-2;
for (int i = 0; i < numParticles; i++) {
ASSERT_EQUAL_VEC(referenceState.getForces()[i], cpuState.getForces()[i], tol);
}
tol = 1e-5;
ASSERT_EQUAL_TOL(referenceState.getPotentialEnergy(), cpuState.getPotentialEnergy(), tol);
// (2) Check whether Ewald method in CPU is self-consistent
double norm = 0.0;
for (int i = 0; i < numParticles; ++i) {
Vec3 f = cpuState.getForces()[i];
norm += f[0]*f[0] + f[1]*f[1] + f[2]*f[2];
}
norm = std::sqrt(norm);
const double delta = 5e-3;
double step = delta/norm;
for (int i = 0; i < numParticles; ++i) {
Vec3 p = positions[i];
Vec3 f = cpuState.getForces()[i];
positions[i] = Vec3(p[0]-f[0]*step, p[1]-f[1]*step, p[2]-f[2]*step);
}
VerletIntegrator integrator3(0.01);
Context cpuContext2(system, integrator3, platform);
cpuContext2.setPositions(positions);
tol = 1e-2;
State cpuState2 = cpuContext2.getState(State::Energy);
ASSERT_EQUAL_TOL(norm, (cpuState2.getPotentialEnergy()-cpuState.getPotentialEnergy())/delta, tol)
// (3) Check whether the Reference and CPU platforms agree when using PME
nonbonded->setNonbondedMethod(NonbondedForce::PME);
cpuContext.reinitialize();
referenceContext.reinitialize();
cpuContext.setPositions(positions);
referenceContext.setPositions(positions);
cpuState = cpuContext.getState(State::Forces | State::Energy);
referenceState = referenceContext.getState(State::Forces | State::Energy);
tol = 1e-2;
for (int i = 0; i < numParticles; i++) {
ASSERT_EQUAL_VEC(referenceState.getForces()[i], cpuState.getForces()[i], tol);
}
tol = 1e-5;
ASSERT_EQUAL_TOL(referenceState.getPotentialEnergy(), cpuState.getPotentialEnergy(), tol);
// (4) Check whether PME method in CPU is self-consistent
norm = 0.0;
for (int i = 0; i < numParticles; ++i) {
Vec3 f = cpuState.getForces()[i];
norm += f[0]*f[0] + f[1]*f[1] + f[2]*f[2];
}
norm = std::sqrt(norm);
step = delta/norm;
for (int i = 0; i < numParticles; ++i) {
Vec3 p = positions[i];
Vec3 f = cpuState.getForces()[i];
positions[i] = Vec3(p[0]-f[0]*step, p[1]-f[1]*step, p[2]-f[2]*step);
}
VerletIntegrator integrator4(0.01);
Context cpuContext3(system, integrator4, platform);
cpuContext3.setPositions(positions);
tol = 1e-2;
State cpuState3 = cpuContext3.getState(State::Energy);
ASSERT_EQUAL_TOL(norm, (cpuState3.getPotentialEnergy()-cpuState.getPotentialEnergy())/delta, tol)
}
void testWater() {
// Create a box of SWM4-NDP water molecules. This involves constraints, virtual sites,
// and Drude particles.
const int gridSize = 3;
const int numMolecules = gridSize*gridSize*gridSize;
const double spacing = 0.6;
const double boxSize = spacing*(gridSize+1);
const double temperature = 300.0;
const double temperatureDrude = 10.0;
System system;
NonbondedForce* nonbonded = new NonbondedForce();
DrudeForce* drude = new DrudeForce();
system.addForce(nonbonded);
system.addForce(drude);
system.setDefaultPeriodicBoxVectors(Vec3(boxSize, 0, 0), Vec3(0, boxSize, 0), Vec3(0, 0, boxSize));
nonbonded->setNonbondedMethod(NonbondedForce::CutoffPeriodic);
nonbonded->setCutoffDistance(1.0);
for (int i = 0; i < numMolecules; i++) {
int startIndex = system.getNumParticles();
system.addParticle(15.6); // O
system.addParticle(0.4); // D
system.addParticle(1.0); // H1
system.addParticle(1.0); // H2
system.addParticle(0.0); // M
nonbonded->addParticle(1.71636, 0.318395, 0.21094*4.184);
nonbonded->addParticle(-1.71636, 1, 0);
nonbonded->addParticle(0.55733, 1, 0);
nonbonded->addParticle(0.55733, 1, 0);
nonbonded->addParticle(-1.11466, 1, 0);
for (int j = 0; j < 5; j++)
for (int k = 0; k < j; k++)
nonbonded->addException(startIndex+j, startIndex+k, 0, 1, 0);
system.addConstraint(startIndex, startIndex+2, 0.09572);
system.addConstraint(startIndex, startIndex+3, 0.09572);
system.addConstraint(startIndex+2, startIndex+3, 0.15139);
system.setVirtualSite(startIndex+4, new ThreeParticleAverageSite(startIndex, startIndex+2, startIndex+3, 0.786646558, 0.106676721, 0.106676721));
drude->addParticle(startIndex+1, startIndex, -1, -1, -1, -1.71636, ONE_4PI_EPS0*1.71636*1.71636/(100000*4.184), 1, 1);
}
vector<Vec3> positions;
for (int i = 0; i < gridSize; i++)
for (int j = 0; j < gridSize; j++)
for (int k = 0; k < gridSize; k++) {
Vec3 pos(i*spacing, j*spacing, k*spacing);
positions.push_back(pos);
positions.push_back(pos);
positions.push_back(pos+Vec3(0.09572, 0, 0));
positions.push_back(pos+Vec3(-0.023999, 0.092663, 0));
positions.push_back(pos);
}
// Simulate it and check the temperature.
DrudeLangevinIntegrator integ(temperature, 50.0, temperatureDrude, 50.0, 0.0005);
Platform& platform = Platform::getPlatformByName("Reference");
Context context(system, integ, platform);
context.setPositions(positions);
context.applyConstraints(1e-5);
// Equilibrate.
integ.step(500);
// Compute the internal and center of mass temperatures.
double ke = 0;
int numSteps = 4000;
for (int i = 0; i < numSteps; i++) {
integ.step(1);
ke += context.getState(State::Energy).getKineticEnergy();
}
ke /= numSteps;
int numStandardDof = 3*3*numMolecules-system.getNumConstraints();
int numDrudeDof = 3*numMolecules;
int numDof = numStandardDof+numDrudeDof;
double expectedTemp = (numStandardDof*temperature+numDrudeDof*temperatureDrude)/numDof;
ASSERT_USUALLY_EQUAL_TOL(expectedTemp, ke/(0.5*numDof*BOLTZ), 0.03);
}
