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 testDispersionCorrection() {
// Create a box full of identical particles.
int gridSize = 5;
int numParticles = gridSize*gridSize*gridSize;
double boxSize = gridSize*0.7;
double cutoff = boxSize/3;
System system;
VerletIntegrator integrator(0.01);
NonbondedForce* nonbonded = new NonbondedForce();
vector<Vec3> positions(numParticles);
int index = 0;
for (int i = 0; i < gridSize; i++)
for (int j = 0; j < gridSize; j++)
for (int k = 0; k < gridSize; k++) {
system.addParticle(1.0);
nonbonded->addParticle(0, 1.1, 0.5);
positions[index] = Vec3(i*boxSize/gridSize, j*boxSize/gridSize, k*boxSize/gridSize);
index++;
}
nonbonded->setNonbondedMethod(NonbondedForce::CutoffPeriodic);
nonbonded->setCutoffDistance(cutoff);
system.setDefaultPeriodicBoxVectors(Vec3(boxSize, 0, 0), Vec3(0, boxSize, 0), Vec3(0, 0, boxSize));
system.addForce(nonbonded);
// See if the correction has the correct value.
Context context(system, integrator, platform);
context.setPositions(positions);
double energy1 = context.getState(State::Energy).getPotentialEnergy();
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, energy1-energy2, 1e-4);
// Now modify half the particles to be different, and see if it is still correct.
int numType2 = 0;
for (int i = 0; i < numParticles; i += 2) {
nonbonded->setParticleParameters(i, 0, 1, 1);
numType2++;
}
int numType1 = numParticles-numType2;
nonbonded->updateParametersInContext(context);
energy2 = context.getState(State::Energy).getPotentialEnergy();
nonbonded->setUseDispersionCorrection(true);
context.reinitialize();
context.setPositions(positions);
energy1 = context.getState(State::Energy).getPotentialEnergy();
term1 = ((numType1*(numType1+1))/2)*(0.5*pow(1.1, 12)/pow(cutoff, 9))/9;
term2 = ((numType1*(numType1+1))/2)*(0.5*pow(1.1, 6)/pow(cutoff, 3))/3;
term1 += ((numType2*(numType2+1))/2)*(1*pow(1.0, 12)/pow(cutoff, 9))/9;
term2 += ((numType2*(numType2+1))/2)*(1*pow(1.0, 6)/pow(cutoff, 3))/3;
double combinedSigma = 0.5*(1+1.1);
double combinedEpsilon = sqrt(1*0.5);
term1 += (numType1*numType2)*(combinedEpsilon*pow(combinedSigma, 12)/pow(cutoff, 9))/9;
term2 += (numType1*numType2)*(combinedEpsilon*pow(combinedSigma, 6)/pow(cutoff, 3))/3;
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, energy1-energy2, 1e-4);
}
void testChangingParameters() {
const int numMolecules = 600;
const int numParticles = numMolecules*2;
const double cutoff = 2.0;
const double boxSize = 20.0;
const double tol = 2e-3;
ReferencePlatform reference;
System system;
for (int i = 0; i < numParticles; i++)
system.addParticle(1.0);
NonbondedForce* nonbonded = new NonbondedForce();
vector<Vec3> positions(numParticles);
OpenMM_SFMT::SFMT sfmt;
init_gen_rand(0, sfmt);
for (int i = 0; i < numMolecules; i++) {
if (i < numMolecules/2) {
nonbonded->addParticle(-1.0, 0.2, 0.1);
nonbonded->addParticle(1.0, 0.1, 0.1);
}
else {
nonbonded->addParticle(-1.0, 0.2, 0.2);
nonbonded->addParticle(1.0, 0.1, 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);
nonbonded->addException(2*i, 2*i+1, 0.0, 0.15, 0.0);
}
nonbonded->setNonbondedMethod(NonbondedForce::PME);
nonbonded->setCutoffDistance(cutoff);
system.addForce(nonbonded);
system.setDefaultPeriodicBoxVectors(Vec3(boxSize, 0, 0), Vec3(0, boxSize, 0), Vec3(0, 0, boxSize));
// See if Reference and Cuda give the same forces and energies.
VerletIntegrator integrator1(0.01);
VerletIntegrator integrator2(0.01);
Context cuContext(system, integrator1, platform);
Context referenceContext(system, integrator2, reference);
cuContext.setPositions(positions);
referenceContext.setPositions(positions);
State cuState = cuContext.getState(State::Forces | State::Energy);
State referenceState = referenceContext.getState(State::Forces | State::Energy);
for (int i = 0; i < numParticles; i++)
ASSERT_EQUAL_VEC(cuState.getForces()[i], referenceState.getForces()[i], tol);
ASSERT_EQUAL_TOL(cuState.getPotentialEnergy(), referenceState.getPotentialEnergy(), tol);
// Now modify parameters and see if they still agree.
for (int i = 0; i < numParticles; i += 5) {
double charge, sigma, epsilon;
nonbonded->getParticleParameters(i, charge, sigma, epsilon);
nonbonded->setParticleParameters(i, 1.5*charge, 1.1*sigma, 1.7*epsilon);
}
nonbonded->updateParametersInContext(cuContext);
nonbonded->updateParametersInContext(referenceContext);
cuState = cuContext.getState(State::Forces | State::Energy);
referenceState = referenceContext.getState(State::Forces | State::Energy);
for (int i = 0; i < numParticles; i++)
ASSERT_EQUAL_VEC(cuState.getForces()[i], referenceState.getForces()[i], tol);
ASSERT_EQUAL_TOL(cuState.getPotentialEnergy(), referenceState.getPotentialEnergy(), tol);
}
void testExclusionsAnd14() {
ReferencePlatform platform;
System system;
VerletIntegrator integrator(0.01);
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);
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);
nonbonded->updateParametersInContext(context);
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);
}
}
