void ReferenceCalcDrudeForceKernel::initialize(const System& system, const DrudeForce& force) {
// Initialize particle parameters.
int numParticles = force.getNumParticles();
particle.resize(numParticles);
particle1.resize(numParticles);
particle2.resize(numParticles);
particle3.resize(numParticles);
particle4.resize(numParticles);
charge.resize(numParticles);
polarizability.resize(numParticles);
aniso12.resize(numParticles);
aniso34.resize(numParticles);
for (int i = 0; i < numParticles; i++)
force.getParticleParameters(i, particle[i], particle1[i], particle2[i], particle3[i], particle4[i], charge[i], polarizability[i], aniso12[i], aniso34[i]);
// Initialize screened pair parameters.
int numPairs = force.getNumScreenedPairs();
pair1.resize(numPairs);
pair2.resize(numPairs);
pairThole.resize(numPairs);
for (int i = 0; i < numPairs; i++)
force.getScreenedPairParameters(i, pair1[i], pair2[i], pairThole[i]);
}
void testAnisotropicParticle() {
const double k = ONE_4PI_EPS0*1.5;
const double charge = 0.1;
const double alpha = ONE_4PI_EPS0*charge*charge/k;
const double a1 = 0.8;
const double a2 = 1.1;
const double k1 = k/a1;
const double k2 = k/a2;
const double k3 = k/(3-a1-a2);
System system;
system.addParticle(1.0);
system.addParticle(1.0);
system.addParticle(1.0);
system.addParticle(1.0);
system.addParticle(1.0);
DrudeForce* drude = new DrudeForce();
drude->addParticle(1, 0, 2, 3, 4, charge, alpha, a1, a2);
system.addForce(drude);
vector<Vec3> positions(5);
positions[0] = Vec3(0, 0, 0);
positions[1] = Vec3(0.1, -0.5, 0.8);
positions[2] = Vec3(0, 2, 0);
positions[3] = Vec3(1, 2, 0);
positions[4] = Vec3(1, 2, 3);
validateForce(system, positions, 0.5*k1*0.5*0.5 + 0.5*k2*0.8*0.8 + 0.5*k3*0.1*0.1);
}
void ReferenceIntegrateDrudeSCFStepKernel::initialize(const System& system, const DrudeSCFIntegrator& integrator, const DrudeForce& force) {
// Identify Drude particles.
for (int i = 0; i < force.getNumParticles(); i++) {
int p, p1, p2, p3, p4;
double charge, polarizability, aniso12, aniso34;
force.getParticleParameters(i, p, p1, p2, p3, p4, charge, polarizability, aniso12, aniso34);
drudeParticles.push_back(p);
}
// Record particle masses.
vector<RealOpenMM> particleMass;
for (int i = 0; i < system.getNumParticles(); i++) {
double mass = system.getParticleMass(i);
particleMass.push_back(mass);
particleInvMass.push_back(mass == 0.0 ? 0.0 : 1.0/mass);
}
// Initialize the energy minimizer.
minimizerPos = lbfgs_malloc(drudeParticles.size()*3);
if (minimizerPos == NULL)
throw OpenMMException("DrudeSCFIntegrator: Failed to allocate memory");
lbfgs_parameter_init(&minimizerParams);
minimizerParams.linesearch = LBFGS_LINESEARCH_BACKTRACKING_STRONG_WOLFE;
if (sizeof(RealOpenMM) < 8)
minimizerParams.xtol = 1e-7;
}
void testThole() {
const double k = ONE_4PI_EPS0*1.5;
const double charge = 0.1;
const double alpha = ONE_4PI_EPS0*charge*charge/k;
const double thole = 2.5;
System system;
system.addParticle(1.0);
system.addParticle(1.0);
system.addParticle(1.0);
system.addParticle(1.0);
DrudeForce* drude = new DrudeForce();
drude->addParticle(1, 0, -1, -1, -1, charge, alpha, 1, 1);
drude->addParticle(3, 2, -1, -1, -1, charge, alpha, 1, 1);
drude->addScreenedPair(0, 1, thole);
system.addForce(drude);
vector<Vec3> positions(4);
positions[0] = Vec3(0, 0, 0);
positions[1] = Vec3(0, -0.5, 0);
positions[2] = Vec3(1, 0, 0);
positions[3] = Vec3(1, 0, 0.3);
double energySpring1 = 0.5*k*0.5*0.5;
double energySpring2 = 0.5*k*0.3*0.3;
double energyDipole = 0.0;
double q[] = {-charge, charge, -charge, charge};
for (int i = 0; i < 2; i++)
for (int j = 2; j < 4; j++) {
Vec3 delta = positions[i]-positions[j];
double r = sqrt(delta.dot(delta));
energyDipole += ONE_4PI_EPS0*q[i]*q[j]*computeScreening(r, thole, alpha, alpha)/r;
}
validateForce(system, positions, energySpring1+energySpring2+energyDipole);
}
void ReferenceIntegrateDrudeLangevinStepKernel::initialize(const System& system, const DrudeLangevinIntegrator& integrator, const DrudeForce& force) {
SimTKOpenMMUtilities::setRandomNumberSeed((unsigned int) integrator.getRandomNumberSeed());
// Identify particle pairs and ordinary particles.
set<int> particles;
for (int i = 0; i < system.getNumParticles(); i++) {
particles.insert(i);
double mass = system.getParticleMass(i);
particleMass.push_back(mass);
particleInvMass.push_back(mass == 0.0 ? 0.0 : 1.0/mass);
}
for (int i = 0; i < force.getNumParticles(); i++) {
int p, p1, p2, p3, p4;
double charge, polarizability, aniso12, aniso34;
force.getParticleParameters(i, p, p1, p2, p3, p4, charge, polarizability, aniso12, aniso34);
particles.erase(p);
particles.erase(p1);
pairParticles.push_back(make_pair(p, p1));
double m1 = system.getParticleMass(p);
double m2 = system.getParticleMass(p1);
pairInvTotalMass.push_back(1.0/(m1+m2));
pairInvReducedMass.push_back((m1+m2)/(m1*m2));
}
normalParticles.insert(normalParticles.begin(), particles.begin(), particles.end());
}
void CudaIntegrateDrudeSCFStepKernel::initialize(const System& system, const DrudeSCFIntegrator& integrator, const DrudeForce& force) {
cu.getPlatformData().initializeContexts(system);
cu.setAsCurrent();
// Identify Drude particles.
for (int i = 0; i < force.getNumParticles(); i++) {
int p, p1, p2, p3, p4;
double charge, polarizability, aniso12, aniso34;
force.getParticleParameters(i, p, p1, p2, p3, p4, charge, polarizability, aniso12, aniso34);
drudeParticles.push_back(p);
}
// Initialize the energy minimizer.
minimizerPos = lbfgs_malloc(drudeParticles.size()*3);
if (minimizerPos == NULL)
throw OpenMMException("DrudeSCFIntegrator: Failed to allocate memory");
lbfgs_parameter_init(&minimizerParams);
minimizerParams.linesearch = LBFGS_LINESEARCH_BACKTRACKING_STRONG_WOLFE;
// Create the kernels.
map<string, string> defines;
defines["NUM_ATOMS"] = cu.intToString(cu.getNumAtoms());
defines["PADDED_NUM_ATOMS"] = cu.intToString(cu.getPaddedNumAtoms());
CUmodule module = cu.createModule(CudaKernelSources::verlet, defines, "");
kernel1 = cu.getKernel(module, "integrateVerletPart1");
kernel2 = cu.getKernel(module, "integrateVerletPart2");
prevStepSize = -1.0;
}
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 testSinglePair() {
const double temperature = 300.0;
const double temperatureDrude = 10.0;
const double k = ONE_4PI_EPS0*1.5;
const double charge = 0.1;
const double alpha = ONE_4PI_EPS0*charge*charge/k;
const double mass1 = 1.0;
const double mass2 = 0.1;
const double totalMass = mass1+mass2;
const double reducedMass = (mass1*mass2)/(mass1+mass2);
const double maxDistance = 0.05;
System system;
system.addParticle(mass1);
system.addParticle(mass2);
DrudeForce* drude = new DrudeForce();
drude->addParticle(1, 0, -1, -1, -1, charge, alpha, 1, 1);
system.addForce(drude);
vector<Vec3> positions(2);
positions[0] = Vec3(0, 0, 0);
positions[1] = Vec3(0, 0, 0);
DrudeLangevinIntegrator integ(temperature, 20.0, temperatureDrude, 20.0, 0.003);
integ.setMaxDrudeDistance(maxDistance);
Platform& platform = Platform::getPlatformByName("Reference");
Context context(system, integ, platform);
context.setPositions(positions);
// Equilibrate.
integ.step(1000);
// Compute the internal and center of mass temperatures.
double keCM = 0, keInternal = 0;
int numSteps = 10000;
for (int i = 0; i < numSteps; i++) {
integ.step(10);
State state = context.getState(State::Velocities | State::Positions);
const vector<Vec3>& vel = state.getVelocities();
Vec3 velCM = vel[0]*(mass1/totalMass) + vel[1]*(mass2/totalMass);
keCM += 0.5*totalMass*velCM.dot(velCM);
Vec3 velInternal = vel[0]-vel[1];
keInternal += 0.5*reducedMass*velInternal.dot(velInternal);
Vec3 delta = state.getPositions()[0]-state.getPositions()[1];
double distance = sqrt(delta.dot(delta));
ASSERT(distance <= maxDistance*(1+1e-6));
}
ASSERT_USUALLY_EQUAL_TOL(3*0.5*BOLTZ*temperature, keCM/numSteps, 0.1);
ASSERT_USUALLY_EQUAL_TOL(3*0.5*BOLTZ*temperatureDrude, keInternal/numSteps, 0.01);
}
void testSingleParticle() {
const double k = ONE_4PI_EPS0*1.5;
const double charge = 0.1;
const double alpha = ONE_4PI_EPS0*charge*charge/k;
System system;
system.addParticle(1.0);
system.addParticle(1.0);
DrudeForce* drude = new DrudeForce();
drude->addParticle(1, 0, -1, -1, -1, charge, alpha, 1, 1);
system.addForce(drude);
vector<Vec3> positions(2);
positions[0] = Vec3(-1, 0, 0);
positions[1] = Vec3(2, 0, 0);
validateForce(system, positions, 0.5*k*3*3);
}
void ReferenceIntegrateDrudeSCFStepKernel::initialize(const System& system, const DrudeSCFIntegrator& integrator, const DrudeForce& force) {
// Identify Drude particles.
for (int i = 0; i < force.getNumParticles(); i++) {
int p, p1, p2, p3, p4;
double charge, polarizability, aniso12, aniso34;
force.getParticleParameters(i, p, p1, p2, p3, p4, charge, polarizability, aniso12, aniso34);
drudeParticles.push_back(p);
}
// Record particle masses.
vector<RealOpenMM> particleMass;
for (int i = 0; i < system.getNumParticles(); i++) {
double mass = system.getParticleMass(i);
particleMass.push_back(mass);
particleInvMass.push_back(mass == 0.0 ? 0.0 : 1.0/mass);
}
// Prepare constraints.
int numConstraints = system.getNumConstraints();
if (numConstraints > 0) {
vector<pair<int, int> > constraintIndices(numConstraints);
vector<RealOpenMM> constraintDistances(numConstraints);
for (int i = 0; i < numConstraints; ++i) {
int particle1, particle2;
double distance;
system.getConstraintParameters(i, particle1, particle2, distance);
constraintIndices[i].first = particle1;
constraintIndices[i].second = particle2;
constraintDistances[i] = static_cast<RealOpenMM>(distance);
}
vector<ReferenceCCMAAlgorithm::AngleInfo> angles;
findAnglesForCCMA(system, angles);
constraints = new ReferenceCCMAAlgorithm(system.getNumParticles(), numConstraints, constraintIndices, constraintDistances, particleMass, angles, (RealOpenMM)integrator.getConstraintTolerance());
}
// Initialize the energy minimizer.
minimizerPos = lbfgs_malloc(drudeParticles.size()*3);
if (minimizerPos == NULL)
throw OpenMMException("DrudeSCFIntegrator: Failed to allocate memory");
lbfgs_parameter_init(&minimizerParams);
minimizerParams.linesearch = LBFGS_LINESEARCH_BACKTRACKING_STRONG_WOLFE;
if (sizeof(RealOpenMM) < 8)
minimizerParams.xtol = 1e-7;
}
void ReferenceIntegrateDrudeLangevinStepKernel::initialize(const System& system, const DrudeLangevinIntegrator& integrator, const DrudeForce& force) {
SimTKOpenMMUtilities::setRandomNumberSeed((unsigned int) integrator.getRandomNumberSeed());
// Identify particle pairs and ordinary particles.
set<int> particles;
vector<RealOpenMM> particleMass;
for (int i = 0; i < system.getNumParticles(); i++) {
particles.insert(i);
double mass = system.getParticleMass(i);
particleMass.push_back(mass);
particleInvMass.push_back(mass == 0.0 ? 0.0 : 1.0/mass);
}
for (int i = 0; i < force.getNumParticles(); i++) {
int p, p1, p2, p3, p4;
double charge, polarizability, aniso12, aniso34;
force.getParticleParameters(i, p, p1, p2, p3, p4, charge, polarizability, aniso12, aniso34);
particles.erase(p);
particles.erase(p1);
pairParticles.push_back(make_pair(p, p1));
double m1 = system.getParticleMass(p);
double m2 = system.getParticleMass(p1);
pairInvTotalMass.push_back(1.0/(m1+m2));
pairInvReducedMass.push_back((m1+m2)/(m1*m2));
}
normalParticles.insert(normalParticles.begin(), particles.begin(), particles.end());
// Prepare constraints.
int numConstraints = system.getNumConstraints();
if (numConstraints > 0) {
vector<pair<int, int> > constraintIndices(numConstraints);
vector<RealOpenMM> constraintDistances(numConstraints);
for (int i = 0; i < numConstraints; ++i) {
int particle1, particle2;
double distance;
system.getConstraintParameters(i, particle1, particle2, distance);
constraintIndices[i].first = particle1;
constraintIndices[i].second = particle2;
constraintDistances[i] = static_cast<RealOpenMM>(distance);
}
vector<ReferenceCCMAAlgorithm::AngleInfo> angles;
findAnglesForCCMA(system, angles);
constraints = new ReferenceCCMAAlgorithm(system.getNumParticles(), numConstraints, constraintIndices, constraintDistances, particleMass, angles, (RealOpenMM)integrator.getConstraintTolerance());
}
}
void CudaIntegrateDrudeLangevinStepKernel::initialize(const System& system, const DrudeLangevinIntegrator& integrator, const DrudeForce& force) {
cu.getPlatformData().initializeContexts(system);
cu.getIntegrationUtilities().initRandomNumberGenerator((unsigned int) integrator.getRandomNumberSeed());
// Identify particle pairs and ordinary particles.
set<int> particles;
vector<int> normalParticleVec;
vector<int2> pairParticleVec;
for (int i = 0; i < system.getNumParticles(); i++)
particles.insert(i);
for (int i = 0; i < force.getNumParticles(); i++) {
int p, p1, p2, p3, p4;
double charge, polarizability, aniso12, aniso34;
force.getParticleParameters(i, p, p1, p2, p3, p4, charge, polarizability, aniso12, aniso34);
particles.erase(p);
particles.erase(p1);
pairParticleVec.push_back(make_int2(p, p1));
}
normalParticleVec.insert(normalParticleVec.begin(), particles.begin(), particles.end());
normalParticles = CudaArray::create<int>(cu, max((int) normalParticleVec.size(), 1), "drudeNormalParticles");
pairParticles = CudaArray::create<int2>(cu, max((int) pairParticleVec.size(), 1), "drudePairParticles");
if (normalParticleVec.size() > 0)
normalParticles->upload(normalParticleVec);
if (pairParticleVec.size() > 0)
pairParticles->upload(pairParticleVec);
// Create kernels.
map<string, string> defines;
defines["NUM_ATOMS"] = cu.intToString(cu.getNumAtoms());
defines["PADDED_NUM_ATOMS"] = cu.intToString(cu.getPaddedNumAtoms());
defines["NUM_NORMAL_PARTICLES"] = cu.intToString(normalParticleVec.size());
defines["NUM_PAIRS"] = cu.intToString(pairParticleVec.size());
map<string, string> replacements;
CUmodule module = cu.createModule(CudaKernelSources::vectorOps+CudaDrudeKernelSources::drudeLangevin, defines, "");
kernel1 = cu.getKernel(module, "integrateDrudeLangevinPart1");
kernel2 = cu.getKernel(module, "integrateDrudeLangevinPart2");
hardwallKernel = cu.getKernel(module, "applyHardWallConstraints");
prevStepSize = -1.0;
}
void CudaCalcDrudeForceKernel::copyParametersToContext(ContextImpl& context, const DrudeForce& force) {
int numContexts = cu.getPlatformData().contexts.size();
// Set the particle parameters.
int startParticleIndex = cu.getContextIndex()*force.getNumParticles()/numContexts;
int endParticleIndex = (cu.getContextIndex()+1)*force.getNumParticles()/numContexts;
int numParticles = endParticleIndex-startParticleIndex;
if (numParticles > 0) {
if (particleParams == NULL || numParticles != particleParams->getSize())
throw OpenMMException("updateParametersInContext: The number of Drude particles has changed");
vector<float4> paramVector(numParticles);
for (int i = 0; i < numParticles; i++) {
int p, p1, p2, p3, p4;
double charge, polarizability, aniso12, aniso34;
force.getParticleParameters(startParticleIndex+i, p, p1, p2, p3, p4, charge, polarizability, aniso12, aniso34);
double a1 = (p2 == -1 ? 1 : aniso12);
double a2 = (p3 == -1 || p4 == -1 ? 1 : aniso34);
double a3 = 3-a1-a2;
double k3 = ONE_4PI_EPS0*charge*charge/(polarizability*a3);
double k1 = ONE_4PI_EPS0*charge*charge/(polarizability*a1) - k3;
double k2 = ONE_4PI_EPS0*charge*charge/(polarizability*a2) - k3;
if (p2 == -1)
k1 = 0;
if (p3 == -1 || p4 == -1)
k2 = 0;
paramVector[i] = make_float4((float) k1, (float) k2, (float) k3, 0.0f);
}
particleParams->upload(paramVector);
}
// Set the pair parameters.
int startPairIndex = cu.getContextIndex()*force.getNumScreenedPairs()/numContexts;
int endPairIndex = (cu.getContextIndex()+1)*force.getNumScreenedPairs()/numContexts;
int numPairs = endPairIndex-startPairIndex;
if (numPairs > 0) {
if (pairParams == NULL || numPairs != pairParams->getSize())
throw OpenMMException("updateParametersInContext: The number of screened pairs has changed");
vector<float2> paramVector(numPairs);
for (int i = 0; i < numPairs; i++) {
int drude1, drude2;
double thole;
force.getScreenedPairParameters(startPairIndex+i, drude1, drude2, thole);
int p, p1, p2, p3, p4;
double charge1, charge2, polarizability1, polarizability2, aniso12, aniso34;
force.getParticleParameters(drude1, p, p1, p2, p3, p4, charge1, polarizability1, aniso12, aniso34);
force.getParticleParameters(drude2, p, p1, p2, p3, p4, charge2, polarizability2, aniso12, aniso34);
double screeningScale = thole/pow(polarizability1*polarizability2, 1.0/6.0);
double energyScale = ONE_4PI_EPS0*charge1*charge2;
paramVector[i] = make_float2((float) screeningScale, (float) energyScale);
}
pairParams->upload(paramVector);
}
}
void testChangingParameters() {
const double k = ONE_4PI_EPS0*1.5;
const double charge = 0.1;
const double alpha = ONE_4PI_EPS0*charge*charge/k;
Platform& platform = Platform::getPlatformByName("OpenCL");
// Create the system.
System system;
system.addParticle(1.0);
system.addParticle(1.0);
DrudeForce* drude = new DrudeForce();
drude->addParticle(1, 0, -1, -1, -1, charge, alpha, 1, 1);
system.addForce(drude);
vector<Vec3> positions(2);
positions[0] = Vec3(-1, 0, 0);
positions[1] = Vec3(2, 0, 0);
// Check the energy.
VerletIntegrator integ(1.0);
Context context(system, integ, platform);
context.setPositions(positions);
State state = context.getState(State::Energy);
ASSERT_EQUAL_TOL(0.5*k*3*3, state.getPotentialEnergy(), 1e-5);
// Modify the parameters.
const double k2 = ONE_4PI_EPS0*2.2;
const double charge2 = 0.3;
const double alpha2 = ONE_4PI_EPS0*charge2*charge2/k2;
drude->setParticleParameters(0, 1, 0, -1, -1, -1, charge2, alpha2, 1, 1);
drude->updateParametersInContext(context);
state = context.getState(State::Energy);
ASSERT_EQUAL_TOL(0.5*k2*3*3, state.getPotentialEnergy(), 1e-5);
}
void ReferenceCalcDrudeForceKernel::copyParametersToContext(ContextImpl& context, const DrudeForce& force) {
if (force.getNumParticles() != particle.size())
throw OpenMMException("updateParametersInContext: The number of Drude particles has changed");
if (force.getNumScreenedPairs() != pair1.size())
throw OpenMMException("updateParametersInContext: The number of screened pairs has changed");
for (int i = 0; i < force.getNumParticles(); i++) {
int p, p1, p2, p3, p4;
force.getParticleParameters(i, p, p1, p2, p3, p4, charge[i], polarizability[i], aniso12[i], aniso34[i]);
if (p != particle[i] || p1 != particle1[i] || p2 != particle2[i] || p3 != particle3[i] || p4 != particle4[i])
throw OpenMMException("updateParametersInContext: A particle index has changed");
}
for (int i = 0; i < force.getNumScreenedPairs(); i++) {
int p1, p2;
force.getScreenedPairParameters(i, p1, p2, pairThole[i]);
if (p1 != pair1[i] || p2 != pair2[i])
throw OpenMMException("updateParametersInContext: A particle index for a screened pair has changed");
}
}
void CudaCalcDrudeForceKernel::initialize(const System& system, const DrudeForce& force) {
cu.setAsCurrent();
int numContexts = cu.getPlatformData().contexts.size();
int startParticleIndex = cu.getContextIndex()*force.getNumParticles()/numContexts;
int endParticleIndex = (cu.getContextIndex()+1)*force.getNumParticles()/numContexts;
int numParticles = endParticleIndex-startParticleIndex;
if (numParticles > 0) {
// Create the harmonic interaction .
vector<vector<int> > atoms(numParticles, vector<int>(5));
particleParams = CudaArray::create<float4>(cu, numParticles, "drudeParticleParams");
vector<float4> paramVector(numParticles);
for (int i = 0; i < numParticles; i++) {
double charge, polarizability, aniso12, aniso34;
force.getParticleParameters(startParticleIndex+i, atoms[i][0], atoms[i][1], atoms[i][2], atoms[i][3], atoms[i][4], charge, polarizability, aniso12, aniso34);
double a1 = (atoms[i][2] == -1 ? 1 : aniso12);
double a2 = (atoms[i][3] == -1 || atoms[i][4] == -1 ? 1 : aniso34);
double a3 = 3-a1-a2;
double k3 = ONE_4PI_EPS0*charge*charge/(polarizability*a3);
double k1 = ONE_4PI_EPS0*charge*charge/(polarizability*a1) - k3;
double k2 = ONE_4PI_EPS0*charge*charge/(polarizability*a2) - k3;
if (atoms[i][2] == -1) {
atoms[i][2] = 0;
k1 = 0;
}
if (atoms[i][3] == -1 || atoms[i][4] == -1) {
atoms[i][3] = 0;
atoms[i][4] = 0;
k2 = 0;
}
paramVector[i] = make_float4((float) k1, (float) k2, (float) k3, 0.0f);
}
particleParams->upload(paramVector);
map<string, string> replacements;
replacements["PARAMS"] = cu.getBondedUtilities().addArgument(particleParams->getDevicePointer(), "float4");
cu.getBondedUtilities().addInteraction(atoms, cu.replaceStrings(CudaDrudeKernelSources::drudeParticleForce, replacements), force.getForceGroup());
}
int startPairIndex = cu.getContextIndex()*force.getNumScreenedPairs()/numContexts;
int endPairIndex = (cu.getContextIndex()+1)*force.getNumScreenedPairs()/numContexts;
int numPairs = endPairIndex-startPairIndex;
if (numPairs > 0) {
// Create the screened interaction between dipole pairs.
vector<vector<int> > atoms(numPairs, vector<int>(4));
pairParams = CudaArray::create<float2>(cu, numPairs, "drudePairParams");
vector<float2> paramVector(numPairs);
for (int i = 0; i < numPairs; i++) {
int drude1, drude2;
double thole;
force.getScreenedPairParameters(startPairIndex+i, drude1, drude2, thole);
int p2, p3, p4;
double charge1, charge2, polarizability1, polarizability2, aniso12, aniso34;
force.getParticleParameters(drude1, atoms[i][0], atoms[i][1], p2, p3, p4, charge1, polarizability1, aniso12, aniso34);
force.getParticleParameters(drude2, atoms[i][2], atoms[i][3], p2, p3, p4, charge2, polarizability2, aniso12, aniso34);
double screeningScale = thole/pow(polarizability1*polarizability2, 1.0/6.0);
double energyScale = ONE_4PI_EPS0*charge1*charge2;
paramVector[i] = make_float2((float) screeningScale, (float) energyScale);
}
pairParams->upload(paramVector);
map<string, string> replacements;
replacements["PARAMS"] = cu.getBondedUtilities().addArgument(pairParams->getDevicePointer(), "float2");
cu.getBondedUtilities().addInteraction(atoms, cu.replaceStrings(CudaDrudeKernelSources::drudePairForce, replacements), force.getForceGroup());
}
cu.addForce(new CudaDrudeForceInfo(force));
}
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);
}
}
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);
}
