void testPeriodic() {
System system;
system.addParticle(1.0);
system.addParticle(1.0);
system.addParticle(1.0);
VerletIntegrator integrator(0.01);
CustomNonbondedForce* forceField = new CustomNonbondedForce("r");
forceField->addParticle(vector<double>());
forceField->addParticle(vector<double>());
forceField->addParticle(vector<double>());
forceField->setNonbondedMethod(CustomNonbondedForce::CutoffPeriodic);
forceField->setCutoffDistance(2.0);
system.setDefaultPeriodicBoxVectors(Vec3(4, 0, 0), Vec3(0, 4, 0), Vec3(0, 0, 4));
system.addForce(forceField);
Context context(system, integrator, platform);
vector<Vec3> positions(3);
positions[0] = Vec3(0, 0, 0);
positions[1] = Vec3(0, 2.1, 0);
positions[2] = Vec3(0, 3, 0);
context.setPositions(positions);
State state = context.getState(State::Forces | State::Energy);
const vector<Vec3>& forces = state.getForces();
ASSERT_EQUAL_VEC(Vec3(0, -2, 0), forces[0], TOL);
ASSERT_EQUAL_VEC(Vec3(0, 2, 0), forces[1], TOL);
ASSERT_EQUAL_VEC(Vec3(0, 0, 0), forces[2], TOL);
ASSERT_EQUAL_TOL(1.9+1+0.9, state.getPotentialEnergy(), TOL);
}
void testDiscrete3DFunction() {
const int xsize = 8;
const int ysize = 5;
const int zsize = 6;
System system;
system.addParticle(1.0);
system.addParticle(1.0);
VerletIntegrator integrator(0.01);
CustomNonbondedForce* forceField = new CustomNonbondedForce("fn(r-1,a,b)+1");
forceField->addGlobalParameter("a", 0.0);
forceField->addGlobalParameter("b", 0.0);
forceField->addParticle(vector<double>());
forceField->addParticle(vector<double>());
vector<double> table;
for (int i = 0; i < xsize; i++)
for (int j = 0; j < ysize; j++)
for (int k = 0; k < zsize; k++)
table.push_back(sin(0.25*i)+cos(0.33*j)+0.12345*k);
forceField->addTabulatedFunction("fn", new Discrete3DFunction(xsize, ysize, zsize, table));
system.addForce(forceField);
Context context(system, integrator, platform);
vector<Vec3> positions(2);
positions[0] = Vec3(0, 0, 0);
for (int i = 0; i < (int) table.size(); i++) {
positions[1] = Vec3((i%xsize)+1, 0, 0);
context.setPositions(positions);
context.setParameter("a", (i/xsize)%ysize);
context.setParameter("b", i/(xsize*ysize));
State state = context.getState(State::Forces | State::Energy);
const vector<Vec3>& forces = state.getForces();
ASSERT_EQUAL_VEC(Vec3(0, 0, 0), forces[0], 1e-6);
ASSERT_EQUAL_VEC(Vec3(0, 0, 0), forces[1], 1e-6);
ASSERT_EQUAL_TOL(table[i]+1.0, state.getPotentialEnergy(), 1e-6);
}
}
void testDiscrete1DFunction() {
System system;
system.addParticle(1.0);
system.addParticle(1.0);
VerletIntegrator integrator(0.01);
CustomNonbondedForce* forceField = new CustomNonbondedForce("fn(r-1)+1");
forceField->addParticle(vector<double>());
forceField->addParticle(vector<double>());
vector<double> table;
for (int i = 0; i < 21; i++)
table.push_back(sin(0.25*i));
forceField->addTabulatedFunction("fn", new Discrete1DFunction(table));
system.addForce(forceField);
Context context(system, integrator, platform);
vector<Vec3> positions(2);
positions[0] = Vec3(0, 0, 0);
for (int i = 0; i < (int) table.size(); i++) {
positions[1] = Vec3(i+1, 0, 0);
context.setPositions(positions);
State state = context.getState(State::Forces | State::Energy);
const vector<Vec3>& forces = state.getForces();
ASSERT_EQUAL_VEC(Vec3(0, 0, 0), forces[0], 1e-6);
ASSERT_EQUAL_VEC(Vec3(0, 0, 0), forces[1], 1e-6);
ASSERT_EQUAL_TOL(table[i]+1.0, state.getPotentialEnergy(), 1e-6);
}
}
void testTriclinic() {
ReferencePlatform platform;
System system;
system.addParticle(1.0);
system.addParticle(1.0);
Vec3 a(3.1, 0, 0);
Vec3 b(0.4, 3.5, 0);
Vec3 c(-0.1, -0.5, 4.0);
system.setDefaultPeriodicBoxVectors(a, b, c);
VerletIntegrator integrator(0.01);
CustomNonbondedForce* nonbonded = new CustomNonbondedForce("r");
nonbonded->addParticle(vector<double>());
nonbonded->addParticle(vector<double>());
nonbonded->setNonbondedMethod(CustomNonbondedForce::CutoffPeriodic);
const double cutoff = 1.5;
nonbonded->setCutoffDistance(cutoff);
system.addForce(nonbonded);
Context context(system, integrator, platform);
vector<Vec3> positions(2);
OpenMM_SFMT::SFMT sfmt;
init_gen_rand(0, sfmt);
for (int iteration = 0; iteration < 50; iteration++) {
// Generate random positions for the two particles.
positions[0] = a*genrand_real2(sfmt) + b*genrand_real2(sfmt) + c*genrand_real2(sfmt);
positions[1] = a*genrand_real2(sfmt) + b*genrand_real2(sfmt) + c*genrand_real2(sfmt);
context.setPositions(positions);
// Loop over all possible periodic copies and find the nearest one.
Vec3 delta;
double distance2 = 100.0;
for (int i = -1; i < 2; i++)
for (int j = -1; j < 2; j++)
for (int k = -1; k < 2; k++) {
Vec3 d = positions[1]-positions[0]+a*i+b*j+c*k;
if (d.dot(d) < distance2) {
delta = d;
distance2 = d.dot(d);
}
}
double distance = sqrt(distance2);
// See if the force and energy are correct.
State state = context.getState(State::Forces | State::Energy);
if (distance >= cutoff) {
ASSERT_EQUAL(0.0, state.getPotentialEnergy());
ASSERT_EQUAL_VEC(Vec3(0, 0, 0), state.getForces()[0], 0);
ASSERT_EQUAL_VEC(Vec3(0, 0, 0), state.getForces()[1], 0);
}
else {
const Vec3 force = delta/sqrt(delta.dot(delta));
ASSERT_EQUAL_TOL(distance, state.getPotentialEnergy(), TOL);
ASSERT_EQUAL_VEC(force, state.getForces()[0], TOL);
ASSERT_EQUAL_VEC(-force, state.getForces()[1], TOL);
}
}
}
void testContinuous3DFunction() {
const int xsize = 10;
const int ysize = 11;
const int zsize = 12;
const double xmin = 0.6;
const double xmax = 1.1;
const double ymin = 0.0;
const double ymax = 0.7;
const double zmin = 0.2;
const double zmax = 0.9;
ReferencePlatform platform;
System system;
system.addParticle(1.0);
system.addParticle(1.0);
VerletIntegrator integrator(0.01);
CustomNonbondedForce* forceField = new CustomNonbondedForce("fn(r,a,b)+1");
forceField->addGlobalParameter("a", 0.0);
forceField->addGlobalParameter("b", 0.0);
forceField->addParticle(vector<double>());
forceField->addParticle(vector<double>());
vector<double> table(xsize*ysize*zsize);
for (int i = 0; i < xsize; i++) {
for (int j = 0; j < ysize; j++) {
for (int k = 0; k < zsize; k++) {
double x = xmin + i*(xmax-xmin)/xsize;
double y = ymin + j*(ymax-ymin)/ysize;
double z = zmin + k*(zmax-zmin)/zsize;
table[i+xsize*j+xsize*ysize*k] = sin(0.25*x)*cos(0.33*y)*(1+z);
}
}
}
forceField->addTabulatedFunction("fn", new Continuous3DFunction(xsize, ysize, zsize, table, xmin, xmax, ymin, ymax, zmin, zmax));
system.addForce(forceField);
Context context(system, integrator, platform);
vector<Vec3> positions(2);
positions[0] = Vec3(0, 0, 0);
for (double x = xmin-0.15; x < xmax+0.2; x += 0.1) {
for (double y = ymin-0.15; y < ymax+0.2; y += 0.1) {
for (double z = zmin-0.15; z < zmax+0.2; z += 0.1) {
positions[1] = Vec3(x, 0, 0);
context.setParameter("a", y);
context.setParameter("b", z);
context.setPositions(positions);
State state = context.getState(State::Forces | State::Energy);
const vector<Vec3>& forces = state.getForces();
double energy = 1;
double force = 0;
if (x >= xmin && x <= xmax && y >= ymin && y <= ymax && z >= zmin && z <= zmax) {
energy = sin(0.25*x)*cos(0.33*y)*(1.0+z)+1.0;
force = -0.25*cos(0.25*x)*cos(0.33*y)*(1.0+z);
}
ASSERT_EQUAL_VEC(Vec3(-force, 0, 0), forces[0], 0.1);
ASSERT_EQUAL_VEC(Vec3(force, 0, 0), forces[1], 0.1);
ASSERT_EQUAL_TOL(energy, state.getPotentialEnergy(), 0.05);
}
}
}
}
void testParameters() {
ReferencePlatform platform;
System system;
system.addParticle(1.0);
system.addParticle(1.0);
VerletIntegrator integrator(0.01);
CustomNonbondedForce* forceField = new CustomNonbondedForce("scale*a*(r*b)^3; a=a1*a2; b=c+b1+b2");
forceField->addPerParticleParameter("a");
forceField->addPerParticleParameter("b");
forceField->addGlobalParameter("scale", 3.0);
forceField->addGlobalParameter("c", -1.0);
vector<double> params(2);
params[0] = 1.5;
params[1] = 2.0;
forceField->addParticle(params);
params[0] = 2.0;
params[1] = 3.0;
forceField->addParticle(params);
system.addForce(forceField);
Context context(system, integrator, platform);
vector<Vec3> positions(2);
positions[0] = Vec3(0, 0, 0);
positions[1] = Vec3(2, 0, 0);
context.setPositions(positions);
context.setParameter("scale", 1.0);
context.setParameter("c", 0.0);
State state = context.getState(State::Forces | State::Energy);
vector<Vec3> forces = state.getForces();
double force = -3.0*3*5.0*(10*10);
ASSERT_EQUAL_VEC(Vec3(-force, 0, 0), forces[0], TOL);
ASSERT_EQUAL_VEC(Vec3(force, 0, 0), forces[1], TOL);
ASSERT_EQUAL_TOL(3.0*(10*10*10), state.getPotentialEnergy(), TOL);
// Try changing the global parameters and make sure it's still correct.
context.setParameter("scale", 1.5);
context.setParameter("c", 1.0);
state = context.getState(State::Forces | State::Energy);
forces = state.getForces();
force = -1.5*3.0*3*6.0*(12*12);
ASSERT_EQUAL_VEC(Vec3(-force, 0, 0), forces[0], TOL);
ASSERT_EQUAL_VEC(Vec3(force, 0, 0), forces[1], TOL);
ASSERT_EQUAL_TOL(1.5*3.0*(12*12*12), state.getPotentialEnergy(), TOL);
// Try changing the per-particle parameters and make sure it's still correct.
params[0] = 1.6;
params[1] = 2.1;
forceField->setParticleParameters(0, params);
params[0] = 1.9;
params[1] = 2.8;
forceField->setParticleParameters(1, params);
forceField->updateParametersInContext(context);
state = context.getState(State::Forces | State::Energy);
forces = state.getForces();
force = -1.5*1.6*1.9*3*5.9*(11.8*11.8);
ASSERT_EQUAL_VEC(Vec3(-force, 0, 0), forces[0], TOL);
ASSERT_EQUAL_VEC(Vec3(force, 0, 0), forces[1], TOL);
ASSERT_EQUAL_TOL(1.5*1.6*1.9*(11.8*11.8*11.8), state.getPotentialEnergy(), TOL);
}
void testInteractionGroupLongRangeCorrection() {
const int numParticles = 10;
const double boxSize = 10.0;
const double cutoff = 0.5;
ReferencePlatform platform;
System system;
system.setDefaultPeriodicBoxVectors(Vec3(boxSize, 0, 0), Vec3(0, boxSize, 0), Vec3(0, 0, boxSize));
CustomNonbondedForce* nonbonded = new CustomNonbondedForce("c1*c2*r^-4");
nonbonded->addPerParticleParameter("c");
vector<Vec3> positions(numParticles);
vector<double> params(1);
for (int i = 0; i < numParticles; i++) {
system.addParticle(1.0);
params[0] = (i%2 == 0 ? 1.1 : 2.0);
nonbonded->addParticle(params);
positions[i] = Vec3(0.5*i, 0, 0);
}
nonbonded->setNonbondedMethod(CustomNonbondedForce::CutoffPeriodic);
nonbonded->setCutoffDistance(cutoff);
system.addForce(nonbonded);
// Setup nonbonded groups. They involve 1 interaction of type AA,
// 2 of type BB, and 5 of type AB.
set<int> set1, set2, set3, set4, set5;
set1.insert(0);
set1.insert(1);
set1.insert(2);
nonbonded->addInteractionGroup(set1, set1);
set2.insert(3);
set3.insert(4);
set3.insert(6);
set3.insert(8);
nonbonded->addInteractionGroup(set2, set3);
set4.insert(5);
set5.insert(7);
set5.insert(9);
nonbonded->addInteractionGroup(set4, set5);
// Compute energy with and without the correction.
VerletIntegrator integrator(0.01);
Context context(system, integrator, platform);
context.setPositions(positions);
double energy1 = context.getState(State::Energy).getPotentialEnergy();
nonbonded->setUseLongRangeCorrection(true);
context.reinitialize();
context.setPositions(positions);
double energy2 = context.getState(State::Energy).getPotentialEnergy();
// Check the result.
double sum = (1.1*1.1 + 2*2.0*2.0 + 5*1.1*2.0)*2.0;
int numPairs = (numParticles*(numParticles+1))/2;
double expected = 2*M_PI*numParticles*numParticles*sum/(numPairs*boxSize*boxSize*boxSize);
ASSERT_EQUAL_TOL(expected, energy2-energy1, 1e-4);
}
void* CustomNonbondedForceProxy::deserialize(const SerializationNode& node) const {
if (node.getIntProperty("version") != 1)
throw OpenMMException("Unsupported version number");
CustomNonbondedForce* force = NULL;
try {
CustomNonbondedForce* force = new CustomNonbondedForce(node.getStringProperty("energy"));
force->setNonbondedMethod((CustomNonbondedForce::NonbondedMethod) node.getIntProperty("method"));
force->setCutoffDistance(node.getDoubleProperty("cutoff"));
const SerializationNode& perParticleParams = node.getChildNode("PerParticleParameters");
for (int i = 0; i < (int) perParticleParams.getChildren().size(); i++) {
const SerializationNode& parameter = perParticleParams.getChildren()[i];
force->addPerParticleParameter(parameter.getStringProperty("name"));
}
const SerializationNode& globalParams = node.getChildNode("GlobalParameters");
for (int i = 0; i < (int) globalParams.getChildren().size(); i++) {
const SerializationNode& parameter = globalParams.getChildren()[i];
force->addGlobalParameter(parameter.getStringProperty("name"), parameter.getDoubleProperty("default"));
}
const SerializationNode& particles = node.getChildNode("Particles");
vector<double> params(force->getNumPerParticleParameters());
for (int i = 0; i < (int) particles.getChildren().size(); i++) {
const SerializationNode& particle = particles.getChildren()[i];
for (int j = 0; j < (int) params.size(); j++) {
stringstream key;
key << "param";
key << j+1;
params[j] = particle.getDoubleProperty(key.str());
}
force->addParticle(params);
}
const SerializationNode& exclusions = node.getChildNode("Exclusions");
for (int i = 0; i < (int) exclusions.getChildren().size(); i++) {
const SerializationNode& exclusion = exclusions.getChildren()[i];
force->addExclusion(exclusion.getIntProperty("p1"), exclusion.getIntProperty("p2"));
}
const SerializationNode& functions = node.getChildNode("Functions");
for (int i = 0; i < (int) functions.getChildren().size(); i++) {
const SerializationNode& function = functions.getChildren()[i];
const SerializationNode& valuesNode = function.getChildNode("Values");
vector<double> values;
for (int j = 0; j < (int) valuesNode.getChildren().size(); j++)
values.push_back(valuesNode.getChildren()[j].getDoubleProperty("v"));
force->addFunction(function.getStringProperty("name"), values, function.getDoubleProperty("min"), function.getDoubleProperty("max"));
}
return force;
}
catch (...) {
if (force != NULL)
delete force;
throw;
}
}
void testSimpleExpression() {
System system;
system.addParticle(1.0);
system.addParticle(1.0);
VerletIntegrator integrator(0.01);
CustomNonbondedForce* forceField = new CustomNonbondedForce("-0.1*r^3");
forceField->addParticle(vector<double>());
forceField->addParticle(vector<double>());
system.addForce(forceField);
Context context(system, integrator, platform);
vector<Vec3> positions(2);
positions[0] = Vec3(0, 0, 0);
positions[1] = Vec3(2, 0, 0);
context.setPositions(positions);
State state = context.getState(State::Forces | State::Energy);
const vector<Vec3>& forces = state.getForces();
double force = 0.1*3*(2*2);
ASSERT_EQUAL_VEC(Vec3(-force, 0, 0), forces[0], TOL);
ASSERT_EQUAL_VEC(Vec3(force, 0, 0), forces[1], TOL);
ASSERT_EQUAL_TOL(-0.1*(2*2*2), state.getPotentialEnergy(), TOL);
}
void testInteractionGroups() {
const int numParticles = 6;
System system;
VerletIntegrator integrator(0.01);
CustomNonbondedForce* nonbonded = new CustomNonbondedForce("v1+v2");
nonbonded->addPerParticleParameter("v");
vector<double> params(1, 0.001);
for (int i = 0; i < numParticles; i++) {
system.addParticle(1.0);
nonbonded->addParticle(params);
params[0] *= 10;
}
set<int> set1, set2, set3, set4;
set1.insert(2);
set2.insert(0);
set2.insert(1);
set2.insert(2);
set2.insert(3);
set2.insert(4);
set2.insert(5);
nonbonded->addInteractionGroup(set1, set2); // Particle 2 interacts with every other particle.
set3.insert(0);
set3.insert(1);
set4.insert(4);
set4.insert(5);
nonbonded->addInteractionGroup(set3, set4); // Particles 0 and 1 interact with 4 and 5.
nonbonded->addExclusion(1, 2); // Add an exclusion to make sure it gets skipped.
system.addForce(nonbonded);
Context context(system, integrator, platform);
vector<Vec3> positions(numParticles);
context.setPositions(positions);
State state = context.getState(State::Energy);
double expectedEnergy = 331.423; // Each digit is the number of interactions a particle particle is involved in.
ASSERT_EQUAL_TOL(expectedEnergy, state.getPotentialEnergy(), TOL);
}
void testCutoff() {
ReferencePlatform platform;
System system;
system.addParticle(1.0);
system.addParticle(1.0);
system.addParticle(1.0);
VerletIntegrator integrator(0.01);
CustomNonbondedForce* forceField = new CustomNonbondedForce("r");
forceField->addParticle(vector<double>());
forceField->addParticle(vector<double>());
forceField->addParticle(vector<double>());
forceField->setNonbondedMethod(CustomNonbondedForce::CutoffNonPeriodic);
forceField->setCutoffDistance(2.5);
system.addForce(forceField);
ASSERT(!forceField->usesPeriodicBoundaryConditions());
ASSERT(!system.usesPeriodicBoundaryConditions());
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();
ASSERT_EQUAL_VEC(Vec3(0, 1, 0), forces[0], TOL);
ASSERT_EQUAL_VEC(Vec3(0, 0, 0), forces[1], TOL);
ASSERT_EQUAL_VEC(Vec3(0, -1, 0), forces[2], TOL);
ASSERT_EQUAL_TOL(2.0+1.0, state.getPotentialEnergy(), TOL);
}
void testExclusions() {
System system;
VerletIntegrator integrator(0.01);
CustomNonbondedForce* nonbonded = new CustomNonbondedForce("a*r; a=a1+a2");
nonbonded->addPerParticleParameter("a");
vector<double> params(1);
vector<Vec3> positions(4);
for (int i = 0; i < 4; i++) {
system.addParticle(1.0);
params[0] = i+1;
nonbonded->addParticle(params);
positions[i] = Vec3(i, 0, 0);
}
nonbonded->addExclusion(0, 1);
nonbonded->addExclusion(1, 2);
nonbonded->addExclusion(2, 3);
nonbonded->addExclusion(0, 2);
nonbonded->addExclusion(1, 3);
system.addForce(nonbonded);
Context context(system, integrator, platform);
context.setPositions(positions);
State state = context.getState(State::Forces | State::Energy);
const vector<Vec3>& forces = state.getForces();
ASSERT_EQUAL_VEC(Vec3(1+4, 0, 0), forces[0], TOL);
ASSERT_EQUAL_VEC(Vec3(0, 0, 0), forces[1], TOL);
ASSERT_EQUAL_VEC(Vec3(0, 0, 0), forces[2], TOL);
ASSERT_EQUAL_VEC(Vec3(-(1+4), 0, 0), forces[3], TOL);
ASSERT_EQUAL_TOL((1+4)*3.0, state.getPotentialEnergy(), TOL);
}
void testTabulatedFunction() {
ReferencePlatform platform;
System system;
system.addParticle(1.0);
system.addParticle(1.0);
VerletIntegrator integrator(0.01);
CustomNonbondedForce* forceField = new CustomNonbondedForce("fn(r)+1");
forceField->addParticle(vector<double>());
forceField->addParticle(vector<double>());
vector<double> table;
for (int i = 0; i < 21; i++)
table.push_back(std::sin(0.25*i));
forceField->addFunction("fn", table, 1.0, 6.0);
system.addForce(forceField);
Context context(system, integrator, platform);
vector<Vec3> positions(2);
positions[0] = Vec3(0, 0, 0);
double tol = 0.01;
for (int i = 1; i < 30; i++) {
double x = (7.0/30.0)*i;
positions[1] = Vec3(x, 0, 0);
context.setPositions(positions);
State state = context.getState(State::Forces | State::Energy);
const vector<Vec3>& forces = state.getForces();
double force = (x < 1.0 || x > 6.0 ? 0.0 : -std::cos(x-1.0));
double energy = (x < 1.0 || x > 6.0 ? 0.0 : std::sin(x-1.0))+1.0;
ASSERT_EQUAL_VEC(Vec3(-force, 0, 0), forces[0], 0.1);
ASSERT_EQUAL_VEC(Vec3(force, 0, 0), forces[1], 0.1);
ASSERT_EQUAL_TOL(energy, state.getPotentialEnergy(), 0.02);
}
for (int i = 1; i < 20; i++) {
double x = 0.25*i+1.0;
positions[1] = Vec3(x, 0, 0);
context.setPositions(positions);
State state = context.getState(State::Energy);
double energy = (x < 1.0 || x > 6.0 ? 0.0 : std::sin(x-1.0))+1.0;
ASSERT_EQUAL_TOL(energy, state.getPotentialEnergy(), 1e-4);
}
}
void CpuCalcCustomNonbondedForceKernel::copyParametersToContext(ContextImpl& context, const CustomNonbondedForce& force) {
if (numParticles != force.getNumParticles())
throw OpenMMException("updateParametersInContext: The number of particles has changed");
// Record the values.
int numParameters = force.getNumPerParticleParameters();
vector<double> params;
for (int i = 0; i < numParticles; ++i) {
vector<double> parameters;
force.getParticleParameters(i, parameters);
for (int j = 0; j < numParameters; j++)
particleParamArray[i][j] = parameters[j];
}
// If necessary, recompute the long range correction.
if (forceCopy != NULL) {
longRangeCoefficient = CustomNonbondedForceImpl::calcLongRangeCorrection(force, context.getOwner());
hasInitializedLongRangeCorrection = true;
*forceCopy = force;
}
}
void testParallelComputation() {
System system;
const int numParticles = 200;
for (int i = 0; i < numParticles; i++)
system.addParticle(1.0);
CustomNonbondedForce* force = new CustomNonbondedForce("4*eps*((sigma/r)^12-(sigma/r)^6); sigma=0.5; eps=1");
vector<double> params;
for (int i = 0; i < numParticles; i++)
force->addParticle(params);
system.addForce(force);
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->addExclusion(i, j);
}
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);
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 testSwitchingFunction() {
ReferencePlatform platform;
System system;
system.addParticle(1.0);
system.addParticle(1.0);
VerletIntegrator integrator(0.01);
CustomNonbondedForce* nonbonded = new CustomNonbondedForce("10/r^2");
vector<double> params;
nonbonded->addParticle(params);
nonbonded->addParticle(params);
nonbonded->setNonbondedMethod(CustomNonbondedForce::CutoffNonPeriodic);
nonbonded->setCutoffDistance(2.0);
nonbonded->setUseSwitchingFunction(true);
nonbonded->setSwitchingDistance(1.5);
system.addForce(nonbonded);
Context context(system, integrator, platform);
vector<Vec3> positions(2);
positions[0] = Vec3(0, 0, 0);
// 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 expectedEnergy = 10/(r*r);
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 testManyParameters() {
System system;
system.addParticle(1.0);
system.addParticle(1.0);
VerletIntegrator integrator(0.01);
CustomNonbondedForce* forceField = new CustomNonbondedForce("(a1*a2+b1*b2+c1*c2+d1*d2+e1*e2)*r");
forceField->addPerParticleParameter("a");
forceField->addPerParticleParameter("b");
forceField->addPerParticleParameter("c");
forceField->addPerParticleParameter("d");
forceField->addPerParticleParameter("e");
vector<double> params(5);
params[0] = 1.0;
params[1] = 2.0;
params[2] = 3.0;
params[3] = 4.0;
params[4] = 5.0;
forceField->addParticle(params);
params[0] = 1.1;
params[1] = 1.2;
params[2] = 1.3;
params[3] = 1.4;
params[4] = 1.5;
forceField->addParticle(params);
system.addForce(forceField);
Context context(system, integrator, platform);
vector<Vec3> positions(2);
positions[0] = Vec3(0, 0, 0);
positions[1] = Vec3(2, 0, 0);
context.setPositions(positions);
State state = context.getState(State::Forces | State::Energy);
vector<Vec3> forces = state.getForces();
double force = 1*1.1 + 2*1.2 + 3*1.3 + 4*1.4 + 5*1.5;
ASSERT_EQUAL_VEC(Vec3(force, 0, 0), forces[0], TOL);
ASSERT_EQUAL_VEC(Vec3(-force, 0, 0), forces[1], TOL);
ASSERT_EQUAL_TOL(2*force, state.getPotentialEnergy(), TOL);
}
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);
}
double CustomNonbondedForceImpl::calcLongRangeCorrection(const CustomNonbondedForce& force, const Context& context) {
if (force.getNonbondedMethod() == CustomNonbondedForce::NoCutoff || force.getNonbondedMethod() == CustomNonbondedForce::CutoffNonPeriodic)
return 0.0;
// Parse the energy expression.
map<string, Lepton::CustomFunction*> functions;
for (int i = 0; i < force.getNumFunctions(); i++) {
string name;
vector<double> values;
double min, max;
force.getFunctionParameters(i, name, values, min, max);
functions[name] = new TabulatedFunction(min, max, values);
}
Lepton::ExpressionProgram expression = Lepton::Parser::parse(force.getEnergyFunction(), functions).optimize().createProgram();
// Identify all particle classes (defined by parameters), and record the class of each particle.
int numParticles = force.getNumParticles();
vector<vector<double> > classes;
map<vector<double>, int> classIndex;
vector<int> atomClass(numParticles);
for (int i = 0; i < numParticles; i++) {
vector<double> parameters;
force.getParticleParameters(i, parameters);
if (classIndex.find(parameters) == classIndex.end()) {
classIndex[parameters] = classes.size();
classes.push_back(parameters);
}
atomClass[i] = classIndex[parameters];
}
int numClasses = classes.size();
// Count the total number of particle pairs for each pair of classes.
map<pair<int, int>, int> interactionCount;
if (force.getNumInteractionGroups() == 0) {
// Count the particles of each class.
vector<int> classCounts(numClasses, 0);
for (int i = 0; i < numParticles; i++)
classCounts[atomClass[i]]++;
for (int i = 0; i < numClasses; i++) {
interactionCount[make_pair(i, i)] = (classCounts[i]*(classCounts[i]+1))/2;
for (int j = i+1; j < numClasses; j++)
interactionCount[make_pair(i, j)] = classCounts[i]*classCounts[j];
}
}
else {
// Initialize the counts to 0.
for (int i = 0; i < numClasses; i++) {
for (int j = i; j < numClasses; j++)
interactionCount[make_pair(i, j)] = 0;
}
// Loop over interaction groups and count the interactions in each one.
for (int group = 0; group < force.getNumInteractionGroups(); group++) {
set<int> set1, set2;
force.getInteractionGroupParameters(group, set1, set2);
for (set<int>::const_iterator a1 = set1.begin(); a1 != set1.end(); ++a1)
for (set<int>::const_iterator a2 = set2.begin(); a2 != set2.end(); ++a2) {
if (*a1 >= *a2 && set1.find(*a2) != set1.end() && set2.find(*a1) != set2.end())
continue;
int class1 = atomClass[*a1];
int class2 = atomClass[*a2];
interactionCount[make_pair(min(class1, class2), max(class1, class2))]++;
}
}
}
// Loop over all pairs of classes to compute the coefficient.
double sum = 0;
for (int i = 0; i < numClasses; i++)
for (int j = i; j < numClasses; j++)
sum += interactionCount[make_pair(i, j)]*integrateInteraction(expression, classes[i], classes[j], force, context);
int numInteractions = (numParticles*(numParticles+1))/2;
sum /= numInteractions;
return 2*M_PI*numParticles*numParticles*sum;
}
void testParaHydrogen() {
const int numParticles = 32;
const int numCopies = 12;
const double temperature = 25.0;
const double mass = 2.0;
const double boxSize = 1.1896;
const int numSteps = 1000;
const int numBins = 200;
const double reference[] = {
0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0,
0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0,
0.0, 0.0, 0.0, 4.932814042206152e-5, 1.244331241336431e-4, 4.052316284060125e-4,
1.544810863683946e-3, 4.376197806690222e-3, 1.025847561714293e-2, 2.286702037465422e-2,
4.371052180263602e-2, 7.518538770734748e-2, 0.122351534531647, 0.185758975626622,
0.266399984652322, 0.363380262153250, 0.473696401293219, 0.595312098494172,
0.726049519422861, 0.862264551954547, 0.991102029379444, 1.1147503922535,
1.23587006992066, 1.33495411932817, 1.42208208736987, 1.49273884004107,
1.54633319690403, 1.58714702233941, 1.60439217751355, 1.61804190608902,
1.60680198476058, 1.58892222973695, 1.56387607986781, 1.52629494593350,
1.48421439018970, 1.43656176771959, 1.38752775598872, 1.33310695719931,
1.28363477223121, 1.23465642750248, 1.18874848666326, 1.14350496170519,
1.10292486009936, 1.06107270157688, 1.02348927970441, 0.989729345271297,
0.959273446941802, 0.932264875865758, 0.908818658748942, 0.890946420768315,
0.869332737718165, 0.856401736350349, 0.842370069917020, 0.834386614237393,
0.826268072171045, 0.821547250199453, 0.818786865315836, 0.819441757028076,
0.819156933383128, 0.822275325148621, 0.828919078023881, 0.837233720599450,
0.846961908186718, 0.855656955481099, 0.864520333201247, 0.876082425547566,
0.886950044046000, 0.900275658318995
};
// Create a box of para-hydrogen.
System system;
for (int i = 0; i < numParticles; i++)
system.addParticle(mass);
system.setDefaultPeriodicBoxVectors(Vec3(boxSize,0,0), Vec3(0,boxSize,0), Vec3(0,0,boxSize));
CustomNonbondedForce* nb = new CustomNonbondedForce("2625.49963*(exp(1.713-1.5671*p-0.00993*p*p)-(12.14/p^6+215.2/p^8-143.1/p^9+4813.9/p^10)*(step(rc-p)*exp(-(rc/p-1)^2)+1-step(rc-p))); p=r/0.05291772108; rc=8.32");
nb->setNonbondedMethod(CustomNonbondedForce::CutoffPeriodic);
nb->setCutoffDistance(boxSize/2);
vector<double> params;
for (int i = 0; i < numParticles; i++)
nb->addParticle(params);
system.addForce(nb);
RPMDIntegrator integ(numCopies, temperature, 10.0, 0.0005);
Platform& platform = Platform::getPlatformByName("CUDA");
Context context(system, integ, platform);
OpenMM_SFMT::SFMT sfmt;
init_gen_rand(0, sfmt);
vector<Vec3> positions(numParticles);
for (int i = 0; i < numParticles; i++)
positions[i] = Vec3(boxSize*genrand_real2(sfmt), boxSize*genrand_real2(sfmt), boxSize*genrand_real2(sfmt));
for (int i = 0; i < numCopies; i++)
integ.setPositions(i, positions);
integ.step(1000);
// Simulate it.
vector<int> counts(numBins, 0);
const double invBoxSize = 1.0/boxSize;
double meanKE = 0.0;
for (int step = 0; step < numSteps; step++) {
integ.step(20);
vector<State> states(numCopies);
for (int i = 0; i < numCopies; i++)
states[i] = integ.getState(i, State::Positions | State::Forces);
// Record the radial distribution function.
const vector<Vec3>& pos = states[0].getPositions();
for (int j = 0; j < numParticles; j++)
for (int k = 0; k < j; k++) {
Vec3 delta = pos[j]-pos[k];
delta[0] -= floor(delta[0]*invBoxSize+0.5)*boxSize;
delta[1] -= floor(delta[1]*invBoxSize+0.5)*boxSize;
delta[2] -= floor(delta[2]*invBoxSize+0.5)*boxSize;
double dist = sqrt(delta.dot(delta));
int bin = (int) (numBins*(dist/boxSize));
counts[bin]++;
}
// Calculate the quantum contribution to the kinetic energy.
vector<Vec3> centroids(numParticles, Vec3());
for (int i = 0; i < numCopies; i++) {
const vector<Vec3>& pos = states[i].getPositions();
for (int j = 0; j < numParticles; j++)
centroids[j] += pos[j];
}
for (int j = 0; j < numParticles; j++)
centroids[j] *= 1.0/numCopies;
double ke = 0.0;
for (int i = 0; i < numCopies; i++) {
const vector<Vec3>& pos = states[i].getPositions();
const vector<Vec3>& f = states[i].getForces();
for (int j = 0; j < numParticles; j++) {
Vec3 delta = centroids[j]-pos[j];
ke += delta.dot(f[j]);
}
}
meanKE += ke/(2*numCopies*numParticles);
}
// Check against expected values.
double scale = (boxSize*boxSize*boxSize)/(numSteps*0.5*numParticles*numParticles);
for (int i = 0; i < numBins/2; i++) {
double r1 = i*boxSize/numBins;
double r2 = (i+1)*boxSize/numBins;
double volume = (4.0/3.0)*M_PI*(r2*r2*r2-r1*r1*r1);
ASSERT_USUALLY_EQUAL_TOL(reference[i], scale*counts[i]/volume, 0.1);
}
meanKE /= numSteps*BOLTZ;
ASSERT_USUALLY_EQUAL_TOL(60.0, 1.5*temperature+meanKE, 0.02);
}
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 CustomNonbondedForceImpl::calcLongRangeCorrection(const CustomNonbondedForce& force, const Context& context, double& coefficient, vector<double>& derivatives) {
if (force.getNonbondedMethod() == CustomNonbondedForce::NoCutoff || force.getNonbondedMethod() == CustomNonbondedForce::CutoffNonPeriodic) {
coefficient = 0.0;
return;
}
// Identify all particle classes (defined by parameters), and record the class of each particle.
int numParticles = force.getNumParticles();
vector<vector<double> > classes;
map<vector<double>, int> classIndex;
vector<int> atomClass(numParticles);
for (int i = 0; i < numParticles; i++) {
vector<double> parameters;
force.getParticleParameters(i, parameters);
if (classIndex.find(parameters) == classIndex.end()) {
classIndex[parameters] = classes.size();
classes.push_back(parameters);
}
atomClass[i] = classIndex[parameters];
}
int numClasses = classes.size();
// Count the total number of particle pairs for each pair of classes.
map<pair<int, int>, long long int> interactionCount;
if (force.getNumInteractionGroups() == 0) {
// Count the particles of each class.
vector<long long int> classCounts(numClasses, 0);
for (int i = 0; i < numParticles; i++)
classCounts[atomClass[i]]++;
for (int i = 0; i < numClasses; i++) {
interactionCount[make_pair(i, i)] = (classCounts[i]*(classCounts[i]+1))/2;
for (int j = i+1; j < numClasses; j++)
interactionCount[make_pair(i, j)] = classCounts[i]*classCounts[j];
}
}
else {
// Initialize the counts to 0.
for (int i = 0; i < numClasses; i++) {
for (int j = i; j < numClasses; j++)
interactionCount[make_pair(i, j)] = 0;
}
// Loop over interaction groups and count the interactions in each one.
for (int group = 0; group < force.getNumInteractionGroups(); group++) {
set<int> set1, set2;
force.getInteractionGroupParameters(group, set1, set2);
for (set<int>::const_iterator a1 = set1.begin(); a1 != set1.end(); ++a1)
for (set<int>::const_iterator a2 = set2.begin(); a2 != set2.end(); ++a2) {
if (*a1 >= *a2 && set1.find(*a2) != set1.end() && set2.find(*a1) != set2.end())
continue;
int class1 = atomClass[*a1];
int class2 = atomClass[*a2];
interactionCount[make_pair(min(class1, class2), max(class1, class2))]++;
}
}
}
// Compute the coefficient.
map<string, Lepton::CustomFunction*> functions;
for (int i = 0; i < force.getNumFunctions(); i++)
functions[force.getTabulatedFunctionName(i)] = createReferenceTabulatedFunction(force.getTabulatedFunction(i));
double nPart = (double) numParticles;
double numInteractions = (nPart*(nPart+1))/2;
Lepton::CompiledExpression expression = Lepton::Parser::parse(force.getEnergyFunction(), functions).createCompiledExpression();
double sum = 0;
for (int i = 0; i < numClasses; i++)
for (int j = i; j < numClasses; j++)
sum += interactionCount[make_pair(i, j)]*integrateInteraction(expression, classes[i], classes[j], force, context);
sum /= numInteractions;
coefficient = 2*M_PI*nPart*nPart*sum;
// Now do the same for parameter derivatives.
int numDerivs = force.getNumEnergyParameterDerivatives();
derivatives.resize(numDerivs);
for (int k = 0; k < numDerivs; k++) {
expression = Lepton::Parser::parse(force.getEnergyFunction(), functions).differentiate(force.getEnergyParameterDerivativeName(k)).createCompiledExpression();
sum = 0;
for (int i = 0; i < numClasses; i++)
for (int j = i; j < numClasses; j++)
sum += interactionCount[make_pair(i, j)]*integrateInteraction(expression, classes[i], classes[j], force, context);
sum /= numInteractions;
derivatives[k] = 2*M_PI*nPart*nPart*sum;
}
}
double CustomNonbondedForceImpl::integrateInteraction(Lepton::CompiledExpression& expression, const vector<double>& params1, const vector<double>& params2,
const CustomNonbondedForce& force, const Context& context) {
const set<string>& variables = expression.getVariables();
for (int i = 0; i < force.getNumPerParticleParameters(); i++) {
stringstream name1, name2;
name1 << force.getPerParticleParameterName(i) << 1;
name2 << force.getPerParticleParameterName(i) << 2;
if (variables.find(name1.str()) != variables.end())
expression.getVariableReference(name1.str()) = params1[i];
if (variables.find(name2.str()) != variables.end())
expression.getVariableReference(name2.str()) = params2[i];
}
for (int i = 0; i < force.getNumGlobalParameters(); i++) {
const string& name = force.getGlobalParameterName(i);
if (variables.find(name) != variables.end())
expression.getVariableReference(name) = context.getParameter(name);
}
// To integrate from r_cutoff to infinity, make the change of variables x=r_cutoff/r and integrate from 0 to 1.
// This introduces another r^2 into the integral, which along with the r^2 in the formula for the correction
// means we multiply the function by r^4. Use the midpoint method.
double* rPointer;
try {
rPointer = &expression.getVariableReference("r");
}
catch (exception& ex) {
throw OpenMMException("CustomNonbondedForce: Cannot use long range correction with a force that does not depend on r.");
}
double cutoff = force.getCutoffDistance();
double sum = 0;
int numPoints = 1;
for (int iteration = 0; ; iteration++) {
double oldSum = sum;
double newSum = 0;
for (int i = 0; i < numPoints; i++) {
if (i%3 == 1)
continue;
double x = (i+0.5)/numPoints;
double r = cutoff/x;
*rPointer = r;
double r2 = r*r;
newSum += expression.evaluate()*r2*r2;
}
sum = newSum/numPoints + oldSum/3;
if (iteration > 2 && (fabs((sum-oldSum)/sum) < 1e-5 || sum == 0))
break;
if (iteration == 8)
throw OpenMMException("CustomNonbondedForce: Long range correction did not converge. Does the energy go to 0 faster than 1/r^2?");
numPoints *= 3;
}
// If a switching function is used, integrate over the switching interval.
double sum2 = 0;
if (force.getUseSwitchingFunction()) {
double rswitch = force.getSwitchingDistance();
sum2 = 0;
numPoints = 1;
for (int iteration = 0; ; iteration++) {
double oldSum = sum2;
double newSum = 0;
for (int i = 0; i < numPoints; i++) {
if (i%3 == 1)
continue;
double x = (i+0.5)/numPoints;
double r = rswitch+x*(cutoff-rswitch);
double switchValue = x*x*x*(10+x*(-15+x*6));
*rPointer = r;
newSum += switchValue*expression.evaluate()*r*r;
}
sum2 = newSum/numPoints + oldSum/3;
if (iteration > 2 && (fabs((sum2-oldSum)/sum2) < 1e-5 || sum2 == 0))
break;
if (iteration == 8)
throw OpenMMException("CustomNonbondedForce: Long range correction did not converge. Is the energy finite everywhere in the switching interval?");
numPoints *= 3;
}
sum2 *= cutoff-rswitch;
}
return sum/cutoff+sum2;
}
void CpuCalcCustomNonbondedForceKernel::initialize(const System& system, const CustomNonbondedForce& force) {
// Record the exclusions.
numParticles = force.getNumParticles();
exclusions.resize(numParticles);
for (int i = 0; i < force.getNumExclusions(); i++) {
int particle1, particle2;
force.getExclusionParticles(i, particle1, particle2);
exclusions[particle1].insert(particle2);
exclusions[particle2].insert(particle1);
}
// Build the arrays.
int numParameters = force.getNumPerParticleParameters();
particleParamArray = new double*[numParticles];
for (int i = 0; i < numParticles; i++)
particleParamArray[i] = new double[numParameters];
for (int i = 0; i < numParticles; ++i) {
vector<double> parameters;
force.getParticleParameters(i, parameters);
for (int j = 0; j < numParameters; j++)
particleParamArray[i][j] = parameters[j];
}
nonbondedMethod = CalcCustomNonbondedForceKernel::NonbondedMethod(force.getNonbondedMethod());
nonbondedCutoff = force.getCutoffDistance();
if (nonbondedMethod == NoCutoff)
useSwitchingFunction = false;
else {
neighborList = new CpuNeighborList(4);
useSwitchingFunction = force.getUseSwitchingFunction();
switchingDistance = force.getSwitchingDistance();
}
// Create custom functions for the tabulated functions.
map<string, Lepton::CustomFunction*> functions;
for (int i = 0; i < force.getNumFunctions(); i++)
functions[force.getTabulatedFunctionName(i)] = createReferenceTabulatedFunction(force.getTabulatedFunction(i));
// Parse the various expressions used to calculate the force.
Lepton::ParsedExpression expression = Lepton::Parser::parse(force.getEnergyFunction(), functions).optimize();
Lepton::CompiledExpression energyExpression = expression.createCompiledExpression();
Lepton::CompiledExpression forceExpression = expression.differentiate("r").createCompiledExpression();
for (int i = 0; i < numParameters; i++)
parameterNames.push_back(force.getPerParticleParameterName(i));
for (int i = 0; i < force.getNumGlobalParameters(); i++) {
globalParameterNames.push_back(force.getGlobalParameterName(i));
globalParamValues[force.getGlobalParameterName(i)] = force.getGlobalParameterDefaultValue(i);
}
// Delete the custom functions.
for (map<string, Lepton::CustomFunction*>::iterator iter = functions.begin(); iter != functions.end(); iter++)
delete iter->second;
// Record information for the long range correction.
if (force.getNonbondedMethod() == CustomNonbondedForce::CutoffPeriodic && force.getUseLongRangeCorrection()) {
forceCopy = new CustomNonbondedForce(force);
hasInitializedLongRangeCorrection = false;
}
else {
longRangeCoefficient = 0.0;
hasInitializedLongRangeCorrection = true;
}
// Record the interaction groups.
for (int i = 0; i < force.getNumInteractionGroups(); i++) {
set<int> set1, set2;
force.getInteractionGroupParameters(i, set1, set2);
interactionGroups.push_back(make_pair(set1, set2));
}
data.isPeriodic = (nonbondedMethod == CutoffPeriodic);
nonbonded = new CpuCustomNonbondedForce(energyExpression, forceExpression, parameterNames, exclusions, data.threads);
if (interactionGroups.size() > 0)
nonbonded->setInteractionGroups(interactionGroups);
}
void testLargeInteractionGroup() {
const int numMolecules = 300;
const int numParticles = numMolecules*2;
const double boxSize = 20.0;
// Create a large system.
System system;
system.setDefaultPeriodicBoxVectors(Vec3(boxSize, 0, 0), Vec3(0, boxSize, 0), Vec3(0, 0, boxSize));
for (int i = 0; i < numParticles; i++)
system.addParticle(1.0);
CustomNonbondedForce* nonbonded = 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)");
nonbonded->addPerParticleParameter("q");
nonbonded->addPerParticleParameter("sigma");
nonbonded->addPerParticleParameter("eps");
vector<Vec3> positions(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) {
params[0] = 1.0;
params[1] = 0.2;
params[2] = 0.1;
nonbonded->addParticle(params);
params[0] = -1.0;
params[1] = 0.1;
nonbonded->addParticle(params);
}
else {
params[0] = 1.0;
params[1] = 0.2;
params[2] = 0.2;
nonbonded->addParticle(params);
params[0] = -1.0;
params[1] = 0.1;
nonbonded->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]);
nonbonded->addExclusion(2*i, 2*i+1);
}
nonbonded->setNonbondedMethod(CustomNonbondedForce::CutoffPeriodic);
system.addForce(nonbonded);
// Compute the forces.
VerletIntegrator integrator(0.01);
Context context(system, integrator, platform);
context.setPositions(positions);
State state1 = context.getState(State::Forces);
// Modify the force so only one particle interacts with everything else.
set<int> set1, set2;
set1.insert(151);
for (int i = 0; i < numParticles; i++)
set2.insert(i);
nonbonded->addInteractionGroup(set1, set2);
context.reinitialize();
context.setPositions(positions);
State state2 = context.getState(State::Forces);
// The force on that one particle should be the same.
ASSERT_EQUAL_VEC(state1.getForces()[151], state2.getForces()[151], 1e-4);
// Modify the interaction group so it includes all interactions. This should now reproduce the original forces
// on all atoms.
for (int i = 0; i < numParticles; i++)
set1.insert(i);
nonbonded->setInteractionGroupParameters(0, set1, set2);
context.reinitialize();
context.setPositions(positions);
State state3 = context.getState(State::Forces);
for (int i = 0; i < numParticles; i++)
ASSERT_EQUAL_VEC(state1.getForces()[i], state3.getForces()[i], 1e-4);
}
void* CustomNonbondedForceProxy::deserialize(const SerializationNode& node) const {
int version = node.getIntProperty("version");
if (version < 1 || version > 2)
throw OpenMMException("Unsupported version number");
CustomNonbondedForce* force = NULL;
try {
CustomNonbondedForce* force = new CustomNonbondedForce(node.getStringProperty("energy"));
force->setForceGroup(node.getIntProperty("forceGroup", 0));
force->setNonbondedMethod((CustomNonbondedForce::NonbondedMethod) node.getIntProperty("method"));
force->setCutoffDistance(node.getDoubleProperty("cutoff"));
force->setUseSwitchingFunction(node.getBoolProperty("useSwitchingFunction", false));
force->setSwitchingDistance(node.getDoubleProperty("switchingDistance", -1.0));
force->setUseLongRangeCorrection(node.getBoolProperty("useLongRangeCorrection", false));
const SerializationNode& perParticleParams = node.getChildNode("PerParticleParameters");
for (int i = 0; i < (int) perParticleParams.getChildren().size(); i++) {
const SerializationNode& parameter = perParticleParams.getChildren()[i];
force->addPerParticleParameter(parameter.getStringProperty("name"));
}
const SerializationNode& globalParams = node.getChildNode("GlobalParameters");
for (int i = 0; i < (int) globalParams.getChildren().size(); i++) {
const SerializationNode& parameter = globalParams.getChildren()[i];
force->addGlobalParameter(parameter.getStringProperty("name"), parameter.getDoubleProperty("default"));
}
if (version > 1) {
const SerializationNode& energyDerivs = node.getChildNode("EnergyParameterDerivatives");
for (int i = 0; i < (int) energyDerivs.getChildren().size(); i++) {
const SerializationNode& parameter = energyDerivs.getChildren()[i];
force->addEnergyParameterDerivative(parameter.getStringProperty("name"));
}
}
const SerializationNode& particles = node.getChildNode("Particles");
vector<double> params(force->getNumPerParticleParameters());
for (int i = 0; i < (int) particles.getChildren().size(); i++) {
const SerializationNode& particle = particles.getChildren()[i];
for (int j = 0; j < (int) params.size(); j++) {
stringstream key;
key << "param";
key << j+1;
params[j] = particle.getDoubleProperty(key.str());
}
force->addParticle(params);
}
const SerializationNode& exclusions = node.getChildNode("Exclusions");
for (int i = 0; i < (int) exclusions.getChildren().size(); i++) {
const SerializationNode& exclusion = exclusions.getChildren()[i];
force->addExclusion(exclusion.getIntProperty("p1"), exclusion.getIntProperty("p2"));
}
const SerializationNode& functions = node.getChildNode("Functions");
for (int i = 0; i < (int) functions.getChildren().size(); i++) {
const SerializationNode& function = functions.getChildren()[i];
if (function.hasProperty("type")) {
force->addTabulatedFunction(function.getStringProperty("name"), function.decodeObject<TabulatedFunction>());
}
else {
// This is an old file created before TabulatedFunction existed.
const SerializationNode& valuesNode = function.getChildNode("Values");
vector<double> values;
for (int j = 0; j < (int) valuesNode.getChildren().size(); j++)
values.push_back(valuesNode.getChildren()[j].getDoubleProperty("v"));
force->addTabulatedFunction(function.getStringProperty("name"), new Continuous1DFunction(values, function.getDoubleProperty("min"), function.getDoubleProperty("max")));
}
}
bool hasInteractionGroups = false; // Older files will be missing this block.
for (int i = 0; i < (int) node.getChildren().size(); i++) {
if (node.getChildren()[i].getName() == "InteractionGroups")
hasInteractionGroups = true;
}
if (hasInteractionGroups) {
const SerializationNode& interactionGroups = node.getChildNode("InteractionGroups");
for (int i = 0; i < (int) interactionGroups.getChildren().size(); i++) {
const SerializationNode& interactionGroup = interactionGroups.getChildren()[i];
// Get set 1.
const SerializationNode& set1node = interactionGroup.getChildNode("Set1");
std::set<int> set1;
for (int j = 0; j < (int) set1node.getChildren().size(); j++)
set1.insert(set1node.getChildren()[j].getIntProperty("index"));
// Get set 2.
const SerializationNode& set2node = interactionGroup.getChildNode("Set2");
std::set<int> set2;
for (int j = 0; j < (int) set2node.getChildren().size(); j++)
set2.insert(set2node.getChildren()[j].getIntProperty("index"));
force->addInteractionGroup(set1, set2);
}
}
return force;
}
catch (...) {
if (force != NULL)
delete force;
throw;
}
}