void testTabulatedFunction() {
ReferencePlatform platform;
System system;
system.addParticle(1.0);
system.addParticle(1.0);
VerletIntegrator integrator(0.01);
CustomGBForce* force = new CustomGBForce();
force->addComputedValue("a", "0", CustomGBForce::ParticlePair);
force->addEnergyTerm("fn(r)+1", CustomGBForce::ParticlePair);
force->addParticle(vector<double>());
force->addParticle(vector<double>());
vector<double> table;
for (int i = 0; i < 21; i++)
table.push_back(std::sin(0.25*i));
force->addFunction("fn", table, 1.0, 6.0);
system.addForce(force);
Context context(system, integrator, platform);
vector<Vec3> positions(2);
positions[0] = Vec3(0, 0, 0);
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);
}
}
void testMultipleChainRules() {
ReferencePlatform platform;
System system;
system.addParticle(1.0);
system.addParticle(1.0);
VerletIntegrator integrator(0.01);
CustomGBForce* force = new CustomGBForce();
force->addComputedValue("a", "2*r", CustomGBForce::ParticlePair);
force->addComputedValue("b", "a+1", CustomGBForce::SingleParticle);
force->addComputedValue("c", "2*b+a", CustomGBForce::SingleParticle);
force->addEnergyTerm("0.1*a+1*b+10*c", CustomGBForce::SingleParticle); // 0.1*(2*r) + 2*r+1 + 10*(3*a+2) = 0.2*r + 2*r+1 + 40*r+20+20*r = 62.2*r+21
force->addParticle(vector<double>());
force->addParticle(vector<double>());
system.addForce(force);
Context context(system, integrator, platform);
vector<Vec3> positions(2);
positions[0] = Vec3(0, 0, 0);
for (int i = 1; i < 5; i++) {
positions[1] = Vec3(i, 0, 0);
context.setPositions(positions);
State state = context.getState(State::Forces | State::Energy);
const vector<Vec3>& forces = state.getForces();
ASSERT_EQUAL_VEC(Vec3(124.4, 0, 0), forces[0], 1e-4);
ASSERT_EQUAL_VEC(Vec3(-124.4, 0, 0), forces[1], 1e-4);
ASSERT_EQUAL_TOL(2*(62.2*i+21), state.getPotentialEnergy(), 0.02);
}
}
void* CustomGBForceProxy::deserialize(const SerializationNode& node) const {
int version = node.getIntProperty("version");
if (version < 1 || version > 2)
throw OpenMMException("Unsupported version number");
CustomGBForce* force = NULL;
try {
CustomGBForce* force = new CustomGBForce();
force->setForceGroup(node.getIntProperty("forceGroup", 0));
force->setNonbondedMethod((CustomGBForce::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"));
}
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& computedValues = node.getChildNode("ComputedValues");
for (int i = 0; i < (int) computedValues.getChildren().size(); i++) {
const SerializationNode& value = computedValues.getChildren()[i];
force->addComputedValue(value.getStringProperty("name"), value.getStringProperty("expression"), (CustomGBForce::ComputationType) value.getIntProperty("type"));
}
const SerializationNode& energyTerms = node.getChildNode("EnergyTerms");
for (int i = 0; i < (int) energyTerms.getChildren().size(); i++) {
const SerializationNode& term = energyTerms.getChildren()[i];
force->addEnergyTerm(term.getStringProperty("expression"), (CustomGBForce::ComputationType) term.getIntProperty("type"));
}
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")));
}
}
return force;
}
catch (...) {
if (force != NULL)
delete force;
throw;
}
}
void testGBVI(GBVIForce::NonbondedMethod gbviMethod, CustomGBForce::NonbondedMethod customGbviMethod, std::string molecule) {
const int numMolecules = 1;
const double boxSize = 10.0;
ReferencePlatform platform;
GBVIForce* gbvi = new GBVIForce();
std::vector<Vec3> positions;
// select molecule
if( molecule == "Monomer" ){
buildMonomer( gbvi, positions );
} else if( molecule == "Dimer" ){
buildDimer( gbvi, positions );
} else {
buildEthane( gbvi, positions );
}
int numParticles = gbvi->getNumParticles();
System standardSystem;
System customGbviSystem;
for (int i = 0; i < numParticles; i++) {
standardSystem.addParticle(1.0);
customGbviSystem.addParticle(1.0);
}
standardSystem.setDefaultPeriodicBoxVectors(Vec3(boxSize, 0.0, 0.0), Vec3(0.0, boxSize, 0.0), Vec3(0.0, 0.0, boxSize));
customGbviSystem.setDefaultPeriodicBoxVectors(Vec3(boxSize, 0.0, 0.0), Vec3(0.0, boxSize, 0.0), Vec3(0.0, 0.0, boxSize));
gbvi->setCutoffDistance(2.0);
// create customGbviForce GBVI force
CustomGBForce* customGbviForce = createCustomGBVI( gbvi->getSolventDielectric(), gbvi->getSoluteDielectric() );
customGbviForce->setCutoffDistance(2.0);
// load parameters from gbvi to customGbviForce
loadGbviParameters( gbvi, customGbviForce );
OpenMM_SFMT::SFMT sfmt;
init_gen_rand(0, sfmt);
vector<Vec3> velocities(numParticles);
for (int ii = 0; ii < numParticles; ii++) {
velocities[ii] = Vec3(genrand_real2(sfmt), genrand_real2(sfmt), genrand_real2(sfmt));
}
gbvi->setNonbondedMethod(gbviMethod);
customGbviForce->setNonbondedMethod(customGbviMethod);
standardSystem.addForce(gbvi);
customGbviSystem.addForce(customGbviForce);
VerletIntegrator integrator1(0.01);
VerletIntegrator integrator2(0.01);
Context context1(standardSystem, integrator1, platform);
context1.setPositions(positions);
context1.setVelocities(velocities);
State state1 = context1.getState(State::Forces | State::Energy);
Context context2(customGbviSystem, integrator2, platform);
context2.setPositions(positions);
context2.setVelocities(velocities);
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 testOBC(GBSAOBCForce::NonbondedMethod obcMethod, CustomGBForce::NonbondedMethod customMethod) {
const int numMolecules = 70;
const int numParticles = numMolecules*2;
const double boxSize = 10.0;
const double cutoff = 2.0;
ReferencePlatform platform;
// Create two systems: one with a GBSAOBCForce, and one using a CustomGBForce to implement the same interaction.
System standardSystem;
System customSystem;
for (int i = 0; i < numParticles; i++) {
standardSystem.addParticle(1.0);
customSystem.addParticle(1.0);
}
standardSystem.setDefaultPeriodicBoxVectors(Vec3(boxSize, 0.0, 0.0), Vec3(0.0, boxSize, 0.0), Vec3(0.0, 0.0, boxSize));
customSystem.setDefaultPeriodicBoxVectors(Vec3(boxSize, 0.0, 0.0), Vec3(0.0, boxSize, 0.0), Vec3(0.0, 0.0, boxSize));
GBSAOBCForce* obc = new GBSAOBCForce();
CustomGBForce* custom = new CustomGBForce();
obc->setCutoffDistance(cutoff);
custom->setCutoffDistance(cutoff);
custom->addPerParticleParameter("q");
custom->addPerParticleParameter("radius");
custom->addPerParticleParameter("scale");
custom->addGlobalParameter("solventDielectric", obc->getSolventDielectric());
custom->addGlobalParameter("soluteDielectric", obc->getSoluteDielectric());
custom->addComputedValue("I", "step(r+sr2-or1)*0.5*(1/L-1/U+0.25*(1/U^2-1/L^2)*(r-sr2*sr2/r)+0.5*log(L/U)/r+C);"
"U=r+sr2;"
"C=2*(1/or1-1/L)*step(sr2-r-or1);"
"L=max(or1, D);"
"D=abs(r-sr2);"
"sr2 = scale2*or2;"
"or1 = radius1-0.009; or2 = radius2-0.009", CustomGBForce::ParticlePairNoExclusions);
custom->addComputedValue("B", "1/(1/or-tanh(1*psi-0.8*psi^2+4.85*psi^3)/radius);"
"psi=I*or; or=radius-0.009", CustomGBForce::SingleParticle);
custom->addEnergyTerm("28.3919551*(radius+0.14)^2*(radius/B)^6-0.5*138.935485*(1/soluteDielectric-1/solventDielectric)*q^2/B", CustomGBForce::SingleParticle);
string invCutoffString = "";
if (obcMethod != GBSAOBCForce::NoCutoff) {
stringstream s;
s<<(1.0/cutoff);
invCutoffString = s.str();
}
custom->addEnergyTerm("138.935485*(1/soluteDielectric-1/solventDielectric)*q1*q2*("+invCutoffString+"-1/f);"
"f=sqrt(r^2+B1*B2*exp(-r^2/(4*B1*B2)))", CustomGBForce::ParticlePairNoExclusions);
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) {
obc->addParticle(1.0, 0.2, 0.5);
params[0] = 1.0;
params[1] = 0.2;
params[2] = 0.5;
custom->addParticle(params);
obc->addParticle(-1.0, 0.1, 0.5);
params[0] = -1.0;
params[1] = 0.1;
custom->addParticle(params);
}
else {
obc->addParticle(1.0, 0.2, 0.8);
params[0] = 1.0;
params[1] = 0.2;
params[2] = 0.8;
custom->addParticle(params);
obc->addParticle(-1.0, 0.1, 0.8);
params[0] = -1.0;
params[1] = 0.1;
custom->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));
}
obc->setNonbondedMethod(obcMethod);
custom->setNonbondedMethod(customMethod);
standardSystem.addForce(obc);
customSystem.addForce(custom);
VerletIntegrator integrator1(0.01);
VerletIntegrator integrator2(0.01);
Context context1(standardSystem, integrator1, platform);
context1.setPositions(positions);
context1.setVelocities(velocities);
State state1 = context1.getState(State::Forces | State::Energy);
Context context2(customSystem, integrator2, platform);
context2.setPositions(positions);
context2.setVelocities(velocities);
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);
}
// Try changing the particle parameters and make sure it's still correct.
for (int i = 0; i < numMolecules/2; i++) {
obc->setParticleParameters(2*i, 1.1, 0.3, 0.6);
params[0] = 1.1;
params[1] = 0.3;
params[2] = 0.6;
custom->setParticleParameters(2*i, params);
obc->setParticleParameters(2*i+1, -1.1, 0.2, 0.4);
params[0] = -1.1;
params[1] = 0.2;
params[2] = 0.4;
custom->setParticleParameters(2*i+1, params);
}
obc->updateParametersInContext(context1);
custom->updateParametersInContext(context2);
state1 = context1.getState(State::Forces | State::Energy);
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);
}
}
static CustomGBForce* createCustomGBVI( double solventDielectric, double soluteDielectric ) {
CustomGBForce* customGbviForce = new CustomGBForce();
customGbviForce->setCutoffDistance(2.0);
customGbviForce->addPerParticleParameter("q");
customGbviForce->addPerParticleParameter("radius");
customGbviForce->addPerParticleParameter("scaleFactor"); // derived in GBVIForce implmentation, but parameter here
customGbviForce->addPerParticleParameter("gamma");
customGbviForce->addGlobalParameter("solventDielectric", solventDielectric);
customGbviForce->addGlobalParameter("soluteDielectric", soluteDielectric);
customGbviForce->addComputedValue("V", " uL - lL + factor3/(radius1*radius1*radius1);"
"uL = 1.5*x2uI*(0.25*rI-0.33333*xuI+0.125*(r2-S2)*rI*x2uI);"
"lL = 1.5*x2lI*(0.25*rI-0.33333*xlI+0.125*(r2-S2)*rI*x2lI);"
"x2lI = 1.0/(xl*xl);"
"xlI = 1.0/(xl);"
"xuI = 1.0/(xu);"
"x2uI = 1.0/(xu*xu);"
"xu = (r+scaleFactor2);"
"rI = 1.0/(r);"
"r2 = (r*r);"
"xl = factor1*lMax + factor2*xuu + factor3*(r-scaleFactor2);"
"xuu = (r+scaleFactor2);"
"S2 = (scaleFactor2*scaleFactor2);"
"factor1 = step(r-absRadiusScaleDiff);"
"absRadiusScaleDiff = abs(radiusScaleDiff);"
"radiusScaleDiff = (radius1-scaleFactor2);"
"factor2 = step(radius1-scaleFactor2-r);"
"factor3 = step(scaleFactor2-radius1-r);"
"lMax = max(radius1,r-scaleFactor2);"
, CustomGBForce::ParticlePairNoExclusions);
customGbviForce->addComputedValue("B", "(1.0/(radius*radius*radius)-V)^(-0.33333333)", CustomGBForce::SingleParticle);
// nonpolar term + polar self energy
customGbviForce->addEnergyTerm("(-138.935485*0.5*((1.0/soluteDielectric)-(1.0/solventDielectric))*q^2/B)-((1.0/soluteDielectric)-(1.0/solventDielectric))*((gamma*(radius/B)^3))", CustomGBForce::SingleParticle);
// polar pair energy
customGbviForce->addEnergyTerm("-138.935485*(1/soluteDielectric-1/solventDielectric)*q1*q2/f;"
"f=sqrt(r^2+B1*B2*exp(-r^2/(4*B1*B2)))", CustomGBForce::ParticlePairNoExclusions);
return customGbviForce;
}
void testExclusions() {
ReferencePlatform platform;
for (int i = 3; i < 4; i++) {
System system;
system.addParticle(1.0);
system.addParticle(1.0);
VerletIntegrator integrator(0.01);
CustomGBForce* force = new CustomGBForce();
force->addComputedValue("a", "r", i < 2 ? CustomGBForce::ParticlePair : CustomGBForce::ParticlePairNoExclusions);
force->addEnergyTerm("a", CustomGBForce::SingleParticle);
force->addEnergyTerm("(1+a1+a2)*r", i%2 == 0 ? CustomGBForce::ParticlePair : CustomGBForce::ParticlePairNoExclusions);
force->addParticle(vector<double>());
force->addParticle(vector<double>());
force->addExclusion(0, 1);
system.addForce(force);
Context context(system, integrator, platform);
vector<Vec3> positions(2);
positions[0] = Vec3(0, 0, 0);
positions[1] = Vec3(1, 0, 0);
context.setPositions(positions);
State state = context.getState(State::Forces | State::Energy);
const vector<Vec3>& forces = state.getForces();
double f, energy;
switch (i)
{
case 0: // e = 0
f = 0;
energy = 0;
break;
case 1: // e = r
f = 1;
energy = 1;
break;
case 2: // e = 2r
f = 2;
energy = 2;
break;
case 3: // e = 3r + 2r^2
f = 7;
energy = 5;
break;
default:
ASSERT(false);
}
ASSERT_EQUAL_VEC(Vec3(f, 0, 0), forces[0], 1e-4);
ASSERT_EQUAL_VEC(Vec3(-f, 0, 0), forces[1], 1e-4);
ASSERT_EQUAL_TOL(energy, state.getPotentialEnergy(), 1e-4);
// Take a small step in the direction of the energy gradient and see whether the potential energy changes by the expected amount.
double norm = 0.0;
for (int i = 0; i < (int) forces.size(); ++i)
norm += forces[i].dot(forces[i]);
norm = std::sqrt(norm);
const double stepSize = 1e-3;
double step = stepSize/norm;
for (int i = 0; i < (int) positions.size(); ++i) {
Vec3 p = positions[i];
Vec3 f = forces[i];
positions[i] = Vec3(p[0]-f[0]*step, p[1]-f[1]*step, p[2]-f[2]*step);
}
context.setPositions(positions);
State state2 = context.getState(State::Energy);
ASSERT_EQUAL_TOL(norm, (state2.getPotentialEnergy()-state.getPotentialEnergy())/stepSize, 1e-3*abs(state.getPotentialEnergy()));
}
}
void testPositionDependence() {
ReferencePlatform platform;
System system;
system.addParticle(1.0);
system.addParticle(1.0);
VerletIntegrator integrator(0.01);
CustomGBForce* force = new CustomGBForce();
force->addComputedValue("a", "r", CustomGBForce::ParticlePair);
force->addComputedValue("b", "a+x*y", CustomGBForce::SingleParticle);
force->addEnergyTerm("b*z", CustomGBForce::SingleParticle);
force->addEnergyTerm("b1+b2", CustomGBForce::ParticlePair); // = 2*r+x1*y1+x2*y2
force->addParticle(vector<double>());
force->addParticle(vector<double>());
system.addForce(force);
Context context(system, integrator, platform);
vector<Vec3> positions(2);
vector<Vec3> forces(2);
OpenMM_SFMT::SFMT sfmt;
init_gen_rand(0, sfmt);
for (int i = 0; i < 5; i++) {
positions[0] = Vec3(genrand_real2(sfmt), genrand_real2(sfmt), genrand_real2(sfmt));
positions[1] = Vec3(genrand_real2(sfmt), genrand_real2(sfmt), genrand_real2(sfmt));
context.setPositions(positions);
State state = context.getState(State::Forces | State::Energy);
const vector<Vec3>& forces = state.getForces();
Vec3 delta = positions[0]-positions[1];
double r = sqrt(delta.dot(delta));
double energy = 2*r+positions[0][0]*positions[0][1]+positions[1][0]*positions[1][1];
for (int j = 0; j < 2; j++)
energy += positions[j][2]*(r+positions[j][0]*positions[j][1]);
Vec3 force1(-(1+positions[0][2])*delta[0]/r-(1+positions[0][2])*positions[0][1]-(1+positions[1][2])*delta[0]/r,
-(1+positions[0][2])*delta[1]/r-(1+positions[0][2])*positions[0][0]-(1+positions[1][2])*delta[1]/r,
-(1+positions[0][2])*delta[2]/r-(r+positions[0][0]*positions[0][1])-(1+positions[1][2])*delta[2]/r);
Vec3 force2((1+positions[0][2])*delta[0]/r+(1+positions[1][2])*delta[0]/r-(1+positions[1][2])*positions[1][1],
(1+positions[0][2])*delta[1]/r+(1+positions[1][2])*delta[1]/r-(1+positions[1][2])*positions[1][0],
(1+positions[0][2])*delta[2]/r+(1+positions[1][2])*delta[2]/r-(r+positions[1][0]*positions[1][1]));
ASSERT_EQUAL_VEC(force1, forces[0], 1e-4);
ASSERT_EQUAL_VEC(force2, forces[1], 1e-4);
ASSERT_EQUAL_TOL(energy, state.getPotentialEnergy(), 0.02);
// Take a small step in the direction of the energy gradient and see whether the potential energy changes by the expected amount.
double norm = 0.0;
for (int i = 0; i < (int) forces.size(); ++i)
norm += forces[i].dot(forces[i]);
norm = std::sqrt(norm);
const double stepSize = 1e-3;
double step = 0.5*stepSize/norm;
vector<Vec3> positions2(2), positions3(2);
for (int i = 0; i < (int) positions.size(); ++i) {
Vec3 p = positions[i];
Vec3 f = forces[i];
positions2[i] = Vec3(p[0]-f[0]*step, p[1]-f[1]*step, p[2]-f[2]*step);
positions3[i] = Vec3(p[0]+f[0]*step, p[1]+f[1]*step, p[2]+f[2]*step);
}
context.setPositions(positions2);
State state2 = context.getState(State::Energy);
context.setPositions(positions3);
State state3 = context.getState(State::Energy);
ASSERT_EQUAL_TOL(norm, (state2.getPotentialEnergy()-state3.getPotentialEnergy())/stepSize, 1e-3);
}
}
void testMembrane() {
const int numMolecules = 70;
const int numParticles = numMolecules*2;
const double boxSize = 10.0;
ReferencePlatform platform;
// Create a system with an implicit membrane.
System system;
for (int i = 0; i < numParticles; i++) {
system.addParticle(1.0);
}
system.setDefaultPeriodicBoxVectors(Vec3(boxSize, 0.0, 0.0), Vec3(0.0, boxSize, 0.0), Vec3(0.0, 0.0, boxSize));
CustomGBForce* custom = new CustomGBForce();
custom->setCutoffDistance(2.0);
custom->addPerParticleParameter("q");
custom->addPerParticleParameter("radius");
custom->addPerParticleParameter("scale");
custom->addGlobalParameter("thickness", 3);
custom->addGlobalParameter("solventDielectric", 78.3);
custom->addGlobalParameter("soluteDielectric", 1);
custom->addComputedValue("Imol", "step(r+sr2-or1)*0.5*(1/L-1/U+0.25*(1/U^2-1/L^2)*(r-sr2*sr2/r)+0.5*log(L/U)/r+C);"
"U=r+sr2;"
"C=2*(1/or1-1/L)*step(sr2-r-or1);"
"L=max(or1, D);"
"D=abs(r-sr2);"
"sr2 = scale2*or2;"
"or1 = radius1-0.009; or2 = radius2-0.009", CustomGBForce::ParticlePairNoExclusions);
custom->addComputedValue("Imem", "(1/radius+2*log(2)/thickness)/(1+exp(7.2*(abs(z)+radius-0.5*thickness)))", CustomGBForce::SingleParticle);
custom->addComputedValue("B", "1/(1/or-tanh(1*psi-0.8*psi^2+4.85*psi^3)/radius);"
"psi=max(Imol,Imem)*or; or=radius-0.009", CustomGBForce::SingleParticle);
custom->addEnergyTerm("28.3919551*(radius+0.14)^2*(radius/B)^6-0.5*138.935456*(1/soluteDielectric-1/solventDielectric)*q^2/B", CustomGBForce::SingleParticle);
custom->addEnergyTerm("-138.935456*(1/soluteDielectric-1/solventDielectric)*q1*q2/f;"
"f=sqrt(r^2+B1*B2*exp(-r^2/(4*B1*B2)))", CustomGBForce::ParticlePairNoExclusions);
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) {
params[0] = 1.0;
params[1] = 0.2;
params[2] = 0.5;
custom->addParticle(params);
params[0] = -1.0;
params[1] = 0.1;
custom->addParticle(params);
}
else {
params[0] = 1.0;
params[1] = 0.2;
params[2] = 0.8;
custom->addParticle(params);
params[0] = -1.0;
params[1] = 0.1;
custom->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));
}
system.addForce(custom);
VerletIntegrator integrator(0.01);
Context context(system, integrator, platform);
context.setPositions(positions);
context.setVelocities(velocities);
State state = context.getState(State::Forces | State::Energy);
const vector<Vec3>& forces = state.getForces();
// Take a small step in the direction of the energy gradient and see whether the potential energy changes by the expected amount.
double norm = 0.0;
for (int i = 0; i < (int) forces.size(); ++i)
norm += forces[i].dot(forces[i]);
norm = std::sqrt(norm);
const double stepSize = 1e-3;
double step = 0.5*stepSize/norm;
vector<Vec3> positions2(numParticles), positions3(numParticles);
for (int i = 0; i < (int) positions.size(); ++i) {
Vec3 p = positions[i];
Vec3 f = forces[i];
positions2[i] = Vec3(p[0]-f[0]*step, p[1]-f[1]*step, p[2]-f[2]*step);
positions3[i] = Vec3(p[0]+f[0]*step, p[1]+f[1]*step, p[2]+f[2]*step);
}
context.setPositions(positions2);
State state2 = context.getState(State::Energy);
context.setPositions(positions3);
State state3 = context.getState(State::Energy);
ASSERT_EQUAL_TOL(norm, (state2.getPotentialEnergy()-state3.getPotentialEnergy())/stepSize, 1e-3);
}
