/**
* Test a multiple time step r-RESPA integrator.
*/
void testRespa() {
const int numParticles = 8;
System system;
system.setDefaultPeriodicBoxVectors(Vec3(4, 0, 0), Vec3(0, 4, 0), Vec3(0, 0, 4));
CustomIntegrator integrator(0.002);
integrator.addComputePerDof("v", "v+0.5*dt*f1/m");
for (int i = 0; i < 2; i++) {
integrator.addComputePerDof("v", "v+0.5*(dt/2)*f0/m");
integrator.addComputePerDof("x", "x+(dt/2)*v");
integrator.addComputePerDof("v", "v+0.5*(dt/2)*f0/m");
}
integrator.addComputePerDof("v", "v+0.5*dt*f1/m");
HarmonicBondForce* bonds = new HarmonicBondForce();
for (int i = 0; i < numParticles-2; i++)
bonds->addBond(i, i+1, 1.0, 0.5);
system.addForce(bonds);
NonbondedForce* nb = new NonbondedForce();
nb->setCutoffDistance(2.0);
nb->setNonbondedMethod(NonbondedForce::Ewald);
for (int i = 0; i < numParticles; ++i) {
system.addParticle(i%2 == 0 ? 5.0 : 10.0);
nb->addParticle((i%2 == 0 ? 0.2 : -0.2), 0.5, 5.0);
}
nb->setForceGroup(1);
nb->setReciprocalSpaceForceGroup(0);
system.addForce(nb);
Context context(system, integrator, platform);
vector<Vec3> positions(numParticles);
vector<Vec3> velocities(numParticles);
OpenMM_SFMT::SFMT sfmt;
init_gen_rand(0, sfmt);
for (int i = 0; i < numParticles; ++i) {
positions[i] = Vec3(i/2, (i+1)/2, 0);
velocities[i] = Vec3(genrand_real2(sfmt)-0.5, genrand_real2(sfmt)-0.5, genrand_real2(sfmt)-0.5);
}
context.setPositions(positions);
context.setVelocities(velocities);
// Simulate it and monitor energy conservations.
double initialEnergy = 0.0;
for (int i = 0; i < 1000; ++i) {
State state = context.getState(State::Energy);
double energy = state.getKineticEnergy()+state.getPotentialEnergy();
if (i == 1)
initialEnergy = energy;
else if (i > 1)
ASSERT_EQUAL_TOL(initialEnergy, energy, 0.05);
integrator.step(2);
}
}
void testWithBarostat() {
const int gridSize = 3;
const int numMolecules = gridSize*gridSize*gridSize;
const int numParticles = numMolecules*2;
const int numCopies = 5;
const double spacing = 2.0;
const double cutoff = 3.0;
const double boxSize = spacing*(gridSize+1);
const double temperature = 300.0;
System system;
system.setDefaultPeriodicBoxVectors(Vec3(boxSize, 0, 0), Vec3(0, boxSize, 0), Vec3(0, 0, boxSize));
HarmonicBondForce* bonds = new HarmonicBondForce();
system.addForce(bonds);
NonbondedForce* nonbonded = new NonbondedForce();
nonbonded->setCutoffDistance(cutoff);
nonbonded->setNonbondedMethod(NonbondedForce::PME);
nonbonded->setForceGroup(1);
nonbonded->setReciprocalSpaceForceGroup(2);
system.addForce(nonbonded);
system.addForce(new MonteCarloBarostat(0.5, temperature));
// Create a cloud of molecules.
OpenMM_SFMT::SFMT sfmt;
init_gen_rand(0, sfmt);
vector<Vec3> positions(numParticles);
for (int i = 0; i < numMolecules; i++) {
system.addParticle(1.0);
system.addParticle(1.0);
nonbonded->addParticle(-0.2, 0.2, 0.2);
nonbonded->addParticle(0.2, 0.2, 0.2);
nonbonded->addException(2*i, 2*i+1, 0, 1, 0);
bonds->addBond(2*i, 2*i+1, 1.0, 10000.0);
}
RPMDIntegrator integ(numCopies, temperature, 50.0, 0.001);
Platform& platform = Platform::getPlatformByName("Reference");
Context context(system, integ, platform);
for (int copy = 0; copy < numCopies; copy++) {
for (int i = 0; i < gridSize; i++)
for (int j = 0; j < gridSize; j++)
for (int k = 0; k < gridSize; k++) {
Vec3 pos = Vec3(spacing*(i+0.02*genrand_real2(sfmt)), spacing*(j+0.02*genrand_real2(sfmt)), spacing*(k+0.02*genrand_real2(sfmt)));
int index = k+gridSize*(j+gridSize*i);
positions[2*index] = pos;
positions[2*index+1] = Vec3(pos[0]+1.0, pos[1], pos[2]);
}
integ.setPositions(copy, positions);
}
// Check the temperature.
const int numSteps = 500;
integ.step(100);
vector<double> ke(numCopies, 0.0);
for (int i = 0; i < numSteps; i++) {
integ.step(1);
vector<State> state(numCopies);
for (int j = 0; j < numCopies; j++)
state[j] = integ.getState(j, State::Velocities, true);
for (int j = 0; j < numParticles; j++) {
for (int k = 0; k < numCopies; k++) {
Vec3 v = state[k].getVelocities()[j];
ke[k] += 0.5*system.getParticleMass(j)*v.dot(v);
}
}
}
double meanKE = 0.0;
for (int i = 0; i < numCopies; i++)
meanKE += ke[i];
meanKE /= numSteps*numCopies;
double expectedKE = 0.5*numCopies*numParticles*3*BOLTZ*temperature;
ASSERT_USUALLY_EQUAL_TOL(expectedKE, meanKE, 1e-2);
}
/**
* Test evaluating force groups separately.
*/
void testForceGroups() {
System system;
system.addParticle(2.0);
system.addParticle(2.0);
CustomIntegrator integrator(0.01);
integrator.addPerDofVariable("outf", 0);
integrator.addPerDofVariable("outf1", 0);
integrator.addPerDofVariable("outf2", 0);
integrator.addGlobalVariable("oute", 0);
integrator.addGlobalVariable("oute1", 0);
integrator.addGlobalVariable("oute2", 0);
integrator.addComputePerDof("outf", "f");
integrator.addComputePerDof("outf1", "f1");
integrator.addComputePerDof("outf2", "f2");
integrator.addComputeGlobal("oute", "energy");
integrator.addComputeGlobal("oute1", "energy1");
integrator.addComputeGlobal("oute2", "energy2");
HarmonicBondForce* bonds = new HarmonicBondForce();
bonds->addBond(0, 1, 1.5, 1.1);
bonds->setForceGroup(1);
system.addForce(bonds);
NonbondedForce* nb = new NonbondedForce();
nb->addParticle(0.2, 1, 0);
nb->addParticle(0.2, 1, 0);
nb->setForceGroup(2);
system.addForce(nb);
Context context(system, integrator, platform);
vector<Vec3> positions(2);
positions[0] = Vec3(-1, 0, 0);
positions[1] = Vec3(1, 0, 0);
context.setPositions(positions);
// See if the various forces are computed correctly.
integrator.step(1);
vector<Vec3> f, f1, f2;
double e1 = 0.5*1.1*0.5*0.5;
double e2 = 138.935456*0.2*0.2/2.0;
integrator.getPerDofVariable(0, f);
integrator.getPerDofVariable(1, f1);
integrator.getPerDofVariable(2, f2);
ASSERT_EQUAL_VEC(Vec3(1.1*0.5, 0, 0), f1[0], 1e-5);
ASSERT_EQUAL_VEC(Vec3(-1.1*0.5, 0, 0), f1[1], 1e-5);
ASSERT_EQUAL_VEC(Vec3(-138.935456*0.2*0.2/4.0, 0, 0), f2[0], 1e-5);
ASSERT_EQUAL_VEC(Vec3(138.935456*0.2*0.2/4.0, 0, 0), f2[1], 1e-5);
ASSERT_EQUAL_VEC(f1[0]+f2[0], f[0], 1e-5);
ASSERT_EQUAL_VEC(f1[1]+f2[1], f[1], 1e-5);
ASSERT_EQUAL_TOL(e1, integrator.getGlobalVariable(1), 1e-5);
ASSERT_EQUAL_TOL(e2, integrator.getGlobalVariable(2), 1e-5);
ASSERT_EQUAL_TOL(e1+e2, integrator.getGlobalVariable(0), 1e-5);
// Make sure they also match the values returned by the Context.
State s = context.getState(State::Forces | State::Energy, false);
State s1 = context.getState(State::Forces | State::Energy, false, 2);
State s2 = context.getState(State::Forces | State::Energy, false, 4);
vector<Vec3> c, c1, c2;
c = context.getState(State::Forces, false).getForces();
c1 = context.getState(State::Forces, false, 2).getForces();
c2 = context.getState(State::Forces, false, 4).getForces();
ASSERT_EQUAL_VEC(f[0], c[0], 1e-5);
ASSERT_EQUAL_VEC(f[1], c[1], 1e-5);
ASSERT_EQUAL_VEC(f1[0], c1[0], 1e-5);
ASSERT_EQUAL_VEC(f1[1], c1[1], 1e-5);
ASSERT_EQUAL_VEC(f2[0], c2[0], 1e-5);
ASSERT_EQUAL_VEC(f2[1], c2[1], 1e-5);
ASSERT_EQUAL_TOL(s.getPotentialEnergy(), integrator.getGlobalVariable(0), 1e-5);
ASSERT_EQUAL_TOL(s1.getPotentialEnergy(), integrator.getGlobalVariable(1), 1e-5);
ASSERT_EQUAL_TOL(s2.getPotentialEnergy(), integrator.getGlobalVariable(2), 1e-5);
}
void testSerialization() {
// Create a Force.
NonbondedForce force;
force.setForceGroup(3);
force.setNonbondedMethod(NonbondedForce::CutoffPeriodic);
force.setSwitchingDistance(1.5);
force.setUseSwitchingFunction(true);
force.setCutoffDistance(2.0);
force.setEwaldErrorTolerance(1e-3);
force.setReactionFieldDielectric(50.0);
force.setUseDispersionCorrection(false);
double alpha = 0.5;
int nx = 3, ny = 5, nz = 7;
force.setPMEParameters(alpha, nx, ny, nz);
double dalpha = 0.8;
int dnx = 4, dny = 6, dnz = 7;
force.setLJPMEParameters(dalpha, dnx, dny, dnz);
force.addParticle(1, 0.1, 0.01);
force.addParticle(0.5, 0.2, 0.02);
force.addParticle(-0.5, 0.3, 0.03);
force.addException(0, 1, 2, 0.5, 0.1);
force.addException(1, 2, 0.2, 0.4, 0.2);
force.addGlobalParameter("scale1", 1.0);
force.addGlobalParameter("scale2", 2.0);
force.addParticleParameterOffset("scale1", 2, 1.5, 2.0, 2.5);
force.addExceptionParameterOffset("scale2", 1, -0.1, -0.2, -0.3);
// Serialize and then deserialize it.
stringstream buffer;
XmlSerializer::serialize<NonbondedForce>(&force, "Force", buffer);
NonbondedForce* copy = XmlSerializer::deserialize<NonbondedForce>(buffer);
// Compare the two forces to see if they are identical.
NonbondedForce& force2 = *copy;
ASSERT_EQUAL(force.getForceGroup(), force2.getForceGroup());
ASSERT_EQUAL(force.getNonbondedMethod(), force2.getNonbondedMethod());
ASSERT_EQUAL(force.getSwitchingDistance(), force2.getSwitchingDistance());
ASSERT_EQUAL(force.getUseSwitchingFunction(), force2.getUseSwitchingFunction());
ASSERT_EQUAL(force.getCutoffDistance(), force2.getCutoffDistance());
ASSERT_EQUAL(force.getEwaldErrorTolerance(), force2.getEwaldErrorTolerance());
ASSERT_EQUAL(force.getReactionFieldDielectric(), force2.getReactionFieldDielectric());
ASSERT_EQUAL(force.getUseDispersionCorrection(), force2.getUseDispersionCorrection());
ASSERT_EQUAL(force.getNumParticles(), force2.getNumParticles());
ASSERT_EQUAL(force.getNumExceptions(), force2.getNumExceptions());
ASSERT_EQUAL(force.getNumGlobalParameters(), force2.getNumGlobalParameters());
ASSERT_EQUAL(force.getNumParticleParameterOffsets(), force2.getNumParticleParameterOffsets());
ASSERT_EQUAL(force.getNumExceptionParameterOffsets(), force2.getNumExceptionParameterOffsets());
double alpha2;
int nx2, ny2, nz2;
force2.getPMEParameters(alpha2, nx2, ny2, nz2);
ASSERT_EQUAL(alpha, alpha2);
ASSERT_EQUAL(nx, nx2);
ASSERT_EQUAL(ny, ny2);
ASSERT_EQUAL(nz, nz2);
double dalpha2;
int dnx2, dny2, dnz2;
force2.getLJPMEParameters(dalpha2, dnx2, dny2, dnz2);
ASSERT_EQUAL(dalpha, dalpha2);
ASSERT_EQUAL(dnx, dnx2);
ASSERT_EQUAL(dny, dny2);
ASSERT_EQUAL(dnz, dnz2);
for (int i = 0; i < force.getNumGlobalParameters(); i++) {
ASSERT_EQUAL(force.getGlobalParameterName(i), force2.getGlobalParameterName(i));
ASSERT_EQUAL(force.getGlobalParameterDefaultValue(i), force2.getGlobalParameterDefaultValue(i));
}
for (int i = 0; i < force.getNumParticleParameterOffsets(); i++) {
int index1, index2;
string param1, param2;
double charge1, sigma1, epsilon1;
double charge2, sigma2, epsilon2;
force.getParticleParameterOffset(i, param1, index1, charge1, sigma1, epsilon1);
force2.getParticleParameterOffset(i, param2, index2, charge2, sigma2, epsilon2);
ASSERT_EQUAL(index1, index1);
ASSERT_EQUAL(param1, param2);
ASSERT_EQUAL(charge1, charge2);
ASSERT_EQUAL(sigma1, sigma2);
ASSERT_EQUAL(epsilon1, epsilon2);
}
for (int i = 0; i < force.getNumExceptionParameterOffsets(); i++) {
int index1, index2;
string param1, param2;
double charge1, sigma1, epsilon1;
double charge2, sigma2, epsilon2;
force.getExceptionParameterOffset(i, param1, index1, charge1, sigma1, epsilon1);
force2.getExceptionParameterOffset(i, param2, index2, charge2, sigma2, epsilon2);
ASSERT_EQUAL(index1, index1);
ASSERT_EQUAL(param1, param2);
ASSERT_EQUAL(charge1, charge2);
ASSERT_EQUAL(sigma1, sigma2);
ASSERT_EQUAL(epsilon1, epsilon2);
}
for (int i = 0; i < force.getNumParticles(); i++) {
double charge1, sigma1, epsilon1;
double charge2, sigma2, epsilon2;
force.getParticleParameters(i, charge1, sigma1, epsilon1);
force2.getParticleParameters(i, charge2, sigma2, epsilon2);
ASSERT_EQUAL(charge1, charge2);
ASSERT_EQUAL(sigma1, sigma2);
ASSERT_EQUAL(epsilon1, epsilon2);
}
ASSERT_EQUAL(force.getNumExceptions(), force2.getNumExceptions());
for (int i = 0; i < force.getNumExceptions(); i++) {
int a1, a2, b1, b2;
double charge1, sigma1, epsilon1;
double charge2, sigma2, epsilon2;
force.getExceptionParameters(i, a1, b1, charge1, sigma1, epsilon1);
force2.getExceptionParameters(i, a2, b2, charge2, sigma2, epsilon2);
ASSERT_EQUAL(a1, a2);
ASSERT_EQUAL(b1, b2);
ASSERT_EQUAL(charge1, charge2);
ASSERT_EQUAL(sigma1, sigma2);
ASSERT_EQUAL(epsilon1, epsilon2);
}
}
