void testBond() {
// Create a system using a CustomCompoundBondForce.
System customSystem;
customSystem.addParticle(1.0);
customSystem.addParticle(1.0);
customSystem.addParticle(1.0);
customSystem.addParticle(1.0);
CustomCompoundBondForce* custom = new CustomCompoundBondForce(4, "0.5*kb*((distance(p1,p2)-b0)^2+(distance(p2,p3)-b0)^2)+0.5*ka*(angle(p2,p3,p4)-a0)^2+kt*(1+cos(dihedral(p1,p2,p3,p4)-t0))");
custom->addPerBondParameter("kb");
custom->addPerBondParameter("ka");
custom->addPerBondParameter("kt");
custom->addPerBondParameter("b0");
custom->addPerBondParameter("a0");
custom->addPerBondParameter("t0");
vector<int> particles(4);
particles[0] = 0;
particles[1] = 1;
particles[2] = 3;
particles[3] = 2;
vector<double> parameters(6);
parameters[0] = 1.5;
parameters[1] = 0.8;
parameters[2] = 0.6;
parameters[3] = 1.1;
parameters[4] = 2.9;
parameters[5] = 1.3;
custom->addBond(particles, parameters);
customSystem.addForce(custom);
// Create an identical system using standard forces.
System standardSystem;
standardSystem.addParticle(1.0);
standardSystem.addParticle(1.0);
standardSystem.addParticle(1.0);
standardSystem.addParticle(1.0);
HarmonicBondForce* bonds = new HarmonicBondForce();
bonds->addBond(0, 1, 1.1, 1.5);
bonds->addBond(1, 3, 1.1, 1.5);
standardSystem.addForce(bonds);
HarmonicAngleForce* angles = new HarmonicAngleForce();
angles->addAngle(1, 3, 2, 2.9, 0.8);
standardSystem.addForce(angles);
PeriodicTorsionForce* torsions = new PeriodicTorsionForce();
torsions->addTorsion(0, 1, 3, 2, 1, 1.3, 0.6);
standardSystem.addForce(torsions);
// Set the atoms in various positions, and verify that both systems give identical forces and energy.
OpenMM_SFMT::SFMT sfmt;
init_gen_rand(0, sfmt);
VerletIntegrator integrator1(0.01);
VerletIntegrator integrator2(0.01);
Context c1(customSystem, integrator1, platform);
Context c2(standardSystem, integrator2, platform);
vector<Vec3> positions(4);
for (int i = 0; i < 10; i++) {
for (int j = 0; j < (int) positions.size(); j++)
positions[j] = Vec3(5.0*genrand_real2(sfmt), 5.0*genrand_real2(sfmt), 5.0*genrand_real2(sfmt));
c1.setPositions(positions);
c2.setPositions(positions);
State s1 = c1.getState(State::Forces | State::Energy);
State s2 = c2.getState(State::Forces | State::Energy);
for (int i = 0; i < customSystem.getNumParticles(); i++)
ASSERT_EQUAL_VEC(s1.getForces()[i], s2.getForces()[i], TOL);
ASSERT_EQUAL_TOL(s1.getPotentialEnergy(), s2.getPotentialEnergy(), TOL);
}
// Try changing the bond parameters and make sure it's still correct.
parameters[0] = 1.6;
parameters[3] = 1.3;
custom->setBondParameters(0, particles, parameters);
custom->updateParametersInContext(c1);
bonds->setBondParameters(0, 0, 1, 1.3, 1.6);
bonds->setBondParameters(1, 1, 3, 1.3, 1.6);
bonds->updateParametersInContext(c2);
{
State s1 = c1.getState(State::Forces | State::Energy);
State s2 = c2.getState(State::Forces | State::Energy);
const vector<Vec3>& forces = s1.getForces();
for (int i = 0; i < customSystem.getNumParticles(); i++)
ASSERT_EQUAL_VEC(s1.getForces()[i], s2.getForces()[i], TOL);
ASSERT_EQUAL_TOL(s1.getPotentialEnergy(), s2.getPotentialEnergy(), TOL);
}
}
