TestReferenceCustomAngleForce.cpp

/* -------------------------------------------------------------------------- *
 *                                   OpenMM                                   *
 * -------------------------------------------------------------------------- *
 * This is part of the OpenMM molecular simulation toolkit originating from   *
 * Simbios, the NIH National Center for Physics-Based Simulation of           *
 * Biological Structures at Stanford, funded under the NIH Roadmap for        *
 * Medical Research, grant U54 GM072970. See https://simtk.org.               *
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 * Authors: Peter Eastman                                                     *
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/**
 * This tests the reference implementation of CustomAngleForce.
 */

#include "../../../tests/AssertionUtilities.h"
#include "openmm/Context.h"
#include "ReferencePlatform.h"
#include "openmm/CustomAngleForce.h"
#include "openmm/HarmonicAngleForce.h"
#include "openmm/System.h"
#include "openmm/VerletIntegrator.h"
#include "../src/sfmt/SFMT.h"
#include <iostream>
#include <vector>

using namespace OpenMM;
using namespace std;

const double TOL = 1e-5;

void testAngles() {
    ReferencePlatform platform;

    // Create a system using a CustomAngleForce.

    System customSystem;
    customSystem.addParticle(1.0);
    customSystem.addParticle(1.0);
    customSystem.addParticle(1.0);
    customSystem.addParticle(1.0);
    CustomAngleForce* custom = new CustomAngleForce("scale*k*(theta-theta0)^2");
    custom->addPerAngleParameter("theta0");
    custom->addPerAngleParameter("k");
    custom->addGlobalParameter("scale", 0.5);
    vector<double> parameters(2);
    parameters[0] = 1.5;
    parameters[1] = 0.8;
    custom->addAngle(0, 1, 2, parameters);
    parameters[0] = 2.0;
    parameters[1] = 0.5;
    custom->addAngle(1, 2, 3, parameters);
    customSystem.addForce(custom);

    // Create an identical system using a HarmonicAngleForce.

    System harmonicSystem;
    harmonicSystem.addParticle(1.0);
    harmonicSystem.addParticle(1.0);
    harmonicSystem.addParticle(1.0);
    harmonicSystem.addParticle(1.0);
    VerletIntegrator integrator(0.01);
    HarmonicAngleForce* harmonic = new HarmonicAngleForce();
    harmonic->addAngle(0, 1, 2, 1.5, 0.8);
    harmonic->addAngle(1, 2, 3, 2.0, 0.5);
    harmonicSystem.addForce(harmonic);

    // Set the atoms in various positions, and verify that both systems give identical forces and energy.

    init_gen_rand(0);
    vector<Vec3> positions(4);
    VerletIntegrator integrator1(0.01);
    VerletIntegrator integrator2(0.01);
    for (int i = 0; i < 10; i++) {
        Context c1(customSystem, integrator1, platform);
        Context c2(harmonicSystem, integrator2, platform);
        for (int j = 0; j < (int) positions.size(); j++)
            positions[j] = Vec3(5.0*genrand_real2(), 5.0*genrand_real2(), 5.0*genrand_real2());
        c1.setPositions(positions);
        c2.setPositions(positions);
        State s1 = c1.getState(State::Forces | State::Energy);
        State s2 = c2.getState(State::Forces | State::Energy);
        const vector<Vec3>& forces = s1.getForces();
        ASSERT_EQUAL_VEC(s1.getForces()[0], s2.getForces()[0], TOL);
        ASSERT_EQUAL_VEC(s1.getForces()[1], s2.getForces()[1], TOL);
        ASSERT_EQUAL_VEC(s1.getForces()[2], s2.getForces()[2], TOL);
        ASSERT_EQUAL_TOL(s1.getPotentialEnergy(), s2.getPotentialEnergy(), TOL);
    }
}

int main() {
    try {
        testAngles();
    }
    catch(const exception& e) {
        cout << "exception: " << e.what() << endl;
        return 1;
    }
    cout << "Done" << endl;
    return 0;
}