TestOpenCLHarmonicBondForce.cpp

/* -------------------------------------------------------------------------- *
 *                                   OpenMM                                   *
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 * 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 OpenCL implementation of HarmonicBondForce.
 */

#include "openmm/internal/AssertionUtilities.h"
#include "openmm/Context.h"
#include "OpenCLPlatform.h"
#include "openmm/HarmonicBondForce.h"
#include "openmm/System.h"
#include "openmm/VerletIntegrator.h"
#include <iostream>
#include <map>
#include <vector>

using namespace OpenMM;
using namespace std;

OpenCLPlatform platform;

const double TOL = 1e-5;

void testBonds() {
    System system;
    system.addParticle(1.0);
    system.addParticle(1.0);
    system.addParticle(1.0);
    VerletIntegrator integrator(0.01);
    HarmonicBondForce* forceField = new HarmonicBondForce();
    forceField->addBond(0, 1, 1.5, 0.8);
    forceField->addBond(1, 2, 1.2, 0.7);
    system.addForce(forceField);
    Context context(system, integrator, platform);
    vector<Vec3> positions(3);
    positions[0] = Vec3(0, 2, 0);
    positions[1] = Vec3(0, 0, 0);
    positions[2] = Vec3(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, -0.8*0.5, 0), forces[0], TOL);
        ASSERT_EQUAL_VEC(Vec3(0.7*0.2, 0, 0), forces[2], TOL);
        ASSERT_EQUAL_VEC(Vec3(-forces[0][0]-forces[2][0], -forces[0][1]-forces[2][1], -forces[0][2]-forces[2][2]), forces[1], TOL);
        ASSERT_EQUAL_TOL(0.5*0.8*0.5*0.5 + 0.5*0.7*0.2*0.2, state.getPotentialEnergy(), TOL);
    }
    
    // Try changing the bond parameters and make sure it's still correct.
    
    forceField->setBondParameters(0, 0, 1, 1.6, 0.9);
    forceField->setBondParameters(1, 1, 2, 1.3, 0.8);
    forceField->updateParametersInContext(context);
    state = context.getState(State::Forces | State::Energy);
    {
        const vector<Vec3>& forces = state.getForces();
        ASSERT_EQUAL_VEC(Vec3(0, -0.9*0.4, 0), forces[0], TOL);
        ASSERT_EQUAL_VEC(Vec3(0.8*0.3, 0, 0), forces[2], TOL);
        ASSERT_EQUAL_VEC(Vec3(-forces[0][0]-forces[2][0], -forces[0][1]-forces[2][1], -forces[0][2]-forces[2][2]), forces[1], TOL);
        ASSERT_EQUAL_TOL(0.5*0.9*0.4*0.4 + 0.5*0.8*0.3*0.3, state.getPotentialEnergy(), TOL);
    }
}

void testParallelComputation() {
    System system;
    const int numParticles = 200;
    for (int i = 0; i < numParticles; i++)
        system.addParticle(1.0);
    HarmonicBondForce* force = new HarmonicBondForce();
    for (int i = 1; i < numParticles; i++)
        force->addBond(i-1, i, 1.1, i);
    system.addForce(force);
    vector<Vec3> positions(numParticles);
    for (int i = 0; i < numParticles; i++)
        positions[i] = Vec3(i, 0, 0);
    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, OpenCLPlatform::OpenCLDeviceIndex());
    map<string, string> props;
    props[OpenCLPlatform::OpenCLDeviceIndex()] = 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);
}

int main(int argc, char* argv[]) {
    try {
        if (argc > 1)
            platform.setPropertyDefaultValue("OpenCLPrecision", string(argv[1]));
        testBonds();
        testParallelComputation();
    }
    catch(const exception& e) {
        cout << "exception: " << e.what() << endl;
        return 1;
    }
    cout << "Done" << endl;
    return 0;
}