TestCudaSettle.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.               *
 *                                                                            *
 * Portions copyright (c) 2008-2009 Stanford University and the Authors.      *
 * Authors: Peter Eastman                                                     *
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/**
 * This tests the Cuda implementation of the SETTLE algorithm.
 */

#include "../../../tests/AssertionUtilities.h"
#include "OpenMMContext.h"
#include "CudaPlatform.h"
#include "NonbondedForce.h"
#include "System.h"
#include "LangevinIntegrator.h"
#include "../src/sfmt/SFMT.h"
#include <iostream>
#include <vector>

using namespace OpenMM;
using namespace std;

void testConstraints() {
    const int numMolecules = 10;
    const int numParticles = numMolecules*3;
    const int numConstraints = numMolecules*3;
    const double temp = 100.0;
    CudaPlatform platform;
    System system(numParticles, numConstraints);
    LangevinIntegrator integrator(temp, 2.0, 0.001);
    integrator.setConstraintTolerance(1e-5);
    NonbondedForce* forceField = new NonbondedForce(numParticles, 0);
    for (int i = 0; i < numMolecules; ++i) {
        system.setParticleMass(i*3, 16.0);
        system.setParticleMass(i*3+1, 1.0);
        system.setParticleMass(i*3+2, 1.0);
        forceField->setParticleParameters(i*3, -0.82, 0.317, 0.65);
        forceField->setParticleParameters(i*3+1, 0.41, 1.0, 0.0);
        forceField->setParticleParameters(i*3+2, 0.41, 1.0, 0.0);
        system.setConstraintParameters(i*3, i*3, i*3+1, 0.1);
        system.setConstraintParameters(i*3+1, i*3, i*3+2, 0.1);
        system.setConstraintParameters(i*3+2, i*3+1, i*3+2, 0.163);
    }
    system.addForce(forceField);
    OpenMMContext context(system, integrator, platform);
    vector<Vec3> positions(numParticles);
    vector<Vec3> velocities(numParticles);
    init_gen_rand(0);
    for (int i = 0; i < numMolecules; ++i) {
        positions[i*3] = Vec3((i%4)*0.4, (i/4)*0.4, 0);
        positions[i*3+1] = positions[i*3]+Vec3(0.1, 0, 0);
        positions[i*3+2] = positions[i*3]+Vec3(-0.03333, 0.09428, 0);
        velocities[i*3] = Vec3(genrand_real2()-0.5, genrand_real2()-0.5, genrand_real2()-0.5);
        velocities[i*3+1] = Vec3(genrand_real2()-0.5, genrand_real2()-0.5, genrand_real2()-0.5);
        velocities[i*3+2] = Vec3(genrand_real2()-0.5, genrand_real2()-0.5, genrand_real2()-0.5);
    }
    context.setPositions(positions);
    context.setVelocities(velocities);

    // Simulate it and see whether the constraints remain satisfied.

    for (int i = 0; i < 1000; ++i) {
        integrator.step(1);
        State state = context.getState(State::Positions | State::Forces);
        for (int j = 0; j < numConstraints; ++j) {
            int particle1, particle2;
            double distance;
            system.getConstraintParameters(j, particle1, particle2, distance);
            Vec3 p1 = state.getPositions()[particle1];
            Vec3 p2 = state.getPositions()[particle2];
            double dist = std::sqrt((p1[0]-p2[0])*(p1[0]-p2[0])+(p1[1]-p2[1])*(p1[1]-p2[1])+(p1[2]-p2[2])*(p1[2]-p2[2]));
            ASSERT_EQUAL_TOL(distance, dist, 1e-5);
        }
    }
}

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