BrownianIntegrator.cpp

/* -------------------------------------------------------------------------- *
 *                                   OpenMM                                   *
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 * This is part of the OpenMM molecular simulation toolkit.                   *
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 * Authors: Peter Eastman                                                     *
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#include "openmm/BrownianIntegrator.h"
#include "openmm/Context.h"
#include "openmm/OpenMMException.h"
#include "openmm/internal/ContextImpl.h"
#include "openmm/kernels.h"
#include <string>

using namespace OpenMM;
using std::string;
using std::vector;

BrownianIntegrator::BrownianIntegrator(double temperature, double frictionCoeff, double stepSize) {
    setTemperature(temperature);
    setFriction(frictionCoeff);
    setStepSize(stepSize);
    setConstraintTolerance(1e-5);
    setRandomNumberSeed(0);
}

void BrownianIntegrator::initialize(ContextImpl& contextRef) {
    if (owner != NULL && &contextRef.getOwner() != owner)
        throw OpenMMException("This Integrator is already bound to a context");
    context = &contextRef;
    owner = &contextRef.getOwner();
    kernel = context->getPlatform().createKernel(IntegrateBrownianStepKernel::Name(), contextRef);
    kernel.getAs<IntegrateBrownianStepKernel>().initialize(contextRef.getSystem(), *this);
}

void BrownianIntegrator::setTemperature(double temp) {
    if (temp < 0)
        throw OpenMMException("Temperature cannot be negative");
    temperature = temp;
}

void BrownianIntegrator::setFriction(double coeff) {
    if (coeff <= 0)
        throw OpenMMException("Friction must be positive");
    friction = coeff;
}

void BrownianIntegrator::cleanup() {
    kernel = Kernel();
}

vector<string> BrownianIntegrator::getKernelNames() {
    std::vector<std::string> names;
    names.push_back(IntegrateBrownianStepKernel::Name());
    return names;
}

double BrownianIntegrator::computeKineticEnergy() {
    return kernel.getAs<IntegrateBrownianStepKernel>().computeKineticEnergy(*context, *this);
}

bool BrownianIntegrator::kineticEnergyRequiresForce() const {
    return false;
}

void BrownianIntegrator::step(int steps) {
    if (context == NULL)
        throw OpenMMException("This Integrator is not bound to a context!");  
    for (int i = 0; i < steps; ++i) {
        context->updateContextState();
        context->calcForcesAndEnergy(true, false, getIntegrationForceGroups());
        kernel.getAs<IntegrateBrownianStepKernel>().execute(*context, *this);
    }
}