/* -------------------------------------------------------------------------- *
 *                                   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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 * Portions copyright (c) 2008-2015 Stanford University and the Authors.      *
 * Authors: Peter Eastman                                                     *
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#include "CudaTests.h"
#include "TestNonbondedForce.h"

void testParallelComputation(NonbondedForce::NonbondedMethod method) {
    System system;
    const int numParticles = 200;
    for (int i = 0; i < numParticles; i++)
        system.addParticle(1.0);
    NonbondedForce* force = new NonbondedForce();
    for (int i = 0; i < numParticles; i++)
        force->addParticle(i%2-0.5, 0.5, 1.0);
    force->setNonbondedMethod(method);
    system.addForce(force);
    system.setDefaultPeriodicBoxVectors(Vec3(5,0,0), Vec3(0,5,0), Vec3(0,0,5));
    OpenMM_SFMT::SFMT sfmt;
    init_gen_rand(0, sfmt);
    vector<Vec3> positions(numParticles);
    for (int i = 0; i < numParticles; i++)
        positions[i] = Vec3(5*genrand_real2(sfmt), 5*genrand_real2(sfmt), 5*genrand_real2(sfmt));
    for (int i = 0; i < numParticles; ++i)
        for (int j = 0; j < i; ++j) {
            Vec3 delta = positions[i]-positions[j];
            if (delta.dot(delta) < 0.1)
                force->addException(i, j, 0, 1, 0);
        }
    
    // Create two contexts, one with a single device and one with two devices.
    
    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, CudaPlatform::CudaDeviceIndex());
    map<string, string> props;
    props[CudaPlatform::CudaDeviceIndex()] = deviceIndex+","+deviceIndex;
    Context context2(system, integrator2, platform, props);
    context2.setPositions(positions);
    State state2 = context2.getState(State::Forces | State::Energy);
    
    // See if they agree.
    
    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);
    
    // Modify some particle parameters and see if they still agree.

    for (int i = 0; i < numParticles; i += 5) {
        double charge, sigma, epsilon;
        force->getParticleParameters(i, charge, sigma, epsilon);
        force->setParticleParameters(i, 0.9*charge, sigma, epsilon);
    }
    force->updateParametersInContext(context1);
    force->updateParametersInContext(context2);
    state1 = context1.getState(State::Forces | State::Energy);
    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);
}

void testReordering() {
    // Check that reordering of atoms doesn't alter their positions.
    
    const int numParticles = 200;
    System system;
    system.setDefaultPeriodicBoxVectors(Vec3(6, 0, 0), Vec3(2.1, 6, 0), Vec3(-1.5, -0.5, 6));
    NonbondedForce *nonbonded = new NonbondedForce();
    nonbonded->setNonbondedMethod(NonbondedForce::PME);
    system.addForce(nonbonded);
    vector<Vec3> positions;
    OpenMM_SFMT::SFMT sfmt;
    init_gen_rand(0, sfmt);
    for (int i = 0; i < numParticles; i++) {
        system.addParticle(1.0);
        nonbonded->addParticle(0.0, 0.0, 0.0);
        positions.push_back(Vec3(genrand_real2(sfmt)-0.5, genrand_real2(sfmt)-0.5, genrand_real2(sfmt)-0.5)*20);
    }
    VerletIntegrator integrator(0.001);
    Context context(system, integrator, platform);
    context.setPositions(positions);
    integrator.step(1);
    State state = context.getState(State::Positions | State::Velocities);
    for (int i = 0; i < numParticles; i++) {
        ASSERT_EQUAL_VEC(positions[i], state.getPositions()[i], 1e-6);
    }
}

void testDeterministicForces() {
    // Check that the CudaDeterministicForces property works correctly.
    
    const int numParticles = 1000;
    System system;
    system.setDefaultPeriodicBoxVectors(Vec3(6, 0, 0), Vec3(2.1, 6, 0), Vec3(-1.5, -0.5, 6));
    NonbondedForce *nonbonded = new NonbondedForce();
    nonbonded->setNonbondedMethod(NonbondedForce::PME);
    system.addForce(nonbonded);
    vector<Vec3> positions;
    OpenMM_SFMT::SFMT sfmt;
    init_gen_rand(0, sfmt);
    for (int i = 0; i < numParticles; i++) {
        system.addParticle(1.0);
        nonbonded->addParticle(i%2 == 0 ? 1 : -1, 1, 0);
        positions.push_back(Vec3(genrand_real2(sfmt)-0.5, genrand_real2(sfmt)-0.5, genrand_real2(sfmt)-0.5)*6);
    }
    VerletIntegrator integrator(0.001);
    map<string, string> properties;
    properties[CudaPlatform::CudaDeterministicForces()] = "true";
    Context context(system, integrator, platform, properties);
    context.setPositions(positions);
    State state1 = context.getState(State::Forces);
    State state2 = context.getState(State::Forces);
    
    // All forces should be *exactly* equal.
    
    for (int i = 0; i < numParticles; i++) {
        ASSERT_EQUAL(state1.getForces()[i][0], state2.getForces()[i][0]);
        ASSERT_EQUAL(state1.getForces()[i][1], state2.getForces()[i][1]);
        ASSERT_EQUAL(state1.getForces()[i][2], state2.getForces()[i][2]);
    }
}

void runPlatformTests() {
    testParallelComputation(NonbondedForce::NoCutoff);
    testParallelComputation(NonbondedForce::Ewald);
    testParallelComputation(NonbondedForce::PME);
    testReordering();
    testDeterministicForces();
}