/* -------------------------------------------------------------------------- *
 *                                   OpenMM                                   *
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 * This is part of the OpenMM molecular simulation toolkit.                   *
 * See https://openmm.org/development.                                        *
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 * Authors: Peter Eastman                                                     *
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#include "CpuTests.h"
#include "TestCheckpoints.h"

void testCheckpoint() {
    const int numParticles = 100;
    const double boxSize = 5.0;
    const double temperature = 200.0;
    System system;
    system.addForce(new AndersenThermostat(0.0, 100.0));
    NonbondedForce* nonbonded = new NonbondedForce();
    system.addForce(nonbonded);
    nonbonded->setNonbondedMethod(NonbondedForce::CutoffPeriodic);
    vector<Vec3> positions(numParticles);
    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 ? 0.1 : -0.1, 0.2, 0.1);
        bool clash;
        do {
            clash = false;
            positions[i] = Vec3(boxSize*genrand_real2(sfmt), boxSize*genrand_real2(sfmt), boxSize*genrand_real2(sfmt));
            for (int j = 0; j < i; j++) {
                Vec3 delta = positions[i]-positions[j];
                if (sqrt(delta.dot(delta)) < 0.1)
                    clash = true;
            }
        } while (clash);
    }
    VerletIntegrator integrator(0.001);
    Context context(system, integrator, platform);
    context.setPositions(positions);
    context.setPeriodicBoxVectors(Vec3(boxSize, 0, 0), Vec3(0, boxSize, 0), Vec3(0, 0, boxSize));
    context.setParameter(AndersenThermostat::Temperature(), temperature);
    
    // Run for a little while.
    
    integrator.step(100);
    
    // Record the current state and make a checkpoint.
    
    State s1 = context.getState(State::Positions | State::Velocities | State::Parameters);
    stringstream stream1(ios_base::out | ios_base::in | ios_base::binary);
    context.createCheckpoint(stream1);
    
    // Continue the simulation for a few more steps and record the state again.
    
    integrator.step(10);
    State s2 = context.getState(State::Positions | State::Velocities | State::Parameters);
    
    // Restore from the checkpoint and see if everything gets restored correctly.
    
    context.setPeriodicBoxVectors(Vec3(2*boxSize, 0, 0), Vec3(0, 2*boxSize, 0), Vec3(0, 0, 2*boxSize));
    context.setParameter(AndersenThermostat::Temperature(), temperature+10);
    context.loadCheckpoint(stream1);
    State s3 = context.getState(State::Positions | State::Velocities | State::Parameters);
    compareStates(s1, s3);
    
    // Now simulate from there and see if the trajectory is identical.
    
    integrator.step(10);
    State s4 = context.getState(State::Positions | State::Velocities | State::Parameters);
    compareStates(s2, s4);
    
    // See if a checkpoint created from one Context can be loaded into a different one.
    
    VerletIntegrator integrator2(0.001);
    Context context2(system, integrator2, platform);
    stream1.seekg(0, stream1.beg);
    context2.loadCheckpoint(stream1);
    State s5 = context2.getState(State::Positions | State::Velocities | State::Parameters | State::Energy);
    compareStates(s1, s5);
}

void runPlatformTests() {
    testCheckpoint();
}
