Program Listing for File XSPH.cpp

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#include "XSPH.h"
#include "TimeManager.h"
#include "Simulation.h"
#include "BoundaryModel_Akinci2012.h"
#include "BoundaryModel_Koschier2017.h"
#include "BoundaryModel_Bender2019.h"

using namespace SPH;
using namespace GenParam;

std::string XSPH::METHOD_NAME = "XSPH";
int XSPH::FLUID_COEFFICIENT = -1;
int XSPH::BOUNDARY_COEFFICIENT = -1;


XSPH::XSPH(FluidModel *model) :
    NonPressureForceBase(model)
{
    m_fluidCoefficient = 0.0;
    m_boundaryCoefficient = 0.0;
}

XSPH::~XSPH(void)
{
}

void XSPH::initParameters()
{
    NonPressureForceBase::initParameters();

    FLUID_COEFFICIENT = createNumericParameter("xsph", "Fluid coefficient", &m_fluidCoefficient);
    setGroup(FLUID_COEFFICIENT, "Fluid Model|XSPH");
    setDescription(FLUID_COEFFICIENT, "Coefficient for the XSPH velocity filter in the fluid");
    RealParameter* rparam = static_cast<RealParameter*>(getParameter(FLUID_COEFFICIENT));
    rparam->setMinValue(0.0);

    BOUNDARY_COEFFICIENT = createNumericParameter("xsphBoundary", "Boundary coefficient", &m_boundaryCoefficient);
    setGroup(BOUNDARY_COEFFICIENT, "Fluid Model|XSPH");
    setDescription(BOUNDARY_COEFFICIENT, "Coefficient for the XSPH velocity filter at the boundary");
    rparam = static_cast<RealParameter*>(getParameter(BOUNDARY_COEFFICIENT));
    rparam->setMinValue(0.0);
}

#ifdef USE_AVX

void XSPH::step()
{
    if ((m_fluidCoefficient == 0.0) && (m_boundaryCoefficient == 0.0))
        return;

    Simulation *sim = Simulation::getCurrent();
    const unsigned int nFluids = sim->numberOfFluidModels();
    const unsigned int nBoundaries = sim->numberOfBoundaryModels();
    const unsigned int fluidModelIndex = m_model->getPointSetIndex();
    const unsigned int numParticles = m_model->numActiveParticles();
    const Real density0 = m_model->getValue<Real>(FluidModel::DENSITY0);

    const Real h = TimeManager::getCurrent()->getTimeStepSize();
    const Real invH = (static_cast<Real>(1.0) / h);

    // Compute viscosity forces (XSPH)
    #pragma omp parallel default(shared)
    {
        #pragma omp for schedule(static)
        for (int i = 0; i < (int)numParticles; i++)
        {
            const Vector3r &xi = m_model->getPosition(i);
            const Vector3r &vi = m_model->getVelocity(i);
            Vector3r &ai = m_model->getAcceleration(i);
            const Real density_i = m_model->getDensity(i);

            const Vector3f8 xi_avx(xi);
            const Vector3f8 vi_avx(vi);
            const Scalarf8 mi_avx(m_model->getMass(i));
            const Scalarf8 density_i_avx(density_i);
            Vector3f8 delta_ai;
            delta_ai.setZero();
            const Scalarf8 dvisc(invH * m_fluidCoefficient);

            // Fluid
            if (m_fluidCoefficient != 0.0)
            {
                forall_fluid_neighbors_avx(
                    const Vector3f8 vj_avx = convertVec_zero(&sim->getNeighborList(fluidModelIndex, pid, i)[j], &fm_neighbor->getVelocity(0), count);
                    const Scalarf8 mj_avx = convert_zero(&sim->getNeighborList(fluidModelIndex, pid, i)[j], &fm_neighbor->getMass(0), count);

                    // Viscosity
                    const Scalarf8 density_j_avx = convert_one(&sim->getNeighborList(fluidModelIndex, pid, i)[j], &fm_neighbor->getDensity(0), count);
                    const Vector3f8 xixj = xi_avx - xj_avx;
                    delta_ai -= (vi_avx - vj_avx) * dvisc * (mj_avx / density_j_avx) * CubicKernel_AVX::W(xixj);
                );
                ai += delta_ai.reduce();
            }

            // Boundary
            if (m_boundaryCoefficient != 0.0)
            {
                if (sim->getBoundaryHandlingMethod() == BoundaryHandlingMethods::Akinci2012)
                {
                    forall_boundary_neighbors(
                        const Vector3r &vj = bm_neighbor->getVelocity(neighborIndex);
                        const Vector3r a = -invH * m_boundaryCoefficient * (density0 * bm_neighbor->getVolume(neighborIndex) / density_i) * (vi-vj)* sim->W(xi - xj);
                        ai += a;
                        bm_neighbor->addForce(xj, -m_model->getMass(i) * a);
                    );
                }
                else if (sim->getBoundaryHandlingMethod() == BoundaryHandlingMethods::Koschier2017)
                {
                    forall_density_maps(
                        Vector3r vj;
                        bm_neighbor->getPointVelocity(xi, vj);
                        const Vector3r a = -invH * m_boundaryCoefficient * (density0 / density_i) * (vi-vj)* rho;
                        ai += a;
                        bm_neighbor->addForce(xj, -m_model->getMass(i) * a);
                    );
                }
                else if (sim->getBoundaryHandlingMethod() == BoundaryHandlingMethods::Bender2019)
                {
                    forall_volume_maps(
                        Vector3r vj;
                        bm_neighbor->getPointVelocity(xj, vj);
                        const Vector3r a = -invH * m_boundaryCoefficient * (density0 * Vj / density_i) * (vi-vj)* sim->W(xi - xj);
                        ai += a;
                        bm_neighbor->addForce(xj, -m_model->getMass(i) * a);
                    );
                }
            }
        }
    }
}

#else

void XSPH::step()
{
    Simulation *sim = Simulation::getCurrent();
    const unsigned int nFluids = sim->numberOfFluidModels();
    const unsigned int nBoundaries = sim->numberOfBoundaryModels();
    const unsigned int fluidModelIndex = m_model->getPointSetIndex();
    const unsigned int numParticles = m_model->numActiveParticles();
    const Real density0 = m_model->getValue<Real>(FluidModel::DENSITY0);

    const Real h = TimeManager::getCurrent()->getTimeStepSize();
    const Real invH = (static_cast<Real>(1.0) / h);

    // Compute viscosity forces (XSPH)
    #pragma omp parallel default(shared)
    {
        #pragma omp for schedule(static)
        for (int i = 0; i < (int)numParticles; i++)
        {
            const Vector3r &xi = m_model->getPosition(i);
            const Vector3r &vi = m_model->getVelocity(i);
            Vector3r &ai = m_model->getAcceleration(i);
            const Real density_i = m_model->getDensity(i);

            // Fluid
            forall_fluid_neighbors(
                const Vector3r &vj = fm_neighbor->getVelocity(neighborIndex);

                // Viscosity
                const Real density_j = fm_neighbor->getDensity(neighborIndex);
                ai -= invH * m_fluidCoefficient * (fm_neighbor->getMass(neighborIndex) / density_j) * (vi - vj) * sim->W(xi - xj);
            );

            // Boundary
            if (m_boundaryCoefficient != 0.0)
            {
                if (sim->getBoundaryHandlingMethod() == BoundaryHandlingMethods::Akinci2012)
                {
                    forall_boundary_neighbors(
                        const Vector3r &vj = bm_neighbor->getVelocity(neighborIndex);
                        const Vector3r a = -invH * m_boundaryCoefficient * (density0 * bm_neighbor->getVolume(neighborIndex) / density_i) * (vi-vj)* sim->W(xi - xj);
                        ai += a;
                        bm_neighbor->addForce(xj, -m_model->getMass(i) * a);
                    );
                }
                else if (sim->getBoundaryHandlingMethod() == BoundaryHandlingMethods::Koschier2017)
                {
                    forall_density_maps(
                        Vector3r vj;
                        bm_neighbor->getPointVelocity(xi, vj);
                        const Vector3r a = -invH * m_boundaryCoefficient * (density0 / density_i) * (vi-vj)* rho;
                        ai += a;
                        bm_neighbor->addForce(xj, -m_model->getMass(i) * a);
                    );
                }
                else if (sim->getBoundaryHandlingMethod() == BoundaryHandlingMethods::Bender2019)
                {
                    forall_volume_maps(
                        Vector3r vj;
                        bm_neighbor->getPointVelocity(xj, vj);
                        const Vector3r a = -invH * m_boundaryCoefficient * (density0 * Vj / density_i) * (vi-vj)* sim->W(xi - xj);
                        ai += a;
                        bm_neighbor->addForce(xj, -m_model->getMass(i) * a);
                    );
                }
            }
        }
    }
}

#endif

void XSPH::reset()
{
}