.. _program_listing_file_SPlisHSPlasH_PCISPH_TimeStepPCISPH.cpp:

Program Listing for File TimeStepPCISPH.cpp
===========================================

|exhale_lsh| :ref:`Return to documentation for file <file_SPlisHSPlasH_PCISPH_TimeStepPCISPH.cpp>` (``SPlisHSPlasH/PCISPH/TimeStepPCISPH.cpp``)

.. |exhale_lsh| unicode:: U+021B0 .. UPWARDS ARROW WITH TIP LEFTWARDS

.. code-block:: cpp

   #include "TimeStepPCISPH.h"
   #include "SPlisHSPlasH/TimeManager.h"
   #include "SPlisHSPlasH/SPHKernels.h"
   #include "SimulationDataPCISPH.h"
   #include <iostream>
   #include "Utilities/Timing.h"
   #include "SPlisHSPlasH/Simulation.h"
   #include "SPlisHSPlasH/BoundaryModel_Akinci2012.h"
   #include "SPlisHSPlasH/BoundaryModel_Koschier2017.h"
   #include "SPlisHSPlasH/BoundaryModel_Bender2019.h"
   
   
   using namespace SPH;
   using namespace std;
   using namespace GenParam;
   
   std::string TimeStepPCISPH::METHOD_NAME = "PCISPH";
   int TimeStepPCISPH::SOLVER_ITERATIONS = -1;
   int TimeStepPCISPH::MIN_ITERATIONS = -1;
   int TimeStepPCISPH::MAX_ITERATIONS = -1;
   int TimeStepPCISPH::MAX_ERROR = -1;
   
   TimeStepPCISPH::TimeStepPCISPH() :
       TimeStep()
   {
       m_simulationData.init();
       m_minIterations = 3;
       m_iterations = 0;
       m_maxIterations = 100;
       m_maxError = static_cast<Real>(0.01);
   
       Simulation *sim = Simulation::getCurrent();
       const unsigned int nModels = sim->numberOfFluidModels();
       for (unsigned int fluidModelIndex = 0; fluidModelIndex < nModels; fluidModelIndex++)
       {
           FluidModel *model = sim->getFluidModel(fluidModelIndex);
           model->addField({ "pressure", METHOD_NAME, FieldType::Scalar, [this, fluidModelIndex](const unsigned int i) -> Real* { return &m_simulationData.getPressure(fluidModelIndex, i); } });
           model->addField({ "advected density", METHOD_NAME, FieldType::Scalar, [this, fluidModelIndex](const unsigned int i) -> Real* { return &m_simulationData.getDensityAdv(fluidModelIndex, i); } });
           model->addField({ "pressure acceleration", METHOD_NAME, FieldType::Vector3, [this, fluidModelIndex](const unsigned int i) -> Real* { return &m_simulationData.getPressureAccel(fluidModelIndex, i)[0]; } });
       }
   }
   
   TimeStepPCISPH::~TimeStepPCISPH(void)
   {
       Simulation *sim = Simulation::getCurrent();
       const unsigned int nModels = sim->numberOfFluidModels();
       for (unsigned int fluidModelIndex = 0; fluidModelIndex < nModels; fluidModelIndex++)
       {
           FluidModel *model = sim->getFluidModel(fluidModelIndex);
           model->removeFieldByName("pressure");
           model->removeFieldByName("advected density");
           model->removeFieldByName("pressure acceleration");
       }
   }
   
   void TimeStepPCISPH::initParameters()
   {
       TimeStep::initParameters();
   
       SOLVER_ITERATIONS = createNumericParameter("iterations", "Iterations", &m_iterations);
       setGroup(SOLVER_ITERATIONS, "Simulation|PCISPH");
       setDescription(SOLVER_ITERATIONS, "Iterations required by the pressure solver.");
       getParameter(SOLVER_ITERATIONS)->setReadOnly(true);
   
       MIN_ITERATIONS = createNumericParameter("minIterations", "Min. iterations", &m_minIterations);
       setGroup(MIN_ITERATIONS, "Simulation|PCISPH");
       setDescription(MIN_ITERATIONS, "Minimal number of iterations of the pressure solver.");
       static_cast<NumericParameter<unsigned int>*>(getParameter(MIN_ITERATIONS))->setMinValue(0);
   
       MAX_ITERATIONS = createNumericParameter("maxIterations", "Max. iterations", &m_maxIterations);
       setGroup(MAX_ITERATIONS, "Simulation|PCISPH");
       setDescription(MAX_ITERATIONS, "Maximal number of iterations of the pressure solver.");
       static_cast<NumericParameter<unsigned int>*>(getParameter(MAX_ITERATIONS))->setMinValue(1);
   
       MAX_ERROR = createNumericParameter("maxError", "Max. density error(%)", &m_maxError);
       setGroup(MAX_ERROR, "Simulation|PCISPH");
       setDescription(MAX_ERROR, "Maximal density error (%).");
       static_cast<RealParameter*>(getParameter(MAX_ERROR))->setMinValue(static_cast<Real>(1e-6));
   }
   
   void TimeStepPCISPH::step()
   {
       Simulation *sim = Simulation::getCurrent();
       TimeManager *tm = TimeManager::getCurrent();
       const Real h = tm->getTimeStepSize();
       const unsigned int nModels = sim->numberOfFluidModels();
   
       for (unsigned int fluidModelIndex = 0; fluidModelIndex < nModels; fluidModelIndex++)
           clearAccelerations(fluidModelIndex);
   
       sim->performNeighborhoodSearch();
   
   #ifdef USE_PERFORMANCE_OPTIMIZATION
       precomputeValues();
   #endif
   
       if (sim->getBoundaryHandlingMethod() == BoundaryHandlingMethods::Bender2019)
           computeVolumeAndBoundaryX();
       else if (sim->getBoundaryHandlingMethod() == BoundaryHandlingMethods::Koschier2017)
           computeDensityAndGradient();
   
       for (unsigned int fluidModelIndex = 0; fluidModelIndex < nModels; fluidModelIndex++)
           computeDensities(fluidModelIndex);
   
       sim->computeNonPressureForces();
   
       sim->updateTimeStepSize();
   
       START_TIMING("pressureSolve");
       pressureSolve();
       STOP_TIMING_AVG;
   
       for (unsigned int fluidModelIndex = 0; fluidModelIndex < nModels; fluidModelIndex++)
       {
           FluidModel *model = sim->getFluidModel(fluidModelIndex);
           const int numParticles = (int)model->numActiveParticles();
   
           #pragma omp parallel default(shared)
           {
               #pragma omp for schedule(static)  
               for (int i = 0; i < numParticles; i++)
               {
                   if (model->getParticleState(i) == ParticleState::Active)
                   {
                       const Vector3r &accel = m_simulationData.getPressureAccel(fluidModelIndex, i);
                       Vector3r &x = model->getPosition(i);
                       Vector3r &v = model->getVelocity(i);
                       v += h * accel;
                       x += h * v;
                   }
               }
           }
       }
   
       sim->emitParticles();
       sim->animateParticles();
   
       // Compute new time     
       tm->setTime(tm->getTime() + h);
   }
   
   void TimeStepPCISPH::pressureSolve()
   {
       Simulation *sim = Simulation::getCurrent();
       const unsigned int nFluids = sim->numberOfFluidModels();
       const Real h = TimeManager::getCurrent()->getTimeStepSize();
   
       // Initialization
       for (unsigned int fluidModelIndex = 0; fluidModelIndex < nFluids; fluidModelIndex++)
       {
           FluidModel *model = sim->getFluidModel(fluidModelIndex);
           const int numParticles = (int)model->numActiveParticles();
           for (int i = 0; i < numParticles; i++)
           {
               Vector3r& vel = model->getVelocity(i);
               const Vector3r& accel = model->getAcceleration(i);
               if (model->getParticleState(i) == ParticleState::Active)
                   vel += h * accel;
   
               m_simulationData.getPressure(fluidModelIndex, i) = 0.0;
               m_simulationData.getPressureAccel(fluidModelIndex, i).setZero();
           }
       }
   
       Real avg_density_err = 0;
       m_iterations = 0;
       bool chk = false;
   
       while ((!chk || (m_iterations < m_minIterations)) && (m_iterations < m_maxIterations))
       {
           chk = true;
           for (unsigned int i = 0; i < nFluids; i++)
           {
               FluidModel *model = sim->getFluidModel(i);
               const Real density0 = model->getDensity0();
   
               avg_density_err = 0.0;
               pressureSolveIteration(i, avg_density_err);
   
               // Maximal allowed density fluctuation
               const Real eta = m_maxError * static_cast<Real>(0.01) * density0;  // maxError is given in percent
               chk = chk && (avg_density_err <= eta);
           }
   
           m_iterations++;
       }
   }
   
   void TimeStepPCISPH::pressureSolveIteration(const unsigned int fluidModelIndex, Real &avg_density_err)
   {
       Simulation *sim = Simulation::getCurrent();
       FluidModel *model = sim->getFluidModel(fluidModelIndex);
       const int numParticles = (int)model->numActiveParticles();
       if (numParticles == 0)
           return;
   
       const Real density0 = model->getDensity0();
       const Real h = TimeManager::getCurrent()->getTimeStepSize();
       const Real h2 = h*h;
       const Real invH2 = static_cast<Real>(1.0) / h2;
       const unsigned int nFluids = sim->numberOfFluidModels();
       const unsigned int nBoundaries = sim->numberOfBoundaryModels();
   
       #pragma omp parallel default(shared)
       {
           #pragma omp for schedule(static)  
           for (int i = 0; i < numParticles; i++)
           {
               if (model->getParticleState(i) == ParticleState::Active)
               {
                   const Vector3r accel = model->getAcceleration(i) + m_simulationData.getPressureAccel(fluidModelIndex, i);
                   Vector3r &predX = m_simulationData.getPredictedPosition(fluidModelIndex, i);
                   Vector3r &predV = m_simulationData.getPredictedVelocity(fluidModelIndex, i);
                   const Vector3r &x = model->getPosition(i);
                   const Vector3r &v = model->getVelocity(i);
                   predV = v + h * accel;
                   predX = x + h * predV;
                   if (sim->getBoundaryHandlingMethod() == BoundaryHandlingMethods::Bender2019)
                       computeVolumeAndBoundaryX(fluidModelIndex, i, predX);
                   else if (sim->getBoundaryHandlingMethod() == BoundaryHandlingMethods::Koschier2017)
                       computeDensityAndGradient(fluidModelIndex, i, predX);
               }
           }
       }
   
   
       // Predict density 
       #pragma omp parallel default(shared)
       {
           #pragma omp for schedule(static)  
           for (int i = 0; i < numParticles; i++)
           {
               const Vector3r &pred_xi = m_simulationData.getPredictedPosition(fluidModelIndex, i);
               Real &densityAdv = m_simulationData.getDensityAdv(fluidModelIndex, i);
               densityAdv = model->getVolume(i) * sim->W_zero();
                   
               // Fluid
               forall_fluid_neighbors(
                   const Vector3r & pred_xj = m_simulationData.getPredictedPosition(pid, neighborIndex);
                   densityAdv += fm_neighbor->getVolume(neighborIndex) * sim->W(pred_xi - pred_xj);
               );
   
               // Boundary
               if (sim->getBoundaryHandlingMethod() == BoundaryHandlingMethods::Akinci2012)
               {
                   forall_boundary_neighbors(
                       densityAdv += bm_neighbor->getVolume(neighborIndex) * sim->W(pred_xi - xj);
                   );
               }
               else if (sim->getBoundaryHandlingMethod() == BoundaryHandlingMethods::Koschier2017)
               {
                   forall_density_maps(
                       densityAdv += rho;
                   );
               }
               else if (sim->getBoundaryHandlingMethod() == BoundaryHandlingMethods::Bender2019)
               {
                   forall_volume_maps(
                       densityAdv += Vj * sim->W(pred_xi - xj);        
                   );
               }
   
               //densityAdv = max(densityAdv, static_cast<Real>(1.0));
               const Real density_err = density0 * (densityAdv - static_cast<Real>(1.0));
               Real &pressure = m_simulationData.getPressure(fluidModelIndex, i);
               pressure += invH2 * m_simulationData.getPCISPH_ScalingFactor(fluidModelIndex) * (densityAdv - static_cast<Real>(1.0));
               pressure = max(pressure, static_cast<Real>(0.0));
   
               #pragma omp atomic
               avg_density_err += density_err;
           }
       }
   
       avg_density_err /= numParticles;
   
       // Compute pressure forces
       #pragma omp parallel default(shared)
       {
           #pragma omp for schedule(static)  
           for (int i = 0; i < (int)numParticles; i++)
           {
               const Vector3r &xi = model->getPosition(i);
   
               Vector3r &ai = m_simulationData.getPressureAccel(fluidModelIndex, i);
               ai.setZero();
   
               const Real dpi = m_simulationData.getPressure(fluidModelIndex, i);  
   
               // Fluid
               forall_fluid_neighbors(
                   // Pressure 
                   const Real dpj = m_simulationData.getPressure(pid, neighborIndex);
                   ai -= fm_neighbor->getVolume(neighborIndex) * (dpi + (fm_neighbor->getDensity0() / density0) * dpj) * sim->gradW(xi - xj);
               );
   
               // Boundary
               if (sim->getBoundaryHandlingMethod() == BoundaryHandlingMethods::Akinci2012)
               {
                   forall_boundary_neighbors(
                       // Pressure 
                       const Vector3r a = bm_neighbor->getVolume(neighborIndex) * dpi * sim->gradW(xi - xj);
                       ai -= a;
                       bm_neighbor->addForce(xj, model->getMass(i) * a);
                   );
               }
               else if (sim->getBoundaryHandlingMethod() == BoundaryHandlingMethods::Koschier2017)
               {
                   forall_density_maps(
                       const Vector3r a = -dpi * gradRho;
                       ai -= a;
                       bm_neighbor->addForce(xj, model->getMass(i) * a);
                   );
               }
               else if (sim->getBoundaryHandlingMethod() == BoundaryHandlingMethods::Bender2019)
               {
                   forall_volume_maps(
                       const Vector3r a = Vj *dpi * sim->gradW(xi - xj);       
                       ai -= a;
                       bm_neighbor->addForce(xj, model->getMass(i) * a);
                   );
               }
           }
       }
   }
   
   void TimeStepPCISPH::reset()
   {
       TimeStep::reset();
       m_simulationData.reset();
       m_iterations = 0;
   }
   
   void TimeStepPCISPH::performNeighborhoodSearchSort()
   {
       m_simulationData.performNeighborhoodSearchSort();
   }
   
   void TimeStepPCISPH::emittedParticles(FluidModel *model, const unsigned int startIndex)
   {
       m_simulationData.emittedParticles(model, startIndex);
   }
   
   void TimeStepPCISPH::resize()
   {
       m_simulationData.init();
   }