rpg/fts/brownian/LMBdStep.tpp

#ifndef RPG_LM_BD_STEP_TPP
#define RPG_LM_BD_STEP_TPP
 
/*
* PSCF - Polymer Self-Consistent Field
*
* Copyright 2015 - 2025, The Regents of the University of Minnesota
* Distributed under the terms of the GNU General Public License.
*/
 
#include "LMBdStep.h"
 
#include <rpg/fts/brownian/BdSimulator.h>
#include <rpg/fts/compressor/Compressor.h>
#include <rpg/system/System.h>
#include <rpg/solvers/Mixture.h>
#include <rpg/field/Domain.h>
#include <prdc/cuda/VecOp.h>
#include <pscf/math/IntVec.h>
#include <pscf/cuda/CudaRandom.h>
 
namespace Pscf {
namespace Rpg {
 
   using namespace Util;
   using namespace Pscf::Prdc;
   using namespace Pscf::Prdc::Cuda;
 
   /*
   * Constructor.
   */
   template <int D>
   LMBdStep<D>::LMBdStep(BdSimulator<D>& simulator)
    : BdStep<D>(simulator),
      w_(),
      etaA_(),
      etaB_(),
      dwc_(),
      etaNewPtr_(0),
      etaOldPtr_(0),
      mobility_(0.0)
   {}
 
   /*
   * Destructor, empty default implementation.
   */
   template <int D>
   LMBdStep<D>::~LMBdStep()
   {}
 
   /*
   * ReadParameters, empty default implementation.
   */
   template <int D>
   void LMBdStep<D>::readParameters(std::istream &in)
   {
      read(in, "mobility", mobility_);
 
      int nMonomer = system().mixture().nMonomer();
      int meshSize = system().domain().mesh().size();
      IntVec<D> meshDimensions = system().domain().mesh().dimensions();
 
      // Allocate memory for private containers
      w_.allocate(nMonomer);
      for (int i=0; i < nMonomer; ++i) {
         w_[i].allocate(meshDimensions);
      }
      etaA_.allocate(nMonomer-1);
      etaB_.allocate(nMonomer-1);
      for (int i=0; i < nMonomer - 1; ++i) {
         etaA_[i].allocate(meshDimensions);
         etaB_[i].allocate(meshDimensions);
      }
      dwc_.allocate(meshDimensions);
      gaussianField_.allocate(meshDimensions);
   }
 
   /*
   * Generate new random displacement values
   */
   template <int D>
   void LMBdStep<D>::generateEtaNew()
   {
      const int nMonomer = system().mixture().nMonomer();
      const int meshSize = system().domain().mesh().size();
      
      // Prefactor b for displacements
      const double vSystem = system().domain().unitCell().volume();
      double b = sqrt(0.5*mobility_*double(meshSize)/vSystem);
 
      // Constants for normal distribution
      double stddev = 1.0;
      double mean = 0;
 
      int j;
      for (j = 0; j < nMonomer - 1; ++j) {
         RField<D>& eta = etaNew(j);
        
         // Generate normal distributed random floating point numbers
         cudaRandom().normal(gaussianField_, stddev, mean);
         VecOp::mulVS(eta, gaussianField_, b);
      
      }
   }
 
   template <int D>
   void LMBdStep<D>::exchangeOldNew()
   {
      DArray< RField<D> >* temp;
      temp = etaOldPtr_;
      etaOldPtr_ = etaNewPtr_;
      etaNewPtr_ = temp;
   }
 
   /*
   * Initial setup before main simulation loop.
   */
   template <int D>
   void LMBdStep<D>::setup()
   {
      int nMonomer = system().mixture().nMonomer();
      int meshSize = system().domain().mesh().size();
 
      // Check array capacities
      UTIL_CHECK(etaA_.capacity() == nMonomer-1);
      UTIL_CHECK(etaB_.capacity() == nMonomer-1);
      for (int i=0; i < nMonomer - 1; ++i) {
         UTIL_CHECK(etaA_[i].capacity() == meshSize);
         UTIL_CHECK(etaB_[i].capacity() == meshSize);
      }
      UTIL_CHECK(dwc_.capacity() == meshSize);
 
      // Initialize pointers
      etaOldPtr_ = &etaA_;
      etaNewPtr_ = &etaB_;
 
      generateEtaNew();
      exchangeOldNew();
   }
 
   /*
   * One step of Leimkuhler-Matthews BD algorithm.
   */
   template <int D>
   bool LMBdStep<D>::step()
   {
      // Array sizes and indices
      const int nMonomer = system().mixture().nMonomer();
      const int meshSize = system().domain().mesh().size();
      int i, j;
      
      // Save current state
      simulator().saveState();
      
      // Copy current W fields from parent system into w_
      for (i = 0; i < nMonomer; ++i) {
         VecOp::eqV(w_[i], system().w().rgrid(i));
      }
 
      // Generate new random displacement values
      generateEtaNew();
 
      // Take LM step:
      double a = -1.0*mobility_;
      double evec;
      
      // Loop over composition eigenvectors of projected chi matrix
      for (j = 0; j < nMonomer - 1; ++j) {
         RField<D> const & etaN = etaNew(j);
         RField<D> const & etaO = etaOld(j);
         RField<D> const & dc = simulator().dc(j);
         VecOp::addVcVcVc(dwc_, etaN, 1.0, etaO, 1.0, dc, a);
         // Loop over monomer types
         for (i = 0; i < nMonomer; ++i) {
            RField<D> & w = w_[i];
            evec = simulator().chiEvecs(j,i);
            VecOp::addEqVc(w, dwc_, evec);
         }
      }
 
      // Set modified fields 
      system().w().setRGrid(w_);
      
      // Enforce incompressibility (also solves MDE repeatedly)
      bool isConverged = false;
      int compress = simulator().compressor().compress();
      if (compress != 0){
         simulator().restoreState();
      } else{
         isConverged = true;
         UTIL_CHECK(system().c().hasData());
         
         // Compute components and derivatives at wp_
         simulator().clearState();
         simulator().clearData();
         simulator().computeWc();
         simulator().computeCc();
         simulator().computeDc();
 
         // Exchange old and new random fields
         exchangeOldNew();
         
      }
      
      return isConverged;
     
   }
 
}
}
#endif