ilusubdomainsolver.hh

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// SPDX-FileCopyrightText: Copyright © DUNE Project contributors, see file LICENSE.md in module root
// SPDX-License-Identifier: LicenseRef-GPL-2.0-only-with-DUNE-exception
// -*- tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 2 -*-
// vi: set et ts=4 sw=2 sts=2:
#ifndef DUNE_ISTL_ILUSUBDOMAINSOLVER_HH
#define DUNE_ISTL_ILUSUBDOMAINSOLVER_HH
 
#include <map>
#include <dune/common/typetraits.hh>
#include <dune/istl/preconditioners.hh>
#include "matrix.hh"
#include <cmath>
#include <cstdlib>
 
namespace Dune {
 
  template<class M, class X, class Y>
  class ILUSubdomainSolver  {
  public:
    typedef typename std::remove_const<M>::type matrix_type;
    typedef X domain_type;
    typedef Y range_type;
 
    virtual void apply (X& v, const Y& d) =0;
 
    virtual ~ILUSubdomainSolver()
    {}
 
  protected:
    template<class S>
    std::size_t copyToLocalMatrix(const M& A, S& rowset);
 
    // for ILUN
    matrix_type ILU;
  };
 
  template<class M, class X, class Y>
  class ILU0SubdomainSolver
    : public ILUSubdomainSolver<M,X,Y>{
  public:
    typedef typename std::remove_const<M>::type matrix_type;
    typedef typename std::remove_const<M>::type rilu_type;
    typedef X domain_type;
    typedef Y range_type;
 
 
    void apply (X& v, const Y& d)
    {
      ILU::blockILUBacksolve(this->ILU,v,d);
    }
    template<class S>
    void setSubMatrix(const M& A, S& rowset);
 
  };
 
  template<class M, class X, class Y>
  class ILUNSubdomainSolver
    : public ILUSubdomainSolver<M,X,Y>{
  public:
    typedef typename std::remove_const<M>::type matrix_type;
    typedef typename std::remove_const<M>::type rilu_type;
    typedef X domain_type;
    typedef Y range_type;
 
    void apply (X& v, const Y& d)
    {
      ILU::blockILUBacksolve(RILU,v,d);
    }
 
    template<class S>
    void setSubMatrix(const M& A, S& rowset);
 
  private:
    rilu_type RILU;
  };
 
 
 
  template<class M, class X, class Y>
  template<class S>
  std::size_t ILUSubdomainSolver<M,X,Y>::copyToLocalMatrix(const M& A, S& rowSet)
  {
    // Calculate consecutive indices for local problem
    // while preserving the ordering
    typedef typename M::size_type size_type;
    typedef std::map<typename S::value_type,size_type> IndexMap;
    typedef typename IndexMap::iterator IMIter;
    IndexMap indexMap;
    IMIter guess = indexMap.begin();
    size_type localIndex=0;
 
    typedef typename S::const_iterator SIter;
    for(SIter rowIdx = rowSet.begin(), rowEnd=rowSet.end();
        rowIdx!= rowEnd; ++rowIdx, ++localIndex)
      guess = indexMap.insert(guess,
                              std::make_pair(*rowIdx,localIndex));
 
 
    // Build Matrix for local subproblem
    ILU.setSize(rowSet.size(),rowSet.size());
    ILU.setBuildMode(matrix_type::row_wise);
 
    // Create sparsity pattern
    typedef typename matrix_type::CreateIterator CIter;
    CIter rowCreator = ILU.createbegin();
    std::size_t offset=0;
    for(SIter rowIdx = rowSet.begin(), rowEnd=rowSet.end();
        rowIdx!= rowEnd; ++rowIdx, ++rowCreator) {
      // See which row entries are in our subset and add them to
      // the sparsity pattern
      guess = indexMap.begin();
 
      for(typename matrix_type::ConstColIterator col=A[*rowIdx].begin(),
          endcol=A[*rowIdx].end(); col != endcol; ++col) {
        // search for the entry in the row set
        guess = indexMap.find(col.index());
        if(guess!=indexMap.end()) {
          // add local index to row
          rowCreator.insert(guess->second);
          offset=std::max(offset,(std::size_t)std::abs((int)(guess->second-rowCreator.index())));
        }
      }
 
    }
 
    // Insert the matrix values for the local problem
    typename matrix_type::iterator iluRow=ILU.begin();
 
    for(SIter rowIdx = rowSet.begin(), rowEnd=rowSet.end();
        rowIdx!= rowEnd; ++rowIdx, ++iluRow) {
      // See which row entries are in our subset and add them to
      // the sparsity pattern
      typename matrix_type::ColIterator localCol=iluRow->begin();
      for(typename matrix_type::ConstColIterator col=A[*rowIdx].begin(),
          endcol=A[*rowIdx].end(); col != endcol; ++col) {
        // search for the entry in the row set
        guess = indexMap.find(col.index());
        if(guess!=indexMap.end()) {
          // set local value
          (*localCol)=(*col);
          ++localCol;
        }
      }
    }
    return offset;
  }
 
 
  template<class M, class X, class Y>
  template<class S>
  void ILU0SubdomainSolver<M,X,Y>::setSubMatrix(const M& A, S& rowSet)
  {
    this->copyToLocalMatrix(A,rowSet);
    ILU::blockILU0Decomposition(this->ILU);
  }
 
  template<class M, class X, class Y>
  template<class S>
  void ILUNSubdomainSolver<M,X,Y>::setSubMatrix(const M& A, S& rowSet)
  {
    std::size_t offset=copyToLocalMatrix(A,rowSet);
    RILU.setSize(rowSet.size(),rowSet.size(), (1+2*offset)*rowSet.size());
    RILU.setBuildMode(matrix_type::row_wise);
    ILU::blockILUDecomposition(this->ILU, (offset+1)/2, RILU);
  }
 
} // end name space DUNE
 
 
#endif