matrixTraits.hh

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/* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * */
/*                                                                           */
/*  This file is part of the library KASKADE 7                               */
/*  https://www.zib.de/research/projects/kaskade7-finite-element-toolbox     */
/*                                                                           */
/*  Copyright (C) 2015-2016 Zuse Institute Berlin                            */
/*                                                                           */
/*  KASKADE 7 is distributed under the terms of the ZIB Academic License.    */
/*    see $KASKADE/academic.txt                                              */
/*                                                                           */
/* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * */
 
#ifndef LINALG_MATRIX_TRAITS
#define LINALG_MATRIX_TRAITS
 
// forward declarations
namespace Dune
{
  template <class Scalar, int n, int m>                          class FieldMatrix;
  template <class Scalar, int n>                                 class FieldVector;
  template <class Entry, class Allocator>                        class BlockVector;
}
 
namespace Kaskade 
{
  // forward declaration
  template <class Entry, class Index> class NumaBCRSMatrix;
 
  // --------------------------------------------------------------------------------------
  
  template <class Matrix>
  struct MatrixTraits
  {
    using NaturalDomain = void;
    
    using NaturalRange = void;
 
    static bool isSquare(Matrix const& A);
  };
  
  template <class Scalar, int n, int m>
  struct MatrixTraits<Dune::FieldMatrix<Scalar,n,m>>
  {
    using NaturalDomain = Dune::FieldVector<Scalar,m>;
    using NaturalRange = Dune::FieldVector<Scalar,n>;
 
    constexpr static bool isSquare(Dune::FieldMatrix<Scalar,n,m> const&)
    {
      return n==m;    // has to have the same number of rows and columns
    }
  };
  
  template <class Entry, class Index>
  struct MatrixTraits<NumaBCRSMatrix<Entry,Index>>
  {
    using NaturalDomain = Dune::BlockVector<typename MatrixTraits<Entry>::NaturalDomain>;
    using NaturalRange  = Dune::BlockVector<typename MatrixTraits<Entry>::NaturalRange>;
 
    static bool isSquare(NumaBCRSMatrix<Entry,Index> const& A)
    {
      int n = A.N();
 
      if (A.M() != n)                                     // matrix needs to have the same number
        return false;                                     // of rows and columns - otherwise it's not square
 
      for (int i=0; i<n; ++i)                             // and every diagonal entry needs to be square
        if ( ! MatrixTraits<Entry>::isSquare(A[i][i]) )   // otherwise it's not square
          return false;
 
      return true;                                        // everything's ok - we're square
    }
  };
}
 
#endif