istl/descriptors.hh

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// -*- tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 2 -*-
// vi: set et ts=4 sw=2 sts=2:
#ifndef DUNE_PDELAB_BACKEND_ISTL_DESCRIPTORS_HH
#define DUNE_PDELAB_BACKEND_ISTL_DESCRIPTORS_HH
 
#include <dune/pdelab/backend/interface.hh>
#include <dune/pdelab/backend/istl/forwarddeclarations.hh>
#include <dune/pdelab/backend/istl/matrixhelpers.hh>
#include <dune/pdelab/backend/istl/utility.hh>
#include <cstddef>
 
namespace Dune {
  namespace PDELab {
 
#ifndef DOXYGEN
      template<typename T>
      constexpr bool deactivate_standard_blocking_for_ordering(const T&)
      {
        return false;
      }
#endif
 
    namespace ISTL {
 
      enum class Blocking
      {
        none,
        bcrs,
 
        fixed,
      };
 
      struct vector_backend_tag {};
 
      template<Blocking blocking = Blocking::none, std::size_t block_size_ = 0>
      struct VectorBackend
      {
 
        using tag = vector_backend_tag;
 
        using size_type = std::size_t;
 
        static const size_type blockSize = block_size_;
 
        struct Traits
        {
          static const Blocking block_type = blocking;
          static const size_type block_size = block_size_;
 
          static const bool blocked = blocking != Blocking::none;
 
          static const size_type max_blocking_depth = blocked ? 1 : 0;
        };
 
        template<typename GFS>
        bool blocked(const GFS& gfs) const
        {
          if (deactivate_standard_blocking_for_ordering(gfs.orderingTag()))
            return false;
          // We have to make an exception for static blocking and block_size == 1:
          // In that case, the ISTL backends expect the redundant index information
          // at that level to be elided, and keeping it in here will break vector
          // and matrix accesses.
          // To work around that problem, we override the user and just turn off
          // blocking internally.
          // A bock size of 0 also needs special handling, as it is actually a marker for
          // automatic block size deduction
          return Traits::blocked && (blocking != Blocking::fixed || !GFS::isLeaf || block_size_ > 1 || block_size_ == 0);
        }
 
      };
 
    }
 
  } // namespace PDELab
} // namespace Dune
 
 
#endif // DUNE_PDELAB_BACKEND_ISTL_DESCRIPTORS_HH