MueLu_PreserveDirichletAggregationAlgorithm_kokkos_def.hpp

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#ifndef MUELU_PRESERVEDIRICHLETAGGREGATIONALGORITHM_KOKKOS_DEF_HPP
#define MUELU_PRESERVEDIRICHLETAGGREGATIONALGORITHM_KOKKOS_DEF_HPP

#ifdef HAVE_MUELU_KOKKOS_REFACTOR

#include <Teuchos_Comm.hpp>
#include <Teuchos_CommHelpers.hpp>

#include <Xpetra_Vector.hpp>

#include "MueLu_PreserveDirichletAggregationAlgorithm_kokkos.hpp"

#include "MueLu_LWGraph_kokkos.hpp"
#include "MueLu_Aggregates_kokkos.hpp"
#include "MueLu_Exceptions.hpp"
#include "MueLu_Monitor.hpp"

namespace MueLu {

  template <class LocalOrdinal, class GlobalOrdinal, class Node>
  void PreserveDirichletAggregationAlgorithm_kokkos<LocalOrdinal, GlobalOrdinal, Node>::
  BuildAggregates(Teuchos::ParameterList const & params,
                  LWGraph_kokkos const & graph,
                  Aggregates_kokkos & aggregates,
                  Kokkos::View<unsigned*, typename LWGraph_kokkos::memory_space>& aggStat,
                  LO& numNonAggregatedNodes) const {
    Monitor m(*this, "BuildAggregates");
    using local_ordinal_type = typename LWGraph_kokkos::local_ordinal_type;

    // Extract parameters and data from:
    // 1) the parameter list
    const bool preserve = params.get<bool>("aggregation: preserve Dirichlet points");

    // 2) the amalgamated graph
    const LO  numNodes  = graph.GetNodeNumVertices();
    const int myRank    = graph.GetComm()->getRank();

    // 3) the aggregates
    auto vertex2AggId   = aggregates.GetVertex2AggId()->template getLocalView<memory_space>();
    auto procWinner     = aggregates.GetProcWinner()  ->template getLocalView<memory_space>();

    // A view is needed to count on the fly the current number of local aggregates
    Kokkos::View<LO, memory_space> aggCount("aggCount");
    if(preserve) {
      Kokkos::deep_copy(aggCount, aggregates.GetNumAggregates());
    }
    Kokkos::parallel_for("MueLu - PreserveDirichlet: tagging ignored nodes",
                         Kokkos::RangePolicy<local_ordinal_type, execution_space>(0, numNodes),
                         KOKKOS_LAMBDA(const local_ordinal_type nodeIdx) {
                           if (aggStat(nodeIdx) == BOUNDARY) {
                             aggStat(nodeIdx) = IGNORED;
                             const LO aggIdx = Kokkos::atomic_fetch_add(&aggCount(), 1);

                             if (preserve) {
                               // aggregates.SetIsRoot(nodeIdx);

                               vertex2AggId(nodeIdx, 0) = aggIdx;
                               procWinner(nodeIdx, 0)   = myRank;
                             }
                           }
                         });
    typename Kokkos::View<LO, memory_space>::HostMirror aggCount_h
      = Kokkos::create_mirror_view(aggCount);
    Kokkos::deep_copy(aggCount_h, aggCount);
    // In this phase the number of new aggregates is the same
    // as the number of newly aggregated nodes.
    numNonAggregatedNodes -= (aggCount_h() - aggregates.GetNumAggregates());

    // update aggregate object
    if(preserve) {
      aggregates.SetNumAggregates(aggCount_h());
    }
  }

} // end namespace

#endif // HAVE_MUELU_KOKKOS_REFACTOR
#endif // MUELU_PRESERVEDIRICHLETAGGREGATIONALGORITHM_KOKKOS_DEF_HPP