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//   Zoltan2: A package of combinatorial algorithms for scientific computing
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#ifndef _ZOLTAN2_ALGSPECTRAL_HPP_
#define _ZOLTAN2_ALGSPECTRAL_HPP_

#include <Zoltan2_Algorithm.hpp>
#include <Zoltan2_GraphModel.hpp>
#include <Zoltan2_OrderingSolution.hpp>


////////////////////////////////////////////////////////////////////////
//! \file Zoltan2_AlgSpectral.hpp
//! \brief Spectral ordering of a graph (local or global).
//! \brief Sorts the Fiedler vector of the graph Laplacian.


namespace Zoltan2{

template <typename Adapter>
int AlgSpectral(
  const RCP<GraphModel<Adapter> > &model, 
  //const RCP<Adapter> &matrixadapter, // Hack: Use matrix adapter directly
  const RCP<OrderingSolution<typename Adapter::lno_t,
                             typename Adapter::gno_t> > &solution,
  const RCP<Teuchos::ParameterList> &pl,
  const RCP<const Teuchos::Comm<int> > &comm
) 
{
#ifndef INCLUDE_ZOLTAN2_EXPERIMENTAL

  Z2_THROW_EXPERIMENTAL("Zoltan2 Spectral ordering is strictly "
                        "experimental software "
                        "while it is being developed and tested.")

#else //INCLUDE_ZOLTAN2_EXPERIMENTAL

  typedef typename Adapter::lno_t lno_t;
  typedef typename Adapter::gno_t gno_t;
  typedef typename Adapter::scalar_t scalar_t;

  int ierr= 0;

  HELLO;

// TODO: Check params to do local or global ordering.
  bool localOrder = true;

  const size_t nVtx = model->getLocalNumVertices();
  lno_t *perm;
  perm = (lno_t *) (solution->getPermutationRCP().getRawPtr());
  for (lno_t i=0; i<nVtx; i++){
    perm[i] = -1;
  }

  // Get local graph.
  ArrayView<const gno_t> edgeIds;
  ArrayView<const lno_t> offsets;
  ArrayView<StridedData<lno_t, scalar_t> > wgts;

  model->getEdgeList(edgeIds, offsets, wgts);

  //cout << "Debug: Local graph from getLocalEdgeList" << endl;
  //cout << "edgeIds: " << edgeIds << endl;
  //cout << "offsets: " << offsets << endl;

  // Form the graph Laplacian: L = D-A
  // Create a new Tpetra matrix, but use views of existing data when possible.
  // TODO

  // TODO: Find smallest eigenvalues using Anasazi

  // TODO: Sort Fiedler vector.

  solution->setHavePerm(true);
  return ierr;
#endif // INCLUDE_ZOLTAN2_EXPERIMENTAL
}

}
#endif
