// Copyright (c) 2017, Lawrence Livermore National Security, LLC.
// Produced at the Lawrence Livermore National Laboratory (LLNL).
// Written by Cosmin G. Petra, petra1@llnl.gov.
// LLNL-CODE-742473. All rights reserved.
//
// This file is part of HiOp. For details, see https://github.com/LLNL/hiop. HiOp 
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// Please also read “Additional BSD Notice” below.
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#ifndef HIOP_KRONRED
#define HIOP_KRONRED

#include "hiop_blasdefs.hpp"
#include "hiopMatrixComplexSparseTriplet.hpp"
#include "hiopMatrixComplexDense.hpp"

#include <string>
#include <vector>
#include <map>

namespace hiop
{
  //forward defs
  class hiopLinSolverUMFPACKZ;
  class hiopMatrixComplexDense;
  
  /* Utility to perform the Kron reduction of the Ybus matrix (sparse symmetric complex)
   * into the reduced Ybus (dense symmetric complex) matrix
   */
  class hiopKronReduction
  {
  public:
    hiopKronReduction();
    virtual ~hiopKronReduction();
    
    /* Performs the Kron reduction (computes Schur complement)
     * In parameters
     *  - idx_nonaux_buses, idx_aux_buses: indexes of the auxiliary and non-auxiliary 
     * buses (in the rows/cols of Ybus)
     *  - Ybus
     * Out parameters
     *  - Ybus_red: reduced Ybus of size (nonaux,nonaux) = Yaa - Yab'*(Ybb\Yba)
     *
     * The function factorizes Ybb and stores the factorization for later use, for example for use
     * in @axpy_nonaux_to_aux
     */
    bool go(const std::vector<int>& idx_nonaux_buses, const std::vector<int>& idx_aux_buses,
	    const hiopMatrixComplexSparseTriplet& Ybus, 
	    hiopMatrixComplexDense& Ybus_red);

    /** 
     * Performs v_aux_out = (Ybb\Yba)* v_nonaux_in
     */
    bool apply_nonaux_to_aux(const std::vector<std::complex<double> >& v_nonaux_in,
			    std::vector<std::complex<double> >& v_aux_out);

    const hiopMatrixComplexDense& map_nonaux_to_aux() const
    {
      return *map_nonaux_to_aux_;
    } 
  private:
    hiopLinSolverUMFPACKZ* linsolver_;
    hiopMatrixComplexDense* map_nonaux_to_aux_;
  };

} //end namespace
#endif
