/*************************************************************************
 *                                                                       *
 * Vega FEM Simulation Library Version 4.0                               *
 *                                                                       *
 * "sparseSolver" library , Copyright (C) 2007 CMU, 2009 MIT, 2018 USC   *
 * All rights reserved.                                                  *
 *                                                                       *
 * Code authors: Hongyi Xu, Jernej Barbic                                *
 * http://www.jernejbarbic.com/vega                                      *
 *                                                                       *
 * Research: Jernej Barbic, Hongyi Xu, Yijing Li,                        *
 *           Danyong Zhao, Bohan Wang,                                   *
 *           Fun Shing Sin, Daniel Schroeder,                            *
 *           Doug L. James, Jovan Popovic                                *
 *                                                                       *
 * Funding: National Science Foundation, Link Foundation,                *
 *          Singapore-MIT GAMBIT Game Lab,                               *
 *          Zumberge Research and Innovation Fund at USC,                *
 *          Sloan Foundation, Okawa Foundation,                          *
 *          USC Annenberg Foundation                                     *
 *                                                                       *
 * This library is free software; you can redistribute it and/or         *
 * modify it under the terms of the BSD-style license that is            *
 * included with this library in the file LICENSE.txt                    *
 *                                                                       *
 * This library is distributed in the hope that it will be useful,       *
 * but WITHOUT ANY WARRANTY; without even the implied warranty of        *
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the file     *
 * LICENSE.TXT for more details.                                         *
 *                                                                       *
 *************************************************************************/

/*
  Helper class for the ARPACK solver.
*/

#ifndef _ZTAZMULTIPLICATOR_H_
#define _ZTAZMULTIPLICATOR_H_

#include "sparseMatrix.h"
#include "matrix.h"

namespace vega 
{

/*
  computes x |--> Z^T A Z x

  Z = P [ -C_p^{-1} C_n  ]
        [   I            ]
*/

class ZTAZMultiplicator
{
public:
  ZTAZMultiplicator(SparseMatrix * A, SparseMatrix * P, Matrix<double> * invCp, Matrix<double> * Cn);
  ~ZTAZMultiplicator();
  void Multiply(const double * x, double * output);

protected:
  SparseMatrix * A;
  SparseMatrix * P;
  Matrix<double> * invCp;
  Matrix<double> * Cn;
  Matrix<double> * invCpCn;
  Matrix<double> * invCpCnT;
  double * buffer1;
  double * buffer2;
};

} // namespace vega

#endif

