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#include "ROL_EqualityConstraint.hpp"
#include "ROL_LinearOperator.hpp"


#ifndef ROL_LINEAR_EQUALITY_CONSTRAINT_H
#define ROL_LINEAR_EQUALITY_CONSTRAINT_H


/** @ingroup func_group
    \class ROL::LinearEqualityConstraint
    \brief Provides the interface to evaluate linear equality constraints.

    This class implements the linear equality constraint
    \f[
       c(x) = Ax-b
    \f]

    Where A is a linear operator

    ---
*/

namespace ROL {

template <class Real>
class LinearEqualityConstraint : public EqualityConstraint<Real> {
private:
  const Teuchos::RCP<const LinearOperator<Real> > A_;
  const Teuchos::RCP<const LinearOperator<Real> > Atrans_;
  const Teuchos::RCP<const Vector<Real> > b_;
  bool  isSymmetric_;
public:
  // Nonsymmetric case
  LinearEqualityConstraint( const Teuchos::RCP<const LinearOperator<Real> > &A,
                            const Teuchos::RCP<const LinearOperator<Real> > &Atrans,
                            const Teuchos::RCP<const Vector<Real> &b ) :
      A_(A), Atrans_(Atrans), b_(b), isSymmetric_(false) {
  }
  // Symmetric case
  LinearEqualityConstraint( const Teuchos::RCP<const LinearOperator<Real> > &A,
                            const Teuchos::RCP<const Vector<Real> &b ) : 
      A_(A), Atrans_(A), b_(b), isSymmetric_(true) {
  }

  void value(Vector<Real> &c, const Vector<Real> &x, Real &tol) {
    A_->apply(c,x,tol);
    c_->axpy(-1.0,*b_);
  }

  void applyJacobian(Vector<Real> &jv, const Vector<Real> &v, 
                     const Vector<Real> &x, Real &tol) {
    A_->apply(jv,v,tol);
  }
 
  void applyAdjointJacobian(Vector<Real> &ajv, const Vector<Real> &v,
                            const Vector<Real> &x, Real &tol) {
    Atrans_->apply(ajv,v,tol);
  }

  void applyAdjointHessian(Vector<Real> &ahuv, const Vector<Real> &u, const Vector<Real> &v,
                           const Vector<Real> &x, Real &tol) {
    ahuv.zero();
  }

  void update( const Vector<Real> &x, bool flag = true, int iter = -1 ) {
    A_->update(x,flag,iter);
    if( !isSymmetric_ ) {
      A_->update(x,flag,iter);
    }
  }
}; // class LinearEqualityConstraint


} // namespace ROL

#endif //ROL_LINEAR_EQUALITY_CONSTRAINT_H
