ROL_NullSpaceOperator.hpp

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// @HEADER
// *****************************************************************************
//               Rapid Optimization Library (ROL) Package
//
// Copyright 2014 NTESS and the ROL contributors.
// SPDX-License-Identifier: BSD-3-Clause
// *****************************************************************************
// @HEADER

#ifndef ROL_NULL_SPACE_OPERATOR_H
#define ROL_NULL_SPACE_OPERATOR_H

#include "ROL_LinearOperator.hpp"
#include "ROL_Constraint.hpp"

namespace ROL {

template <class Real>
class NullSpaceOperator : public LinearOperator<Real> {
private:
  const Ptr<Constraint<Real>> con_;
  const Ptr<Vector<Real>> x_;
  const bool useAugSys_;

  mutable Ptr<Vector<Real>> b1_;
  mutable Ptr<Vector<Real>> b1dual_;
  mutable Ptr<Vector<Real>> b2_;
  mutable Ptr<Vector<Real>> mul_;

  int dim_;
  Real b1sqr_;

public:
  virtual ~NullSpaceOperator() {}
  NullSpaceOperator(const Ptr<Constraint<Real>> &con,
                    const Vector<Real> &dom,
                    const Vector<Real> &ran,
                    const bool useAugSys = false)
    : con_(con), x_(dom.clone()), useAugSys_(useAugSys) {
    x_->set(dom);
    dim_ = ran.dimension();
    if (dim_==1 && !useAugSys_) {
      Real tol = std::sqrt(ROL_EPSILON<Real>());
      b1_     = dom.dual().clone();
      b1dual_ = dom.clone();
      b2_     = ran.dual().clone(); b2_->setScalar(1.0);
      con_->applyAdjointJacobian(*b1_,*b2_,dom,tol);
      b1dual_->set(b1_->dual());
      b1sqr_ = b1_->dot(*b1_);
    }
    else {
      b1_  = dom.dual().clone();
      b2_  = ran.clone();
      mul_ = ran.dual().clone();
    }
  }

  NullSpaceOperator(const Ptr<Constraint<Real>>   &con,
                    const Ptr<const Vector<Real>> &dom,
                    const Ptr<const Vector<Real>> &ran)
    : NullSpaceOperator(con,*dom,*ran) {}

  virtual void update( const Vector<Real> &x, bool flag = true, int iter = -1 ) {
    x_->set(x);
    if (dim_==1 && !useAugSys_) {
      Real tol = std::sqrt(ROL_EPSILON<Real>());
      con_->applyAdjointJacobian(*b1_,*b2_,x,tol);
      b1dual_->set(b1_->dual());
      b1sqr_ = b1_->dot(*b1_);
    }
  }

  virtual void apply( Vector<Real> &Hv, const Vector<Real> &v, Real &tol ) const {
    if (dim_==1 && !useAugSys_) {
      Real dot = v.dot(*b1dual_);
      Hv.set(v);
      Hv.axpy(-dot/b1sqr_,*b1dual_);
    }
    else {
      b1_->set(v.dual()); b2_->zero();
      con_->solveAugmentedSystem(Hv,*mul_,*b1_,*b2_,*x_,tol);
    }
  }

  void applyAdjoint( Vector<Real> &Hv, const Vector<Real> &v, Real &tol ) const {
    apply(Hv,v,tol);
  }

  void applyInverse( Vector<Real> &Hv, const Vector<Real> &v, Real &tol ) const {
    throw Exception::NotImplemented(">>> NullSpaceOperator::applyInverse : Not Implemented!");
  }

  void applyAdjointInverse( Vector<Real> &Hv, const Vector<Real> &v, Real &tol ) const {
    throw Exception::NotImplemented(">>> NullSpaceOperator::applyAdjointInverse : Not Implemented!");
  }

}; // class NullSpaceOperator

} // namespace ROL

#endif