ROL_LinearOperatorSum.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_LINEAROPERATORSUM_H
#define ROL_LINEAROPERATORSUM_H
 
#include "ROL_LinearOperator.hpp"
 
namespace ROL {
 
template <class Real>
class LinearOperatorSum : public LinearOperator<Real>  {
 
  typedef Vector<Real>         V;
  typedef LinearOperator<Real> OP;
 
  typedef typename std::vector<ROL::Ptr<OP> >::size_type size_type;
 
private:
 
  ROL::Ptr<std::vector<ROL::Ptr<OP> > > ops_;
  ROL::Ptr<V> scratch_;
 
public:
 
  LinearOperatorSum( ROL::Ptr<OP> &A, 
                     ROL::Ptr<OP> &B, 
                     ROL::Ptr<V> & scratch ) :
    scratch_(scratch) {
    ops_ = ROL::makePtr<std::vector<OP> >>();
    ops_->push_back(A);
    ops_->push_back(B);
  }
 
  LinearOperatorSum( ROL::Ptr<OP> &A, 
                     ROL::Ptr<OP> &B, 
                     ROL::Ptr<OP> &C, 
                     ROL::Ptr<V> & scratch ) :
    scratch_(scratch) {
    ops_ = ROL::makePtr<std::vector<OP> >>();
    ops_->push_back(A);
    ops_->push_back(B);
    ops_->push_back(C);
  }
 
  // TODO: implementation for arbitrary sum
 
  virtual void update( const Vector<Real> &x, bool flag = true, int iter = -1 ) {
    for( size_type i=0; i<ops_->size(); ++i ) {
      (*ops_)[i]->update(x,flag,true);
    }
  }
 
  virtual void apply( Vector<Real> &Hv, const Vector<Real> &v, Real &tol ) const {
    (*ops_)[0]->apply(Hv,v,tol);
    for( size_type i=1; i<ops_->size(); ++i ) {
      (*ops_)[i]->apply(*scratch_,v,tol);
      Hv.plus(*scratch_);
    }
  }
 
  virtual void applyInverse( Vector<Real> &Hv, const Vector<Real> &v, Real &tol ) const {
      ROL_TEST_FOR_EXCEPTION( true, std::invalid_argument, 
                                  ">>> ERROR (ROL_LinearOperatorSum, applyInverse): "
                                  "Inverse is not defined for general sum of operators.");     
  }
 
}; // class LinearOperatorSum
 
} // namespace ROL
 
#endif // ROL_LINEAROPERATOR_PRODUCT_H