ActionBase.h

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// ========================================================================= //
// This file is part of MyraMath, copyright (c) 2014-2019 by Ryan A Chilton  //
// and distributed by MyraCore, LLC. See LICENSE.txt for license terms.      //
// ========================================================================= //

#ifndef MYRAMATH_ITERATIVE_ACTIONBASE_H
#define MYRAMATH_ITERATIVE_ACTIONBASE_H

#include <myramath/MYRAMATH_EXPORT.h>
#include <myramath/utility/Number.h>

#include <utility>

namespace myra {

// Forward declarations.
template<class Number> class Matrix;
template<class Number> class CMatrixRange;
template<class Number> class MatrixRange;
template<class Number> class Action;

namespace detail {

// Implementation detail. Base class for all Action's.
template<class Number> class MYRAMATH_EXPORT ActionBase
  {
  protected:

    // Useful typedefs.
    typedef CMatrixRange<Number> X;
    typedef  MatrixRange<Number> B;

    // Size inspector.
    virtual std::pair<int,int> size() const = 0;

    // Subclasses must implement at least one of these two multiply() 
    // methods. Choose whichever signature is most natural/efficient.
    // Whichever one you choose, the *other* one will just delegate.
    // (if you implement neither, infinite delegation/recursion ensues)

    // Assigns B = alpha*A*X + beta*B
    virtual void multiply(const X& x, const B& b, Number alpha, Number beta) const;

    // Assigns B = A*X
    virtual void multiply(const X& x, const B& b) const;

    // Virtual destructor, so subtypes can release resources.
    virtual ~ActionBase();

    // Virtual copy constructor.
    virtual ActionBase<Number>* clone() const = 0;

    // Friendship for encapsulating Action, so it can clone()/copy.
    friend class ::myra::Action<Number>;
  
  };

// Default constructed value of an Action, does nothing.
template<class Number> class NullAction : public ActionBase<Number>
  {
  public:
  
    // Useful typedefs.
    typedef CMatrixRange<Number> X;
    typedef MatrixRange<Number> B;

    // Default constructor.
    NullAction()
      { }

  protected:
  
    // Size inspector.
    virtual std::pair<int,int> size() const
      { return std::pair<int,int>(0,0); }

    // Does nothing.
    virtual void multiply(const X& x, const B& b, Number alpha, Number beta) const
      { }

    // Does nothing.
    virtual void multiply(const X& x, const B& b) const
      { }

    // Virtual copy constructor.
    virtual ActionBase<Number>* clone() const
      { return new NullAction(); }
    
  };

} // namespace detail

} // namespace

#endif