/usr/include/linbox/switch/cekstv.h is in liblinbox-dev 1.1.6~rc0-4.1.
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/* linbox/switch/cekstv.h
* Copyright (C) 1999-2001 William J Turner
*
* Written by William J Turner <wjturner@math.ncsu.edu>
*
* -----------------------------------------------------------
* 2002-09-26 Bradford Hovinen <bghovinen@math.uwaterloo.ca>
*
* Refactoring: The switch object now contains only the information for one 2x2
* block. A vector of switches is maintained by the butterfly preconditioner
* instead of the switch object. Since there will be many switch objects, they
* should be kept very lightweight, so the field is not maintained in the object
* itself, but instead passed to apply and applyTranspose. Since those methods
* are inline, this does not create overhead. apply and applyTranspose now take
* four field elements: the source elements and destination elements. This
* eliminates the need to keep an additional temporary in the class, and
* eliminates the need for copying in the butterfly.
*
* -----------------------------------------------------------
* 2002-08-20 Bradford Hovinen <hovinen@cis.udel.edu>
*
* Brought this file into the current Linbox framework:
* - Renamed file as cekstv.h
* - Renamed class cekstv_switch as CekstvSwitch
* - Reindent
* -----------------------------------------------------------
*
* See COPYING for license information.
*/
#ifndef __CEKSTV_H
#define __CEKSTV_H
#include <vector>
namespace LinBox
{
template <class Field>
class CekstvSwitchFactory;
/** Butterfly switch object from preconditioner paper.
* This is a switch predicate object that is applied
* to two references to elements to switch them as needed
* by the \Ref{Butterfly Switching Network BlackBox Matrix Object}
* following the exchange matrix introduced in "Efficient Matrix
* Preconditioners for Black Box Linear Algebra" by Chen, Eberly,
* Kaltofen, Saunders, Turner, and Villard.
* This class is templatized by the field in which the arithmetic
* is done.
*/
template <class Field>
class CekstvSwitch
{
public:
/// Typedef
typedef typename Field::Element Element;
typedef CekstvSwitchFactory<Field> Factory;
/** Constructor from a field and a field element.
* @param F field in which arithmetic is done
* @param switches vector of switches
*/
CekstvSwitch (const typename Field::Element &a)
: _a (a)
{}
/** Destructor.
*/
~CekstvSwitch () {}
/** Apply switch function.
* Switches the elements in references according to the
* exchange matrix introduced in "Efficient Matrix
* Preconditioners for Black Box Linear Algebra" by Chen, Eberly,
* Kaltofen, Saunders, Turner, and Villard and the current field element
* specified in the switch object.
* @return bool true if swapped, false otherwise
* @param x reference to first element to be switched
* @param y reference to second element to be switched
*/
bool apply (const Field &F, Element &x, Element &y) const;
/** Apply switch transpose function.
* Switches the elements in references according to the
* transpose of the exchange matrix introduced in "Efficient Matrix
* Preconditioners for Black Box Linear Algebra" by Chen, Eberly,
* Kaltofen, Saunders, Turner, and Villard and the current field element
* specified in the switch object.
* @return bool true if swapped, false otherwise
* @param x reference to first element to be switched
* @param y reference to second element to be switched
*/
bool applyTranspose (const Field &F, Element &x, Element &y) const;
private:
// Parameter of this 2x2 block
typename Field::Element _a;
};
/** Cekstv switch factory
*
* This class facilitates construction of cekstv switch objects by the
* butterfly matrix.
*/
template <class Field>
class CekstvSwitchFactory
{
public:
/** Constructor from an STL vector of bools
*/
CekstvSwitchFactory (typename Field::RandIter r)
: _r (r)
{}
/** Construct and return a boolean switch object
*/
CekstvSwitch<Field> makeSwitch ()
{ typename Field::Element a; return CekstvSwitch<Field> (_r.random (a)); }
private:
typename Field::RandIter _r;
};
template <class Field>
inline bool CekstvSwitch<Field>::apply (const Field &F,
typename Field::Element &x,
typename Field::Element &y) const
{
F.axpyin (x, _a, y);
F.addin (y, x);
return true;
}
template <class Field>
inline bool CekstvSwitch<Field>::applyTranspose (const Field &F,
typename Field::Element &x,
typename Field::Element &y) const
{
F.addin (x, y);
F.axpyin (y, _a, x);
return true;
}
}
#endif // __CEKSTV_H
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