/usr/include/linbox/util/field-axpy.h is in liblinbox-dev 1.1.6~rc0-4.1.
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/* linbox/util/field-axpy.h
* Copyright (C) 1999-2001 William J Turner,
* 2001 Bradford Hovinen
*
* Written by William J Turner <wjturner@math.ncsu.edu>,
* Bradford Hovinen <hovinen@cis.udel.edu>
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 2 of the License, or (at your option) any later version.
*
* This library is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with this library; if not, write to the
* Free Software Foundation, Inc., 59 Temple Place - Suite 330,
* Boston, MA 02111-1307, USA.
*/
#ifndef __UTIL_FIELD_AXPY_H
#define __UTIL_FIELD_AXPY_H
// Namespace in which all LinBox library code resides
namespace LinBox
{
/** FieldAXPY object.
*
* This class is used to wrap the operation y = y + a * x. It acts as an
* accumulator for y.
*
* Through the use of template specialization, objects of this type can
* be used to speed up vector dot product operations. In particular, for
* finite fields, dividing by the modulus and taking the remainder is
* expensive. In many cases, this can be postponed until the end of the
* dot product operation, thus vastly improving performance.
*
* This object is constructed from the field object F and a field
* element a which it stores and thus can use several times. The use of
* an object instead of a static variable to store the element a makes
* this method thread-safe.
*
* @param Field \Ref{LinBox} {@link Fields field}
*/
template <class Field>
class FieldAXPY
{
public:
/// Definition of element type
typedef typename Field::Element Element;
/** Constructor.
* A faxpy object if constructed from a Field and a field element.
* Copies of this objects are stored in the faxpy object.
* @param F field F in which arithmetic is done
*/
FieldAXPY (const Field &F) : _F (F) { _F.init (_y, 0); }
/** Copy constructor.
* @param faxpy
*/
FieldAXPY (const FieldAXPY<Field> &faxpy) : _F (faxpy._F), _y (faxpy._y) {}
/** Assignment operator
* @param faxpy
*/
FieldAXPY<Field> &operator = (const FieldAXPY &faxpy)
{ _y = faxpy._y; return *this; }
/** Add a*x to y
* y += a*x.
* @param a constant reference to element a
* @param x constant reference to element x
*/
inline Element& mulacc (const Element &a, const Element &x)
{ return _F.axpyin (_y, a, x); }
inline Element& accumulate (const Element &t)
{ return _F.addin (_y, t); }
/** Retrieve y
*
* Performs the delayed modding out if necessary
*/
inline Element &get (Element &y) { y = _y; return y; }
/** Assign method.
* Stores new field element for arithmetic.
* @return reference to self
* @param y_init constant reference to element a
*/
inline FieldAXPY &assign (const Element y)
{
_y = y;
return *this;
}
inline void reset() {
_F.init(_y,0);
}
private:
/// Field in which arithmetic is done
/// Not sure why it must be mutable, but the compiler complains otherwise
Field _F;
/// Field element for arithmetic
Element _y;
}; // class FieldAXPY
} // namespace LinBox
#endif // __UTIL_FIELD_AXPY_H
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