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/*
* vim: ts=4 sw=4 et tw=0 wm=0
*
* libvpsc - A solver for the problem of Variable Placement with
* Separation Constraints.
*
* Copyright (C) 2005-2008 Monash University
*
* 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 2.1 of the License, or (at your option) any later version.
* See the file LICENSE.LGPL distributed with the library.
*
* 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.
*
* Author(s): Tim Dwyer
*/
#ifndef VPSC_VARIABLE_H
#define VPSC_VARIABLE_H
#include <vector>
#include <iostream>
#include "libvpsc/block.h"
#include "libvpsc/assertions.h"
namespace vpsc {
class Constraint;
typedef std::vector<Constraint*> Constraints;
/**
* @brief A variable is comprised of an ideal position, final position and
* a weight.
*
* When creating a variable you specify an ideal value, and a weight---how
* much the variable wants to be at its ideal position. After solving the
* problem you can read back the final position for the variable.
*/
class Variable
{
friend std::ostream& operator <<(std::ostream &os, const Variable &v);
friend class Block;
friend class Constraint;
friend class Solver;
public:
int id; // useful in log files
double desiredPosition;
double finalPosition;
double weight; // how much the variable wants to
// be at it's desired position
double scale; // translates variable to another space
double offset;
Block *block;
bool visited;
bool fixedDesiredPosition;
Constraints in;
Constraints out;
char *toString();
inline Variable(const int id, const double desiredPos=-1.0,
const double weight=1.0, const double scale=1.0)
: id(id)
, desiredPosition(desiredPos)
, finalPosition(desiredPos)
, weight(weight)
, scale(scale)
, offset(0)
, block(nullptr)
, visited(false)
, fixedDesiredPosition(false)
{
}
double dfdv(void) const {
return 2. * weight * ( position() - desiredPosition );
}
private:
inline double position(void) const {
return (block->ps.scale*block->posn+offset)/scale;
}
inline double unscaledPosition(void) const {
COLA_ASSERT(block->ps.scale == 1);
COLA_ASSERT(scale == 1);
return block->posn + offset;
}
};
//! @brief A vector of pointers to Variable objects.
typedef std::vector<Variable*> Variables;
}
#endif // VPSC_VARIABLE_H
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