Couenne  0.5.8
CouenneExprBDiv.hpp
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1 /* $Id: CouenneExprBDiv.hpp 490 2011-01-14 16:07:12Z pbelotti $ */
2 /*
3  * Name: exprBDiv.hpp
4  * Author: Pietro Belotti
5  * Purpose: definition of operators to compute lower/upper bounds of divisions
6  *
7  * (C) Carnegie-Mellon University, 2006.
8  * This file is licensed under the Eclipse Public License (EPL)
9  */
10 
11 #ifndef COUENNE_EXPRBDIV_H
12 #define COUENNE_EXPRBDIV_H
13 
14 #include "CouenneExprOp.hpp"
15 
16 namespace Couenne {
17 
19 static inline CouNumber safeDiv (register CouNumber a, register CouNumber b, int sign) {
20 
21  if (fabs (a) < COUENNE_EPS) return 0;
22  // if (fabs (b) < COUENNE_EPS)) return 0;
23  // else return 0
24 
25  if (fabs (b) < COUENNE_EPS) return ((sign < 0) ? -COUENNE_INFINITY : COUENNE_INFINITY);
26 
27  if (a > COUENNE_INFINITY) return ((sign < 0) ? -COUENNE_INFINITY : COUENNE_INFINITY);
28  if (a < -COUENNE_INFINITY) return ((sign < 0) ? -COUENNE_INFINITY : COUENNE_INFINITY);
29 
30  return a/b;
31 }
32 
33 
36 
37 class exprLBDiv: public exprOp {
38 
39  public:
40 
42  exprLBDiv (expression **al, int n):
43  exprOp (al, n) {} //< non-leaf expression, with argument list
44 
46  expression *clone (Domain *d = NULL) const
47  {return new exprLBDiv (clonearglist (d), nargs_);}
48 
51 
53  enum pos printPos () const
54  {return PRE;}
55 
57  std::string printOp () const
58  {return "LB_Div";}
59 };
60 
61 
63 
65 
66  register CouNumber n = (*(arglist_ [0])) ();
67  register CouNumber N = (*(arglist_ [1])) ();
68  register CouNumber d = (*(arglist_ [2])) ();
69  register CouNumber D = (*(arglist_ [3])) ();
70  // (n,N,d,D) lb
71  if (d > 0) // (?,?,+,+)
72  if (n > 0) return safeDiv (n,D,-1); // (+,+,+,+) --> n/D
73  else return safeDiv (n,d,-1); // (-,?,+,+) --> n/d
74  else { // d <= 0
75  if (D > 0) return - COUENNE_INFINITY; // (?,?,-,+) --> unbounded
76  else if (N > 0) return safeDiv (N,D,-1); // (?,+,-,-) --> N/D
77  else return safeDiv (N,d,-1); // (-,-,-,-) --> N/d
78  }
79 }
80 
81 
84 
85 class exprUBDiv: public exprOp {
86 
87  public:
88 
90  exprUBDiv (expression **al, int n):
91  exprOp (al, n) {} //< non-leaf expression, with argument list
92 
94  expression *clone (Domain *d = NULL) const
95  {return new exprUBDiv (clonearglist (d), nargs_);}
96 
99 
101  enum pos printPos () const
102  {return PRE;}
103 
105  std::string printOp () const
106  {return "UB_Div";}
107 };
108 
109 
111 
113 
114  register CouNumber n = (*(arglist_ [0])) ();
115  register CouNumber N = (*(arglist_ [1])) ();
116  register CouNumber d = (*(arglist_ [2])) ();
117  register CouNumber D = (*(arglist_ [3])) ();
118 
119  if (d > 0) // (n,N,d,D) lb
120  if (N < 0) return safeDiv (N,D,1); // (-,-,+,+) --> N/D
121  else return safeDiv (N,d,1); // (?,+,+,+) --> N/d
122  else { // d <= 0
123  if (D > 0) return + COUENNE_INFINITY; // (?,?,-,+) --> unbounded
124  else if (n < 0) return safeDiv (n,D,1); // (-,?,-,-) --> n/D
125  else return safeDiv (n,d,1); // (+,+,-,-) --> n/d
126  }
127 }
128 
129 }
130 
131 #endif
#define COUENNE_EPS
#define COUENNE_INFINITY
Define a dynamic point+bounds, with a way to save and restore previous points+bounds through a LIFO s...
class to compute lower bound of a fraction based on the bounds of both numerator and denominator
expression * clone(Domain *d=NULL) const
cloning method
exprLBDiv(expression **al, int n)
Constructors, destructor.
std::string printOp() const
print operator
CouNumber operator()()
function for the evaluation of the expression
enum pos printPos() const
print position (PRE, INSIDE, POST)
general n-ary operator-type expression: requires argument list.
int nargs_
number of arguments (cardinality of arglist)
expression ** arglist_
argument list is an array of pointers to other expressions
expression ** clonearglist(Domain *d=NULL) const
clone argument list (for use with clone method)
class to compute upper bound of a fraction based on the bounds of both numerator and denominator
CouNumber operator()()
function for the evaluation of the expression
enum pos printPos() const
print position (PRE, INSIDE, POST)
std::string printOp() const
print operator
exprUBDiv(expression **al, int n)
Constructors, destructor.
expression * clone(Domain *d=NULL) const
cloning method
Expression base class.
general include file for different compilers
pos
position where the operator should be printed when printing the expression
static CouNumber safeDiv(register CouNumber a, register CouNumber b, int sign)
division that avoids NaN's and considers a sign when returning infinity
double CouNumber
main number type in Couenne