1/* $Id: ClpPrimalColumnPivot.hpp 1753 2011-06-19 16:27:26Z stefan $ */
2// Copyright (C) 2002, International Business Machines
3// Corporation and others. All Rights Reserved.
4// This code is licensed under the terms of the Eclipse Public License (EPL).
5
6#ifndef ClpPrimalcolumnPivot_H
7#define ClpPrimalcolumnPivot_H
8
9class ClpSimplex;
10class CoinIndexedVector;
11
12//#############################################################################
13
14/** Primal Column Pivot Abstract Base Class
15
16Abstract Base Class for describing an interface to an algorithm
17to choose column pivot in primal simplex algorithm. For some algorithms
18e.g. Dantzig choice then some functions may be null. For Dantzig
19the only one of any importance is pivotColumn.
20
21If you wish to inherit from this look at ClpPrimalColumnDantzig.cpp
22as that is simplest version.
23*/
24
25class ClpPrimalColumnPivot {
26
27public:
28
29 ///@name Algorithmic methods
30 //@{
31
32 /** Returns pivot column, -1 if none
33
34 Normally updates reduced costs using result of last iteration
35 before selecting incoming column.
36
37 The Packed CoinIndexedVector updates has cost updates - for normal LP
38 that is just +-weight where a feasibility changed. It also has
39 reduced cost from last iteration in pivot row
40
41 Inside pivotColumn the pivotRow_ and reduced cost from last iteration
42 are also used.
43
44 So in the simplest case i.e. feasible we compute the row of the
45 tableau corresponding to last pivot and add a multiple of this
46 to current reduced costs.
47
48 We can use other arrays to help updates
49 */
50 virtual int pivotColumn(CoinIndexedVector * updates,
51 CoinIndexedVector * spareRow1,
52 CoinIndexedVector * spareRow2,
53 CoinIndexedVector * spareColumn1,
54 CoinIndexedVector * spareColumn2) = 0;
55
56 /// Updates weights - part 1 (may be empty)
57 virtual void updateWeights(CoinIndexedVector * input);
58
59 /** Saves any weights round factorization as pivot rows may change
60 Will be empty unless steepest edge (will save model)
61 May also recompute infeasibility stuff
62 1) before factorization
63 2) after good factorization (if weights empty may initialize)
64 3) after something happened but no factorization
65 (e.g. check for infeasible)
66 4) as 2 but restore weights from previous snapshot
67 5) forces some initialization e.g. weights
68 Also sets model
69 */
70 virtual void saveWeights(ClpSimplex * model, int mode) = 0;
71 /** Signals pivot row choice:
72 -2 (default) - use normal pivot row choice
73 -1 to numberRows-1 - use this (will be checked)
74 way should be -1 to go to lower bound, +1 to upper bound
75 */
76 virtual int pivotRow(double & way) {
77 way = 0;
78 return -2;
79 }
80 /// Gets rid of all arrays (may be empty)
81 virtual void clearArrays();
82 /// Returns true if would not find any column
83 virtual bool looksOptimal() const {
84 return looksOptimal_;
85 }
86 /// Sets optimality flag (for advanced use)
87 virtual void setLooksOptimal(bool flag) {
88 looksOptimal_ = flag;
89 }
90 //@}
91
92
93 ///@name Constructors and destructors
94 //@{
95 /// Default Constructor
96 ClpPrimalColumnPivot();
97
98 /// Copy constructor
99 ClpPrimalColumnPivot(const ClpPrimalColumnPivot &);
100
101 /// Assignment operator
102 ClpPrimalColumnPivot & operator=(const ClpPrimalColumnPivot& rhs);
103
104 /// Destructor
105 virtual ~ClpPrimalColumnPivot ();
106
107 /// Clone
108 virtual ClpPrimalColumnPivot * clone(bool copyData = true) const = 0;
109
110 //@}
111
112 ///@name Other
113 //@{
114 /// Returns model
115 inline ClpSimplex * model() {
116 return model_;
117 }
118 /// Sets model
119 inline void setModel(ClpSimplex * newmodel) {
120 model_ = newmodel;
121 }
122
123 /// Returns type (above 63 is extra information)
124 inline int type() {
125 return type_;
126 }
127
128 /** Returns number of extra columns for sprint algorithm - 0 means off.
129 Also number of iterations before recompute
130 */
131 virtual int numberSprintColumns(int & numberIterations) const;
132 /// Switch off sprint idea
133 virtual void switchOffSprint();
134 /// Called when maximum pivots changes
135 virtual void maximumPivotsChanged() {}
136
137 //@}
138
139 //---------------------------------------------------------------------------
140
141protected:
142 ///@name Protected member data
143 //@{
144 /// Pointer to model
145 ClpSimplex * model_;
146 /// Type of column pivot algorithm
147 int type_;
148 /// Says if looks optimal (normally computed)
149 bool looksOptimal_;
150 //@}
151};
152#ifndef CLP_PRIMAL_SLACK_MULTIPLIER
153#define CLP_PRIMAL_SLACK_MULTIPLIER 1.01
154#endif
155#endif
156