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4    	/*         SCIP --- Solving Constraint Integer Programs                      */
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24   	
25   	/**@file   type_pricer.h
26   	 * @ingroup TYPEDEFINITIONS
27   	 * @brief  type definitions for variable pricers
28   	 * @author Tobias Achterberg
29   	 */
30   	
31   	/*---+----1----+----2----+----3----+----4----+----5----+----6----+----7----+----8----+----9----+----0----+----1----+----2*/
32   	
33   	#ifndef __SCIP_TYPE_PRICER_H__
34   	#define __SCIP_TYPE_PRICER_H__
35   	
36   	#include "scip/def.h"
37   	#include "scip/type_retcode.h"
38   	#include "scip/type_scip.h"
39   	
40   	#ifdef __cplusplus
41   	extern "C" {
42   	#endif
43   	
44   	typedef struct SCIP_Pricer SCIP_PRICER;           /**< variable pricer data */
45   	typedef struct SCIP_PricerData SCIP_PRICERDATA;   /**< locally defined variable pricer data */
46   	
47   	
48   	/** copy method for pricer plugins (called when SCIP copies plugins)
49   	 *
50   	 *  input:
51   	 *  - scip            : SCIP main data structure
52   	 *  - pricer          : the variable pricer itself
53   	 *  - valid           : was the copying process valid? 
54   	 */
55   	#define SCIP_DECL_PRICERCOPY(x) SCIP_RETCODE x (SCIP* scip, SCIP_PRICER* pricer, SCIP_Bool* valid)
56   	
57   	/** destructor of variable pricer to free user data (called when SCIP is exiting)
58   	 *
59   	 *  input:
60   	 *  - scip            : SCIP main data structure
61   	 *  - pricer          : the variable pricer itself
62   	 */
63   	#define SCIP_DECL_PRICERFREE(x) SCIP_RETCODE x (SCIP* scip, SCIP_PRICER* pricer)
64   	
65   	/** initialization method of variable pricer (called after problem was transformed and pricer is active)
66   	 *
67   	 *  input:
68   	 *  - scip            : SCIP main data structure
69   	 *  - pricer          : the variable pricer itself
70   	 */
71   	#define SCIP_DECL_PRICERINIT(x) SCIP_RETCODE x (SCIP* scip, SCIP_PRICER* pricer)
72   	
73   	/** deinitialization method of variable pricer (called before transformed problem is freed and pricer is active)
74   	 *
75   	 *  input:
76   	 *  - scip            : SCIP main data structure
77   	 *  - pricer          : the variable pricer itself
78   	 */
79   	#define SCIP_DECL_PRICEREXIT(x) SCIP_RETCODE x (SCIP* scip, SCIP_PRICER* pricer)
80   	
81   	/** solving process initialization method of variable pricer (called when branch and bound process is about to begin)
82   	 *
83   	 *  This method is called when the presolving was finished and the branch and bound process is about to begin.
84   	 *  The variable pricer may use this call to initialize its branch and bound specific data.
85   	 *
86   	 *  input:
87   	 *  - scip            : SCIP main data structure
88   	 *  - pricer          : the variable pricer itself
89   	 */
90   	#define SCIP_DECL_PRICERINITSOL(x) SCIP_RETCODE x (SCIP* scip, SCIP_PRICER* pricer)
91   	
92   	/** solving process deinitialization method of variable pricer (called before branch and bound process data is freed)
93   	 *
94   	 *  This method is called before the branch and bound process is freed.
95   	 *  The variable pricer should use this call to clean up its branch and bound data.
96   	 *
97   	 *  input:
98   	 *  - scip            : SCIP main data structure
99   	 *  - pricer          : the variable pricer itself
100  	 */
101  	#define SCIP_DECL_PRICEREXITSOL(x) SCIP_RETCODE x (SCIP* scip, SCIP_PRICER* pricer)
102  	
103  	/** reduced cost pricing method of variable pricer for feasible LPs
104  	 *
105  	 *  Searches for variables that can contribute to improve the current LP's solution value.
106  	 *  In standard branch-and-price, these are variables with negative dual feasibility, that is negative
107  	 *  reduced costs for non-negative variables, positive reduced costs for non-positive variables,
108  	 *  and non-zero reduced costs for variables that can be negative and positive.
109  	 *
110  	 *  The method is called in the LP solving loop after an LP was proven to be feasible.
111  	 *
112  	 *  Whenever the pricer finds a variable with negative dual feasibility, it should call SCIPcreateVar()
113  	 *  and SCIPaddPricedVar() to add the variable to the problem. Furthermore, it should call the appropriate
114  	 *  methods of the constraint handlers to add the necessary variable entries to the constraints.
115  	 *
116  	 *  In the usual case that the pricer either adds a new variable or ensures that there are no further variables with
117  	 *  negative dual feasibility, the result pointer should be set to SCIP_SUCCESS. Only if the pricer aborts pricing
118  	 *  without creating a new variable, but there might exist additional variables with negative dual feasibility, the
119  	 *  result pointer should be set to SCIP_DIDNOTRUN.  In this case, which sometimes is referred to as "early branching",
120  	 *  the lp solution will not be used as a lower bound. The pricer can, however, store a valid lower bound in the
121  	 *  lowerbound pointer.  If you use your own branching rule (e.g., to branch on constraints), make sure that it is able
122  	 *  to branch on pseudo solutions. Otherwise, SCIP will use its default branching rules (which all branch on
123  	 *  variables). This could disturb the pricing problem or branching might not even be possible, e.g., if all yet created
124  	 *  variables have already been fixed.
125  	 *
126  	 *  input:
127  	 *  - scip            : SCIP main data structure
128  	 *  - pricer          : the variable pricer itself
129  	 *  - lowerbound      : pointer to store a lower bound found by the pricer
130  	 *  - stopearly       : should pricing be stopped, although new variables were added? (doing early branching)
131  	 *  - result          : pointer to store the result of the pricer call
132  	 *
133  	 *  possible return values for *result:
134  	 *  - SCIP_SUCCESS    : at least one improving variable was found, or it is ensured that no such variable exists
135  	 *  - SCIP_DIDNOTRUN  : the pricing process was aborted by the pricer, there is no guarantee that the current LP solution is
136  	 *                      optimal
137  	 *
138  	 */
139  	#define SCIP_DECL_PRICERREDCOST(x) SCIP_RETCODE x (SCIP* scip, SCIP_PRICER* pricer, SCIP_Real* lowerbound, SCIP_Bool* stopearly, SCIP_RESULT* result)
140  	
141  	/** Farkas pricing method of variable pricer for infeasible LPs
142  	 *
143  	 *  Searches for variables that can contribute to the feasibility of the current LP.
144  	 *  In standard branch-and-price, these are variables with positive Farkas values:
145  	 *
146  	 *  The LP was proven infeasible, so we have an infeasibility proof by the dual Farkas multipliers y.
147  	 *  With the values of y, an implicit inequality  y^T A x >= y^T b  is associated, with b given
148  	 *  by the sides of the LP rows and the sign of y:
149  	 *   - if y_i is positive, b_i is the left hand side of the row,
150  	 *   - if y_i is negative, b_i is the right hand side of the row.
151  	 *
152  	 *  y is chosen in a way, such that the valid inequality  y^T A x >= y^T b  is violated by all x,
153  	 *  especially by the (for this inequality least infeasible solution) x' defined by 
154  	 *     x'_i := ub_i, if y^T A_i >= 0
155  	 *     x'_i := lb_i, if y^T A_i < 0.
156  	 *  Pricing in this case means to add variables i with positive Farkas value, i.e. y^T A_i x'_i > 0.
157  	 *
158  	 *  The method is called in the LP solving loop after an LP was proven to be infeasible.
159  	 *
160  	 *  Whenever the pricer finds a variable with positive Farkas value, it should call SCIPcreateVar()
161  	 *  and SCIPaddPricedVar() to add the variable to the problem. Furthermore, it should call the appropriate
162  	 *  methods of the constraint handlers to add the necessary variable entries to the constraints.
163  	 *
164  	 *  input:
165  	 *  - scip            : SCIP main data structure
166  	 *  - pricer          : the variable pricer itself
167  	 *  - result          : pointer to store the result of the pricer call
168  	 *
169  	 *  possible return values for *result:
170  	 *  - SCIP_SUCCESS    : at least one variable was found, which can contribute to the feasibility of the current LP,
171  	 *                      or it is ensured that no such variable exists
172  	 *  - SCIP_DIDNOTRUN  : the pricing process was aborted by the pricer, there is no guarantee that the current LP is indeed infeasible
173  	 */
174  	#define SCIP_DECL_PRICERFARKAS(x) SCIP_RETCODE x (SCIP* scip, SCIP_PRICER* pricer, SCIP_RESULT* result)
175  	
176  	#ifdef __cplusplus
177  	}
178  	#endif
179  	
180  	#endif
181