Scippy

SCIP

Solving Constraint Integer Programs

cons_knapsack.h
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1/* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * */
2/* */
3/* This file is part of the program and library */
4/* SCIP --- Solving Constraint Integer Programs */
5/* */
6/* Copyright (c) 2002-2024 Zuse Institute Berlin (ZIB) */
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8/* Licensed under the Apache License, Version 2.0 (the "License"); */
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23/* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * */
24
25/**@file cons_knapsack.h
26 * @ingroup CONSHDLRS
27 * @brief Constraint handler for knapsack constraints of the form \f$a^T x \le b\f$, x binary and \f$a \ge 0\f$.
28 * @author Tobias Achterberg
29 * @author Kati Wolter
30 * @author Michael Winkler
31 *
32 */
33
34/*---+----1----+----2----+----3----+----4----+----5----+----6----+----7----+----8----+----9----+----0----+----1----+----2*/
35
36#ifndef __SCIP_CONS_KNAPSACK_H__
37#define __SCIP_CONS_KNAPSACK_H__
38
39#include "scip/def.h"
40#include "scip/type_cons.h"
41#include "scip/type_lp.h"
42#include "scip/type_retcode.h"
43#include "scip/type_scip.h"
44#include "scip/type_sepa.h"
45#include "scip/type_sol.h"
46#include "scip/type_var.h"
47
48#ifdef __cplusplus
49extern "C" {
50#endif
51
52/** creates the handler for knapsack constraints and includes it in SCIP
53 *
54 * @ingroup ConshdlrIncludes
55 * */
56SCIP_EXPORT
58 SCIP* scip /**< SCIP data structure */
59 );
60
61/**@addtogroup CONSHDLRS
62 *
63 * @{
64 *
65 * @name Knapsack Constraints
66 *
67 * @{
68 *
69 * This constraint handler handles a special type of linear constraints, namely knapsack constraints.
70 * A knapsack constraint has the form
71 * \f[
72 * \sum_{i=1}^n a_i x_i \leq b
73 * \f]
74 * with non-negative integer coefficients \f$a_i\f$, integer right-hand side \f$b\f$, and binary variables \f$x_i\f$.
75 */
76
77/** creates and captures a knapsack constraint
78 *
79 * @note the constraint gets captured, hence at one point you have to release it using the method SCIPreleaseCons()
80 */
81SCIP_EXPORT
83 SCIP* scip, /**< SCIP data structure */
84 SCIP_CONS** cons, /**< pointer to hold the created constraint */
85 const char* name, /**< name of constraint */
86 int nvars, /**< number of items in the knapsack */
87 SCIP_VAR** vars, /**< array with item variables */
88 SCIP_Longint* weights, /**< array with item weights */
89 SCIP_Longint capacity, /**< capacity of knapsack (right hand side of inequality) */
90 SCIP_Bool initial, /**< should the LP relaxation of constraint be in the initial LP?
91 * Usually set to TRUE. Set to FALSE for 'lazy constraints'. */
92 SCIP_Bool separate, /**< should the constraint be separated during LP processing?
93 * Usually set to TRUE. */
94 SCIP_Bool enforce, /**< should the constraint be enforced during node processing?
95 * TRUE for model constraints, FALSE for additional, redundant constraints. */
96 SCIP_Bool check, /**< should the constraint be checked for feasibility?
97 * TRUE for model constraints, FALSE for additional, redundant constraints. */
98 SCIP_Bool propagate, /**< should the constraint be propagated during node processing?
99 * Usually set to TRUE. */
100 SCIP_Bool local, /**< is constraint only valid locally?
101 * Usually set to FALSE. Has to be set to TRUE, e.g., for branching constraints. */
102 SCIP_Bool modifiable, /**< is constraint modifiable (subject to column generation)?
103 * Usually set to FALSE. In column generation applications, set to TRUE if pricing
104 * adds coefficients to this constraint. */
105 SCIP_Bool dynamic, /**< is constraint subject to aging?
106 * Usually set to FALSE. Set to TRUE for own cuts which
107 * are separated as constraints. */
108 SCIP_Bool removable, /**< should the relaxation be removed from the LP due to aging or cleanup?
109 * Usually set to FALSE. Set to TRUE for 'lazy constraints' and 'user cuts'. */
110 SCIP_Bool stickingatnode /**< should the constraint always be kept at the node where it was added, even
111 * if it may be moved to a more global node?
112 * Usually set to FALSE. Set to TRUE to for constraints that represent node data. */
113 );
114
115/** creates and captures a knapsack constraint
116 * in its most basic version, i. e., all constraint flags are set to their basic value as explained for the
117 * method SCIPcreateConsKnapsack(); all flags can be set via SCIPsetConsFLAGNAME-methods in scip.h
118 *
119 * @see SCIPcreateConsKnapsack() for information about the basic constraint flag configuration
120 *
121 * @note the constraint gets captured, hence at one point you have to release it using the method SCIPreleaseCons()
122 */
123SCIP_EXPORT
125 SCIP* scip, /**< SCIP data structure */
126 SCIP_CONS** cons, /**< pointer to hold the created constraint */
127 const char* name, /**< name of constraint */
128 int nvars, /**< number of items in the knapsack */
129 SCIP_VAR** vars, /**< array with item variables */
130 SCIP_Longint* weights, /**< array with item weights */
131 SCIP_Longint capacity /**< capacity of knapsack */
132 );
133
134/** adds new item to knapsack constraint */
135SCIP_EXPORT
137 SCIP* scip, /**< SCIP data structure */
138 SCIP_CONS* cons, /**< constraint data */
139 SCIP_VAR* var, /**< item variable */
140 SCIP_Longint weight /**< item weight */
141 );
142
143/** gets the capacity of the knapsack constraint */
144SCIP_EXPORT
146 SCIP* scip, /**< SCIP data structure */
147 SCIP_CONS* cons /**< constraint data */
148 );
149
150/** changes capacity of the knapsack constraint
151 *
152 * @note This method can only be called during problem creation stage (SCIP_STAGE_PROBLEM)
153 */
154SCIP_EXPORT
156 SCIP* scip, /**< SCIP data structure */
157 SCIP_CONS* cons, /**< constraint data */
158 SCIP_Longint capacity /**< new capacity of knapsack */
159 );
160
161/** gets the number of items in the knapsack constraint */
162SCIP_EXPORT
164 SCIP* scip, /**< SCIP data structure */
165 SCIP_CONS* cons /**< constraint data */
166 );
167
168/** gets the array of variables in the knapsack constraint; the user must not modify this array! */
169SCIP_EXPORT
171 SCIP* scip, /**< SCIP data structure */
172 SCIP_CONS* cons /**< constraint data */
173 );
174
175/** gets the array of weights in the knapsack constraint; the user must not modify this array! */
176SCIP_EXPORT
178 SCIP* scip, /**< SCIP data structure */
179 SCIP_CONS* cons /**< constraint data */
180 );
181
182/** gets the dual solution of the knapsack constraint in the current LP */
183SCIP_EXPORT
185 SCIP* scip, /**< SCIP data structure */
186 SCIP_CONS* cons /**< constraint data */
187 );
188
189/** gets the dual Farkas value of the knapsack constraint in the current infeasible LP */
190SCIP_EXPORT
192 SCIP* scip, /**< SCIP data structure */
193 SCIP_CONS* cons /**< constraint data */
194 );
195
196/** returns the linear relaxation of the given knapsack constraint; may return NULL if no LP row was yet created;
197 * the user must not modify the row!
198 */
199SCIP_EXPORT
201 SCIP* scip, /**< SCIP data structure */
202 SCIP_CONS* cons /**< constraint data */
203 );
204
205/** solves knapsack problem in maximization form exactly using dynamic programming;
206 * if needed, one can provide arrays to store all selected items and all not selected items
207 *
208 * @note in case you provide the solitems or nonsolitems array you also have to provide the counter part, as well
209 *
210 * @note the algorithm will first compute a greedy solution and terminate
211 * if the greedy solution is proven to be optimal.
212 * The dynamic programming algorithm runs with a time and space complexity
213 * of O(nitems * capacity).
214 */
215SCIP_EXPORT
217 SCIP* scip, /**< SCIP data structure */
218 int nitems, /**< number of available items */
219 SCIP_Longint* weights, /**< item weights */
220 SCIP_Real* profits, /**< item profits */
221 SCIP_Longint capacity, /**< capacity of knapsack */
222 int* items, /**< item numbers */
223 int* solitems, /**< array to store items in solution, or NULL */
224 int* nonsolitems, /**< array to store items not in solution, or NULL */
225 int* nsolitems, /**< pointer to store number of items in solution, or NULL */
226 int* nnonsolitems, /**< pointer to store number of items not in solution, or NULL */
227 SCIP_Real* solval, /**< pointer to store optimal solution value, or NULL */
228 SCIP_Bool* success /**< pointer to store if an error occured during solving
229 * (normally a memory problem) */
230 );
231
232/** solves knapsack problem in maximization form approximately by solving the LP-relaxation of the problem using Dantzig's
233 * method and rounding down the solution; if needed, one can provide arrays to store all selected items and all not
234 * selected items
235 */
236SCIP_EXPORT
238 SCIP* scip, /**< SCIP data structure */
239 int nitems, /**< number of available items */
240 SCIP_Longint* weights, /**< item weights */
241 SCIP_Real* profits, /**< item profits */
242 SCIP_Longint capacity, /**< capacity of knapsack */
243 int* items, /**< item numbers */
244 int* solitems, /**< array to store items in solution, or NULL */
245 int* nonsolitems, /**< array to store items not in solution, or NULL */
246 int* nsolitems, /**< pointer to store number of items in solution, or NULL */
247 int* nnonsolitems, /**< pointer to store number of items not in solution, or NULL */
248 SCIP_Real* solval /**< pointer to store optimal solution value, or NULL */
249 );
250
251/** separates different classes of valid inequalities for the 0-1 knapsack problem */
252SCIP_EXPORT
254 SCIP* scip, /**< SCIP data structure */
255 SCIP_CONS* cons, /**< originating constraint of the knapsack problem, or NULL */
256 SCIP_SEPA* sepa, /**< originating separator of the knapsack problem, or NULL */
257 SCIP_VAR** vars, /**< variables in knapsack constraint */
258 int nvars, /**< number of variables in knapsack constraint */
259 SCIP_Longint* weights, /**< weights of variables in knapsack constraint */
260 SCIP_Longint capacity, /**< capacity of knapsack */
261 SCIP_SOL* sol, /**< primal SCIP solution to separate, NULL for current LP solution */
262 SCIP_Bool usegubs, /**< should GUB information be used for separation? */
263 SCIP_Bool* cutoff, /**< pointer to store whether a cutoff has been detected */
264 int* ncuts /**< pointer to add up the number of found cuts */
265 );
266
267/* relaxes given general linear constraint into a knapsack constraint and separates lifted knapsack cover inequalities */
268SCIP_EXPORT
270 SCIP* scip, /**< SCIP data structure */
271 SCIP_CONS* cons, /**< originating constraint of the knapsack problem, or NULL */
272 SCIP_SEPA* sepa, /**< originating separator of the knapsack problem, or NULL */
273 int nknapvars, /**< number of variables in the continuous knapsack constraint */
274 SCIP_VAR** knapvars, /**< variables in the continuous knapsack constraint */
275 SCIP_Real* knapvals, /**< coefficients of the variables in the continuous knapsack constraint */
276 SCIP_Real valscale, /**< -1.0 if lhs of row is used as rhs of c. k. constraint, +1.0 otherwise */
277 SCIP_Real rhs, /**< right hand side of the continuous knapsack constraint */
278 SCIP_SOL* sol, /**< primal CIP solution, NULL for current LP solution */
279 SCIP_Bool* cutoff, /**< pointer to store whether a cutoff was found */
280 int* ncuts /**< pointer to add up the number of found cuts */
281 );
282
283/** cleans up (multi-)aggregations and fixings from knapsack constraints */
284SCIP_EXPORT
286 SCIP* scip, /**< SCIP data structure */
287 SCIP_Bool onlychecked, /**< should only checked constraints be cleaned up? */
288 SCIP_Bool* infeasible /**< pointer to return whether the problem was detected to be infeasible */
289 );
290
291/** @} */
292
293/** @} */
294
295#ifdef __cplusplus
296}
297#endif
298
299#endif
common defines and data types used in all packages of SCIP
#define SCIP_Longint
Definition: def.h:158
#define SCIP_Bool
Definition: def.h:91
#define SCIP_Real
Definition: def.h:173
int SCIPgetNVarsKnapsack(SCIP *scip, SCIP_CONS *cons)
SCIP_RETCODE SCIPaddCoefKnapsack(SCIP *scip, SCIP_CONS *cons, SCIP_VAR *var, SCIP_Longint weight)
SCIP_RETCODE SCIPsolveKnapsackApproximately(SCIP *scip, int nitems, SCIP_Longint *weights, SCIP_Real *profits, SCIP_Longint capacity, int *items, int *solitems, int *nonsolitems, int *nsolitems, int *nnonsolitems, SCIP_Real *solval)
SCIP_RETCODE SCIPcleanupConssKnapsack(SCIP *scip, SCIP_Bool onlychecked, SCIP_Bool *infeasible)
SCIP_RETCODE SCIPseparateKnapsackCuts(SCIP *scip, SCIP_CONS *cons, SCIP_SEPA *sepa, SCIP_VAR **vars, int nvars, SCIP_Longint *weights, SCIP_Longint capacity, SCIP_SOL *sol, SCIP_Bool usegubs, SCIP_Bool *cutoff, int *ncuts)
SCIP_RETCODE SCIPcreateConsBasicKnapsack(SCIP *scip, SCIP_CONS **cons, const char *name, int nvars, SCIP_VAR **vars, SCIP_Longint *weights, SCIP_Longint capacity)
SCIP_RETCODE SCIPchgCapacityKnapsack(SCIP *scip, SCIP_CONS *cons, SCIP_Longint capacity)
SCIP_RETCODE SCIPseparateRelaxedKnapsack(SCIP *scip, SCIP_CONS *cons, SCIP_SEPA *sepa, int nknapvars, SCIP_VAR **knapvars, SCIP_Real *knapvals, SCIP_Real valscale, SCIP_Real rhs, SCIP_SOL *sol, SCIP_Bool *cutoff, int *ncuts)
SCIP_RETCODE SCIPsolveKnapsackExactly(SCIP *scip, int nitems, SCIP_Longint *weights, SCIP_Real *profits, SCIP_Longint capacity, int *items, int *solitems, int *nonsolitems, int *nsolitems, int *nnonsolitems, SCIP_Real *solval, SCIP_Bool *success)
SCIP_RETCODE SCIPcreateConsKnapsack(SCIP *scip, SCIP_CONS **cons, const char *name, int nvars, SCIP_VAR **vars, SCIP_Longint *weights, SCIP_Longint capacity, SCIP_Bool initial, SCIP_Bool separate, SCIP_Bool enforce, SCIP_Bool check, SCIP_Bool propagate, SCIP_Bool local, SCIP_Bool modifiable, SCIP_Bool dynamic, SCIP_Bool removable, SCIP_Bool stickingatnode)
SCIP_Longint * SCIPgetWeightsKnapsack(SCIP *scip, SCIP_CONS *cons)
SCIP_Longint SCIPgetCapacityKnapsack(SCIP *scip, SCIP_CONS *cons)
SCIP_VAR ** SCIPgetVarsKnapsack(SCIP *scip, SCIP_CONS *cons)
SCIP_Real SCIPgetDualfarkasKnapsack(SCIP *scip, SCIP_CONS *cons)
SCIP_ROW * SCIPgetRowKnapsack(SCIP *scip, SCIP_CONS *cons)
SCIP_Real SCIPgetDualsolKnapsack(SCIP *scip, SCIP_CONS *cons)
SCIP_RETCODE SCIPincludeConshdlrKnapsack(SCIP *scip)
type definitions for constraints and constraint handlers
type definitions for LP management
type definitions for return codes for SCIP methods
enum SCIP_Retcode SCIP_RETCODE
Definition: type_retcode.h:63
type definitions for SCIP's main datastructure
type definitions for separators
type definitions for storing primal CIP solutions
type definitions for problem variables