1 /* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * */ 2 /* */ 3 /* This file is part of the program and library */ 4 /* SCIP --- Solving Constraint Integer Programs */ 5 /* */ 6 /* Copyright (c) 2002-2023 Zuse Institute Berlin (ZIB) */ 7 /* */ 8 /* Licensed under the Apache License, Version 2.0 (the "License"); */ 9 /* you may not use this file except in compliance with the License. */ 10 /* You may obtain a copy of the License at */ 11 /* */ 12 /* http://www.apache.org/licenses/LICENSE-2.0 */ 13 /* */ 14 /* Unless required by applicable law or agreed to in writing, software */ 15 /* distributed under the License is distributed on an "AS IS" BASIS, */ 16 /* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. */ 17 /* See the License for the specific language governing permissions and */ 18 /* limitations under the License. */ 19 /* */ 20 /* You should have received a copy of the Apache-2.0 license */ 21 /* along with SCIP; see the file LICENSE. If not visit scipopt.org. */ 22 /* */ 23 /* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * */ 24 25 /**@file scip_dcmp.h 26 * @ingroup DecompMethods 27 * @brief public methods for decompositions 28 * @author Gregor Hendel 29 */ 30 31 /*---+----1----+----2----+----3----+----4----+----5----+----6----+----7----+----8----+----9----+----0----+----1----+----2*/ 32 33 #ifndef SCIP_SCIP_DECOMP_H_ 34 #define SCIP_SCIP_DECOMP_H_ 35 36 #include "scip/def.h" 37 #include "scip/type_cons.h" 38 #include "scip/type_dcmp.h" 39 #include "scip/type_retcode.h" 40 #include "scip/type_scip.h" 41 42 #ifdef __cplusplus 43 extern "C" { 44 #endif 45 46 /**@addtogroup DecompMethods 47 * 48 * @{ 49 */ 50 51 /** creates a decomposition */ 52 SCIP_EXPORT 53 SCIP_RETCODE SCIPcreateDecomp( 54 SCIP* scip, /**< SCIP data structure */ 55 SCIP_DECOMP** decomp, /**< pointer to store the decomposition data structure */ 56 int nblocks, /**< the number of blocks (without the linking block) */ 57 SCIP_Bool original, /**< is this a decomposition in the original (TRUE) or transformed space? */ 58 SCIP_Bool benderslabels /**< should the variables be labeled for the application of Benders' decomposition */ 59 ); 60 61 /** frees a decomposition */ 62 SCIP_EXPORT 63 void SCIPfreeDecomp( 64 SCIP* scip, /**< SCIP data structure */ 65 SCIP_DECOMP** decomp /**< pointer to free the decomposition data structure */ 66 ); 67 68 /** adds decomposition to SCIP */ 69 SCIP_EXPORT 70 SCIP_RETCODE SCIPaddDecomp( 71 SCIP* scip, /**< SCIP data structure */ 72 SCIP_DECOMP* decomp /**< decomposition to add */ 73 ); 74 75 /** gets available user decompositions for either the original or transformed problem */ 76 SCIP_EXPORT 77 void SCIPgetDecomps( 78 SCIP* scip, /**< SCIP data structure */ 79 SCIP_DECOMP*** decomps, /**< pointer to store decompositions array */ 80 int* ndecomps, /**< pointer to store number of decompositions */ 81 SCIP_Bool original /**< should the decompositions for the original problem be returned? */ 82 ); 83 84 /** returns TRUE if the constraint \p cons contains only linking variables in decomposition \p decomp */ 85 SCIP_EXPORT 86 SCIP_RETCODE SCIPhasConsOnlyLinkVars( 87 SCIP* scip, /**< SCIP data structure */ 88 SCIP_DECOMP* decomp, /**< decomposition data structure */ 89 SCIP_CONS* cons, /**< the constraint */ 90 SCIP_Bool* hasonlylinkvars /**< will be set to TRUE if this constraint has only linking variables */ 91 ); 92 93 /** computes constraint labels from variable labels 94 * 95 * Existing labels for the constraints are simply overridden 96 * 97 * The computed labels depend on the flag SCIPdecompUseBendersLabels() of the decomposition. If the flag is set 98 * to FALSE, the labeling assigns 99 * 100 * - label i, if only variables labeled i are present in the constraint (and optionally linking variables) 101 * - SCIP_DECOMP_LINKCONS, if there are either only variables labeled with SCIP_DECOMP_LINKVAR present, or 102 * if there are variables with more than one block label. 103 * 104 * If the flag is set to TRUE, the assignment is the same, unless variables from 2 named blocks occur in the same 105 * constraint, which is an invalid labeling for the Benders case. 106 */ 107 SCIP_EXPORT 108 SCIP_RETCODE SCIPcomputeDecompConsLabels( 109 SCIP* scip, /**< SCIP data structure */ 110 SCIP_DECOMP* decomp, /**< decomposition data structure */ 111 SCIP_CONS** conss, /**< array of constraints */ 112 int nconss /**< number of constraints */ 113 ); 114 115 /** creates a decomposition of the variables from a labeling of the constraints 116 * 117 * NOTE: by default, the variable labeling is based on a Dantzig-Wolfe decomposition. This means that constraints in named 118 * blocks have have precedence over linking constraints. If a variable exists in constraints from 119 * two or more named blocks, then this variable is marked as a linking variable. 120 * If a variable occurs in exactly one named block i>=0, it is assigned label i. 121 * Variables which are only in linking constraints are unlabeled. However, SCIPdecompGetVarsLabels() will 122 * label them as linking variables. 123 * 124 * If the variables should be labeled for the application of Benders' decomposition, the decomposition must be 125 * flagged explicitly via SCIPdecompSetUseBendersLabels(). 126 * With this setting, the presence in linking constraints takes precedence over the presence in named blocks. 127 * Now, a variable is considered linking if it is present in at least one linking constraint and an arbitrary 128 * number of constraints from named blocks. 129 */ 130 SCIP_EXPORT 131 SCIP_RETCODE SCIPcomputeDecompVarsLabels( 132 SCIP* scip, /**< SCIP data structure */ 133 SCIP_DECOMP* decomp, /**< decomposition data structure */ 134 SCIP_CONS** conss, /**< array of constraints */ 135 int nconss /**< number of constraints */ 136 ); 137 138 /** assigns linking constraints to blocks 139 * 140 * Each linking constraint is assigned to the most frequent block among its variables. 141 * Variables of other blocks are relabeled as linking variables. 142 * Constraints that have only linking variables are skipped. 143 * 144 * @note: In contrast to SCIPcomputeDecompConsLabels(), this method potentially relabels variables. 145 */ 146 SCIP_EXPORT 147 SCIP_RETCODE SCIPassignDecompLinkConss( 148 SCIP* scip, /**< SCIP data structure */ 149 SCIP_DECOMP* decomp, /**< decomposition data structure */ 150 SCIP_CONS** conss, /**< array of linking constraints that should be reassigned */ 151 int nconss, /**< number of constraints */ 152 int* nskipconss /**< pointer to store the number of constraints that were skipped, or NULL */ 153 ); 154 155 /** computes decomposition statistics and store them in the decomposition object */ 156 SCIP_EXPORT 157 SCIP_RETCODE SCIPcomputeDecompStats( 158 SCIP* scip, /**< SCIP data structure */ 159 SCIP_DECOMP* decomp, /**< decomposition data structure */ 160 SCIP_Bool uselimits /**< respect user limits on potentially expensive graph statistics? */ 161 ); 162 163 /** @} */ 164 165 #ifdef __cplusplus 166 } 167 #endif 168 169 #endif 170