/* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * */ /* */ /* This file is part of the program and library */ /* SCIP --- Solving Constraint Integer Programs */ /* */ /* Copyright 2002-2022 Zuse Institute Berlin */ /* */ /* Licensed under the Apache License, Version 2.0 (the "License"); */ /* you may not use this file except in compliance with the License. */ /* You may obtain a copy of the License at */ /* */ /* http://www.apache.org/licenses/LICENSE-2.0 */ /* */ /* Unless required by applicable law or agreed to in writing, software */ /* distributed under the License is distributed on an "AS IS" BASIS, */ /* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. */ /* See the License for the specific language governing permissions and */ /* limitations under the License. */ /* */ /* You should have received a copy of the Apache-2.0 license */ /* along with SCIP; see the file LICENSE. If not visit scipopt.org. */ /* */ /* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * */ /**@file scip_dcmp.h * @ingroup DecompMethods * @brief public methods for decompositions * @author Gregor Hendel */ /*---+----1----+----2----+----3----+----4----+----5----+----6----+----7----+----8----+----9----+----0----+----1----+----2*/ #ifndef SCIP_SCIP_DECOMP_H_ #define SCIP_SCIP_DECOMP_H_ #include "scip/def.h" #include "scip/type_cons.h" #include "scip/type_dcmp.h" #include "scip/type_retcode.h" #include "scip/type_scip.h" #ifdef __cplusplus extern "C" { #endif /**@addtogroup DecompMethods * * @{ */ /** creates a decomposition */ SCIP_EXPORT SCIP_RETCODE SCIPcreateDecomp( SCIP* scip, /**< SCIP data structure */ SCIP_DECOMP** decomp, /**< pointer to store the decomposition data structure */ int nblocks, /**< the number of blocks (without the linking block) */ SCIP_Bool original, /**< is this a decomposition in the original (TRUE) or transformed space? */ SCIP_Bool benderslabels /**< should the variables be labeled for the application of Benders' decomposition */ ); /** frees a decomposition */ SCIP_EXPORT void SCIPfreeDecomp( SCIP* scip, /**< SCIP data structure */ SCIP_DECOMP** decomp /**< pointer to free the decomposition data structure */ ); /** adds decomposition to SCIP */ SCIP_EXPORT SCIP_RETCODE SCIPaddDecomp( SCIP* scip, /**< SCIP data structure */ SCIP_DECOMP* decomp /**< decomposition to add */ ); /** gets available user decompositions for either the original or transformed problem */ SCIP_EXPORT void SCIPgetDecomps( SCIP* scip, /**< SCIP data structure */ SCIP_DECOMP*** decomps, /**< pointer to store decompositions array */ int* ndecomps, /**< pointer to store number of decompositions */ SCIP_Bool original /**< should the decompositions for the original problem be returned? */ ); /** returns TRUE if the constraint \p cons contains only linking variables in decomposition \p decomp */ SCIP_EXPORT SCIP_RETCODE SCIPhasConsOnlyLinkVars( SCIP* scip, /**< SCIP data structure */ SCIP_DECOMP* decomp, /**< decomposition data structure */ SCIP_CONS* cons, /**< the constraint */ SCIP_Bool* hasonlylinkvars /**< will be set to TRUE if this constraint has only linking variables */ ); /** computes constraint labels from variable labels * * Existing labels for the constraints are simply overridden * * The computed labels depend on the flag SCIPdecompUseBendersLabels() of the decomposition. If the flag is set * to FALSE, the labeling assigns * * - label i, if only variables labeled i are present in the constraint (and optionally linking variables) * - SCIP_DECOMP_LINKCONS, if there are either only variables labeled with SCIP_DECOMP_LINKVAR present, or * if there are variables with more than one block label. * * If the flag is set to TRUE, the assignment is the same, unless variables from 2 named blocks occur in the same * constraint, which is an invalid labeling for the Benders case. */ SCIP_EXPORT SCIP_RETCODE SCIPcomputeDecompConsLabels( SCIP* scip, /**< SCIP data structure */ SCIP_DECOMP* decomp, /**< decomposition data structure */ SCIP_CONS** conss, /**< array of constraints */ int nconss /**< number of constraints */ ); /** creates a decomposition of the variables from a labeling of the constraints * * NOTE: by default, the variable labeling is based on a Dantzig-Wolfe decomposition. This means that constraints in named * blocks have have precedence over linking constraints. If a variable exists in constraints from * two or more named blocks, then this variable is marked as a linking variable. * If a variable occurs in exactly one named block i>=0, it is assigned label i. * Variables which are only in linking constraints are unlabeled. However, SCIPdecompGetVarsLabels() will * label them as linking variables. * * If the variables should be labeled for the application of Benders' decomposition, the decomposition must be * flagged explicitly via SCIPdecompSetUseBendersLabels(). * With this setting, the presence in linking constraints takes precedence over the presence in named blocks. * Now, a variable is considered linking if it is present in at least one linking constraint and an arbitrary * number of constraints from named blocks. */ SCIP_EXPORT SCIP_RETCODE SCIPcomputeDecompVarsLabels( SCIP* scip, /**< SCIP data structure */ SCIP_DECOMP* decomp, /**< decomposition data structure */ SCIP_CONS** conss, /**< array of constraints */ int nconss /**< number of constraints */ ); /** assigns linking constraints to blocks * * Each linking constraint is assigned to the most frequent block among its variables. * Variables of other blocks are relabeled as linking variables. * Constraints that have only linking variables are skipped. * * @note: In contrast to SCIPcomputeDecompConsLabels(), this method potentially relabels variables. */ SCIP_EXPORT SCIP_RETCODE SCIPassignDecompLinkConss( SCIP* scip, /**< SCIP data structure */ SCIP_DECOMP* decomp, /**< decomposition data structure */ SCIP_CONS** conss, /**< array of linking constraints that should be reassigned */ int nconss, /**< number of constraints */ int* nskipconss /**< pointer to store the number of constraints that were skipped, or NULL */ ); /** computes decomposition statistics and store them in the decomposition object */ SCIP_EXPORT SCIP_RETCODE SCIPcomputeDecompStats( SCIP* scip, /**< SCIP data structure */ SCIP_DECOMP* decomp, /**< decomposition data structure */ SCIP_Bool uselimits /**< respect user limits on potentially expensive graph statistics? */ ); /** @} */ #ifdef __cplusplus } #endif #endif