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 presol_dualagg.h 26 * @ingroup PRESOLVERS 27 * @brief aggregate variables by dual arguments 28 * @author Dieter Weninger 29 * 30 * This presolver looks for variables which could not be handled by 31 * duality fixing because of one up-/downlock. 32 * If the constraint which delivers the up-/downlock has 33 * a specific structure, we can aggregate the corresponding variable. 34 * 35 * In more detail (for a minimization problem and the case of only one uplock): 36 * 37 * Given a variable \f$x_i\f$ with \f$c_i \leq 0\f$ and only one up lock (originating from a constraint c), 38 * we are looking for a binary variable \f$x_j\f$ such that: 39 * 1. if \f$x_j = 0\f$, constraint c can only be fulfilled for \f$x_i = lb_i\f$, and 40 * 2. if \f$x_j = 1\f$, constraint c becomes redundant and \f$x_i\f$ can be dual-fixed to its upper bound \f$ub_i\f$ 41 * (or vice versa). Then we can perform the following aggregation: \f$x_i = lb_i + x_j (ub_i - lb_i)\f$. 42 * 43 * Similar arguments apply for the case of only one down lock and \f$c_i \geq 0\f$. 44 */ 45 46 /*---+----1----+----2----+----3----+----4----+----5----+----6----+----7----+----8----+----9----+----0----+----1----+----2*/ 47 48 #ifndef __SCIP_PRESOL_DUALAGG_H__ 49 #define __SCIP_PRESOL_DUALAGG_H__ 50 51 #include "scip/def.h" 52 #include "scip/type_retcode.h" 53 #include "scip/type_scip.h" 54 55 #ifdef __cplusplus 56 extern "C" { 57 #endif 58 59 /** creates the dualagg presolver and includes it in SCIP 60 * 61 * @ingroup PresolverIncludes 62 */ 63 SCIP_EXPORT 64 SCIP_RETCODE SCIPincludePresolDualagg( 65 SCIP* scip /**< SCIP data structure */ 66 ); 67 68 #ifdef __cplusplus 69 } 70 #endif 71 72 #endif 73