1 /* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * */ 2 /* */ 3 /* This file is part of the program and library */ 4 /* SCIP --- Solving Constraint Integer Programs */ 5 /* */ 6 /* Copyright (C) 2002-2021 Konrad-Zuse-Zentrum */ 7 /* fuer Informationstechnik Berlin */ 8 /* */ 9 /* SCIP is distributed under the terms of the ZIB Academic License. */ 10 /* */ 11 /* You should have received a copy of the ZIB Academic License */ 12 /* along with SCIP; see the file COPYING. If not visit scipopt.org. */ 13 /* */ 14 /* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * */ 15 16 /**@file presol_dualagg.h 17 * @ingroup PRESOLVERS 18 * @brief aggregate variables by dual arguments 19 * @author Dieter Weninger 20 * 21 * This presolver looks for variables which could not be handled by 22 * duality fixing because of one up-/downlock. 23 * If the constraint which delivers the up-/downlock has 24 * a specific structure, we can aggregate the corresponding variable. 25 * 26 * In more detail (for a minimization problem and the case of only one uplock): 27 * 28 * Given a variable \f$x_i\f$ with \f$c_i \leq 0\f$ and only one up lock (originating from a constraint c), 29 * we are looking for a binary variable \f$x_j\f$ such that: 30 * 1. if \f$x_j = 0\f$, constraint c can only be fulfilled for \f$x_i = lb_i\f$, and 31 * 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$ub_i\f$ 32 * (or vice versa). Then we can perform the following aggregation: \f$x_i = lb_i + x_j (ub_i - lb_i)\f$. 33 * 34 * Similar arguments apply for the case of only one down lock and \f$c_i \geq 0\f$. 35 */ 36 37 /*---+----1----+----2----+----3----+----4----+----5----+----6----+----7----+----8----+----9----+----0----+----1----+----2*/ 38 39 #ifndef __SCIP_PRESOL_DUALAGG_H__ 40 #define __SCIP_PRESOL_DUALAGG_H__ 41 42 #include "scip/def.h" 43 #include "scip/type_retcode.h" 44 #include "scip/type_scip.h" 45 46 #ifdef __cplusplus 47 extern "C" { 48 #endif 49 50 /** creates the dualagg presolver and includes it in SCIP 51 * 52 * @ingroup PresolverIncludes 53 */ 54 SCIP_EXPORT 55 SCIP_RETCODE SCIPincludePresolDualagg( 56 SCIP* scip /**< SCIP data structure */ 57 ); 58 59 #ifdef __cplusplus 60 } 61 #endif 62 63 #endif 64