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_dualinfer.h 17 * @ingroup PRESOLVERS 18 * @brief dual inference presolver 19 * @author Dieter Weninger 20 * @author Patrick Gemander 21 * 22 * This presolver does bound strengthening on continuous variables (columns) for getting bounds on dual variables y. 23 * The bounds of the dual variables are then used to fix primal variables or change the side of constraints. 24 * For ranged rows one needs to decide which side (rhs or lhs) determines the equality. 25 * 26 * We distinguish two cases concerning complementary slackness: 27 * i) reduced cost fixing: c_j - sup_y(y^T A_{.j}) > 0 => x_j = l_j 28 * c_j - inf_y(y^T A_{.j}) < 0 => x_j = u_j 29 * ii) positive dual lower bound: y_i > 0 => A_{i.}x = b_i 30 * 31 * Further information on this presolving approach are given in 32 * Achterberg et al. "Presolve reductions in mixed integer programming" 33 * and for a two-column extension in 34 * Chen et al. "Two-row and two-column mixed-integer presolve using hasing-based pairing methods". 35 */ 36 37 /*---+----1----+----2----+----3----+----4----+----5----+----6----+----7----+----8----+----9----+----0----+----1----+----2*/ 38 39 #ifndef __SCIP_PRESOL_DUALINFER_H__ 40 #define __SCIP_PRESOL_DUALINFER_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 dual inference presolver and includes it in SCIP 51 * 52 * @ingroup PresolverIncludes 53 */ 54 SCIP_EXPORT 55 SCIP_RETCODE SCIPincludePresolDualinfer( 56 SCIP* scip /**< SCIP data structure */ 57 ); 58 59 #ifdef __cplusplus 60 } 61 #endif 62 63 #endif 64