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_dualinfer.h 26 * @ingroup PRESOLVERS 27 * @brief dual inference presolver 28 * @author Dieter Weninger 29 * @author Patrick Gemander 30 * 31 * This presolver does bound strengthening on continuous variables (columns) for getting bounds on dual variables y. 32 * The bounds of the dual variables are then used to fix primal variables or change the side of constraints. 33 * For ranged rows one needs to decide which side (rhs or lhs) determines the equality. 34 * 35 * We distinguish two cases concerning complementary slackness: 36 * i) reduced cost fixing: c_j - sup_y(y^T A_{.j}) > 0 => x_j = l_j 37 * c_j - inf_y(y^T A_{.j}) < 0 => x_j = u_j 38 * ii) positive dual lower bound: y_i > 0 => A_{i.}x = b_i 39 * 40 * Further information on this presolving approach are given in 41 * Achterberg et al. "Presolve reductions in mixed integer programming" 42 * and for a two-column extension in 43 * Chen et al. "Two-row and two-column mixed-integer presolve using hasing-based pairing methods". 44 */ 45 46 /*---+----1----+----2----+----3----+----4----+----5----+----6----+----7----+----8----+----9----+----0----+----1----+----2*/ 47 48 #ifndef __SCIP_PRESOL_DUALINFER_H__ 49 #define __SCIP_PRESOL_DUALINFER_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 dual inference presolver and includes it in SCIP 60 * 61 * @ingroup PresolverIncludes 62 */ 63 SCIP_EXPORT 64 SCIP_RETCODE SCIPincludePresolDualinfer( 65 SCIP* scip /**< SCIP data structure */ 66 ); 67 68 #ifdef __cplusplus 69 } 70 #endif 71 72 #endif 73