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 heur_pscostdiving.h 26 * @ingroup PRIMALHEURISTICS 27 * @brief LP diving heuristic that chooses fixings w.r.t. the pseudo cost values 28 * @author Tobias Achterberg 29 * 30 * Diving heuristic: Iteratively fixes some fractional variable and resolves the LP-relaxation, thereby simulating a 31 * depth-first-search in the tree. Pseudocost Diving chooses the variable with the smallest ratio of estimated objective 32 * increase if rounding to either direction. If the variable is significantly different from its root LP vlaue, it will 33 * be rounded into the direction it developed (see @ref heur_linesearchdiving.h), if it is close to an integral point, 34 * it will be rounded to that one, otherwise it will be rounded into the direction of lower pseudocosts. One-level 35 * backtracking is applied: If the LP gets infeasible, the last fixing is undone, and the opposite fixing is tried. If 36 * this is infeasible, too, the procedure aborts. 37 */ 38 39 /*---+----1----+----2----+----3----+----4----+----5----+----6----+----7----+----8----+----9----+----0----+----1----+----2*/ 40 41 #ifndef __SCIP_HEUR_PSCOSTDIVING_H__ 42 #define __SCIP_HEUR_PSCOSTDIVING_H__ 43 44 #include "scip/def.h" 45 #include "scip/type_retcode.h" 46 #include "scip/type_scip.h" 47 48 #ifdef __cplusplus 49 extern "C" { 50 #endif 51 52 /** creates the pscostdiving heuristic and includes it in SCIP 53 * 54 * @ingroup PrimalHeuristicIncludes 55 */ 56 SCIP_EXPORT 57 SCIP_RETCODE SCIPincludeHeurPscostdiving( 58 SCIP* scip /**< SCIP data structure */ 59 ); 60 61 #ifdef __cplusplus 62 } 63 #endif 64 65 #endif 66