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Diffstat (limited to 'test/monniaux/glpk-4.65/src/draft/glpios12.c')
| -rw-r--r-- | test/monniaux/glpk-4.65/src/draft/glpios12.c | 177 |
1 files changed, 177 insertions, 0 deletions
diff --git a/test/monniaux/glpk-4.65/src/draft/glpios12.c b/test/monniaux/glpk-4.65/src/draft/glpios12.c new file mode 100644 index 00000000..bec6fa2c --- /dev/null +++ b/test/monniaux/glpk-4.65/src/draft/glpios12.c @@ -0,0 +1,177 @@ +/* glpios12.c (node selection heuristics) */ + +/*********************************************************************** +* This code is part of GLPK (GNU Linear Programming Kit). +* +* Copyright (C) 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008, +* 2009, 2010, 2011, 2013, 2018 Andrew Makhorin, Department for Applied +* Informatics, Moscow Aviation Institute, Moscow, Russia. All rights +* reserved. E-mail: <mao@gnu.org>. +* +* GLPK is free software: you can redistribute it and/or modify it +* under the terms of the GNU General Public License as published by +* the Free Software Foundation, either version 3 of the License, or +* (at your option) any later version. +* +* GLPK is distributed in the hope that it will be useful, but WITHOUT +* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY +* or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public +* License for more details. +* +* You should have received a copy of the GNU General Public License +* along with GLPK. If not, see <http://www.gnu.org/licenses/>. +***********************************************************************/ + +#include "env.h" +#include "ios.h" + +/*********************************************************************** +* NAME +* +* ios_choose_node - select subproblem to continue the search +* +* SYNOPSIS +* +* #include "glpios.h" +* int ios_choose_node(glp_tree *T); +* +* DESCRIPTION +* +* The routine ios_choose_node selects a subproblem from the active +* list to continue the search. The choice depends on the backtracking +* technique option. +* +* RETURNS +* +* The routine ios_choose_node return the reference number of the +* subproblem selected. */ + +static int most_feas(glp_tree *T); +static int best_proj(glp_tree *T); +static int best_node(glp_tree *T); + +int ios_choose_node(glp_tree *T) +{ int p; + if (T->parm->bt_tech == GLP_BT_DFS) + { /* depth first search */ + xassert(T->tail != NULL); + p = T->tail->p; + } + else if (T->parm->bt_tech == GLP_BT_BFS) + { /* breadth first search */ + xassert(T->head != NULL); + p = T->head->p; + } + else if (T->parm->bt_tech == GLP_BT_BLB) + { /* select node with best local bound */ + p = best_node(T); + } + else if (T->parm->bt_tech == GLP_BT_BPH) + { if (T->mip->mip_stat == GLP_UNDEF) + { /* "most integer feasible" subproblem */ + p = most_feas(T); + } + else + { /* best projection heuristic */ + p = best_proj(T); + } + } + else + xassert(T != T); + return p; +} + +static int most_feas(glp_tree *T) +{ /* select subproblem whose parent has minimal sum of integer + infeasibilities */ + IOSNPD *node; + int p; + double best; + p = 0, best = DBL_MAX; + for (node = T->head; node != NULL; node = node->next) + { xassert(node->up != NULL); + if (best > node->up->ii_sum) + p = node->p, best = node->up->ii_sum; + } + return p; +} + +static int best_proj(glp_tree *T) +{ /* select subproblem using the best projection heuristic */ + IOSNPD *root, *node; + int p; + double best, deg, obj; + /* the global bound must exist */ + xassert(T->mip->mip_stat == GLP_FEAS); + /* obtain pointer to the root node, which must exist */ + root = T->slot[1].node; + xassert(root != NULL); + /* deg estimates degradation of the objective function per unit + of the sum of integer infeasibilities */ + xassert(root->ii_sum > 0.0); + deg = (T->mip->mip_obj - root->bound) / root->ii_sum; + /* nothing has been selected so far */ + p = 0, best = DBL_MAX; + /* walk through the list of active subproblems */ + for (node = T->head; node != NULL; node = node->next) + { xassert(node->up != NULL); + /* obj estimates optimal objective value if the sum of integer + infeasibilities were zero */ + obj = node->up->bound + deg * node->up->ii_sum; + if (T->mip->dir == GLP_MAX) obj = - obj; + /* select the subproblem which has the best estimated optimal + objective value */ + if (best > obj) p = node->p, best = obj; + } + return p; +} + +static int best_node(glp_tree *T) +{ /* select subproblem with best local bound */ + IOSNPD *node, *best = NULL; + double bound, eps; + switch (T->mip->dir) + { case GLP_MIN: + bound = +DBL_MAX; + for (node = T->head; node != NULL; node = node->next) + if (bound > node->bound) bound = node->bound; + xassert(bound != +DBL_MAX); + eps = 1e-10 * (1.0 + fabs(bound)); + for (node = T->head; node != NULL; node = node->next) + { if (node->bound <= bound + eps) + { xassert(node->up != NULL); + if (best == NULL || +#if 1 + best->up->ii_sum > node->up->ii_sum) best = node; +#else + best->lp_obj > node->lp_obj) best = node; +#endif + } + } + break; + case GLP_MAX: + bound = -DBL_MAX; + for (node = T->head; node != NULL; node = node->next) + if (bound < node->bound) bound = node->bound; + xassert(bound != -DBL_MAX); + eps = 1e-10 * (1.0 + fabs(bound)); + for (node = T->head; node != NULL; node = node->next) + { if (node->bound >= bound - eps) + { xassert(node->up != NULL); + if (best == NULL || +#if 1 + best->up->ii_sum > node->up->ii_sum) best = node; +#else + best->lp_obj < node->lp_obj) best = node; +#endif + } + } + break; + default: + xassert(T != T); + } + xassert(best != NULL); + return best->p; +} + +/* eof */ |