alpar@1: /* glpapi13.c (branch-and-bound interface routines) */
alpar@1: 
alpar@1: /***********************************************************************
alpar@1: *  This code is part of GLPK (GNU Linear Programming Kit).
alpar@1: *
alpar@1: *  Copyright (C) 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008,
alpar@1: *  2009, 2010 Andrew Makhorin, Department for Applied Informatics,
alpar@1: *  Moscow Aviation Institute, Moscow, Russia. All rights reserved.
alpar@1: *  E-mail: <mao@gnu.org>.
alpar@1: *
alpar@1: *  GLPK is free software: you can redistribute it and/or modify it
alpar@1: *  under the terms of the GNU General Public License as published by
alpar@1: *  the Free Software Foundation, either version 3 of the License, or
alpar@1: *  (at your option) any later version.
alpar@1: *
alpar@1: *  GLPK is distributed in the hope that it will be useful, but WITHOUT
alpar@1: *  ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
alpar@1: *  or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public
alpar@1: *  License for more details.
alpar@1: *
alpar@1: *  You should have received a copy of the GNU General Public License
alpar@1: *  along with GLPK. If not, see <http://www.gnu.org/licenses/>.
alpar@1: ***********************************************************************/
alpar@1: 
alpar@1: #include "glpios.h"
alpar@1: 
alpar@1: /***********************************************************************
alpar@1: *  NAME
alpar@1: *
alpar@1: *  glp_ios_reason - determine reason for calling the callback routine
alpar@1: *
alpar@1: *  SYNOPSIS
alpar@1: *
alpar@1: *  glp_ios_reason(glp_tree *tree);
alpar@1: *
alpar@1: *  RETURNS
alpar@1: *
alpar@1: *  The routine glp_ios_reason returns a code, which indicates why the
alpar@1: *  user-defined callback routine is being called. */
alpar@1: 
alpar@1: int glp_ios_reason(glp_tree *tree)
alpar@1: {     return
alpar@1:          tree->reason;
alpar@1: }
alpar@1: 
alpar@1: /***********************************************************************
alpar@1: *  NAME
alpar@1: *
alpar@1: *  glp_ios_get_prob - access the problem object
alpar@1: *
alpar@1: *  SYNOPSIS
alpar@1: *
alpar@1: *  glp_prob *glp_ios_get_prob(glp_tree *tree);
alpar@1: *
alpar@1: *  DESCRIPTION
alpar@1: *
alpar@1: *  The routine glp_ios_get_prob can be called from the user-defined
alpar@1: *  callback routine to access the problem object, which is used by the
alpar@1: *  MIP solver. It is the original problem object passed to the routine
alpar@1: *  glp_intopt if the MIP presolver is not used; otherwise it is an
alpar@1: *  internal problem object built by the presolver. If the current
alpar@1: *  subproblem exists, LP segment of the problem object corresponds to
alpar@1: *  its LP relaxation.
alpar@1: *
alpar@1: *  RETURNS
alpar@1: *
alpar@1: *  The routine glp_ios_get_prob returns a pointer to the problem object
alpar@1: *  used by the MIP solver. */
alpar@1: 
alpar@1: glp_prob *glp_ios_get_prob(glp_tree *tree)
alpar@1: {     return
alpar@1:          tree->mip;
alpar@1: }
alpar@1: 
alpar@1: /***********************************************************************
alpar@1: *  NAME
alpar@1: *
alpar@1: *  glp_ios_tree_size - determine size of the branch-and-bound tree
alpar@1: *
alpar@1: *  SYNOPSIS
alpar@1: *
alpar@1: *  void glp_ios_tree_size(glp_tree *tree, int *a_cnt, int *n_cnt,
alpar@1: *     int *t_cnt);
alpar@1: *
alpar@1: *  DESCRIPTION
alpar@1: *
alpar@1: *  The routine glp_ios_tree_size stores the following three counts which
alpar@1: *  characterize the current size of the branch-and-bound tree:
alpar@1: *
alpar@1: *  a_cnt is the current number of active nodes, i.e. the current size of
alpar@1: *        the active list;
alpar@1: *
alpar@1: *  n_cnt is the current number of all (active and inactive) nodes;
alpar@1: *
alpar@1: *  t_cnt is the total number of nodes including those which have been
alpar@1: *        already removed from the tree. This count is increased whenever
alpar@1: *        a new node appears in the tree and never decreased.
alpar@1: *
alpar@1: *  If some of the parameters a_cnt, n_cnt, t_cnt is a null pointer, the
alpar@1: *  corresponding count is not stored. */
alpar@1: 
alpar@1: void glp_ios_tree_size(glp_tree *tree, int *a_cnt, int *n_cnt,
alpar@1:       int *t_cnt)
alpar@1: {     if (a_cnt != NULL) *a_cnt = tree->a_cnt;
alpar@1:       if (n_cnt != NULL) *n_cnt = tree->n_cnt;
alpar@1:       if (t_cnt != NULL) *t_cnt = tree->t_cnt;
alpar@1:       return;
alpar@1: }
alpar@1: 
alpar@1: /***********************************************************************
alpar@1: *  NAME
alpar@1: *
alpar@1: *  glp_ios_curr_node - determine current active subproblem
alpar@1: *
alpar@1: *  SYNOPSIS
alpar@1: *
alpar@1: *  int glp_ios_curr_node(glp_tree *tree);
alpar@1: *
alpar@1: *  RETURNS
alpar@1: *
alpar@1: *  The routine glp_ios_curr_node returns the reference number of the
alpar@1: *  current active subproblem. However, if the current subproblem does
alpar@1: *  not exist, the routine returns zero. */
alpar@1: 
alpar@1: int glp_ios_curr_node(glp_tree *tree)
alpar@1: {     IOSNPD *node;
alpar@1:       /* obtain pointer to the current subproblem */
alpar@1:       node = tree->curr;
alpar@1:       /* return its reference number */
alpar@1:       return node == NULL ? 0 : node->p;
alpar@1: }
alpar@1: 
alpar@1: /***********************************************************************
alpar@1: *  NAME
alpar@1: *
alpar@1: *  glp_ios_next_node - determine next active subproblem
alpar@1: *
alpar@1: *  SYNOPSIS
alpar@1: *
alpar@1: *  int glp_ios_next_node(glp_tree *tree, int p);
alpar@1: *
alpar@1: *  RETURNS
alpar@1: *
alpar@1: *  If the parameter p is zero, the routine glp_ios_next_node returns
alpar@1: *  the reference number of the first active subproblem. However, if the
alpar@1: *  tree is empty, zero is returned.
alpar@1: *
alpar@1: *  If the parameter p is not zero, it must specify the reference number
alpar@1: *  of some active subproblem, in which case the routine returns the
alpar@1: *  reference number of the next active subproblem. However, if there is
alpar@1: *  no next active subproblem in the list, zero is returned.
alpar@1: *
alpar@1: *  All subproblems in the active list are ordered chronologically, i.e.
alpar@1: *  subproblem A precedes subproblem B if A was created before B. */
alpar@1: 
alpar@1: int glp_ios_next_node(glp_tree *tree, int p)
alpar@1: {     IOSNPD *node;
alpar@1:       if (p == 0)
alpar@1:       {  /* obtain pointer to the first active subproblem */
alpar@1:          node = tree->head;
alpar@1:       }
alpar@1:       else
alpar@1:       {  /* obtain pointer to the specified subproblem */
alpar@1:          if (!(1 <= p && p <= tree->nslots))
alpar@1: err:        xerror("glp_ios_next_node: p = %d; invalid subproblem refer"
alpar@1:                "ence number\n", p);
alpar@1:          node = tree->slot[p].node;
alpar@1:          if (node == NULL) goto err;
alpar@1:          /* the specified subproblem must be active */
alpar@1:          if (node->count != 0)
alpar@1:             xerror("glp_ios_next_node: p = %d; subproblem not in the ac"
alpar@1:                "tive list\n", p);
alpar@1:          /* obtain pointer to the next active subproblem */
alpar@1:          node = node->next;
alpar@1:       }
alpar@1:       /* return the reference number */
alpar@1:       return node == NULL ? 0 : node->p;
alpar@1: }
alpar@1: 
alpar@1: /***********************************************************************
alpar@1: *  NAME
alpar@1: *
alpar@1: *  glp_ios_prev_node - determine previous active subproblem
alpar@1: *
alpar@1: *  SYNOPSIS
alpar@1: *
alpar@1: *  int glp_ios_prev_node(glp_tree *tree, int p);
alpar@1: *
alpar@1: *  RETURNS
alpar@1: *
alpar@1: *  If the parameter p is zero, the routine glp_ios_prev_node returns
alpar@1: *  the reference number of the last active subproblem. However, if the
alpar@1: *  tree is empty, zero is returned.
alpar@1: *
alpar@1: *  If the parameter p is not zero, it must specify the reference number
alpar@1: *  of some active subproblem, in which case the routine returns the
alpar@1: *  reference number of the previous active subproblem. However, if there
alpar@1: *  is no previous active subproblem in the list, zero is returned.
alpar@1: *
alpar@1: *  All subproblems in the active list are ordered chronologically, i.e.
alpar@1: *  subproblem A precedes subproblem B if A was created before B. */
alpar@1: 
alpar@1: int glp_ios_prev_node(glp_tree *tree, int p)
alpar@1: {     IOSNPD *node;
alpar@1:       if (p == 0)
alpar@1:       {  /* obtain pointer to the last active subproblem */
alpar@1:          node = tree->tail;
alpar@1:       }
alpar@1:       else
alpar@1:       {  /* obtain pointer to the specified subproblem */
alpar@1:          if (!(1 <= p && p <= tree->nslots))
alpar@1: err:        xerror("glp_ios_prev_node: p = %d; invalid subproblem refer"
alpar@1:                "ence number\n", p);
alpar@1:          node = tree->slot[p].node;
alpar@1:          if (node == NULL) goto err;
alpar@1:          /* the specified subproblem must be active */
alpar@1:          if (node->count != 0)
alpar@1:             xerror("glp_ios_prev_node: p = %d; subproblem not in the ac"
alpar@1:                "tive list\n", p);
alpar@1:          /* obtain pointer to the previous active subproblem */
alpar@1:          node = node->prev;
alpar@1:       }
alpar@1:       /* return the reference number */
alpar@1:       return node == NULL ? 0 : node->p;
alpar@1: }
alpar@1: 
alpar@1: /***********************************************************************
alpar@1: *  NAME
alpar@1: *
alpar@1: *  glp_ios_up_node - determine parent subproblem
alpar@1: *
alpar@1: *  SYNOPSIS
alpar@1: *
alpar@1: *  int glp_ios_up_node(glp_tree *tree, int p);
alpar@1: *
alpar@1: *  RETURNS
alpar@1: *
alpar@1: *  The parameter p must specify the reference number of some (active or
alpar@1: *  inactive) subproblem, in which case the routine iet_get_up_node
alpar@1: *  returns the reference number of its parent subproblem. However, if
alpar@1: *  the specified subproblem is the root of the tree and, therefore, has
alpar@1: *  no parent, the routine returns zero. */
alpar@1: 
alpar@1: int glp_ios_up_node(glp_tree *tree, int p)
alpar@1: {     IOSNPD *node;
alpar@1:       /* obtain pointer to the specified subproblem */
alpar@1:       if (!(1 <= p && p <= tree->nslots))
alpar@1: err:     xerror("glp_ios_up_node: p = %d; invalid subproblem reference "
alpar@1:             "number\n", p);
alpar@1:       node = tree->slot[p].node;
alpar@1:       if (node == NULL) goto err;
alpar@1:       /* obtain pointer to the parent subproblem */
alpar@1:       node = node->up;
alpar@1:       /* return the reference number */
alpar@1:       return node == NULL ? 0 : node->p;
alpar@1: }
alpar@1: 
alpar@1: /***********************************************************************
alpar@1: *  NAME
alpar@1: *
alpar@1: *  glp_ios_node_level - determine subproblem level
alpar@1: *
alpar@1: *  SYNOPSIS
alpar@1: *
alpar@1: *  int glp_ios_node_level(glp_tree *tree, int p);
alpar@1: *
alpar@1: *  RETURNS
alpar@1: *
alpar@1: *  The routine glp_ios_node_level returns the level of the subproblem,
alpar@1: *  whose reference number is p, in the branch-and-bound tree. (The root
alpar@1: *  subproblem has level 0, and the level of any other subproblem is the
alpar@1: *  level of its parent plus one.) */
alpar@1: 
alpar@1: int glp_ios_node_level(glp_tree *tree, int p)
alpar@1: {     IOSNPD *node;
alpar@1:       /* obtain pointer to the specified subproblem */
alpar@1:       if (!(1 <= p && p <= tree->nslots))
alpar@1: err:     xerror("glp_ios_node_level: p = %d; invalid subproblem referen"
alpar@1:             "ce number\n", p);
alpar@1:       node = tree->slot[p].node;
alpar@1:       if (node == NULL) goto err;
alpar@1:       /* return the node level */
alpar@1:       return node->level;
alpar@1: }
alpar@1: 
alpar@1: /***********************************************************************
alpar@1: *  NAME
alpar@1: *
alpar@1: *  glp_ios_node_bound - determine subproblem local bound
alpar@1: *
alpar@1: *  SYNOPSIS
alpar@1: *
alpar@1: *  double glp_ios_node_bound(glp_tree *tree, int p);
alpar@1: *
alpar@1: *  RETURNS
alpar@1: *
alpar@1: *  The routine glp_ios_node_bound returns the local bound for (active or
alpar@1: *  inactive) subproblem, whose reference number is p.
alpar@1: *
alpar@1: *  COMMENTS
alpar@1: *
alpar@1: *  The local bound for subproblem p is an lower (minimization) or upper
alpar@1: *  (maximization) bound for integer optimal solution to this subproblem
alpar@1: *  (not to the original problem). This bound is local in the sense that
alpar@1: *  only subproblems in the subtree rooted at node p cannot have better
alpar@1: *  integer feasible solutions.
alpar@1: *
alpar@1: *  On creating a subproblem (due to the branching step) its local bound
alpar@1: *  is inherited from its parent and then may get only stronger (never
alpar@1: *  weaker). For the root subproblem its local bound is initially set to
alpar@1: *  -DBL_MAX (minimization) or +DBL_MAX (maximization) and then improved
alpar@1: *  as the root LP relaxation has been solved.
alpar@1: *
alpar@1: *  Note that the local bound is not necessarily the optimal objective
alpar@1: *  value to corresponding LP relaxation; it may be stronger. */
alpar@1: 
alpar@1: double glp_ios_node_bound(glp_tree *tree, int p)
alpar@1: {     IOSNPD *node;
alpar@1:       /* obtain pointer to the specified subproblem */
alpar@1:       if (!(1 <= p && p <= tree->nslots))
alpar@1: err:     xerror("glp_ios_node_bound: p = %d; invalid subproblem referen"
alpar@1:             "ce number\n", p);
alpar@1:       node = tree->slot[p].node;
alpar@1:       if (node == NULL) goto err;
alpar@1:       /* return the node local bound */
alpar@1:       return node->bound;
alpar@1: }
alpar@1: 
alpar@1: /***********************************************************************
alpar@1: *  NAME
alpar@1: *
alpar@1: *  glp_ios_best_node - find active subproblem with best local bound
alpar@1: *
alpar@1: *  SYNOPSIS
alpar@1: *
alpar@1: *  int glp_ios_best_node(glp_tree *tree);
alpar@1: *
alpar@1: *  RETURNS
alpar@1: *
alpar@1: *  The routine glp_ios_best_node returns the reference number of the
alpar@1: *  active subproblem, whose local bound is best (i.e. smallest in case
alpar@1: *  of minimization or largest in case of maximization). However, if the
alpar@1: *  tree is empty, the routine returns zero.
alpar@1: *
alpar@1: *  COMMENTS
alpar@1: *
alpar@1: *  The best local bound is an lower (minimization) or upper
alpar@1: *  (maximization) bound for integer optimal solution to the original
alpar@1: *  MIP problem. */
alpar@1: 
alpar@1: int glp_ios_best_node(glp_tree *tree)
alpar@1: {     return
alpar@1:          ios_best_node(tree);
alpar@1: }
alpar@1: 
alpar@1: /***********************************************************************
alpar@1: *  NAME
alpar@1: *
alpar@1: *  glp_ios_mip_gap - compute relative MIP gap
alpar@1: *
alpar@1: *  SYNOPSIS
alpar@1: *
alpar@1: *  double glp_ios_mip_gap(glp_tree *tree);
alpar@1: *
alpar@1: *  DESCRIPTION
alpar@1: *
alpar@1: *  The routine glp_ios_mip_gap computes the relative MIP gap with the
alpar@1: *  following formula:
alpar@1: *
alpar@1: *     gap = |best_mip - best_bnd| / (|best_mip| + DBL_EPSILON),
alpar@1: *
alpar@1: *  where best_mip is the best integer feasible solution found so far,
alpar@1: *  best_bnd is the best (global) bound. If no integer feasible solution
alpar@1: *  has been found yet, gap is set to DBL_MAX.
alpar@1: *
alpar@1: *  RETURNS
alpar@1: *
alpar@1: *  The routine glp_ios_mip_gap returns the relative MIP gap. */
alpar@1: 
alpar@1: double glp_ios_mip_gap(glp_tree *tree)
alpar@1: {     return
alpar@1:          ios_relative_gap(tree);
alpar@1: }
alpar@1: 
alpar@1: /***********************************************************************
alpar@1: *  NAME
alpar@1: *
alpar@1: *  glp_ios_node_data - access subproblem application-specific data
alpar@1: *
alpar@1: *  SYNOPSIS
alpar@1: *
alpar@1: *  void *glp_ios_node_data(glp_tree *tree, int p);
alpar@1: *
alpar@1: *  DESCRIPTION
alpar@1: *
alpar@1: *  The routine glp_ios_node_data allows the application accessing a
alpar@1: *  memory block allocated for the subproblem (which may be active or
alpar@1: *  inactive), whose reference number is p.
alpar@1: *
alpar@1: *  The size of the block is defined by the control parameter cb_size
alpar@1: *  passed to the routine glp_intopt. The block is initialized by binary
alpar@1: *  zeros on creating corresponding subproblem, and its contents is kept
alpar@1: *  until the subproblem will be removed from the tree.
alpar@1: *
alpar@1: *  The application may use these memory blocks to store specific data
alpar@1: *  for each subproblem.
alpar@1: *
alpar@1: *  RETURNS
alpar@1: *
alpar@1: *  The routine glp_ios_node_data returns a pointer to the memory block
alpar@1: *  for the specified subproblem. Note that if cb_size = 0, the routine
alpar@1: *  returns a null pointer. */
alpar@1: 
alpar@1: void *glp_ios_node_data(glp_tree *tree, int p)
alpar@1: {     IOSNPD *node;
alpar@1:       /* obtain pointer to the specified subproblem */
alpar@1:       if (!(1 <= p && p <= tree->nslots))
alpar@1: err:     xerror("glp_ios_node_level: p = %d; invalid subproblem referen"
alpar@1:             "ce number\n", p);
alpar@1:       node = tree->slot[p].node;
alpar@1:       if (node == NULL) goto err;
alpar@1:       /* return pointer to the application-specific data */
alpar@1:       return node->data;
alpar@1: }
alpar@1: 
alpar@1: /***********************************************************************
alpar@1: *  NAME
alpar@1: *
alpar@1: *  glp_ios_row_attr - retrieve additional row attributes
alpar@1: *
alpar@1: *  SYNOPSIS
alpar@1: *
alpar@1: *  void glp_ios_row_attr(glp_tree *tree, int i, glp_attr *attr);
alpar@1: *
alpar@1: *  DESCRIPTION
alpar@1: *
alpar@1: *  The routine glp_ios_row_attr retrieves additional attributes of row
alpar@1: *  i and stores them in the structure glp_attr. */
alpar@1: 
alpar@1: void glp_ios_row_attr(glp_tree *tree, int i, glp_attr *attr)
alpar@1: {     GLPROW *row;
alpar@1:       if (!(1 <= i && i <= tree->mip->m))
alpar@1:          xerror("glp_ios_row_attr: i = %d; row number out of range\n",
alpar@1:             i);
alpar@1:       row = tree->mip->row[i];
alpar@1:       attr->level = row->level;
alpar@1:       attr->origin = row->origin;
alpar@1:       attr->klass = row->klass;
alpar@1:       return;
alpar@1: }
alpar@1: 
alpar@1: /**********************************************************************/
alpar@1: 
alpar@1: int glp_ios_pool_size(glp_tree *tree)
alpar@1: {     /* determine current size of the cut pool */
alpar@1:       if (tree->reason != GLP_ICUTGEN)
alpar@1:          xerror("glp_ios_pool_size: operation not allowed\n");
alpar@1:       xassert(tree->local != NULL);
alpar@1:       return tree->local->size;
alpar@1: }
alpar@1: 
alpar@1: /**********************************************************************/
alpar@1: 
alpar@1: int glp_ios_add_row(glp_tree *tree,
alpar@1:       const char *name, int klass, int flags, int len, const int ind[],
alpar@1:       const double val[], int type, double rhs)
alpar@1: {     /* add row (constraint) to the cut pool */
alpar@1:       int num;
alpar@1:       if (tree->reason != GLP_ICUTGEN)
alpar@1:          xerror("glp_ios_add_row: operation not allowed\n");
alpar@1:       xassert(tree->local != NULL);
alpar@1:       num = ios_add_row(tree, tree->local, name, klass, flags, len,
alpar@1:          ind, val, type, rhs);
alpar@1:       return num;
alpar@1: }
alpar@1: 
alpar@1: /**********************************************************************/
alpar@1: 
alpar@1: void glp_ios_del_row(glp_tree *tree, int i)
alpar@1: {     /* remove row (constraint) from the cut pool */
alpar@1:       if (tree->reason != GLP_ICUTGEN)
alpar@1:          xerror("glp_ios_del_row: operation not allowed\n");
alpar@1:       ios_del_row(tree, tree->local, i);
alpar@1:       return;
alpar@1: }
alpar@1: 
alpar@1: /**********************************************************************/
alpar@1: 
alpar@1: void glp_ios_clear_pool(glp_tree *tree)
alpar@1: {     /* remove all rows (constraints) from the cut pool */
alpar@1:       if (tree->reason != GLP_ICUTGEN)
alpar@1:          xerror("glp_ios_clear_pool: operation not allowed\n");
alpar@1:       ios_clear_pool(tree, tree->local);
alpar@1:       return;
alpar@1: }
alpar@1: 
alpar@1: /***********************************************************************
alpar@1: *  NAME
alpar@1: *
alpar@1: *  glp_ios_can_branch - check if can branch upon specified variable
alpar@1: *
alpar@1: *  SYNOPSIS
alpar@1: *
alpar@1: *  int glp_ios_can_branch(glp_tree *tree, int j);
alpar@1: *
alpar@1: *  RETURNS
alpar@1: *
alpar@1: *  If j-th variable (column) can be used to branch upon, the routine
alpar@1: *  glp_ios_can_branch returns non-zero, otherwise zero. */
alpar@1: 
alpar@1: int glp_ios_can_branch(glp_tree *tree, int j)
alpar@1: {     if (!(1 <= j && j <= tree->mip->n))
alpar@1:          xerror("glp_ios_can_branch: j = %d; column number out of range"
alpar@1:             "\n", j);
alpar@1:       return tree->non_int[j];
alpar@1: }
alpar@1: 
alpar@1: /***********************************************************************
alpar@1: *  NAME
alpar@1: *
alpar@1: *  glp_ios_branch_upon - choose variable to branch upon
alpar@1: *
alpar@1: *  SYNOPSIS
alpar@1: *
alpar@1: *  void glp_ios_branch_upon(glp_tree *tree, int j, int sel);
alpar@1: *
alpar@1: *  DESCRIPTION
alpar@1: *
alpar@1: *  The routine glp_ios_branch_upon can be called from the user-defined
alpar@1: *  callback routine in response to the reason GLP_IBRANCH to choose a
alpar@1: *  branching variable, whose ordinal number is j. Should note that only
alpar@1: *  variables, for which the routine glp_ios_can_branch returns non-zero,
alpar@1: *  can be used to branch upon.
alpar@1: *
alpar@1: *  The parameter sel is a flag that indicates which branch (subproblem)
alpar@1: *  should be selected next to continue the search:
alpar@1: *
alpar@1: *  GLP_DN_BRNCH - select down-branch;
alpar@1: *  GLP_UP_BRNCH - select up-branch;
alpar@1: *  GLP_NO_BRNCH - use general selection technique. */
alpar@1: 
alpar@1: void glp_ios_branch_upon(glp_tree *tree, int j, int sel)
alpar@1: {     if (!(1 <= j && j <= tree->mip->n))
alpar@1:          xerror("glp_ios_branch_upon: j = %d; column number out of rang"
alpar@1:             "e\n", j);
alpar@1:       if (!(sel == GLP_DN_BRNCH || sel == GLP_UP_BRNCH ||
alpar@1:             sel == GLP_NO_BRNCH))
alpar@1:          xerror("glp_ios_branch_upon: sel = %d: invalid branch selectio"
alpar@1:             "n flag\n", sel);
alpar@1:       if (!(tree->non_int[j]))
alpar@1:          xerror("glp_ios_branch_upon: j = %d; variable cannot be used t"
alpar@1:             "o branch upon\n", j);
alpar@1:       if (tree->br_var != 0)
alpar@1:          xerror("glp_ios_branch_upon: branching variable already chosen"
alpar@1:             "\n");
alpar@1:       tree->br_var = j;
alpar@1:       tree->br_sel = sel;
alpar@1:       return;
alpar@1: }
alpar@1: 
alpar@1: /***********************************************************************
alpar@1: *  NAME
alpar@1: *
alpar@1: *  glp_ios_select_node - select subproblem to continue the search
alpar@1: *
alpar@1: *  SYNOPSIS
alpar@1: *
alpar@1: *  void glp_ios_select_node(glp_tree *tree, int p);
alpar@1: *
alpar@1: *  DESCRIPTION
alpar@1: *
alpar@1: *  The routine glp_ios_select_node can be called from the user-defined
alpar@1: *  callback routine in response to the reason GLP_ISELECT to select an
alpar@1: *  active subproblem, whose reference number is p. The search will be
alpar@1: *  continued from the subproblem selected. */
alpar@1: 
alpar@1: void glp_ios_select_node(glp_tree *tree, int p)
alpar@1: {     IOSNPD *node;
alpar@1:       /* obtain pointer to the specified subproblem */
alpar@1:       if (!(1 <= p && p <= tree->nslots))
alpar@1: err:     xerror("glp_ios_select_node: p = %d; invalid subproblem refere"
alpar@1:             "nce number\n", p);
alpar@1:       node = tree->slot[p].node;
alpar@1:       if (node == NULL) goto err;
alpar@1:       /* the specified subproblem must be active */
alpar@1:       if (node->count != 0)
alpar@1:          xerror("glp_ios_select_node: p = %d; subproblem not in the act"
alpar@1:             "ive list\n", p);
alpar@1:       /* no subproblem must be selected yet */
alpar@1:       if (tree->next_p != 0)
alpar@1:          xerror("glp_ios_select_node: subproblem already selected\n");
alpar@1:       /* select the specified subproblem to continue the search */
alpar@1:       tree->next_p = p;
alpar@1:       return;
alpar@1: }
alpar@1: 
alpar@1: /***********************************************************************
alpar@1: *  NAME
alpar@1: *
alpar@1: *  glp_ios_heur_sol - provide solution found by heuristic
alpar@1: *
alpar@1: *  SYNOPSIS
alpar@1: *
alpar@1: *  int glp_ios_heur_sol(glp_tree *tree, const double x[]);
alpar@1: *
alpar@1: *  DESCRIPTION
alpar@1: *
alpar@1: *  The routine glp_ios_heur_sol can be called from the user-defined
alpar@1: *  callback routine in response to the reason GLP_IHEUR to provide an
alpar@1: *  integer feasible solution found by a primal heuristic.
alpar@1: *
alpar@1: *  Primal values of *all* variables (columns) found by the heuristic
alpar@1: *  should be placed in locations x[1], ..., x[n], where n is the number
alpar@1: *  of columns in the original problem object. Note that the routine
alpar@1: *  glp_ios_heur_sol *does not* check primal feasibility of the solution
alpar@1: *  provided.
alpar@1: *
alpar@1: *  Using the solution passed in the array x the routine computes value
alpar@1: *  of the objective function. If the objective value is better than the
alpar@1: *  best known integer feasible solution, the routine computes values of
alpar@1: *  auxiliary variables (rows) and stores all solution components in the
alpar@1: *  problem object.
alpar@1: *
alpar@1: *  RETURNS
alpar@1: *
alpar@1: *  If the provided solution is accepted, the routine glp_ios_heur_sol
alpar@1: *  returns zero. Otherwise, if the provided solution is rejected, the
alpar@1: *  routine returns non-zero. */
alpar@1: 
alpar@1: int glp_ios_heur_sol(glp_tree *tree, const double x[])
alpar@1: {     glp_prob *mip = tree->mip;
alpar@1:       int m = tree->orig_m;
alpar@1:       int n = tree->n;
alpar@1:       int i, j;
alpar@1:       double obj;
alpar@1:       xassert(mip->m >= m);
alpar@1:       xassert(mip->n == n);
alpar@1:       /* check values of integer variables and compute value of the
alpar@1:          objective function */
alpar@1:       obj = mip->c0;
alpar@1:       for (j = 1; j <= n; j++)
alpar@1:       {  GLPCOL *col = mip->col[j];
alpar@1:          if (col->kind == GLP_IV)
alpar@1:          {  /* provided value must be integral */
alpar@1:             if (x[j] != floor(x[j])) return 1;
alpar@1:          }
alpar@1:          obj += col->coef * x[j];
alpar@1:       }
alpar@1:       /* check if the provided solution is better than the best known
alpar@1:          integer feasible solution */
alpar@1:       if (mip->mip_stat == GLP_FEAS)
alpar@1:       {  switch (mip->dir)
alpar@1:          {  case GLP_MIN:
alpar@1:                if (obj >= tree->mip->mip_obj) return 1;
alpar@1:                break;
alpar@1:             case GLP_MAX:
alpar@1:                if (obj <= tree->mip->mip_obj) return 1;
alpar@1:                break;
alpar@1:             default:
alpar@1:                xassert(mip != mip);
alpar@1:          }
alpar@1:       }
alpar@1:       /* it is better; store it in the problem object */
alpar@1:       if (tree->parm->msg_lev >= GLP_MSG_ON)
alpar@1:          xprintf("Solution found by heuristic: %.12g\n", obj);
alpar@1:       mip->mip_stat = GLP_FEAS;
alpar@1:       mip->mip_obj = obj;
alpar@1:       for (j = 1; j <= n; j++)
alpar@1:          mip->col[j]->mipx = x[j];
alpar@1:       for (i = 1; i <= m; i++)
alpar@1:       {  GLPROW *row = mip->row[i];
alpar@1:          GLPAIJ *aij;
alpar@1:          row->mipx = 0.0;
alpar@1:          for (aij = row->ptr; aij != NULL; aij = aij->r_next)
alpar@1:             row->mipx += aij->val * aij->col->mipx;
alpar@1:       }
alpar@1:       return 0;
alpar@1: }
alpar@1: 
alpar@1: /***********************************************************************
alpar@1: *  NAME
alpar@1: *
alpar@1: *  glp_ios_terminate - terminate the solution process.
alpar@1: *
alpar@1: *  SYNOPSIS
alpar@1: *
alpar@1: *  void glp_ios_terminate(glp_tree *tree);
alpar@1: *
alpar@1: *  DESCRIPTION
alpar@1: *
alpar@1: *  The routine glp_ios_terminate sets a flag indicating that the MIP
alpar@1: *  solver should prematurely terminate the search. */
alpar@1: 
alpar@1: void glp_ios_terminate(glp_tree *tree)
alpar@1: {     if (tree->parm->msg_lev >= GLP_MSG_DBG)
alpar@1:          xprintf("The search is prematurely terminated due to applicati"
alpar@1:             "on request\n");
alpar@1:       tree->stop = 1;
alpar@1:       return;
alpar@1: }
alpar@1: 
alpar@1: /* eof */