static void show_progress(glp_tree *T, int bingo)
{ int p;
double temp;
char best_mip[50], best_bound[50], *rho, rel_gap[50];
/* format the best known integer feasible solution */
if (T->mip->mip_stat == GLP_FEAS)
sprintf(best_mip, "%17.9e", T->mip->mip_obj);
else
sprintf(best_mip, "%17s", "not found yet");
/* determine reference number of an active subproblem whose local
bound is best */
p = ios_best_node(T);
/* format the best bound */
if (p == 0)
sprintf(best_bound, "%17s", "tree is empty");
else
{ temp = T->slot[p].node->bound;
if (temp == -DBL_MAX)
sprintf(best_bound, "%17s", "-inf");
else if (temp == +DBL_MAX)
sprintf(best_bound, "%17s", "+inf");
else
sprintf(best_bound, "%17.9e", temp);
}
/* choose the relation sign between global bounds */
if (T->mip->dir == GLP_MIN)
rho = ">=";
else if (T->mip->dir == GLP_MAX)
rho = "<=";
else
xassert(T != T);
/* format the relative mip gap */
temp = ios_relative_gap(T);
if (temp == 0.0)
sprintf(rel_gap, " 0.0%%");
else if (temp < 0.001)
sprintf(rel_gap, "< 0.1%%");
else if (temp <= 9.999)
sprintf(rel_gap, "%5.1f%%", 100.0 * temp);
else
sprintf(rel_gap, "%6s", "");
/* display progress of the search */
xprintf("+%6d: %s %s %s %s %s (%d; %d)\n",
T->mip->it_cnt, bingo ? ">>>>>" : "mip =", best_mip, rho,
best_bound, rel_gap, T->a_cnt, T->t_cnt - T->n_cnt);
T->tm_lag = xtime();
return;
}
double glp_ios_mip_gap(glp_tree *tree)
{ return
ios_relative_gap(tree);
}
int ios_driver(glp_tree *T)
{ int p, curr_p, p_stat, d_stat, ret;
#if 1 /* carry out to glp_tree */
int pred_p = 0;
/* if the current subproblem has been just created due to
branching, pred_p is the reference number of its parent
subproblem, otherwise pred_p is zero */
#endif
glp_long ttt = T->tm_beg;
#if 0
((glp_iocp *)T->parm)->msg_lev = GLP_MSG_DBG;
#endif
/* on entry to the B&B driver it is assumed that the active list
contains the only active (i.e. root) subproblem, which is the
original MIP problem to be solved */
loop: /* main loop starts here */
/* at this point the current subproblem does not exist */
xassert(T->curr == NULL);
/* if the active list is empty, the search is finished */
if (T->head == NULL)
{ if (T->parm->msg_lev >= GLP_MSG_DBG)
xprintf("Active list is empty!\n");
xassert(dmp_in_use(T->pool).lo == 0);
ret = 0;
goto done;
}
/* select some active subproblem to continue the search */
xassert(T->next_p == 0);
/* let the application program select subproblem */
if (T->parm->cb_func != NULL)
{ xassert(T->reason == 0);
T->reason = GLP_ISELECT;
T->parm->cb_func(T, T->parm->cb_info);
T->reason = 0;
if (T->stop)
{ ret = GLP_ESTOP;
goto done;
}
}
if (T->next_p != 0)
{ /* the application program has selected something */
;
}
else if (T->a_cnt == 1)
{ /* the only active subproblem exists, so select it */
xassert(T->head->next == NULL);
T->next_p = T->head->p;
}
else if (T->child != 0)
{ /* select one of branching childs suggested by the branching
heuristic */
T->next_p = T->child;
}
else
{ /* select active subproblem as specified by the backtracking
technique option */
T->next_p = ios_choose_node(T);
}
/* the active subproblem just selected becomes current */
ios_revive_node(T, T->next_p);
T->next_p = T->child = 0;
/* invalidate pred_p, if it is not the reference number of the
parent of the current subproblem */
if (T->curr->up != NULL && T->curr->up->p != pred_p) pred_p = 0;
/* determine the reference number of the current subproblem */
p = T->curr->p;
if (T->parm->msg_lev >= GLP_MSG_DBG)
{ xprintf("-----------------------------------------------------"
"-------------------\n");
xprintf("Processing node %d at level %d\n", p, T->curr->level);
}
/* if it is the root subproblem, initialize cut generators */
if (p == 1)
{ if (T->parm->gmi_cuts == GLP_ON)
{ if (T->parm->msg_lev >= GLP_MSG_ALL)
xprintf("Gomory's cuts enabled\n");
}
if (T->parm->mir_cuts == GLP_ON)
{ if (T->parm->msg_lev >= GLP_MSG_ALL)
xprintf("MIR cuts enabled\n");
xassert(T->mir_gen == NULL);
T->mir_gen = ios_mir_init(T);
}
if (T->parm->cov_cuts == GLP_ON)
{ if (T->parm->msg_lev >= GLP_MSG_ALL)
xprintf("Cover cuts enabled\n");
}
if (T->parm->clq_cuts == GLP_ON)
{ xassert(T->clq_gen == NULL);
if (T->parm->msg_lev >= GLP_MSG_ALL)
xprintf("Clique cuts enabled\n");
T->clq_gen = ios_clq_init(T);
}
}
more: /* minor loop starts here */
/* at this point the current subproblem needs either to be solved
for the first time or re-optimized due to reformulation */
/* display current progress of the search */
if (T->parm->msg_lev >= GLP_MSG_DBG ||
T->parm->msg_lev >= GLP_MSG_ON &&
(double)(T->parm->out_frq - 1) <=
1000.0 * xdifftime(xtime(), T->tm_lag))
show_progress(T, 0);
if (T->parm->msg_lev >= GLP_MSG_ALL &&
xdifftime(xtime(), ttt) >= 60.0)
#if 0 /* 16/II-2012 */
{ glp_long total;
glp_mem_usage(NULL, NULL, &total, NULL);
xprintf("Time used: %.1f secs. Memory used: %.1f Mb.\n",
xdifftime(xtime(), T->tm_beg), xltod(total) / 1048576.0);
ttt = xtime();
}
#else
{ size_t total;
glp_mem_usage(NULL, NULL, &total, NULL);
xprintf("Time used: %.1f secs. Memory used: %.1f Mb.\n",
xdifftime(xtime(), T->tm_beg), (double)total / 1048576.0);
ttt = xtime();
}
#endif
/* check the mip gap */
if (T->parm->mip_gap > 0.0 &&
ios_relative_gap(T) <= T->parm->mip_gap)
{ if (T->parm->msg_lev >= GLP_MSG_DBG)
xprintf("Relative gap tolerance reached; search terminated "
"\n");
ret = GLP_EMIPGAP;
goto done;
}
/* check if the time limit has been exhausted */
if (T->parm->tm_lim < INT_MAX &&
(double)(T->parm->tm_lim - 1) <=
1000.0 * xdifftime(xtime(), T->tm_beg))
{ if (T->parm->msg_lev >= GLP_MSG_DBG)
xprintf("Time limit exhausted; search terminated\n");
ret = GLP_ETMLIM;
goto done;
}
/* let the application program preprocess the subproblem */
if (T->parm->cb_func != NULL)
{ xassert(T->reason == 0);
T->reason = GLP_IPREPRO;
T->parm->cb_func(T, T->parm->cb_info);
T->reason = 0;
if (T->stop)
{ ret = GLP_ESTOP;
goto done;
}
}
/* perform basic preprocessing */
if (T->parm->pp_tech == GLP_PP_NONE)
;
else if (T->parm->pp_tech == GLP_PP_ROOT)
{ if (T->curr->level == 0)
{ if (ios_preprocess_node(T, 100))
goto fath;
}
}
else if (T->parm->pp_tech == GLP_PP_ALL)
{ if (ios_preprocess_node(T, T->curr->level == 0 ? 100 : 10))
goto fath;
}
else
xassert(T != T);
/* preprocessing may improve the global bound */
if (!is_branch_hopeful(T, p))
{ xprintf("*** not tested yet ***\n");
goto fath;
}
/* solve LP relaxation of the current subproblem */
if (T->parm->msg_lev >= GLP_MSG_DBG)
xprintf("Solving LP relaxation...\n");
ret = ios_solve_node(T);
if (!(ret == 0 || ret == GLP_EOBJLL || ret == GLP_EOBJUL))
{ if (T->parm->msg_lev >= GLP_MSG_ERR)
xprintf("ios_driver: unable to solve current LP relaxation;"
" glp_simplex returned %d\n", ret);
ret = GLP_EFAIL;
goto done;
}
/* analyze status of the basic solution to LP relaxation found */
p_stat = T->mip->pbs_stat;
d_stat = T->mip->dbs_stat;
if (p_stat == GLP_FEAS && d_stat == GLP_FEAS)
{ /* LP relaxation has optimal solution */
if (T->parm->msg_lev >= GLP_MSG_DBG)
xprintf("Found optimal solution to LP relaxation\n");
}
else if (d_stat == GLP_NOFEAS)
{ /* LP relaxation has no dual feasible solution */
/* since the current subproblem cannot have a larger feasible
region than its parent, there is something wrong */
if (T->parm->msg_lev >= GLP_MSG_ERR)
xprintf("ios_driver: current LP relaxation has no dual feas"
"ible solution\n");
ret = GLP_EFAIL;
goto done;
}
else if (p_stat == GLP_INFEAS && d_stat == GLP_FEAS)
{ /* LP relaxation has no primal solution which is better than
the incumbent objective value */
xassert(T->mip->mip_stat == GLP_FEAS);
if (T->parm->msg_lev >= GLP_MSG_DBG)
xprintf("LP relaxation has no solution better than incumben"
"t objective value\n");
/* prune the branch */
goto fath;
}
else if (p_stat == GLP_NOFEAS)
{ /* LP relaxation has no primal feasible solution */
if (T->parm->msg_lev >= GLP_MSG_DBG)
xprintf("LP relaxation has no feasible solution\n");
/* prune the branch */
goto fath;
}
else
{ /* other cases cannot appear */
xassert(T->mip != T->mip);
}
/* at this point basic solution to LP relaxation of the current
subproblem is optimal */
xassert(p_stat == GLP_FEAS && d_stat == GLP_FEAS);
xassert(T->curr != NULL);
T->curr->lp_obj = T->mip->obj_val;
/* thus, it defines a local bound to integer optimal solution of
the current subproblem */
{ double bound = T->mip->obj_val;
/* some local bound to the current subproblem could be already
set before, so we should only improve it */
bound = ios_round_bound(T, bound);
if (T->mip->dir == GLP_MIN)
{ if (T->curr->bound < bound)
T->curr->bound = bound;
}
else if (T->mip->dir == GLP_MAX)
{ if (T->curr->bound > bound)
T->curr->bound = bound;
}
else
xassert(T->mip != T->mip);
if (T->parm->msg_lev >= GLP_MSG_DBG)
xprintf("Local bound is %.9e\n", bound);
}
/* if the local bound indicates that integer optimal solution of
the current subproblem cannot be better than the global bound,
prune the branch */
if (!is_branch_hopeful(T, p))
{ if (T->parm->msg_lev >= GLP_MSG_DBG)
xprintf("Current branch is hopeless and can be pruned\n");
goto fath;
}
/* let the application program generate additional rows ("lazy"
constraints) */
xassert(T->reopt == 0);
xassert(T->reinv == 0);
if (T->parm->cb_func != NULL)
{ xassert(T->reason == 0);
T->reason = GLP_IROWGEN;
T->parm->cb_func(T, T->parm->cb_info);
T->reason = 0;
if (T->stop)
{ ret = GLP_ESTOP;
goto done;
}
if (T->reopt)
{ /* some rows were added; re-optimization is needed */
T->reopt = T->reinv = 0;
goto more;
}
if (T->reinv)
{ /* no rows were added, however, some inactive rows were
removed */
T->reinv = 0;
xassert(glp_factorize(T->mip) == 0);
}
}
/* check if the basic solution is integer feasible */
check_integrality(T);
/* if the basic solution satisfies to all integrality conditions,
it is a new, better integer feasible solution */
if (T->curr->ii_cnt == 0)
{ if (T->parm->msg_lev >= GLP_MSG_DBG)
xprintf("New integer feasible solution found\n");
if (T->parm->msg_lev >= GLP_MSG_ALL)
display_cut_info(T);
record_solution(T);
if (T->parm->msg_lev >= GLP_MSG_ON)
show_progress(T, 1);
/* make the application program happy */
if (T->parm->cb_func != NULL)
{ xassert(T->reason == 0);
T->reason = GLP_IBINGO;
T->parm->cb_func(T, T->parm->cb_info);
T->reason = 0;
if (T->stop)
{ ret = GLP_ESTOP;
goto done;
}
}
/* since the current subproblem has been fathomed, prune its
branch */
goto fath;
}
/* at this point basic solution to LP relaxation of the current
subproblem is optimal, but integer infeasible */
/* try to fix some non-basic structural variables of integer kind
on their current bounds due to reduced costs */
if (T->mip->mip_stat == GLP_FEAS)
fix_by_red_cost(T);
/* let the application program try to find some solution to the
original MIP with a primal heuristic */
if (T->parm->cb_func != NULL)
{ xassert(T->reason == 0);
T->reason = GLP_IHEUR;
T->parm->cb_func(T, T->parm->cb_info);
T->reason = 0;
if (T->stop)
{ ret = GLP_ESTOP;
goto done;
}
/* check if the current branch became hopeless */
if (!is_branch_hopeful(T, p))
{ if (T->parm->msg_lev >= GLP_MSG_DBG)
xprintf("Current branch became hopeless and can be prune"
"d\n");
goto fath;
}
}
/* try to find solution with the feasibility pump heuristic */
if (T->parm->fp_heur)
{ xassert(T->reason == 0);
T->reason = GLP_IHEUR;
ios_feas_pump(T);
T->reason = 0;
/* check if the current branch became hopeless */
if (!is_branch_hopeful(T, p))
{ if (T->parm->msg_lev >= GLP_MSG_DBG)
xprintf("Current branch became hopeless and can be prune"
"d\n");
goto fath;
}
}
/* it's time to generate cutting planes */
xassert(T->local != NULL);
xassert(T->local->size == 0);
/* let the application program generate some cuts; note that it
can add cuts either to the local cut pool or directly to the
current subproblem */
if (T->parm->cb_func != NULL)
{ xassert(T->reason == 0);
T->reason = GLP_ICUTGEN;
T->parm->cb_func(T, T->parm->cb_info);
T->reason = 0;
if (T->stop)
{ ret = GLP_ESTOP;
goto done;
}
}
/* try to generate generic cuts with built-in generators
(as suggested by Matteo Fischetti et al. the built-in cuts
are not generated at each branching node; an intense attempt
of generating new cuts is only made at the root node, and then
a moderate effort is spent after each backtracking step) */
if (T->curr->level == 0 || pred_p == 0)
{ xassert(T->reason == 0);
T->reason = GLP_ICUTGEN;
generate_cuts(T);
T->reason = 0;
}
/* if the local cut pool is not empty, select useful cuts and add
them to the current subproblem */
if (T->local->size > 0)
{ xassert(T->reason == 0);
T->reason = GLP_ICUTGEN;
ios_process_cuts(T);
T->reason = 0;
}
/* clear the local cut pool */
ios_clear_pool(T, T->local);
/* perform re-optimization, if necessary */
if (T->reopt)
{ T->reopt = 0;
T->curr->changed++;
goto more;
}
/* no cuts were generated; remove inactive cuts */
remove_cuts(T);
if (T->parm->msg_lev >= GLP_MSG_ALL && T->curr->level == 0)
display_cut_info(T);
/* update history information used on pseudocost branching */
if (T->pcost != NULL) ios_pcost_update(T);
/* it's time to perform branching */
xassert(T->br_var == 0);
xassert(T->br_sel == 0);
/* let the application program choose variable to branch on */
if (T->parm->cb_func != NULL)
{ xassert(T->reason == 0);
xassert(T->br_var == 0);
xassert(T->br_sel == 0);
T->reason = GLP_IBRANCH;
T->parm->cb_func(T, T->parm->cb_info);
T->reason = 0;
if (T->stop)
{ ret = GLP_ESTOP;
goto done;
}
}
/* if nothing has been chosen, choose some variable as specified
by the branching technique option */
if (T->br_var == 0)
T->br_var = ios_choose_var(T, &T->br_sel);
/* perform actual branching */
curr_p = T->curr->p;
ret = branch_on(T, T->br_var, T->br_sel);
T->br_var = T->br_sel = 0;
if (ret == 0)
{ /* both branches have been created */
pred_p = curr_p;
goto loop;
}
else if (ret == 1)
{ /* one branch is hopeless and has been pruned, so now the
current subproblem is other branch */
/* the current subproblem should be considered as a new one,
since one bound of the branching variable was changed */
T->curr->solved = T->curr->changed = 0;
goto more;
}
else if (ret == 2)
{ /* both branches are hopeless and have been pruned; new
subproblem selection is needed to continue the search */
goto fath;
}
else
xassert(ret != ret);
fath: /* the current subproblem has been fathomed */
if (T->parm->msg_lev >= GLP_MSG_DBG)
xprintf("Node %d fathomed\n", p);
/* freeze the current subproblem */
ios_freeze_node(T);
/* and prune the corresponding branch of the tree */
ios_delete_node(T, p);
/* if a new integer feasible solution has just been found, other
branches may become hopeless and therefore must be pruned */
if (T->mip->mip_stat == GLP_FEAS) cleanup_the_tree(T);
/* new subproblem selection is needed due to backtracking */
pred_p = 0;
goto loop;
done: /* display progress of the search on exit from the solver */
if (T->parm->msg_lev >= GLP_MSG_ON)
show_progress(T, 0);
if (T->mir_gen != NULL)
ios_mir_term(T->mir_gen), T->mir_gen = NULL;
if (T->clq_gen != NULL)
ios_clq_term(T->clq_gen), T->clq_gen = NULL;
/* return to the calling program */
return ret;
}
