static void fill_smcp(LPX *lp, glp_smcp *parm)
{ glp_init_smcp(parm);
switch (lpx_get_int_parm(lp, LPX_K_MSGLEV))
{ case 0: parm->msg_lev = GLP_MSG_OFF; break;
case 1: parm->msg_lev = GLP_MSG_ERR; break;
case 2: parm->msg_lev = GLP_MSG_ON; break;
case 3: parm->msg_lev = GLP_MSG_ALL; break;
default: xassert(lp != lp);
}
switch (lpx_get_int_parm(lp, LPX_K_DUAL))
{ case 0: parm->meth = GLP_PRIMAL; break;
case 1: parm->meth = GLP_DUAL; break;
default: xassert(lp != lp);
}
switch (lpx_get_int_parm(lp, LPX_K_PRICE))
{ case 0: parm->pricing = GLP_PT_STD; break;
case 1: parm->pricing = GLP_PT_PSE; break;
default: xassert(lp != lp);
}
if (lpx_get_real_parm(lp, LPX_K_RELAX) == 0.0)
parm->r_test = GLP_RT_STD;
else
parm->r_test = GLP_RT_HAR;
parm->tol_bnd = lpx_get_real_parm(lp, LPX_K_TOLBND);
parm->tol_dj = lpx_get_real_parm(lp, LPX_K_TOLDJ);
parm->tol_piv = lpx_get_real_parm(lp, LPX_K_TOLPIV);
parm->obj_ll = lpx_get_real_parm(lp, LPX_K_OBJLL);
parm->obj_ul = lpx_get_real_parm(lp, LPX_K_OBJUL);
if (lpx_get_int_parm(lp, LPX_K_ITLIM) < 0)
parm->it_lim = INT_MAX;
else
parm->it_lim = lpx_get_int_parm(lp, LPX_K_ITLIM);
if (lpx_get_real_parm(lp, LPX_K_TMLIM) < 0.0)
parm->tm_lim = INT_MAX;
else
parm->tm_lim =
(int)(1000.0 * lpx_get_real_parm(lp, LPX_K_TMLIM));
parm->out_frq = lpx_get_int_parm(lp, LPX_K_OUTFRQ);
parm->out_dly =
(int)(1000.0 * lpx_get_real_parm(lp, LPX_K_OUTDLY));
switch (lpx_get_int_parm(lp, LPX_K_PRESOL))
{ case 0: parm->presolve = GLP_OFF; break;
case 1: parm->presolve = GLP_ON; break;
default: xassert(lp != lp);
}
return;
}
static PyObject* Params_parameter_get(ParamsObject *self,
struct param_getsets *pgs) {
switch (pgs->type) {
case 0: // Boolean.
return PyBool_FromLong(lpx_get_int_parm(LP, pgs->code));
case 1: // Integer.
return PyInt_FromLong(lpx_get_int_parm(LP, pgs->code));
case 2: // Float.
return PyFloat_FromDouble(lpx_get_real_parm(LP, pgs->code));
default: // Um, apparently I made a mistake in the PGS definition array.
PyErr_Format(PyExc_RuntimeError, "parameter type code %d unrecognized",
pgs->type);
return NULL;
}
}
static void show_status(LPX *prob, int prob_m, int prob_nz)
{ int n, j, count;
double x, tol_int;
/* determine the number of structural variables of integer kind
whose current values are still fractional */
n = lpx_get_num_cols(prob);
tol_int = lpx_get_real_parm(prob, LPX_K_TOLINT);
count = 0;
for (j = 1; j <= n; j++)
{ if (lpx_get_col_kind(prob, j) != LPX_IV) continue;
x = lpx_get_col_prim(prob, j);
if (fabs(x - floor(x + 0.5)) <= tol_int) continue;
count++;
}
print("&%6d: obj = %17.9e frac = %5d cuts = %5d (%d)",
lpx_get_int_parm(prob, LPX_K_ITCNT),
lpx_get_obj_val(prob), count,
lpx_get_num_rows(prob) - prob_m,
lpx_get_num_nz(prob) - prob_nz);
return;
}
static int solve_mip(LPX *lp, int presolve)
{ glp_iocp parm;
int ret;
glp_init_iocp(&parm);
switch (lpx_get_int_parm(lp, LPX_K_MSGLEV))
{ case 0: parm.msg_lev = GLP_MSG_OFF; break;
case 1: parm.msg_lev = GLP_MSG_ERR; break;
case 2: parm.msg_lev = GLP_MSG_ON; break;
case 3: parm.msg_lev = GLP_MSG_ALL; break;
default: xassert(lp != lp);
}
switch (lpx_get_int_parm(lp, LPX_K_BRANCH))
{ case 0: parm.br_tech = GLP_BR_FFV; break;
case 1: parm.br_tech = GLP_BR_LFV; break;
case 2: parm.br_tech = GLP_BR_DTH; break;
case 3: parm.br_tech = GLP_BR_MFV; break;
default: xassert(lp != lp);
}
switch (lpx_get_int_parm(lp, LPX_K_BTRACK))
{ case 0: parm.bt_tech = GLP_BT_DFS; break;
case 1: parm.bt_tech = GLP_BT_BFS; break;
case 2: parm.bt_tech = GLP_BT_BPH; break;
case 3: parm.bt_tech = GLP_BT_BLB; break;
default: xassert(lp != lp);
}
parm.tol_int = lpx_get_real_parm(lp, LPX_K_TOLINT);
parm.tol_obj = lpx_get_real_parm(lp, LPX_K_TOLOBJ);
if (lpx_get_real_parm(lp, LPX_K_TMLIM) < 0.0 ||
lpx_get_real_parm(lp, LPX_K_TMLIM) > 1e6)
parm.tm_lim = INT_MAX;
else
parm.tm_lim =
(int)(1000.0 * lpx_get_real_parm(lp, LPX_K_TMLIM));
parm.mip_gap = lpx_get_real_parm(lp, LPX_K_MIPGAP);
if (lpx_get_int_parm(lp, LPX_K_USECUTS) & LPX_C_GOMORY)
parm.gmi_cuts = GLP_ON;
else
parm.gmi_cuts = GLP_OFF;
if (lpx_get_int_parm(lp, LPX_K_USECUTS) & LPX_C_MIR)
parm.mir_cuts = GLP_ON;
else
parm.mir_cuts = GLP_OFF;
if (lpx_get_int_parm(lp, LPX_K_USECUTS) & LPX_C_COVER)
parm.cov_cuts = GLP_ON;
else
parm.cov_cuts = GLP_OFF;
if (lpx_get_int_parm(lp, LPX_K_USECUTS) & LPX_C_CLIQUE)
parm.clq_cuts = GLP_ON;
else
parm.clq_cuts = GLP_OFF;
parm.presolve = presolve;
if (lpx_get_int_parm(lp, LPX_K_BINARIZE))
parm.binarize = GLP_ON;
ret = glp_intopt(lp, &parm);
switch (ret)
{ case 0: ret = LPX_E_OK; break;
case GLP_ENOPFS: ret = LPX_E_NOPFS; break;
case GLP_ENODFS: ret = LPX_E_NODFS; break;
case GLP_EBOUND:
case GLP_EROOT: ret = LPX_E_FAULT; break;
case GLP_EFAIL: ret = LPX_E_SING; break;
case GLP_EMIPGAP: ret = LPX_E_MIPGAP; break;
case GLP_ETMLIM: ret = LPX_E_TMLIM; break;
default: xassert(ret != ret);
}
return ret;
}
int lpx_integer(LPX *mip)
{ int m = lpx_get_num_rows(mip);
int n = lpx_get_num_cols(mip);
MIPTREE *tree;
LPX *lp;
int ret, i, j, stat, type, len, *ind;
double lb, ub, coef, *val;
#if 0
/* the problem must be of MIP class */
if (lpx_get_class(mip) != LPX_MIP)
{ print("lpx_integer: problem is not of MIP class");
ret = LPX_E_FAULT;
goto done;
}
#endif
/* an optimal solution of LP relaxation must be known */
if (lpx_get_status(mip) != LPX_OPT)
{ print("lpx_integer: optimal solution of LP relaxation required"
);
ret = LPX_E_FAULT;
goto done;
}
/* bounds of all integer variables must be integral */
for (j = 1; j <= n; j++)
{ if (lpx_get_col_kind(mip, j) != LPX_IV) continue;
type = lpx_get_col_type(mip, j);
if (type == LPX_LO || type == LPX_DB || type == LPX_FX)
{ lb = lpx_get_col_lb(mip, j);
if (lb != floor(lb))
{ print("lpx_integer: integer column %d has non-integer lo"
"wer bound or fixed value %g", j, lb);
ret = LPX_E_FAULT;
goto done;
}
}
if (type == LPX_UP || type == LPX_DB)
{ ub = lpx_get_col_ub(mip, j);
if (ub != floor(ub))
{ print("lpx_integer: integer column %d has non-integer up"
"per bound %g", j, ub);
ret = LPX_E_FAULT;
goto done;
}
}
}
/* it seems all is ok */
if (lpx_get_int_parm(mip, LPX_K_MSGLEV) >= 2)
print("Integer optimization begins...");
/* create the branch-and-bound tree */
tree = mip_create_tree(m, n, lpx_get_obj_dir(mip));
/* set up column kinds */
for (j = 1; j <= n; j++)
tree->int_col[j] = (lpx_get_col_kind(mip, j) == LPX_IV);
/* access the LP relaxation template */
lp = tree->lp;
/* set up the objective function */
tree->int_obj = 1;
for (j = 0; j <= tree->n; j++)
{ coef = lpx_get_obj_coef(mip, j);
lpx_set_obj_coef(lp, j, coef);
if (coef != 0.0 && !(tree->int_col[j] && coef == floor(coef)))
tree->int_obj = 0;
}
if (lpx_get_int_parm(mip, LPX_K_MSGLEV) >= 2 && tree->int_obj)
print("Objective function is integral");
/* set up the constraint matrix */
ind = xcalloc(1+n, sizeof(int));
val = xcalloc(1+n, sizeof(double));
for (i = 1; i <= m; i++)
{ len = lpx_get_mat_row(mip, i, ind, val);
lpx_set_mat_row(lp, i, len, ind, val);
}
xfree(ind);
xfree(val);
/* set up scaling matrices */
for (i = 1; i <= m; i++)
lpx_set_rii(lp, i, lpx_get_rii(mip, i));
for (j = 1; j <= n; j++)
lpx_set_sjj(lp, j, lpx_get_sjj(mip, j));
/* revive the root subproblem */
mip_revive_node(tree, 1);
/* set up row attributes for the root subproblem */
for (i = 1; i <= m; i++)
{ type = lpx_get_row_type(mip, i);
lb = lpx_get_row_lb(mip, i);
ub = lpx_get_row_ub(mip, i);
stat = lpx_get_row_stat(mip, i);
lpx_set_row_bnds(lp, i, type, lb, ub);
lpx_set_row_stat(lp, i, stat);
}
/* set up column attributes for the root subproblem */
for (j = 1; j <= n; j++)
{ type = lpx_get_col_type(mip, j);
lb = lpx_get_col_lb(mip, j);
ub = lpx_get_col_ub(mip, j);
stat = lpx_get_col_stat(mip, j);
lpx_set_col_bnds(lp, j, type, lb, ub);
lpx_set_col_stat(lp, j, stat);
}
/* freeze the root subproblem */
mip_freeze_node(tree);
/* inherit some control parameters and statistics */
tree->msg_lev = lpx_get_int_parm(mip, LPX_K_MSGLEV);
if (tree->msg_lev > 2) tree->msg_lev = 2;
tree->branch = lpx_get_int_parm(mip, LPX_K_BRANCH);
tree->btrack = lpx_get_int_parm(mip, LPX_K_BTRACK);
tree->tol_int = lpx_get_real_parm(mip, LPX_K_TOLINT);
tree->tol_obj = lpx_get_real_parm(mip, LPX_K_TOLOBJ);
tree->tm_lim = lpx_get_real_parm(mip, LPX_K_TMLIM);
lpx_set_int_parm(lp, LPX_K_BFTYPE, lpx_get_int_parm(mip,
LPX_K_BFTYPE));
lpx_set_int_parm(lp, LPX_K_PRICE, lpx_get_int_parm(mip,
LPX_K_PRICE));
lpx_set_real_parm(lp, LPX_K_RELAX, lpx_get_real_parm(mip,
LPX_K_RELAX));
lpx_set_real_parm(lp, LPX_K_TOLBND, lpx_get_real_parm(mip,
LPX_K_TOLBND));
lpx_set_real_parm(lp, LPX_K_TOLDJ, lpx_get_real_parm(mip,
LPX_K_TOLDJ));
lpx_set_real_parm(lp, LPX_K_TOLPIV, lpx_get_real_parm(mip,
LPX_K_TOLPIV));
lpx_set_int_parm(lp, LPX_K_ITLIM, lpx_get_int_parm(mip,
LPX_K_ITLIM));
lpx_set_int_parm(lp, LPX_K_ITCNT, lpx_get_int_parm(mip,
LPX_K_ITCNT));
/* reset the status of MIP solution */
lpx_put_mip_soln(mip, LPX_I_UNDEF, NULL, NULL);
/* try solving the problem */
ret = mip_driver(tree);
/* if an integer feasible solution has been found, copy it to the
MIP problem object */
if (tree->found)
lpx_put_mip_soln(mip, LPX_I_FEAS, &tree->mipx[0],
&tree->mipx[m]);
/* copy back statistics about spent resources */
lpx_set_real_parm(mip, LPX_K_TMLIM, tree->tm_lim);
lpx_set_int_parm(mip, LPX_K_ITLIM, lpx_get_int_parm(lp,
LPX_K_ITLIM));
lpx_set_int_parm(mip, LPX_K_ITCNT, lpx_get_int_parm(lp,
LPX_K_ITCNT));
/* analyze exit code reported by the mip driver */
switch (ret)
{ case MIP_E_OK:
if (tree->found)
{ if (lpx_get_int_parm(mip, LPX_K_MSGLEV) >= 3)
print("INTEGER OPTIMAL SOLUTION FOUND");
lpx_put_mip_soln(mip, LPX_I_OPT, NULL, NULL);
}
else
{ if (lpx_get_int_parm(mip, LPX_K_MSGLEV) >= 3)
print("PROBLEM HAS NO INTEGER FEASIBLE SOLUTION");
lpx_put_mip_soln(mip, LPX_I_NOFEAS, NULL, NULL);
}
ret = LPX_E_OK;
break;
case MIP_E_ITLIM:
if (lpx_get_int_parm(mip, LPX_K_MSGLEV) >= 3)
print("ITERATIONS LIMIT EXCEEDED; SEARCH TERMINATED");
ret = LPX_E_ITLIM;
break;
case MIP_E_TMLIM:
if (lpx_get_int_parm(mip, LPX_K_MSGLEV) >= 3)
print("TIME LIMIT EXCEEDED; SEARCH TERMINATED");
ret = LPX_E_TMLIM;
break;
case MIP_E_ERROR:
if (lpx_get_int_parm(mip, LPX_K_MSGLEV) >= 1)
print("lpx_integer: cannot solve current LP relaxation");
ret = LPX_E_SING;
break;
default:
xassert(ret != ret);
}
/* delete the branch-and-bound tree */
mip_delete_tree(tree);
done: /* return to the application program */
return ret;
}
int lpx_warm_up(LPX *lp)
{ int m, n, j, k, ret, type, stat, p_stat, d_stat;
double lb, ub, prim, dual, tol_bnd, tol_dj, dir;
double *row_prim, *row_dual, *col_prim, *col_dual, sum;
m = lpx_get_num_rows(lp);
n = lpx_get_num_cols(lp);
/* reinvert the basis matrix, if necessary */
if (lpx_is_b_avail(lp))
ret = LPX_E_OK;
else
{ if (m == 0 || n == 0)
{ ret = LPX_E_EMPTY;
goto done;
}
#if 0
ret = lpx_invert(lp);
switch (ret)
{ case 0:
ret = LPX_E_OK;
break;
case 1:
case 2:
ret = LPX_E_SING;
goto done;
case 3:
ret = LPX_E_BADB;
goto done;
default:
xassert(ret != ret);
}
#else
switch (glp_factorize(lp))
{ case 0:
ret = LPX_E_OK;
break;
case GLP_EBADB:
ret = LPX_E_BADB;
goto done;
case GLP_ESING:
case GLP_ECOND:
ret = LPX_E_SING;
goto done;
default:
xassert(lp != lp);
}
#endif
}
/* allocate working arrays */
row_prim = xcalloc(1+m, sizeof(double));
row_dual = xcalloc(1+m, sizeof(double));
col_prim = xcalloc(1+n, sizeof(double));
col_dual = xcalloc(1+n, sizeof(double));
/* compute primal basic solution components */
lpx_eval_b_prim(lp, row_prim, col_prim);
/* determine primal status of basic solution */
tol_bnd = 3.0 * lpx_get_real_parm(lp, LPX_K_TOLBND);
p_stat = LPX_P_FEAS;
for (k = 1; k <= m+n; k++)
{ if (k <= m)
{ type = lpx_get_row_type(lp, k);
lb = lpx_get_row_lb(lp, k);
ub = lpx_get_row_ub(lp, k);
prim = row_prim[k];
}
else
{ type = lpx_get_col_type(lp, k-m);
lb = lpx_get_col_lb(lp, k-m);
ub = lpx_get_col_ub(lp, k-m);
prim = col_prim[k-m];
}
if (type == LPX_LO || type == LPX_DB || type == LPX_FX)
{ /* variable x[k] has lower bound */
if (prim < lb - tol_bnd * (1.0 + fabs(lb)))
{ p_stat = LPX_P_INFEAS;
break;
}
}
if (type == LPX_UP || type == LPX_DB || type == LPX_FX)
{ /* variable x[k] has upper bound */
if (prim > ub + tol_bnd * (1.0 + fabs(ub)))
{ p_stat = LPX_P_INFEAS;
break;
}
}
}
/* compute dual basic solution components */
lpx_eval_b_dual(lp, row_dual, col_dual);
/* determine dual status of basic solution */
tol_dj = 3.0 * lpx_get_real_parm(lp, LPX_K_TOLDJ);
dir = (lpx_get_obj_dir(lp) == LPX_MIN ? +1.0 : -1.0);
d_stat = LPX_D_FEAS;
for (k = 1; k <= m+n; k++)
{ if (k <= m)
{ stat = lpx_get_row_stat(lp, k);
dual = row_dual[k];
}
else
{ stat = lpx_get_col_stat(lp, k-m);
dual = col_dual[k-m];
}
if (stat == LPX_BS || stat == LPX_NL || stat == LPX_NF)
{ /* reduced cost of x[k] must be non-negative (minimization)
or non-positive (maximization) */
if (dir * dual < - tol_dj)
{ d_stat = LPX_D_INFEAS;
break;
}
}
if (stat == LPX_BS || stat == LPX_NU || stat == LPX_NF)
{ /* reduced cost of x[k] must be non-positive (minimization)
or non-negative (maximization) */
if (dir * dual > + tol_dj)
{ d_stat = LPX_D_INFEAS;
break;
}
}
}
/* store basic solution components */
p_stat = p_stat - LPX_P_UNDEF + GLP_UNDEF;
d_stat = d_stat - LPX_D_UNDEF + GLP_UNDEF;
sum = lpx_get_obj_coef(lp, 0);
for (j = 1; j <= n; j++)
sum += lpx_get_obj_coef(lp, j) * col_prim[j];
glp_put_solution(lp, 0, &p_stat, &d_stat, &sum,
NULL, row_prim, row_dual, NULL, col_prim, col_dual);
xassert(lpx_is_b_avail(lp));
/* free working arrays */
xfree(row_prim);
xfree(row_dual);
xfree(col_prim);
xfree(col_dual);
done: /* return to the calling program */
return ret;
}
int lpx_intopt(LPX *_mip)
{ IPP *ipp = NULL;
LPX *orig = _mip, *prob = NULL;
int orig_m, orig_n, i, j, ret, i_stat;
/* the problem must be of MIP class */
if (lpx_get_class(orig) != LPX_MIP)
{ print("lpx_intopt: problem is not of MIP class");
ret = LPX_E_FAULT;
goto done;
}
/* the problem must have at least one row and one column */
orig_m = lpx_get_num_rows(orig);
orig_n = lpx_get_num_cols(orig);
if (!(orig_m > 0 && orig_n > 0))
{ print("lpx_intopt: problem has no rows/columns");
ret = LPX_E_FAULT;
goto done;
}
/* check that each double-bounded row and column has bounds */
for (i = 1; i <= orig_m; i++)
{ if (lpx_get_row_type(orig, i) == LPX_DB)
{ if (lpx_get_row_lb(orig, i) >= lpx_get_row_ub(orig, i))
{ print("lpx_intopt: row %d has incorrect bounds", i);
ret = LPX_E_FAULT;
goto done;
}
}
}
for (j = 1; j <= orig_n; j++)
{ if (lpx_get_col_type(orig, j) == LPX_DB)
{ if (lpx_get_col_lb(orig, j) >= lpx_get_col_ub(orig, j))
{ print("lpx_intopt: column %d has incorrect bounds", j);
ret = LPX_E_FAULT;
goto done;
}
}
}
/* bounds of all integer variables must be integral */
for (j = 1; j <= orig_n; j++)
{ int type;
double lb, ub;
if (lpx_get_col_kind(orig, j) != LPX_IV) continue;
type = lpx_get_col_type(orig, j);
if (type == LPX_LO || type == LPX_DB || type == LPX_FX)
{ lb = lpx_get_col_lb(orig, j);
if (lb != floor(lb))
{ print("lpx_intopt: integer column %d has non-integer low"
"er bound or fixed value %g", j, lb);
ret = LPX_E_FAULT;
goto done;
}
}
if (type == LPX_UP || type == LPX_DB)
{ ub = lpx_get_col_ub(orig, j);
if (ub != floor(ub))
{ print("lpx_intopt: integer column %d has non-integer upp"
"er bound %g", j, ub);
ret = LPX_E_FAULT;
goto done;
}
}
}
/* reset the status of MIP solution */
lpx_put_mip_soln(orig, LPX_I_UNDEF, NULL, NULL);
/* create MIP presolver workspace */
ipp = ipp_create_wksp();
/* load the original problem into the presolver workspace */
ipp_load_orig(ipp, orig);
/* perform basic MIP presolve analysis */
switch (ipp_basic_tech(ipp))
{ case 0:
/* no infeasibility is detected */
break;
case 1:
nopfs: /* primal infeasibility is detected */
print("PROBLEM HAS NO PRIMAL FEASIBLE SOLUTION");
ret = LPX_E_NOPFS;
goto done;
case 2:
/* dual infeasibility is detected */
nodfs: print("LP RELAXATION HAS NO DUAL FEASIBLE SOLUTION");
ret = LPX_E_NODFS;
goto done;
default:
insist(ipp != ipp);
}
/* reduce column bounds */
switch (ipp_reduce_bnds(ipp))
{ case 0: break;
case 1: goto nopfs;
default: insist(ipp != ipp);
}
/* perform basic MIP presolve analysis */
switch (ipp_basic_tech(ipp))
{ case 0: break;
case 1: goto nopfs;
case 2: goto nodfs;
default: insist(ipp != ipp);
}
/* replace general integer variables by sum of binary variables,
if required */
if (lpx_get_int_parm(orig, LPX_K_BINARIZE))
ipp_binarize(ipp);
/* perform coefficient reduction */
ipp_reduction(ipp);
/* if the resultant problem is empty, it has an empty solution,
which is optimal */
if (ipp->row_ptr == NULL || ipp->col_ptr == NULL)
{ insist(ipp->row_ptr == NULL);
insist(ipp->col_ptr == NULL);
print("Objective value = %.10g",
ipp->orig_dir == LPX_MIN ? +ipp->c0 : -ipp->c0);
print("INTEGER OPTIMAL SOLUTION FOUND BY MIP PRESOLVER");
/* allocate recovered solution segment */
ipp->col_stat = ucalloc(1+ipp->ncols, sizeof(int));
ipp->col_mipx = ucalloc(1+ipp->ncols, sizeof(double));
for (j = 1; j <= ipp->ncols; j++) ipp->col_stat[j] = 0;
/* perform MIP postsolve processing */
ipp_postsolve(ipp);
/* unload recovered MIP solution and store it in the original
problem object */
ipp_unload_sol(ipp, orig, LPX_I_OPT);
ret = LPX_E_OK;
goto done;
}
/* build resultant MIP problem object */
prob = ipp_build_prob(ipp);
/* display some statistics */
{ int m = lpx_get_num_rows(prob);
int n = lpx_get_num_cols(prob);
int nnz = lpx_get_num_nz(prob);
int ni = lpx_get_num_int(prob);
int nb = lpx_get_num_bin(prob);
char s[50];
print("lpx_intopt: presolved MIP has %d row%s, %d column%s, %d"
" non-zero%s", m, m == 1 ? "" : "s", n, n == 1 ? "" : "s",
nnz, nnz == 1 ? "" : "s");
if (nb == 0)
strcpy(s, "none of");
else if (ni == 1 && nb == 1)
strcpy(s, "");
else if (nb == 1)
strcpy(s, "one of");
else if (nb == ni)
strcpy(s, "all of");
else
sprintf(s, "%d of", nb);
print("lpx_intopt: %d integer column%s, %s which %s binary",
ni, ni == 1 ? "" : "s", s, nb == 1 ? "is" : "are");
}
/* inherit some control parameters and statistics */
lpx_set_int_parm(prob, LPX_K_PRICE, lpx_get_int_parm(orig,
LPX_K_PRICE));
lpx_set_real_parm(prob, LPX_K_RELAX, lpx_get_real_parm(orig,
LPX_K_RELAX));
lpx_set_real_parm(prob, LPX_K_TOLBND, lpx_get_real_parm(orig,
LPX_K_TOLBND));
lpx_set_real_parm(prob, LPX_K_TOLDJ, lpx_get_real_parm(orig,
LPX_K_TOLDJ));
lpx_set_real_parm(prob, LPX_K_TOLPIV, lpx_get_real_parm(orig,
LPX_K_TOLPIV));
lpx_set_int_parm(prob, LPX_K_ITLIM, lpx_get_int_parm(orig,
LPX_K_ITLIM));
lpx_set_int_parm(prob, LPX_K_ITCNT, lpx_get_int_parm(orig,
LPX_K_ITCNT));
lpx_set_real_parm(prob, LPX_K_TMLIM, lpx_get_real_parm(orig,
LPX_K_TMLIM));
lpx_set_int_parm(prob, LPX_K_BRANCH, lpx_get_int_parm(orig,
LPX_K_BRANCH));
lpx_set_int_parm(prob, LPX_K_BTRACK, lpx_get_int_parm(orig,
LPX_K_BTRACK));
lpx_set_real_parm(prob, LPX_K_TOLINT, lpx_get_real_parm(orig,
LPX_K_TOLINT));
lpx_set_real_parm(prob, LPX_K_TOLOBJ, lpx_get_real_parm(orig,
LPX_K_TOLOBJ));
/* build an advanced initial basis */
lpx_adv_basis(prob);
/* solve LP relaxation */
print("Solving LP relaxation...");
switch (lpx_simplex(prob))
{ case LPX_E_OK:
break;
case LPX_E_ITLIM:
ret = LPX_E_ITLIM;
goto done;
case LPX_E_TMLIM:
ret = LPX_E_TMLIM;
goto done;
default:
print("lpx_intopt: cannot solve LP relaxation");
ret = LPX_E_SING;
goto done;
}
/* analyze status of the basic solution */
switch (lpx_get_status(prob))
{ case LPX_OPT:
break;
case LPX_NOFEAS:
ret = LPX_E_NOPFS;
goto done;
case LPX_UNBND:
ret = LPX_E_NODFS;
goto done;
default:
insist(prob != prob);
}
/* generate cutting planes, if necessary */
if (lpx_get_int_parm(orig, LPX_K_USECUTS))
{ ret = generate_cuts(prob);
if (ret != LPX_E_OK) goto done;
}
/* call the branch-and-bound solver */
ret = lpx_integer(prob);
/* determine status of MIP solution */
i_stat = lpx_mip_status(prob);
if (i_stat == LPX_I_OPT || i_stat == LPX_I_FEAS)
{ /* load MIP solution of the resultant problem into presolver
workspace */
ipp_load_sol(ipp, prob);
/* perform MIP postsolve processing */
ipp_postsolve(ipp);
/* unload recovered MIP solution and store it in the original
problem object */
ipp_unload_sol(ipp, orig, i_stat);
}
else
{ /* just set the status of MIP solution */
lpx_put_mip_soln(orig, i_stat, NULL, NULL);
}
done: /* copy back statistics about spent resources */
if (prob != NULL)
{ lpx_set_int_parm(orig, LPX_K_ITLIM, lpx_get_int_parm(prob,
LPX_K_ITLIM));
lpx_set_int_parm(orig, LPX_K_ITCNT, lpx_get_int_parm(prob,
LPX_K_ITCNT));
lpx_set_real_parm(orig, LPX_K_TMLIM, lpx_get_real_parm(prob,
LPX_K_TMLIM));
}
/* delete the resultant problem object */
if (prob != NULL) lpx_delete_prob(prob);
/* delete MIP presolver workspace */
if (ipp != NULL) ipp_delete_wksp(ipp);
return ret;
}
static int generate_cuts(LPX *prob)
{ int prob_m, prob_n, prob_nz, msg_lev, dual, nrows, it_cnt, ret;
double out_dly, tm_lim, tm_lag = 0.0, tm_beg = utime();
print("Generating cutting planes...");
/* determine the number of rows, columns, and non-zeros on entry
to the routine */
prob_m = lpx_get_num_rows(prob);
prob_n = lpx_get_num_cols(prob);
prob_nz = lpx_get_num_nz(prob);
/* save some control parameters */
msg_lev = lpx_get_int_parm(prob, LPX_K_MSGLEV);
dual = lpx_get_int_parm(prob, LPX_K_DUAL);
out_dly = lpx_get_real_parm(prob, LPX_K_OUTDLY);
tm_lim = lpx_get_real_parm(prob, LPX_K_TMLIM);
/* and set their new values needed for re-optimization */
lpx_set_int_parm(prob, LPX_K_MSGLEV, 1);
lpx_set_int_parm(prob, LPX_K_DUAL, 1);
lpx_set_real_parm(prob, LPX_K_OUTDLY, 10.0);
lpx_set_real_parm(prob, LPX_K_TMLIM, -1.0);
loop: /* main loop starts here */
/* display current status of the problem */
if (utime() - tm_lag >= 5.0 - 0.001)
show_status(prob, prob_m, prob_nz), tm_lag = utime();
/* check if the patience has been exhausted */
if (tm_lim >= 0.0 && tm_lim <= utime() - tm_beg)
{ ret = LPX_E_TMLIM;
goto done;
}
/* not more than 500 cut inequalities are allowed */
if (lpx_get_num_rows(prob) - prob_m >= 500)
{ ret = LPX_E_OK;
goto done;
}
/* not more than 50,000 cut coefficients are allowed */
if (lpx_get_num_nz(prob) - prob_nz >= 50000)
{ ret = LPX_E_OK;
goto done;
}
/* try to generate Gomory's mixed integer cut */
nrows = lpx_get_num_rows(prob);
gen_gomory_cut(prob, prob_n);
if (nrows == lpx_get_num_rows(prob))
{ /* nothing has been generated */
ret = LPX_E_OK;
goto done;
}
/* re-optimize current LP relaxation using dual simplex */
it_cnt = lpx_get_int_parm(prob, LPX_K_ITCNT);
switch (lpx_simplex(prob))
{ case LPX_E_OK:
break;
case LPX_E_ITLIM:
ret = LPX_E_ITLIM;
goto done;
default:
ret = LPX_E_SING;
goto done;
}
if (it_cnt == lpx_get_int_parm(prob, LPX_K_ITCNT))
{ ret = LPX_E_OK;
goto done;
}
/* analyze status of the basic solution */
switch (lpx_get_status(prob))
{ case LPX_OPT:
break;
case LPX_NOFEAS:
ret = LPX_E_NOPFS;
goto done;
default:
insist(prob != prob);
}
/* continue generating cutting planes */
goto loop;
done: /* display final status of the problem */
show_status(prob, prob_m, prob_nz);
switch (ret)
{ case LPX_E_OK:
break;
case LPX_E_NOPFS:
print("PROBLEM HAS NO INTEGER FEASIBLE SOLUTION");
break;
case LPX_E_ITLIM:
print("ITERATIONS LIMIT EXCEEDED; SEARCH TERMINATED");
break;
case LPX_E_TMLIM:
print("TIME LIMIT EXCEEDED; SEARCH TERMINATED");
break;
case LPX_E_SING:
print("lpx_intopt: cannot re-optimize LP relaxation");
break;
default:
insist(ret != ret);
}
/* decrease the time limit by spent amount of the time */
if (tm_lim >= 0.0)
{ tm_lim -= (utime() - tm_beg);
if (tm_lim < 0.0) tm_lim = 0.0;
}
/* restore some control parameters and update statistics */
lpx_set_int_parm(prob, LPX_K_MSGLEV, msg_lev);
lpx_set_int_parm(prob, LPX_K_DUAL, dual);
lpx_set_real_parm(prob, LPX_K_OUTDLY, out_dly);
lpx_set_real_parm(prob, LPX_K_TMLIM, tm_lim);
return ret;
}