int lpx_write_pb(LPX *lp, const char *fname, int normalized,
int binarize)
{
FILE* fp;
int m,n,i,j,k,o,nonfree=0, obj_dir, dbl, *ndx, row_type, emptylhs=0;
double coeff, *val, bound, constant/*=0.0*/;
char* objconstname = "dummy_one";
char* emptylhsname = "dummy_zero";
/* Variables needed for possible binarization */
/*LPX* tlp;*/
IPP *ipp = NULL;
/*tlp=lp;*/
if(binarize) /* Transform integer variables to binary ones */
{
ipp = ipp_create_wksp();
ipp_load_orig(ipp, lp);
ipp_binarize(ipp);
lp = ipp_build_prob(ipp);
}
fp = fopen(fname, "w");
if(fp!= NULL)
{
xprintf(
"lpx_write_pb: writing problem in %sOPB format to `%s'...\n",
(normalized?"normalized ":""), fname);
m = glp_get_num_rows(lp);
n = glp_get_num_cols(lp);
for(i=1;i<=m;i++)
{
switch(glp_get_row_type(lp,i))
{
case GLP_LO:
case GLP_UP:
case GLP_FX:
{
nonfree += 1;
break;
}
case GLP_DB:
{
nonfree += 2;
break;
}
}
}
constant=glp_get_obj_coef(lp,0);
fprintf(fp,"* #variables = %d #constraints = %d\n",
n + (constant == 0?1:0), nonfree + (constant == 0?1:0));
/* Objective function */
obj_dir = glp_get_obj_dir(lp);
fprintf(fp,"min: ");
for(i=1;i<=n;i++)
{
coeff = glp_get_obj_coef(lp,i);
if(coeff != 0.0)
{
if(obj_dir == GLP_MAX)
coeff=-coeff;
if(normalized)
fprintf(fp, " %d x%d", (int)coeff, i);
else
fprintf(fp, " %d*%s", (int)coeff,
glp_get_col_name(lp,i));
}
}
if(constant)
{
if(normalized)
fprintf(fp, " %d x%d", (int)constant, n+1);
else
fprintf(fp, " %d*%s", (int)constant, objconstname);
}
fprintf(fp,";\n");
if(normalized && !binarize) /* Name substitution */
{
fprintf(fp,"* Variable name substitution:\n");
for(j=1;j<=n;j++)
{
fprintf(fp, "* x%d = %s\n", j, glp_get_col_name(lp,j));
}
if(constant)
fprintf(fp, "* x%d = %s\n", n+1, objconstname);
}
ndx = xcalloc(1+n, sizeof(int));
val = xcalloc(1+n, sizeof(double));
/* Constraints */
for(j=1;j<=m;j++)
{
row_type=glp_get_row_type(lp,j);
if(row_type!=GLP_FR)
{
if(row_type == GLP_DB)
{
dbl=2;
row_type = GLP_UP;
}
else
{
dbl=1;
}
k=glp_get_mat_row(lp, j, ndx, val);
for(o=1;o<=dbl;o++)
{
if(o==2)
{
row_type = GLP_LO;
}
if(k==0) /* Empty LHS */
{
emptylhs = 1;
if(normalized)
{
fprintf(fp, "0 x%d ", n+2);
}
else
{
fprintf(fp, "0*%s ", emptylhsname);
}
}
for(i=1;i<=k;i++)
{
if(val[i] != 0.0)
{
if(normalized)
{
fprintf(fp, "%d x%d ",
(row_type==GLP_UP)?(-(int)val[i]):((int)val[i]), ndx[i]);
}
else
{
fprintf(fp, "%d*%s ", (int)val[i],
glp_get_col_name(lp,ndx[i]));
}
}
}
switch(row_type)
{
case GLP_LO:
{
fprintf(fp, ">=");
bound = glp_get_row_lb(lp,j);
break;
}
case GLP_UP:
{
if(normalized)
{
fprintf(fp, ">=");
bound = -glp_get_row_ub(lp,j);
}
else
{
fprintf(fp, "<=");
bound = glp_get_row_ub(lp,j);
}
break;
}
case GLP_FX:
{
fprintf(fp, "=");
bound = glp_get_row_lb(lp,j);
break;
}
}
fprintf(fp," %d;\n",(int)bound);
}
}
}
xfree(ndx);
xfree(val);
if(constant)
{
xprintf(
"lpx_write_pb: adding constant objective function variable\n");
if(normalized)
fprintf(fp, "1 x%d = 1;\n", n+1);
else
fprintf(fp, "1*%s = 1;\n", objconstname);
}
if(emptylhs)
{
xprintf(
"lpx_write_pb: adding dummy variable for empty left-hand si"
"de constraint\n");
if(normalized)
fprintf(fp, "1 x%d = 0;\n", n+2);
else
fprintf(fp, "1*%s = 0;\n", emptylhsname);
}
}
else
{
xprintf("Problems opening file for writing: %s\n", fname);
return(1);
}
fflush(fp);
if (ferror(fp))
{ xprintf("lpx_write_pb: can't write to `%s' - %s\n", fname,
strerror(errno));
goto fail;
}
fclose(fp);
if(binarize)
{
/* delete the resultant problem object */
if (lp != NULL) lpx_delete_prob(lp);
/* delete MIP presolver workspace */
if (ipp != NULL) ipp_delete_wksp(ipp);
/*lp=tlp;*/
}
return 0;
fail: if (fp != NULL) fclose(fp);
return 1;
}
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;
}
