/* Do a generic readable data dump of key lp_solve model variables;
principally for run difference and debugging purposes */
MYBOOL REPORT_debugdump(lprec *lp, char *filename, MYBOOL livedata)
{
/* FILE *output = stdout; */
FILE *output;
MYBOOL ok;
ok = (MYBOOL) ((filename == NULL) || ((output = fopen(filename,"w")) != NULL));
if(!ok)
return(ok);
if((filename == NULL) && (lp->outstream != NULL))
output = lp->outstream;
fprintf(output, "\nGENERAL INFORMATION\n-------------------\n\n");
fprintf(output, "Model size: %d rows (%d equalities, %d Lagrangean), %d columns (%d integers, %d SC, %d SOS, %d GUB)\n",
lp->rows, lp->equalities, get_Lrows(lp), lp->columns,
lp->int_vars, lp->sc_vars, SOS_count(lp), GUB_count(lp));
fprintf(output, "Data size: %d model non-zeros, %d invB non-zeros (engine is %s)\n",
get_nonzeros(lp), my_if(lp->invB == NULL, 0, lp->bfp_nonzeros(lp, FALSE)), lp->bfp_name());
fprintf(output, "Internal sizes: %d rows allocated, %d columns allocated, %d columns used, %d eta length\n",
lp->rows_alloc, lp->columns_alloc, lp->columns, my_if(lp->invB == NULL, 0, lp->bfp_colcount(lp)));
fprintf(output, "Memory use: %d sparse matrix, %d eta\n",
lp->matA->mat_alloc, my_if(lp->invB == NULL, 0, lp->bfp_memallocated(lp)));
fprintf(output, "Parameters: Maximize=%d, Names used=%d, Scalingmode=%d, Presolve=%d, SimplexPivot=%d\n",
is_maxim(lp), lp->names_used, lp->scalemode, lp->do_presolve, lp->piv_strategy);
fprintf(output, "Precision: EpsValue=%g, EpsPrimal=%g, EpsDual=%g, EpsPivot=%g, EpsPerturb=%g\n",
lp->epsvalue, lp->epsprimal, lp->epsdual, lp->epspivot, lp->epsperturb);
fprintf(output, "Stability: AntiDegen=%d, Improvement=%d, Split variables at=%g\n",
lp->improve, lp->anti_degen, lp->negrange);
fprintf(output, "B&B settings: BB pivot rule=%d, BB branching=%s, BB strategy=%d, Integer precision=%g, MIP gaps=%g,%g\n",
lp->bb_rule, my_boolstr(lp->bb_varbranch), lp->bb_floorfirst, lp->epsint, lp->mip_absgap, lp->mip_relgap);
fprintf(output, "\nCORE DATA\n---------\n\n");
blockWriteINT(output, "Column starts", lp->matA->col_end, 0, lp->columns);
blockWriteINT(output, "row_type", lp->row_type, 0, lp->rows);
blockWriteREAL(output, "orig_rhs", lp->orig_rhs, 0, lp->rows);
blockWriteREAL(output, "orig_lowbo", lp->orig_lowbo, 0, lp->sum);
blockWriteREAL(output, "orig_upbo", lp->orig_upbo, 0, lp->sum);
blockWriteINT(output, "row_type", lp->row_type, 0, lp->rows);
blockWriteBOOL(output, "var_type", lp->var_type, 0, lp->columns, TRUE);
blockWriteAMAT(output, "A", lp, 0, lp->rows);
if(livedata) {
fprintf(output, "\nPROCESS DATA\n------------\n\n");
blockWriteREAL(output, "Active rhs", lp->rhs, 0, lp->rows);
blockWriteINT(output, "Basic variables", lp->var_basic, 0, lp->rows);
blockWriteBOOL(output, "is_basic", lp->is_basic, 0, lp->sum, TRUE);
blockWriteREAL(output, "lowbo", lp->lowbo, 0, lp->sum);
blockWriteREAL(output, "upbo", lp->upbo, 0, lp->sum);
if(lp->scalars != NULL)
blockWriteREAL(output, "scalars", lp->scalars, 0, lp->sum);
}
if(filename != NULL)
fclose(output);
return(ok);
}
STATIC REAL getPricer(lprec *lp, int item, MYBOOL isdual)
{
REAL value = 1.0;
if(!applyPricer(lp))
return( value );
value = *lp->edgeVector;
/* Make sure we have a price vector to use */
if(value < 0) {
#ifdef Paranoia
report(lp, SEVERE, "getPricer: Called without having being initialized!\n");
#endif
return( 1.0 );
}
/* We may be calling the primal from the dual (and vice-versa) for validation
of feasibility; ignore calling origin and simply return 1 */
else if(isdual != value) {
return( 1.0 );
}
/* Do the normal norm retrieval */
else {
if(isdual)
item = lp->var_basic[item];
value = lp->edgeVector[item];
if(value == 0) {
value = 1.0;
report(lp, SEVERE, "getPricer: Detected a zero-valued price at index %d\n", item);
}
#ifdef Paranoia
else if(value < 0)
report(lp, SEVERE, "getPricer: Invalid %s reduced cost norm %g at index %d\n",
my_if(isdual, "dual", "primal"), value, item);
#endif
/* Return the norm */
return( sqrt(value) );
}
}
void REPORT_modelinfo(lprec *lp, MYBOOL doName, char *datainfo)
{
if(doName) {
report(lp, NORMAL, "\nModel name: '%s' - run #%-5d\n",
get_lp_name(lp), lp->solvecount);
report(lp, NORMAL, "Objective: %simize(%s)\n",
my_if(is_maxim(lp), "Max", "Min"), get_row_name(lp, 0));
report(lp, NORMAL, " \n");
}
if(datainfo != NULL)
report(lp, NORMAL, "%s\n", datainfo);
report(lp, NORMAL, "Model size: %7d constraints, %7d variables, %12d non-zeros.\n",
lp->rows, lp->columns, get_nonzeros(lp));
if(GUB_count(lp)+SOS_count(lp) > 0)
report(lp, NORMAL, "Var-types: %7d integer, %7d semi-cont., %7d SOS.\n",
lp->int_vars, lp->sc_vars, lp->sos_vars);
report(lp, NORMAL, "Sets: %7d GUB, %7d SOS.\n",
GUB_count(lp), SOS_count(lp));
}
STATIC int dualloop(lprec *lp, MYBOOL feasible)
{
int i, ok = TRUE;
LREAL theta = 0.0;
REAL *drow = NULL, *prow = NULL, *pcol = NULL, prevobj, epsvalue;
MYBOOL primal = FALSE, forceoutEQ = FALSE;
MYBOOL minit, pivdynamic, bfpfinal = FALSE;
int oldpivrule, oldpivmode, pivrule, Blandswitches,
colnr, rownr, lastnr, minitcount = 0;
int Rcycle = 0, Ccycle = 0, Ncycle = 0, changedphase = TRUE;
#ifdef FixInaccurateDualMinit
int minitcolnr = 0;
#endif
int *nzprow = NULL, *workINT = NULL;
if(lp->spx_trace)
report(lp, DETAILED, "Entering dual simplex algorithm\n");
/* Set Extrad value to force dual feasibility; reset when
"local optimality" has been achieved or a dual non-feasibility
has been encountered (no candidate for a first leaving variable) */
if(feasible)
lp->Extrad = 0;
else
lp->Extrad = feasibilityOffset(lp, (MYBOOL)!primal);
if(lp->spx_trace)
report(lp, DETAILED, "Extrad = %g\n", (double)lp->Extrad);
/* Allocate work arrays */
allocREAL(lp, &drow, lp->sum + 1, TRUE);
#ifdef UseSparseReducedCost
allocINT(lp, &nzprow, lp->sum + 1, FALSE);
#endif
allocREAL(lp, &prow, lp->sum + 1, TRUE);
allocREAL(lp, &pcol, lp->rows + 1, TRUE);
/* Refactorize the basis and set status variables */
i = my_if(is_bb_action(lp, ACTION_REBASE), INITSOL_SHIFTZERO, INITSOL_USEZERO);
if(((lp->spx_status == SWITCH_TO_DUAL) && !lp->justInverted) ||
(lp->Extrad != 0) ||
is_bb_action(lp, ACTION_REINVERT)) {
simplexPricer(lp, (MYBOOL)!primal);
/* Do basis crashing before refactorization, if specified */
invert(lp, (MYBOOL) i, TRUE);
}
else {
if(is_bb_action(lp, ACTION_RECOMPUTE))
recompute_solution(lp, (MYBOOL) i);
restartPricer(lp, (MYBOOL)!primal);
}
lp->bb_action = ACTION_NONE;
lp->spx_status = RUNNING;
lp->doIterate = FALSE;
minit = ITERATE_MAJORMAJOR;
prevobj = lp->rhs[0];
oldpivmode = lp->piv_strategy;
oldpivrule = get_piv_rule(lp);
pivdynamic = ANTICYCLEBLAND && is_piv_mode(lp, PRICE_ADAPTIVE);
epsvalue = lp->epspivot;
Blandswitches = 0;
rownr = 0;
colnr = -1; /* Used to detect infeasibility at the beginning of the dual loop */
lastnr = 0;
lp->rejectpivot[0] = 0;
if(feasible)
lp->simplex_mode = SIMPLEX_Phase2_DUAL;
else
lp->simplex_mode = SIMPLEX_Phase1_DUAL;
/* Check if we have equality slacks in the basis and we should try to
drive them out in order to reduce chance of degeneracy in Phase 1 */
if(!feasible && (lp->fixedvars > 0) && is_anti_degen(lp, ANTIDEGEN_FIXEDVARS)) {
forceoutEQ = AUTOMATIC;
}
while(lp->spx_status == RUNNING) {
if(lp->spx_trace)
if(lastnr > 0)
report(lp, NORMAL, "dualloop: Objective at iteration %8d is " RESULTVALUEMASK " (%4d: %4d %s- %4d)\n",
get_total_iter(lp), lp->rhs[0], rownr, lastnr,
my_if(minit == ITERATE_MAJORMAJOR, "<","|"), colnr);
pivrule = get_piv_rule(lp);
if(pivdynamic && ((pivrule != PRICER_FIRSTINDEX) ||
(pivrule != oldpivrule))
#if DualPivotStickiness==2
/* Stays with pricing rule as long as possible (also preserves accuracy) */
&& (lp->fixedvars == 0)
#elif DualPivotStickiness==1
/* Stays with pricing rule only if the model is infeasible */
&& feasible
#endif
) {
/* Check if we have a stationary solution */
if((minit == ITERATE_MAJORMAJOR) && !lp->justInverted &&
(fabs(my_reldiff(lp->rhs[0], prevobj)) < epsvalue)) {
Ncycle++;
/* Start to monitor for variable cycling if this is the initial stationarity */
if(Ncycle <= 1) {
Ccycle = colnr;
Rcycle = rownr;
}
/* Check if we should change pivoting strategy due to stationary variable cycling */
else if((pivrule == oldpivrule) && (((MAX_STALLCOUNT > 1) && (Ncycle > MAX_STALLCOUNT)) ||
(Ccycle == rownr) || (Rcycle == colnr))) {
/* First check if we should give up on Bland's rule and try perturbed bound
relaxation instead */
#ifdef EnableStallAntiDegen
if((MAX_BLANDSWITCH >= 0) && (Blandswitches >= MAX_BLANDSWITCH)) {
lp->spx_status = DEGENERATE;
break;
}
#endif
Blandswitches++;
lp->piv_strategy = PRICER_FIRSTINDEX; /* There is no advanced normalization for Bland's rule, restart at end */
Ccycle = 0;
Rcycle = 0;
Ncycle = 0;
if(lp->spx_trace)
report(lp, DETAILED, "dualloop: Detected cycling at iteration %d; changed to FIRST INDEX rule!\n",
get_total_iter(lp));
}
}
/* Handle cycling or stationary situations by switching to the primal simplex */
else if((pivrule == oldpivrule) && feasible && (lp->simplex_strategy & SIMPLEX_DYNAMIC)) {
lp->spx_status = SWITCH_TO_PRIMAL;
break;
}
/* Change back to original selection strategy as soon as possible */
else if((minit == ITERATE_MAJORMAJOR) && (pivrule != oldpivrule)) {
lp->piv_strategy = oldpivmode;
restartPricer(lp, AUTOMATIC); /* Pricer restart following Bland's rule */
Ccycle = 0;
Rcycle = 0;
Ncycle = 0;
if(lp->spx_trace)
report(lp, DETAILED, "...returned to original pivot selection rule at iteration %d.\n",
get_total_iter(lp));
}
}
/* Store current LP value for reference at next iteration */
changedphase = FALSE;
prevobj = lp->rhs[0];
lastnr = lp->var_basic[rownr];
lp->doInvert = FALSE;
/* Do minor iterations (non-basic variable bound switches) for as
long as possible since this is a cheap way of iterating */
#ifdef Phase1DualPriceEqualities
RetryRow:
#endif
if(minit != ITERATE_MINORRETRY) {
/* forceoutEQ
FALSE : Only eliminate assured "good" violated equality constraint slacks
AUTOMATIC: Seek more elimination of equality constraint slacks
(but not as aggressive as the rule used in lp_solve v4.0 and earlier)
TRUE: Force remaining equality slacks out of the basis */
i = 0;
do {
if(partial_countBlocks(lp, (MYBOOL) !primal) > 1)
partial_blockStep(lp, (MYBOOL) !primal);
rownr = rowdual(lp, forceoutEQ);
i++;
} while ((rownr == 0) && (i < partial_countBlocks(lp, (MYBOOL) !primal)));
lastnr = lp->var_basic[rownr];
}
if(rownr > 0) {
#ifdef UseRejectionList
RetryCol:
#endif
lp->doIterate = FALSE;
colnr = coldual(lp, rownr, (MYBOOL)(minit == ITERATE_MINORRETRY),
prow, nzprow, drow, NULL);
if(colnr > 0) {
lp->doIterate = TRUE;
fsolve(lp, colnr, pcol, workINT, lp->epsmachine, 1.0, TRUE);
#ifdef FixInaccurateDualMinit
/* Prevent bound flip-flops during minor iterations; used to detect
infeasibility after triggering of minor iteration accuracy management */
if(colnr != minitcolnr)
minitcolnr = 0;
#endif
/* Getting division by zero here; catch it and try to recover */
if(pcol[rownr] == 0) {
if(lp->spx_trace)
report(lp, DETAILED, "dualloop: Attempt to divide by zero (pcol[%d])\n", rownr);
lp->doIterate = FALSE;
if(!lp->justInverted) {
report(lp, DETAILED, "...trying to recover by reinverting!\n");
lp->doInvert = TRUE;
bfpfinal = FALSE;
}
#ifdef UseRejectionList
else if(lp->rejectpivot[0] < DEF_MAXPIVOTRETRY) {
lp->rejectpivot[0]++;
lp->rejectpivot[lp->rejectpivot[0]] = colnr;
if(lp->bb_totalnodes == 0)
report(lp, DETAILED, "...trying to recover via another pivot column!\n");
goto RetryCol;
}
#endif
else {
if(lp->bb_totalnodes == 0)
report(lp, DETAILED, "...cannot recover by reinverting.\n");
lp->spx_status = NUMFAILURE;
ok = FALSE;
}
}
else {
lp->rejectpivot[0] = 0;
theta = lp->bfp_prepareupdate(lp, rownr, colnr, pcol);
/* Verify numeric accuracy of the inverse and change to
the "theoretically" correct version of the theta */
if((lp->improve & IMPROVE_INVERSE) &&
(my_reldiff(fabs(theta),fabs(prow[colnr])) >
lp->epspivot*10.0*log(2.0+50.0*lp->rows))) {
lp->doInvert = TRUE;
bfpfinal = TRUE;
#ifdef IncreasePivotOnReducedAccuracy
if(lp->bfp_pivotcount(lp) < 2*DEF_MAXPIVOTRETRY)
lp->epspivot *= 2.0;
#endif
report(lp, DETAILED, "dualloop: Refactorizing at iteration %d due to loss of accuracy.\n",
get_total_iter(lp));
}
theta = prow[colnr];
compute_theta(lp, rownr, &theta, !lp->is_lower[colnr], 0, primal);
}
}
#ifdef FixInaccurateDualMinit
/* Reinvert and try another row if we did not find a bound-violated leaving column */
else if((minit != ITERATE_MAJORMAJOR) && (colnr != minitcolnr)) {
minitcolnr = colnr;
lp->doInvert = TRUE;
i = invert(lp, INITSOL_USEZERO, TRUE);
if((lp->spx_status == USERABORT) || (lp->spx_status == TIMEOUT))
break;
else if(!i) {
lp->spx_status = SINGULAR_BASIS;
break;
}
minit = ITERATE_MAJORMAJOR;
continue;
}
#endif
else {
if(lp->justInverted && (lp->simplex_mode == SIMPLEX_Phase2_DUAL))
lp->spx_status = LOSTFEAS;
#if 1
else if(!lp->justInverted && (lp->bb_level <= 1)) {
#else
else if(!lp->justInverted) {
#endif
lp->doIterate = FALSE;
lp->doInvert = TRUE;
bfpfinal = TRUE;
}
else {
if((lp->spx_trace && (lp->bb_totalnodes == 0)) ||
(lp->bb_trace && (lp->bb_totalnodes > 0)))
report(lp, DETAILED, "Model lost dual feasibility.\n");
lp->spx_status = INFEASIBLE;
ok = FALSE;
break;
}
}
}
else {
/* New code to solve to optimality using the dual, but only if the user
has specified a preference for the dual simplex - KE added 20030731 */
lp->doIterate = FALSE;
bfpfinal = TRUE;
if((lp->Extrad != 0) && (colnr < 0) && !isPrimalFeasible(lp, lp->epsprimal)) {
if(feasible) {
if(lp->bb_totalnodes == 0)
report(lp, DETAILED, "Model is dual infeasible and primal feasible\n");
lp->spx_status = SWITCH_TO_PRIMAL;
lp->doInvert = (MYBOOL) (lp->Extrad != 0);
lp->Extrad = 0;
}
else {
if(lp->bb_totalnodes == 0)
report(lp, NORMAL, "Model is primal and dual infeasible\n");
lp->spx_status = INFEASIBLE;
ok = FALSE;
}
break;
}
else if(lp->Extrad == 0) {
/* We are feasible (and possibly also optimal) */
feasible = TRUE;
lp->simplex_mode = SIMPLEX_Phase2_DUAL;
/* Check if we still have equality slacks stuck in the basis; drive them out? */
if((lp->fixedvars > 0) && lp->bb_totalnodes == 0)
#ifdef Paranoia
report(lp, NORMAL,
#else
report(lp, DETAILED,
#endif
"Found dual solution with %d fixed slack variables left basic\n",
lp->fixedvars);
#ifdef Phase1DualPriceEqualities
if(forceoutEQ != TRUE) {
forceoutEQ = TRUE;
goto RetryRow;
}
colnr = 0;
#else
#if 1
/* Problem: Check if we are dual degenerate and need to switch to the
primal simplex (there is a flaw in the dual simplex code) */
colnr = colprim(lp, FALSE, drow, nzprow);
#else
colnr = 0;
#endif
#endif
if(colnr == 0)
lp->spx_status = OPTIMAL;
else {
lp->spx_status = SWITCH_TO_PRIMAL;
if(lp->total_iter == 0)
report(lp, NORMAL, "Use primal simplex for finalization at iteration %8d\n",
get_total_iter(lp));
}
if((lp->total_iter == 0) && (lp->spx_status == OPTIMAL))
report(lp, NORMAL, "Optimal solution with dual simplex at iteration %8d\n",
get_total_iter(lp));
break;
}
else {
STATIC int primloop(lprec *lp, MYBOOL feasible)
{
int i, j, k, ok = TRUE;
LREAL theta = 0.0;
REAL *prow = NULL, *drow = NULL, *pcol = NULL, prevobj, epsvalue;
MYBOOL primal = TRUE, minit;
MYBOOL pivdynamic, bfpfinal = FALSE;
int oldpivrule, oldpivmode, pivrule, Blandswitches,
colnr, rownr, lastnr, minitcount = 0;
int Rcycle = 0, Ccycle = 0, Ncycle = 0, changedphase = FALSE;
int *nzdrow = NULL, *workINT = NULL;
/* Add sufficent number of artificial variables to make the problem feasible
through the first phase; delete when primal feasibility has been achieved */
lp->Extrap = 0;
#ifdef EnablePrimalPhase1
if(!feasible) {
#ifdef Paranoia
if(!verifyBasis(lp))
report(lp, SEVERE, "primloop: No valid basis for artificial variables\n");
#endif
#if 0
/* First check if we can get away with a single artificial variable */
if(lp->equalities == 0) {
i = (int) feasibilityOffset(lp, !primal);
add_artificial(lp, i);
}
else
#endif
/* Otherwise add as many as is necessary to force basic feasibility */
for(i = 1; i <= lp->rows; i++)
add_artificial(lp, i);
}
if(lp->spx_trace)
report(lp, DETAILED, "Extrap count = %d\n", lp->Extrap);
#endif
if(lp->spx_trace)
report(lp, DETAILED, "Entered primal simplex algorithm with feasibility %s\n",
my_boolstr(feasible));
/* Create work arrays */
#ifdef UseSparseReducedCost
allocINT(lp, &nzdrow, lp->sum + 1, FALSE);
#endif
allocREAL(lp, &prow, lp->sum + 1, TRUE);
allocREAL(lp, &drow, lp->sum + 1, TRUE);
allocREAL(lp, &pcol, lp->rows + 1, TRUE);
/* Refactorize the basis and set status variables */
i = my_if(is_bb_action(lp, ACTION_REBASE), INITSOL_SHIFTZERO, INITSOL_USEZERO);
if(((lp->spx_status == SWITCH_TO_PRIMAL) && !lp->justInverted) ||
(lp->Extrap != 0) ||
is_bb_action(lp, ACTION_REINVERT)) {
simplexPricer(lp, (MYBOOL)!primal);
/* Do basis crashing before refactorization, if specified */
invert(lp, (MYBOOL) i, TRUE);
}
else {
if(is_bb_action(lp, ACTION_RECOMPUTE))
recompute_solution(lp, (MYBOOL) i);
restartPricer(lp, (MYBOOL)!primal);
}
lp->bb_action = ACTION_NONE;
lp->spx_status = RUNNING;
lp->doIterate = FALSE;
minit = ITERATE_MAJORMAJOR;
prevobj = lp->rhs[0];
oldpivmode = lp->piv_strategy;
oldpivrule = get_piv_rule(lp);
pivdynamic = ANTICYCLEBLAND && is_piv_mode(lp, PRICE_ADAPTIVE);
epsvalue = lp->epspivot;
Blandswitches = 0;
rownr = 0;
colnr = 0;
lastnr = 0;
lp->rejectpivot[0] = 0;
if(feasible)
lp->simplex_mode = SIMPLEX_Phase2_PRIMAL;
else
lp->simplex_mode = SIMPLEX_Phase1_PRIMAL;
/* Iterate while we are successful; exit when the model is infeasible/unbounded,
or we must terminate due to numeric instability or user-determined reasons */
while(lp->spx_status == RUNNING) {
if(lp->spx_trace)
if(lastnr > 0)
report(lp, NORMAL, "primloop: Objective at iteration %8d is " RESULTVALUEMASK " (%4d: %4d %s- %4d)\n",
get_total_iter(lp), lp->rhs[0], rownr, lastnr,
my_if(minit == ITERATE_MAJORMAJOR, "<","|"), colnr);
pivrule = get_piv_rule(lp);
if(pivdynamic && ((pivrule != PRICER_FIRSTINDEX) ||
(pivrule != oldpivrule))
#if PrimalPivotStickiness==2
&& (lp->fixedvars == 0)
#elif PrimalPivotStickiness==1
&& feasible
#endif
) {
/* Check if we have a stationary solution */
if((minit == ITERATE_MAJORMAJOR) && !lp->justInverted &&
(fabs(my_reldiff(lp->rhs[0], prevobj)) < epsvalue)) {
Ncycle++;
/* Start to monitor for variable cycling if this is the initial stationarity */
if(Ncycle <= 1) {
Ccycle = colnr;
Rcycle = rownr;
}
/* Check if we should change pivoting strategy due to stationary variable cycling */
else if((pivrule == oldpivrule) && (((MAX_STALLCOUNT > 1) && (Ncycle > MAX_STALLCOUNT)) ||
(Ccycle == rownr) || (Rcycle == colnr))) {
/* First check if we should give up on Bland's rule and try perturbed bound
relaxation instead */
#ifdef EnableStallAntiDegen
if((MAX_BLANDSWITCH >= 0) && (Blandswitches >= MAX_BLANDSWITCH)) {
lp->spx_status = DEGENERATE;
break;
}
#endif
Blandswitches++;
lp->piv_strategy = PRICER_FIRSTINDEX; /* There is no advanced normalization for Bland's rule, restart at end */
Ccycle = 0;
Rcycle = 0;
Ncycle = 0;
if(lp->spx_trace)
report(lp, DETAILED, "primloop: Detected cycling at iteration %d; changed to FIRST INDEX rule!\n",
get_total_iter(lp));
}
}
#if 0
/* Handle cycling or stationary situations by switching to the dual simplex */
else if((pivrule == oldpivrule) && feasible && (lp->simplex_strategy & SIMPLEX_DYNAMIC)) {
lp->spx_status = SWITCH_TO_DUAL;
if(lp->total_iter == 0)
report(lp, NORMAL, "Start dual simplex for finalization at iteration %8d\n",
get_total_iter(lp));
break;
}
#endif
/* Change back to original selection strategy as soon as possible */
else if((minit == ITERATE_MAJORMAJOR) && (pivrule != oldpivrule)) {
lp->piv_strategy = oldpivmode;
restartPricer(lp, AUTOMATIC); /* Pricer restart following Bland's rule */
Ccycle = 0;
Rcycle = 0;
Ncycle = 0;
if(lp->spx_trace)
report(lp, DETAILED, "...returned to original pivot selection rule at iteration %d.\n",
get_total_iter(lp));
}
}
/* Store current LP value for reference at next iteration */
prevobj = lp->rhs[0];
lp->doIterate = FALSE;
lp->doInvert = FALSE;
/* Find best column to enter the basis */
RetryCol:
if(!changedphase) {
i = 0;
do {
if(partial_countBlocks(lp, (MYBOOL) !primal) > 1)
partial_blockStep(lp, (MYBOOL) !primal);
colnr = colprim(lp, (MYBOOL) (minit == ITERATE_MINORRETRY), drow, nzdrow);
i++;
} while ((colnr == 0) && (i < partial_countBlocks(lp, (MYBOOL) !primal)));
#ifdef FinalOptimalErrorLimitation
/* Do additional checking that we have a correct identification of optimality */
if((colnr == 0) && !lp->justInverted) {
lp->doInvert = TRUE;
i = invert(lp, INITSOL_USEZERO, TRUE);
colnr = colprim(lp, FALSE, drow, nzdrow);
}
#endif
}
if(colnr > 0) {
changedphase = FALSE;
fsolve(lp, colnr, pcol, workINT, lp->epsmachine, 1.0, TRUE); /* Solve entering column for Pi */
#ifdef UseRejectionList
if(is_anti_degen(lp, ANTIDEGEN_COLUMNCHECK) && !check_degeneracy(lp, pcol, NULL)) {
if(lp->rejectpivot[0] < DEF_MAXPIVOTRETRY/3) {
i = ++lp->rejectpivot[0];
lp->rejectpivot[i] = colnr;
report(lp, DETAILED, "Entering column %d found to be non-improving due to degeneracy!\n",
colnr);
goto RetryCol;
}
else {
lp->rejectpivot[0] = 0;
report(lp, DETAILED, "Gave up trying to find a strictly improving entering column!\n");
}
}
#endif
/* Find the leaving variable that gives the most stringent bound on the entering variable */
theta = drow[colnr];
rownr = rowprim(lp, colnr, &theta, pcol);
#if 0
report(lp, NORMAL, "Iteration %d: Enter %d, Leave %d\n", lp->current_iter, colnr, rownr);
#endif
/* See if we can do a straight artificial<->slack replacement (when "colnr" is a slack) */
if((lp->Extrap != 0) && (rownr == 0) && (colnr <= lp->rows))
rownr = findAnti_artificial(lp, colnr);
if(rownr > 0) {
lp->rejectpivot[0] = 0;
lp->bfp_prepareupdate(lp, rownr, colnr, pcol);
}
else if(lp->spx_status == UNBOUNDED) {
report(lp, DETAILED, "primloop: The model is primal unbounded.\n");
break;
}
#ifdef UseRejectionList
else if(lp->rejectpivot[0] < DEF_MAXPIVOTRETRY) {
lp->spx_status = RUNNING;
if(lp->justInverted) {
lp->rejectpivot[0]++;
lp->rejectpivot[lp->rejectpivot[0]] = colnr;
report(lp, DETAILED, "...trying to recover via another pivot column!\n");
}
else {
lp->doInvert = TRUE;
invert(lp, INITSOL_USEZERO, TRUE);
}
goto RetryCol;
}
#endif
else {
/* Assume failure if we are still unsuccessful and the model is not unbounded */
if((rownr == 0) && (lp->spx_status == RUNNING)) {
report(lp, IMPORTANT, "primloop: Could not find a leaving variable for entering %d (iteration %d)\n",
colnr, get_total_iter(lp));
lp->spx_status = NUMFAILURE;
}
}
}
#ifdef EnablePrimalPhase1
else if(!feasible || isPhase1(lp)) {
if(feasiblePhase1(lp, epsvalue)) {
lp->spx_status = RUNNING;
if(lp->bb_totalnodes == 0) {
report(lp, NORMAL, "Found feasibility by primal simplex at iteration %8d\n",
get_total_iter(lp));
if((lp->usermessage != NULL) && (lp->msgmask & MSG_LPFEASIBLE))
lp->usermessage(lp, lp->msghandle, MSG_LPFEASIBLE);
}
changedphase = FALSE;
feasible = TRUE;
lp->simplex_mode = SIMPLEX_Phase2_PRIMAL;
/* We can do two things now;
1) delete the rows belonging to those variables, since they are redundant, OR
2) drive out the existing artificial variables via pivoting. */
if(lp->Extrap > 0) {
#ifdef Phase1EliminateRedundant
/* If it is not a MIP model we can try to delete redundant rows */
if((lp->bb_totalnodes == 0) && (MIP_count(lp) == 0)) {
while(lp->Extrap > 0) {
i = lp->rows;
while((i > 0) && (lp->var_basic[i] <= lp->sum-lp->Extrap))
i--;
#ifdef Paranoia
if(i <= 0) {
report(lp, SEVERE, "primloop: Could not find redundant artificial.\n");
break;
}
#endif
/* Obtain column and row indeces */
j = lp->var_basic[i]-lp->rows;
k = get_artificialRow(lp, j);
/* Delete row before column due to basis "compensation logic" */
if(lp->is_basic[k]) {
lp->is_basic[lp->rows+j] = FALSE;
del_constraint(lp, k);
}
else
setBasisVar(lp, i, k);
del_column(lp, j);
lp->Extrap--;
}
lp->basis_valid = TRUE;
}
/* Otherwise we drive out the artificials by elimination pivoting */
else {
eliminate_artificials(lp, prow);
lp->doIterate = FALSE;
}
#else
lp->Extrap = my_flipsign(lp->Extrap);
#endif
}
lp->doInvert = TRUE;
prevobj = lp->infinite;
}
else {
lp->spx_status = INFEASIBLE;
minit = ITERATE_MAJORMAJOR;
if(lp->spx_trace)
report(lp, NORMAL, "Model infeasible by primal simplex at iteration %8d\n",
get_total_iter(lp));
}
}
#endif
/* Pivot row/col and update the inverse */
if(lp->doIterate) {
lastnr = lp->var_basic[rownr];
if(lp->justInverted)
minitcount = 0;
else if(minitcount > MAX_MINITUPDATES) {
recompute_solution(lp, INITSOL_USEZERO);
minitcount = 0;
}
minit = performiteration(lp, rownr, colnr, theta, primal, NULL, NULL,
pcol, NULL);
if(minit != ITERATE_MAJORMAJOR)
minitcount++;
if((lp->spx_status == USERABORT) || (lp->spx_status == TIMEOUT))
break;
else if(minit == ITERATE_MINORMAJOR)
continue;
#ifdef UsePrimalReducedCostUpdate
/* Do a fast update of the reduced costs in preparation for the next iteration */
if(minit == ITERATE_MAJORMAJOR)
update_reducedcosts(lp, primal, lastnr, colnr, pcol, drow);
#endif
#ifdef EnablePrimalPhase1
/* Detect if an auxiliary variable has left the basis and delete it; if
the non-basic variable only changed bound (a "minor iteration"), the
basic artificial variable did not leave and there is nothing to do */
if((minit == ITERATE_MAJORMAJOR) && (lastnr > lp->sum - abs(lp->Extrap))) {
#ifdef Paranoia
if(lp->is_basic[lastnr] || !lp->is_basic[colnr])
report(lp, SEVERE, "primloop: Invalid basis indicator for variable %d at iteration %d\n",
lastnr, get_total_iter(lp));
#endif
del_column(lp, lastnr-lp->rows);
if(lp->Extrap > 0)
lp->Extrap--;
else
lp->Extrap++;
if(lp->Extrap == 0) {
colnr = 0;
prevobj = lp->infinite;
changedphase = TRUE;
}
}
#endif
}
if(lp->spx_status == SWITCH_TO_DUAL)
;
else if(!changedphase && lp->bfp_mustrefactorize(lp)) {
i = invert(lp, INITSOL_USEZERO, FALSE);
#ifdef ResetMinitOnReinvert
minit = ITERATE_MAJORMAJOR;
#endif
if((lp->spx_status == USERABORT) || (lp->spx_status == TIMEOUT))
break;
else if(!i) {
lp->spx_status = SINGULAR_BASIS;
break;
}
/* Check whether we are still feasible or not... */
if(!isPrimalFeasible(lp, lp->epspivot)) {
lp->spx_status = LOSTFEAS;
}
}
userabort(lp, -1);
}
if (lp->piv_strategy != oldpivmode)
lp->piv_strategy = oldpivmode;
#ifdef EnablePrimalPhase1
/* Remove any remaining artificial variables (feasible or infeasible model) */
lp->Extrap = abs(lp->Extrap);
if(lp->Extrap > 0) {
clear_artificials(lp);
if(lp->spx_status != OPTIMAL)
restore_basis(lp);
i = invert(lp, INITSOL_USEZERO, TRUE);
}
#ifdef Paranoia
if(!verifyBasis(lp))
report(lp, SEVERE, "primloop: Invalid basis detected due to internal error\n");
#endif
/* Switch to dual phase 1 simplex for MIP models during B&B phases */
if((lp->bb_totalnodes == 0) && (MIP_count(lp) > 0) &&
((lp->simplex_strategy & SIMPLEX_Phase1_DUAL) == 0)) {
lp->simplex_strategy &= !SIMPLEX_Phase1_PRIMAL;
lp->simplex_strategy += SIMPLEX_Phase1_DUAL;
}
#endif
FREE(nzdrow);
FREE(drow);
FREE(prow);
FREE(pcol);
return(ok);
} /* primloop */
