void LKH::LKHAlg::GenerateCandidates(int MaxCandidates, GainType MaxAlpha,
int Symmetric)
{
Node *From, *To;
Candidate *NFrom, *NN;
int a, d, Count;
if (TraceLevel >= 2)
printff("Generating candidates ... ");
if (MaxAlpha < 0 || MaxAlpha > INT_MAX)
MaxAlpha = INT_MAX;
/* Initialize CandidateSet for each node */
FreeCandidateSets();
From = FirstNode;
do
From->Mark = 0;
while ((From = From->Suc) != FirstNode);
if (MaxCandidates > 0) {
do {
assert(From->CandidateSet =
(Candidate *) malloc((MaxCandidates + 1) *
sizeof(Candidate)));
From->CandidateSet[0].To = 0;
}
while ((From = From->Suc) != FirstNode);
} else {
AddTourCandidates();
do {
if (!From->CandidateSet)
eprintf("MAX_CANDIDATES = 0: No candidates");
} while ((From = From->Suc) != FirstNode);
return;
}
/* Loop for each node, From */
do {
NFrom = From->CandidateSet;
if (From != FirstNode) {
From->Beta = INT_MIN;
for (To = From; To->Dad != 0; To = To->Dad) {
To->Dad->Beta =
!FixedOrCommon(To, To->Dad) ?
Max(To->Beta, To->Cost) : To->Beta;
To->Dad->Mark = From;
}
}
Count = 0;
/* Loop for each node, To */
To = FirstNode;
do {
if (To == From)
continue;
d = c && !FixedOrCommon(From, To) ? (this->*c)(From, To) : (this->*D)(From, To);
if (From == FirstNode)
a = To == From->Dad ? 0 : d - From->NextCost;
else if (To == FirstNode)
a = From == To->Dad ? 0 : d - To->NextCost;
else {
if (To->Mark != From)
To->Beta =
!FixedOrCommon(To, To->Dad) ?
Max(To->Dad->Beta, To->Cost) : To->Dad->Beta;
a = d - To->Beta;
}
if (FixedOrCommon(From, To))
a = INT_MIN;
else {
if (From->FixedTo2 || To->FixedTo2 || Forbidden(From, To))
continue;
if (InInputTour(From, To)) {
a = 0;
if (c)
d = (this->*D)(From, To);
} else if (c) {
if (a > MaxAlpha ||
(Count == MaxCandidates &&
(a > (NFrom - 1)->Alpha ||
(a == (NFrom - 1)->Alpha
&& d >= (NFrom - 1)->Cost))))
continue;
if (To == From->Dad) {
d = From->Cost;
a = 0;
} else if (From == To->Dad) {
d = To->Cost;
a = 0;
} else {
a -= d;
a += (d = (this->*D)(From, To));
}
}
}
if (a <= MaxAlpha && IsPossibleCandidate(From, To)) {
/* Insert new candidate edge in From->CandidateSet */
NN = NFrom;
while (--NN >= From->CandidateSet) {
if (a > NN->Alpha || (a == NN->Alpha && d >= NN->Cost))
break;
*(NN + 1) = *NN;
}
NN++;
NN->To = To;
NN->Cost = d;
NN->Alpha = a;
if (Count < MaxCandidates) {
Count++;
NFrom++;
}
NFrom->To = 0;
}
}
while ((To = To->Suc) != FirstNode);
}
while ((From = From->Suc) != FirstNode);
AddTourCandidates();
if (Symmetric)
SymmetrizeCandidateSet();
if (TraceLevel >= 2)
printff("done\n");
}
void CreateQuadrantCandidateSet(int K)
{
Node *From, *To;
Candidate *NFrom;
int L, Q, CandPerQ, Added, Count, i;
if (K <= 0)
return;
if (TraceLevel >= 2)
printff("Creating quadrant candidate set ... ");
KDTree = BuildKDTree(1);
assert(XMin =
(double *) malloc((1 + DimensionSaved) * sizeof(double)));
assert(XMax =
(double *) malloc((1 + DimensionSaved) * sizeof(double)));
assert(YMin =
(double *) malloc((1 + DimensionSaved) * sizeof(double)));
assert(YMax =
(double *) malloc((1 + DimensionSaved) * sizeof(double)));
if (CoordType == THREED_COORDS) {
assert(ZMin =
(double *) malloc((1 + DimensionSaved) * sizeof(double)));
assert(ZMax =
(double *) malloc((1 + DimensionSaved) * sizeof(double)));
}
ComputeBounds(0, Dimension - 1);
Contains = CoordType == THREED_COORDS ? Contains3D : Contains2D;
BoxOverlaps =
CoordType == THREED_COORDS ? BoxOverlaps3D : BoxOverlaps2D;
L = CoordType == THREED_COORDS ? 8 : 4;
CandPerQ = K / L;
assert(CandidateSet =
(Candidate *) malloc((K + 1) * sizeof(Candidate)));
From = FirstNode;
do {
Count = 0;
for (NFrom = From->CandidateSet; NFrom && NFrom->To; NFrom++)
if (FixedOrCommon(From, NFrom->To) && ++Count == 2)
break;
if (Count == 2)
continue;
Added = 0;
for (Q = 1; Q <= L; Q++) {
NearestQuadrantNeighbors(From, Q, CandPerQ);
for (i = 0; i < Candidates; i++) {
To = CandidateSet[i].To;
if (AddCandidate(From, To, D(From, To), 1))
Added++;
}
}
if (K > Added) {
NearestQuadrantNeighbors(From, 0, K - Added);
for (i = 0; i < Candidates; i++) {
To = CandidateSet[i].To;
AddCandidate(From, To, D(From, To), 2);
}
}
} while ((From = From->Suc) != FirstNode);
free(CandidateSet);
free(KDTree);
free(XMin);
free(XMax);
free(YMin);
free(YMax);
if (CoordType == THREED_COORDS) {
free(ZMin);
free(ZMax);
}
if (Level == 0 &&
(WeightType == GEO || WeightType == GEOM ||
WeightType == GEO_MEEUS || WeightType == GEOM_MEEUS)) {
Candidate **SavedCandidateSet;
assert(SavedCandidateSet =
(Candidate **) malloc((1 + DimensionSaved) *
sizeof(Candidate *)));
if (TraceLevel >= 2)
printff("done\n");
From = FirstNode;
while ((From = From->Suc) != FirstNode)
if ((From->Y > 0) != (FirstNode->Y > 0))
break;
if (From != FirstNode) {
/* Transform longitude (180 and -180 map to 0) */
From = FirstNode;
do {
SavedCandidateSet[From->Id] = From->CandidateSet;
From->CandidateSet = 0;
From->Zc = From->Y;
if (WeightType == GEO || WeightType == GEO_MEEUS)
From->Y =
(int) From->Y + 5.0 * (From->Y -
(int) From->Y) / 3.0;
From->Y += From->Y > 0 ? -180 : 180;
if (WeightType == GEO || WeightType == GEO_MEEUS)
From->Y =
(int) From->Y + 3.0 * (From->Y -
(int) From->Y) / 5.0;
} while ((From = From->Suc) != FirstNode);
Level++;
CreateQuadrantCandidateSet(K);
Level--;
From = FirstNode;
do
From->Y = From->Zc;
while ((From = From->Suc) != FirstNode);
do {
Candidate *QCandidateSet = From->CandidateSet;
From->CandidateSet = SavedCandidateSet[From->Id];
for (NFrom = QCandidateSet; (To = NFrom->To); NFrom++)
AddCandidate(From, To, NFrom->Cost, NFrom->Alpha);
free(QCandidateSet);
} while ((From = From->Suc) != FirstNode);
free(SavedCandidateSet);
}
}
if (Level == 0) {
ResetCandidateSet();
AddTourCandidates();
if (CandidateSetSymmetric)
SymmetrizeCandidateSet();
if (TraceLevel >= 2)
printff("done\n");
}
}
void CreateNearestNeighborCandidateSet(int K)
{
Node *From, *To;
int i;
if (TraceLevel >= 2)
printff("Creating nearest neighbor candidate set ... ");
KDTree = BuildKDTree(1);
assert(XMin =
(double *) malloc((1 + DimensionSaved) * sizeof(double)));
assert(XMax =
(double *) malloc((1 + DimensionSaved) * sizeof(double)));
assert(YMin =
(double *) malloc((1 + DimensionSaved) * sizeof(double)));
assert(YMax =
(double *) malloc((1 + DimensionSaved) * sizeof(double)));
if (CoordType == THREED_COORDS) {
assert(ZMin =
(double *) malloc((1 + DimensionSaved) * sizeof(double)));
assert(ZMax =
(double *) malloc((1 + DimensionSaved) * sizeof(double)));
}
ComputeBounds(0, Dimension - 1);
Contains = CoordType == THREED_COORDS ? Contains3D : Contains2D;
BoxOverlaps =
CoordType == THREED_COORDS ? BoxOverlaps3D : BoxOverlaps2D;
assert(CandidateSet =
(Candidate *) malloc((K + 1) * sizeof(Candidate)));
From = FirstNode;
do {
NearestQuadrantNeighbors(From, 0, K);
for (i = 0; i < Candidates; i++) {
To = CandidateSet[i].To;
AddCandidate(From, To, D(From, To), 1);
}
} while ((From = From->Suc) != FirstNode);
free(CandidateSet);
free(KDTree);
free(XMin);
free(XMax);
free(YMin);
free(YMax);
if (CoordType == THREED_COORDS) {
free(ZMin);
free(ZMax);
}
if (Level == 0 && (WeightType == GEOM || WeightType == GEOM_MEEUS)) {
Candidate **SavedCandidateSet;
assert(SavedCandidateSet =
(Candidate **) malloc((1 + DimensionSaved) *
sizeof(Candidate *)));
if (TraceLevel >= 2)
printff("done\n");
/* Transform longitude (180 and -180 map to 0) */
From = FirstNode;
do {
SavedCandidateSet[From->Id] = From->CandidateSet;
From->CandidateSet = 0;
From->Yc = From->Y;
From->Y += From->Y > 0 ? -180 : 180;
} while ((From = From->Suc) != FirstNode);
Level++;
CreateNearestNeighborCandidateSet(K);
Level--;
From = FirstNode;
do
From->Y = From->Yc;
while ((From = From->Suc) != FirstNode);
do {
Candidate *QCandidateSet = From->CandidateSet;
Candidate *NFrom;
From->CandidateSet = SavedCandidateSet[From->Id];
for (NFrom = QCandidateSet; (To = NFrom->To); NFrom++)
AddCandidate(From, To, NFrom->Cost, NFrom->Alpha);
free(QCandidateSet);
} while ((From = From->Suc) != FirstNode);
free(SavedCandidateSet);
}
if (Level == 0) {
ResetCandidateSet();
AddTourCandidates();
if (CandidateSetSymmetric)
SymmetrizeCandidateSet();
if (TraceLevel >= 2)
printff("done\n");
}
}
void LKH::LKHAlg::CreateCandidateSet()
{
GainType Cost, MaxAlpha, A;
Node *Na;
int CandidatesRead = 0, i;
double EntryTime = GetTime();
Norm = 9999;
if (C == &LKH::LKHAlg::C_EXPLICIT) {
Na = FirstNode;
do {
for (i = 1; i < Na->Id; i++)
Na->C[i] *= Precision;
}
while ((Na = Na->Suc) != FirstNode);
}
if (Distance == &LKH::LKHAlg::Distance_1 ||
(MaxTrials == 0 &&
(FirstNode->InitialSuc || InitialTourAlgorithm == SIERPINSKI ||
InitialTourAlgorithm == MOORE))) {
ReadCandidates(MaxCandidates);
AddTourCandidates();
if (ProblemType == HCP || ProblemType == HPP)
Ascent();
goto End_CreateCandidateSet;
}
if (TraceLevel >= 2)
printff("Creating candidates ...\n");
if (MaxCandidates > 0 &&
(CandidateSetType == QUADRANT || CandidateSetType == NN)) {
ReadPenalties();
if (!(CandidatesRead = ReadCandidates(MaxCandidates)) &&
MaxCandidates > 0) {
if (CandidateSetType == QUADRANT)
CreateQuadrantCandidateSet(MaxCandidates);
else if (CandidateSetType == NN)
CreateNearestNeighborCandidateSet(MaxCandidates);
} else {
AddTourCandidates();
if (CandidateSetSymmetric)
SymmetrizeCandidateSet();
}
goto End_CreateCandidateSet;
}
if (!ReadPenalties()) {
/* No PiFile specified or available */
Na = FirstNode;
do
Na->Pi = 0;
while ((Na = Na->Suc) != FirstNode);
CandidatesRead = ReadCandidates(MaxCandidates);
Cost = Ascent();
if (Subgradient && SubproblemSize == 0) {
WritePenalties();
PiFile = 0;
}
} else if ((CandidatesRead = ReadCandidates(MaxCandidates)) ||
MaxCandidates == 0) {
AddTourCandidates();
if (CandidateSetSymmetric)
SymmetrizeCandidateSet();
goto End_CreateCandidateSet;
} else {
if (CandidateSetType != DELAUNAY && MaxCandidates > 0) {
if (TraceLevel >= 2)
printff("Computing lower bound ... ");
Cost = Minimum1TreeCost(0);
if (TraceLevel >= 2)
printff("done\n");
} else {
CreateDelaunayCandidateSet();
Na = FirstNode;
do {
Na->BestPi = Na->Pi;
Na->Pi = 0;
}
while ((Na = Na->Suc) != FirstNode);
if (TraceLevel >= 2)
printff("Computing lower bound ... ");
Cost = Minimum1TreeCost(1);
if (TraceLevel >= 2)
printff("done\n");
Na = FirstNode;
do {
Na->Pi = Na->BestPi;
Cost -= 2 * Na->Pi;
}
while ((Na = Na->Suc) != FirstNode);
}
}
LowerBound = (double) Cost / Precision;
if (TraceLevel >= 1) {
/* printff("Lower bound = %0.1f", LowerBound);
if (Optimum != MINUS_INFINITY && Optimum != 0)
printff(", Gap = %0.2f%%",
100.0 * (Optimum - LowerBound) / Optimum);
if (!PiFile)
printff(", Ascent time = %0.2f sec.",
fabs(GetTime() - EntryTime));
printff("\n"); */
if (Optimum != MINUS_INFINITY && Optimum != 0)
m_Gap=100.0 * (Optimum - LowerBound) / Optimum;
if (!PiFile)
m_AscentTime=fabs(GetTime() - EntryTime);
}
MaxAlpha = (GainType) fabs(Excess * Cost);
if ((A = Optimum * Precision - Cost) > 0 && A < MaxAlpha)
MaxAlpha = A;
if (CandidateSetType == DELAUNAY || MaxCandidates == 0)
OrderCandidateSet(MaxCandidates, MaxAlpha, CandidateSetSymmetric);
else
GenerateCandidates(MaxCandidates, MaxAlpha, CandidateSetSymmetric);
End_CreateCandidateSet:
if (ExtraCandidates > 0) {
AddExtraCandidates(ExtraCandidates,
ExtraCandidateSetType,
ExtraCandidateSetSymmetric);
AddTourCandidates();
}
ResetCandidateSet();
Na = FirstNode;
do {
if (!Na->CandidateSet || !Na->CandidateSet[0].To) {
if (MaxCandidates == 0)
eprintf("MAX_CANDIDATES = 0: Node %d has no candidates",
Na->Id);
else
eprintf("Node %d has no candidates", Na->Id);
}
}
while ((Na = Na->Suc) != FirstNode);
if (!CandidatesRead && SubproblemSize == 0)
WriteCandidates();
if (C == &LKH::LKHAlg::C_EXPLICIT) {
Na = FirstNode;
do
for (i = 1; i < Na->Id; i++)
Na->C[i] += Na->Pi + NodeSet[i].Pi;
while ((Na = Na->Suc) != FirstNode);
}
if (TraceLevel >= 1) {
CandidateReport();
// printff("Preprocessing time = %0.2f sec.\n",
// fabs(GetTime() - EntryTime));
}
}
GainType Ascent()
{
Node *t;
GainType BestW, W, W0, Alpha, MaxAlpha = INT_MAX;
int T, Period, P, InitialPhase, BestNorm;
Start:
/* Initialize Pi and BestPi */
t = FirstNode;
do
t->Pi = t->BestPi = 0;
while ((t = t->Suc) != FirstNode);
if (CandidateSetType == DELAUNAY)
CreateDelaunayCandidateSet();
else
AddTourCandidates();
/* Compute the cost of a minimum 1-tree */
W = Minimum1TreeCost(CandidateSetType == DELAUNAY
|| MaxCandidates == 0);
/* Return this cost
if either
(1) subgradient optimization is not wanted, or
(2) the norm of the tree (its deviation from a tour) is zero
(in that case the true optimum has been found).
*/
if (!Subgradient || !Norm)
return W;
if (Optimum != MINUS_INFINITY && (Alpha = Optimum * Precision - W) > 0)
MaxAlpha = Alpha;
if (MaxCandidates > 0) {
/* Generate symmetric candididate sets for all nodes */
if (CandidateSetType != DELAUNAY)
GenerateCandidates(AscentCandidates, MaxAlpha, 1);
else {
OrderCandidateSet(AscentCandidates, MaxAlpha, 1);
W = Minimum1TreeCost(1);
if (!Norm || W / Precision == Optimum)
return W;
}
}
if (ExtraCandidates > 0)
AddExtraCandidates(ExtraCandidates, ExtraCandidateSetType,
ExtraCandidateSetSymmetric);
if (TraceLevel >= 2) {
CandidateReport();
printff("Subgradient optimization ...\n");
}
/* Set LastV of every node to V (the node's degree in the 1-tree) */
t = FirstNode;
do
t->LastV = t->V;
while ((t = t->Suc) != FirstNode);
BestW = W0 = W;
BestNorm = Norm;
InitialPhase = 1;
/* Perform subradient optimization with decreasing period length
and decreasing step size */
for (Period = InitialPeriod, T = InitialStepSize * Precision;
Period > 0 && T > 0 && Norm != 0; Period /= 2, T /= 2) {
/* Period and step size are halved at each iteration */
if (TraceLevel >= 2)
printff
(" T = %d, Period = %d, BestW = %0.1f, Norm = %d\n",
T, Period, (double) BestW / Precision, Norm);
for (P = 1; T && P <= Period && Norm != 0; P++) {
/* Adjust the Pi-values */
t = FirstNode;
do {
if (t->V != 0) {
t->Pi += T * (7 * t->V + 3 * t->LastV) / 10;
if (t->Pi > INT_MAX / 4)
t->Pi = INT_MAX / 4;
else if (t->Pi < -INT_MAX / 4)
t->Pi = -INT_MAX / 4;
}
t->LastV = t->V;
}
while ((t = t->Suc) != FirstNode);
/* Compute a minimum 1-tree in the sparse graph */
W = Minimum1TreeCost(1);
/* Test if an improvement has been found */
if (W > BestW || (W == BestW && Norm < BestNorm)) {
/* If the lower bound becomes greater than twice its
initial value it is taken as a sign that the graph might be
too sparse */
if (W - W0 > (W0 >= 0 ? W0 : -W0) && AscentCandidates > 0
&& AscentCandidates < Dimension) {
W = Minimum1TreeCost(CandidateSetType == DELAUNAY
|| MaxCandidates == 0);
if (W < W0) {
/* Double the number of candidate edges
and start all over again */
if (TraceLevel >= 2)
printff("Warning: AscentCandidates doubled\n");
if ((AscentCandidates *= 2) > Dimension)
AscentCandidates = Dimension;
goto Start;
}
W0 = W;
}
BestW = W;
BestNorm = Norm;
/* Update the BestPi-values */
t = FirstNode;
do
t->BestPi = t->Pi;
while ((t = t->Suc) != FirstNode);
if (TraceLevel >= 2)
printff
("* T = %d, Period = %d, P = %d, BestW = %0.1f, Norm = %d\n",
T, Period, P, (double) BestW / Precision, Norm);
/* If in the initial phase, the step size is doubled */
if (InitialPhase && T * sqrt((double) Norm) > 0)
T *= 2;
/* If the improvement was found at the last iteration of the
current period, then double the period */
if (CandidateSetType != DELAUNAY && P == Period
&& (Period *= 2) > InitialPeriod)
Period = InitialPeriod;
} else {
if (TraceLevel >= 3)
printff
(" T = %d, Period = %d, P = %d, W = %0.1f, Norm = %d\n",
T, Period, P, (double) W / Precision, Norm);
if (InitialPhase && P > Period / 2) {
/* Conclude the initial phase */
InitialPhase = 0;
P = 0;
T = 3 * T / 4;
}
}
}
}
t = FirstNode;
do {
t->Pi = t->BestPi;
t->BestPi = 0;
} while ((t = t->Suc) != FirstNode);
/* Compute a minimum 1-tree */
W = BestW = Minimum1TreeCost(CandidateSetType == DELAUNAY
|| MaxCandidates == 0);
if (MaxCandidates > 0) {
FreeCandidateSets();
if (CandidateSetType == DELAUNAY)
CreateDelaunayCandidateSet();
} else {
Candidate *Nt;
t = FirstNode;
do {
for (Nt = t->CandidateSet; Nt && Nt->To; Nt++)
Nt->Cost += t->Pi + Nt->To->Pi;
}
while ((t = t->Suc) != FirstNode);
}
if (TraceLevel >= 2)
printff("Ascent: BestW = %0.1f, Norm = %d\n",
(double) BestW / Precision, Norm);
return W;
}
void CreateDelaunayCandidateSet()
{
Node *From, *To;
point *u, *v;
edge *e_start, *e;
int d, i, Count;
if (TraceLevel >= 2)
printff("Creating Delaunay candidate set ... ");
if (Level == 0 && MaxCandidates == 0) {
AddTourCandidates();
From = FirstNode;
do {
if (!From->CandidateSet)
eprintf("MAX_CANDIDATES = 0: No candidates");
} while ((From = From->Suc) != FirstNode);
if (TraceLevel >= 2)
printff("done\n");
return;
}
/* Find the Delaunay edges */
delaunay(Dimension);
/* Add the Delaunay edges to the candidate set */
for (i = 0; i < Dimension; i++) {
u = &p_array[i];
From = &NodeSet[u->id];
e_start = e = u->entry_pt;
Count = 0;
do {
v = Other_point(e, u);
if (u < v) {
To = &NodeSet[v->id];
d = D(From, To);
AddCandidate(From, To, d, 1);
AddCandidate(To, From, d, 1);
}
} while ((e = Next(e, u)) != e_start && ++Count < Dimension);
}
free_memory();
if (Level == 0 &&
(WeightType == GEO || WeightType == GEOM ||
WeightType == GEO_MEEUS || WeightType == GEOM_MEEUS)) {
if (TraceLevel >= 2)
printff("done\n");
From = FirstNode;
while ((From = From->Suc) != FirstNode)
if ((From->Y > 0) != (FirstNode->Y > 0))
break;
if (From != FirstNode) {
/* Transform longitude (180 and -180 map to 0) */
From = FirstNode;
do {
From->Zc = From->Y;
if (WeightType == GEO || WeightType == GEO_MEEUS)
From->Y =
(int) From->Y + 5.0 * (From->Y -
(int) From->Y) / 3.0;
From->Y += From->Y > 0 ? -180 : 180;
if (WeightType == GEO || WeightType == GEO_MEEUS)
From->Y =
(int) From->Y + 3.0 * (From->Y -
(int) From->Y) / 5.0;
} while ((From = From->Suc) != FirstNode);
Level++;
CreateDelaunayCandidateSet();
Level--;
From = FirstNode;
do
From->Y = From->Zc;
while ((From = From->Suc) != FirstNode);
}
}
if (Level == 0) {
AddTourCandidates();
/* Add quadrant neighbors if any node has less than two candidates.
That is, if it should happen that delaunay_edges fails. */
From = FirstNode;
do {
if (From->CandidateSet == 0 ||
From->CandidateSet[0].To == 0 ||
From->CandidateSet[1].To == 0) {
if (TraceLevel >= 2)
printff("*** Not complete ***\n");
AddExtraCandidates(CoordType == THREED_COORDS ? 8 : 4,
QUADRANT, 1);
break;
}
} while ((From = From->Suc) != FirstNode);
if (TraceLevel >= 2)
printff("done\n");
}
}
