bool RandomMerger::buildOneLevel(MultilevelGraph &MLG)
{
Graph &G = MLG.getGraph();
int level = MLG.getLevel() + 1;
int numNodes = G.numberOfNodes();
if (numNodes <= 3) {
return false;
}
int index = 0;
Array<node> candidates(numNodes);
for(node v : G.nodes) {
candidates[index] = v;
index++;
}
int candSize = candidates.size();
while (candSize > numNodes / m_levelSizeFactor)
{
index = randomNumber(0, candSize-1);
node mergeNode = candidates[index];
candidates[index] = candidates[candSize-1];
candSize--;
node parent = nullptr;
if (mergeNode->degree() > 0) {
int index = randomNumber(0, mergeNode->degree()-1);
int i = 0;
for(adjEntry adj : mergeNode->adjEntries) {
if (i == index) {
parent = adj->twinNode();
break;
} else {
i++;
}
}
} else {
do {
index = randomNumber(0, candSize-1);
parent = candidates[index];
} while (parent == mergeNode);
candidates[index] = candidates[candSize-1];
candSize--;
}
NodeMerge * NM = new NodeMerge(level);
bool ret = MLG.changeNode(NM, parent, MLG.radius(parent), mergeNode);
OGDF_ASSERT( ret );
MLG.moveEdgesToParent(NM, mergeNode, parent, true, m_adjustEdgeLengths);
ret = MLG.postMerge(NM, mergeNode);
if( !ret ) {
delete NM;
}
}
return true;
}
bool MatchingMerger::buildOneLevel(MultilevelGraph &MLG)
{
Graph &G = MLG.getGraph();
int level = MLG.getLevel() + 1;
int numNodes = G.numberOfNodes();
if (level == 1 && m_selectByMass) {
m_mass.init(G, 1);
}
if (numNodes <= 3) {
return false;
}
NodeArray<bool> nodeMarks(G, false);
std::vector<edge> matching;
std::vector<node> candidates;
for(node v : G.nodes) {
candidates.push_back(v);
}
while (!candidates.empty())
{
int rndIndex = randomNumber(0, (int)candidates.size()-1);
node one = candidates[rndIndex];
candidates[rndIndex] = candidates.back();
candidates.pop_back();
if (nodeMarks[one]) {
continue;
}
nodeMarks[one] = true;
std::vector<node> candNeighbors;
std::vector<edge> candEdges;
unsigned int minMass = numeric_limits<unsigned int>::max();
for(adjEntry adj : one->adjEntries) {
node cand = adj->twinNode();
if (!nodeMarks[cand] && (!m_selectByMass || m_mass[cand] <= minMass))
{
if (m_selectByMass && m_mass[cand] < minMass) {
minMass = m_mass[cand];
candNeighbors.clear();
candEdges.clear();
}
candNeighbors.push_back(cand);
candEdges.push_back(adj->theEdge());
}
}
if (candNeighbors.empty()) {
continue;
}
int index = randomNumber(0, int(candNeighbors.size())-1);
nodeMarks[candNeighbors[index]] = true;
matching.push_back(candEdges[index]);
}
while (!matching.empty()) {
edge matchingEdge = matching.back();
matching.pop_back();
node mergeNode;
node parent;
// choose high degree node as parent!
mergeNode = matchingEdge->source();
parent = matchingEdge->target();
if (mergeNode->degree() > parent->degree()) {
mergeNode = matchingEdge->target();
parent = matchingEdge->source();
}
NodeMerge * NM = new NodeMerge(level);
bool ret = MLG.changeNode(NM, parent, MLG.radius(parent), mergeNode);
OGDF_ASSERT( ret );
if (m_selectByMass) {
m_mass[parent] = m_mass[parent] + m_mass[mergeNode];
}
MLG.moveEdgesToParent(NM, mergeNode, parent, true, m_adjustEdgeLengths);
ret = MLG.postMerge(NM, mergeNode);
if( !ret ) {
delete NM;
}
}
return true;
}