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KM.cpp
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KM.cpp
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#include <KM.h>
KM::KM(const vector< vector<double> > & _edges) :
edges(_edges) {
nodes_n = edges.size();
lx = vector<double>(nodes_n, 0);
ly = vector<double>(nodes_n, 0);
match_x = vector<int>(nodes_n, -1);
slack = vector<double>(nodes_n, numeric_limits<double>::max());
for (int i = 0; i < nodes_n; i++) {
lx[i] = numeric_limits<double>::min();
for (int j = 0; j < nodes_n; j++) {
lx[i] = max(lx[i], edges[i][j]);
}
}
}
vector<int> KM::solve() {
for (int i = 0; i < nodes_n; i++) {
for (int j = 0; j < nodes_n; j++) {
slack[j] = numeric_limits<int>::max();
}
while (true) {
vx = vector<bool>(nodes_n, false);
vy = vector<bool>(nodes_n, false);
if (Hungarian(i)) break;
double d = numeric_limits<double>::max();
for (int j = 0; j < nodes_n; j++) {
if (!vy[j]) d = min(d, slack[j]);
}
for (int j = 0; j < nodes_n; j++) {
if (vx[j]) lx[j] -= d;
}
for (int j = 0; j < nodes_n; j++) {
if (vy[j]) ly[j] += d;
}
}
}
return match_x;
}
vector< vector<int> > KM::cut_loops() {
vector<int> arr;
vector<bool> visited(nodes_n, false);
vector< vector<int> > groups;
for (int i = 0; i < nodes_n; i++) {
if (visited[i]) continue;
double match_score = numeric_limits<double>::max();
int p = i;
int st_idx = i;
do {
if (match_score > edges[match_x[p]][p]) {
match_score = edges[match_x[p]][p];
st_idx = p;
}
p = match_x[p];
} while (p != st_idx);
vector<int> group;
p = match_x[st_idx];
do {
group.push_back(p);
visited[p] = true;
p = match_x[p];
} while (p != match_x[st_idx]);
reverse(group.begin(), group.end());
groups.push_back(group);
}
return groups;
}
void KM::print_edges() {
cout << "Edges:" << endl;
for (int i = 0; i < nodes_n; i++) {
for (int j = 0; j < nodes_n; j++) {
cout << edges[i][j] << " ";
}
cout << endl;
}
cout << endl;
}
void KM::print_matches() {
cout << "Matches:" << endl;
for (int i = 0; i < nodes_n; i++) {
cout << match_x[i] << "\t-->\t" << i << endl;
}
cout << endl;
}
bool KM::Hungarian(int cur_node) {
vx[cur_node] = 1;
for (int i = 0; i < nodes_n; i++) {
if (cur_node == i) continue;
if (vy[i]) continue;
double t = lx[cur_node] + ly[i] - edges[cur_node][i];
if (abs(t) < eps) {
vy[i] = true;
if (match_x[i] == -1 || Hungarian(match_x[i])) {
match_x[i] = cur_node;
return true;
}
} else {
slack[i] = min(slack[i], t);
}
}
return false;
}