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algorithms.cpp
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algorithms.cpp
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#include "algorithms.hpp"
// Computes the weight of an edge from the lists of neighbors
float intersectSize (vector<int> & v1, vector<int> & v2, long & total);
// Insert e in v, sorting according to the first component
void insert (vector< tuple<float, int, int> > & v, tuple<float, int, int> e);
// Checks if there is a non-direct path from x to y
bool still_connex (Graph<Component> & metaGraph, int x, int y);
// Deletes an edge from the meta graph
void remove (Graph<Component> & metaGraph, int x, int y);
// Weights the graph
void weight (Graph<Node> & graph) {
int c=0;
long total=0;
for (Node & node : graph.nodes) {
for (int i : node.neighbors) {
c++;
float w = intersectSize(node.neighbors, graph.getNodeFromIdx(i).neighbors, total);
node.weights.push_back(w);
}
}
}
// Computes the components by doing a BFS where edges below edgeFilter are omitted
void component (Graph<Node> & graph, float edgeFilter) {
set<int> toAnnotate;
for (int i=0 ; i<graph.nodes.size() ; i++)
toAnnotate.insert(i);
int currentColor = 0;
while (toAnnotate.size() > 0) {
int startIdx = *toAnnotate.begin();
graph.componentSize.push_back(0);
set<int> nextIdxs;
nextIdxs.insert(startIdx);
while (nextIdxs.size() > 0) {
int nodeIdx = *nextIdxs.begin();
nextIdxs.erase(nodeIdx);
if (graph.components[nodeIdx] == -1) {
graph.components[nodeIdx] = currentColor;
graph.componentSize[currentColor]++;
toAnnotate.erase(nodeIdx);
Node & node = graph.getNodeFromIdx(nodeIdx);
for (int i=0; i<node.neighbors.size(); i++) {
if (node.weights[i] > edgeFilter)
nextIdxs.insert(node.neighbors[i]);
}
}
}
currentColor++;
}
}
// Fuse nodes from a small component to (if applicable) the only neighbor
void fuse (Graph<Node> & graph, int sizeFilter) {
for (Node & node : graph.nodes) {
set<int> adjacent;
for (int i : node.neighbors) {
if (graph.componentSize[graph.components[i]] > sizeFilter) {
// If node is not in a small component, adjacent will contain its component
adjacent.insert(graph.components[i]);
}
}
if (adjacent.size() == 1) {
graph.componentSize[graph.components[node.idx]]--;
graph.components[node.idx] = *adjacent.begin();
graph.componentSize[*adjacent.begin()]++;
}
}
}
// Join an element by himself in his component with its closest neighbor
void alone (Graph<Node> & graph) {
for (Node & node : graph.nodes) {
if (graph.componentSize[graph.components[node.idx]] == 1) {
if (node.neighbors.size() > 0) {
int closest = 0;
for (int j=0; j<node.neighbors.size(); j++) {
if (node.weights[j] > node.weights[closest]) {
closest = j;
}
}
closest = node.neighbors[closest];
graph.componentSize[graph.components[node.idx]]--;
graph.components[node.idx] = graph.components[closest];
graph.componentSize[graph.components[closest]]++;
}
}
}
}
// Fuse small components together
void lower_fuse (Graph<Node> & graph, int sizeFilter) {
for (int i=0; i<graph.nodes.size(); i++) {
if (graph.componentSize[graph.components[i]] < sizeFilter) {
set<int> neighbors;
neighbors.insert(i);
set<int> seen;
while (neighbors.size() > 0) {
int id = *neighbors.begin();
neighbors.erase(id);
if (seen.count(id)==0) {
seen.insert(id);
graph.componentSize[graph.components[id]]--;
graph.components[id] = graph.components[i];
graph.componentSize[graph.components[i]]++;
for (int j : graph.getNodeFromIdx(id).neighbors) {
if (graph.componentSize[graph.components[j]] < sizeFilter and seen.count(j) == 0) {
neighbors.insert(j);
}
}
}
}
}
}
}
// Remove all edges below metaFilter and all edges below metaCeil that preserve the connexity
void meta_filter (Graph<Component> & metaGraph, float metaFilter, float metaCeil) {
vector< tuple<float, int, int> > toRemove;
for (Component & cmp : metaGraph.nodes) {
for (int i=0; i<cmp.neighbors.size(); i++) {
if (cmp.weights[i] < metaFilter and cmp.idx < cmp.neighbors[i]) {
insert(toRemove, make_tuple(cmp.weights[i], cmp.idx, cmp.neighbors[i]));
}
}
}
for (tuple<float, int, int> t : toRemove) {
float w = get<0>(t); int x = get<1>(t); int y = get<2>(t);
if (still_connex(metaGraph, x, y) or w < metaCeil) {
remove(metaGraph, x, y);
}
}
}
float intersectSize (vector<int> & v1, vector<int> & v2, long & total) {
int i, j = 0;
float c = 0;
while( i<v1.size() and j<v2.size() ) {
if (v1[i] < v2[j]) {
i++;
} else if (v2[j] < v1[i]) {
j++;
} else {
i++; j++; c++;
}
total++;
}
return 2*c/(v1.size()+v2.size());
}
void insert (vector< tuple<float, int, int> > & v, tuple<float, int, int> e) {
vector< tuple<float, int, int> >::iterator it = v.begin();
float w = get<0>(e);
while (it < v.end() and w > get<0>(*it)) {
it++;
}
v.insert(it, e);
}
bool still_connex (Graph<Component> & metaGraph, int x, int y) {
set<int> toSee;
vector<int> seen (metaGraph.nodes.size(), 0);
seen[x]++;
for (int i : metaGraph.nodes[x].neighbors) {
if (i != y) {
toSee.insert(i);
}
}
while (toSee.size() > 0) {
int id = *toSee.begin();
toSee.erase(id);
seen[id]++;
if (id == y) {
return true;
}
for (int i : metaGraph.nodes[id].neighbors) {
if (not(seen[i])) {
toSee.insert(i);
}
}
}
return false;
}
void remove (Graph<Component> & metaGraph, int x, int y) {
vector<int> new_neighbors;
vector<float> new_weights;
for (int i=0; i<metaGraph.nodes[x].neighbors.size(); i++) {
if (metaGraph.nodes[x].neighbors[i] != y) {
new_neighbors.push_back(metaGraph.nodes[x].neighbors[i]);
new_weights.push_back(metaGraph.nodes[x].weights[i]);
}
}
metaGraph.nodes[x].neighbors = new_neighbors;
metaGraph.nodes[x].weights = new_weights;
new_neighbors.clear();
new_weights.clear();
for (int i=0; i<metaGraph.nodes[y].neighbors.size(); i++) {
if (metaGraph.nodes[y].neighbors[i] != x) {
new_neighbors.push_back(metaGraph.nodes[y].neighbors[i]);
new_weights.push_back(metaGraph.nodes[y].weights[i]);
}
}
metaGraph.nodes[y].neighbors = new_neighbors;
metaGraph.nodes[y].weights = new_weights;
}