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-rw-r--r--src/util/bipartite.rs694
1 files changed, 346 insertions, 348 deletions
diff --git a/src/util/bipartite.rs b/src/util/bipartite.rs
index aec7b042..ade831a4 100644
--- a/src/util/bipartite.rs
+++ b/src/util/bipartite.rs
@@ -1,378 +1,376 @@
/*
- * This module deals with graph algorithm in complete bipartite
+ * This module deals with graph algorithm in complete bipartite
* graphs. It is used in layout.rs to build the partition to node
* assignation.
* */
-use std::cmp::{min,max};
-use std::collections::VecDeque;
use rand::prelude::SliceRandom;
+use std::cmp::{max, min};
+use std::collections::VecDeque;
//Graph data structure for the flow algorithm.
-#[derive(Clone,Copy,Debug)]
-struct EdgeFlow{
- c : i32,
- flow : i32,
- v : usize,
- rev : usize,
+#[derive(Clone, Copy, Debug)]
+struct EdgeFlow {
+ c: i32,
+ flow: i32,
+ v: usize,
+ rev: usize,
}
//Graph data structure for the detection of positive cycles.
-#[derive(Clone,Copy,Debug)]
-struct WeightedEdge{
- w : i32,
- u : usize,
- v : usize,
+#[derive(Clone, Copy, Debug)]
+struct WeightedEdge {
+ w: i32,
+ u: usize,
+ v: usize,
}
-
-/* This function takes two matchings (old_match and new_match) in a
- * complete bipartite graph. It returns a matching that has the
+/* This function takes two matchings (old_match and new_match) in a
+ * complete bipartite graph. It returns a matching that has the
* same degree as new_match at every vertex, and that is as close
* as possible to old_match.
* */
-pub fn optimize_matching( old_match : &Vec<Vec<usize>> ,
- new_match : &Vec<Vec<usize>> ,
- nb_right : usize )
- -> Vec<Vec<usize>> {
- let nb_left = old_match.len();
- let ed = WeightedEdge{w:-1,u:0,v:0};
- let mut edge_vec = vec![ed ; nb_left*nb_right];
-
- //We build the complete bipartite graph structure, represented
- //by the list of all edges.
- for i in 0..nb_left {
- for j in 0..nb_right{
- edge_vec[i*nb_right + j].u = i;
- edge_vec[i*nb_right + j].v = nb_left+j;
- }
- }
-
- for i in 0..edge_vec.len() {
- //We add the old matchings
- if old_match[edge_vec[i].u].contains(&(edge_vec[i].v-nb_left)) {
- edge_vec[i].w *= -1;
- }
- //We add the new matchings
- if new_match[edge_vec[i].u].contains(&(edge_vec[i].v-nb_left)) {
- (edge_vec[i].u,edge_vec[i].v) =
- (edge_vec[i].v,edge_vec[i].u);
- edge_vec[i].w *= -1;
- }
- }
- //Now edge_vec is a graph where edges are oriented LR if we
- //can add them to new_match, and RL otherwise. If
- //adding/removing them makes the matching closer to old_match
- //they have weight 1; and -1 otherwise.
-
- //We shuffle the edge list so that there is no bias depending in
- //partitions/zone label in the triplet dispersion
- let mut rng = rand::thread_rng();
- edge_vec.shuffle(&mut rng);
-
- //Discovering and flipping a cycle with positive weight in this
- //graph will make the matching closer to old_match.
- //We use Bellman Ford algorithm to discover positive cycles
- loop{
- if let Some(cycle) = positive_cycle(&edge_vec, nb_left, nb_right) {
- for i in cycle {
- //We flip the edges of the cycle.
- (edge_vec[i].u,edge_vec[i].v) =
- (edge_vec[i].v,edge_vec[i].u);
- edge_vec[i].w *= -1;
- }
- }
- else {
- //If there is no cycle, we return the optimal matching.
- break;
- }
- }
-
- //The optimal matching is build from the graph structure.
- let mut matching = vec![Vec::<usize>::new() ; nb_left];
- for e in edge_vec {
- if e.u > e.v {
- matching[e.v].push(e.u-nb_left);
- }
- }
- matching
+pub fn optimize_matching(
+ old_match: &Vec<Vec<usize>>,
+ new_match: &Vec<Vec<usize>>,
+ nb_right: usize,
+) -> Vec<Vec<usize>> {
+ let nb_left = old_match.len();
+ let ed = WeightedEdge { w: -1, u: 0, v: 0 };
+ let mut edge_vec = vec![ed; nb_left * nb_right];
+
+ //We build the complete bipartite graph structure, represented
+ //by the list of all edges.
+ for i in 0..nb_left {
+ for j in 0..nb_right {
+ edge_vec[i * nb_right + j].u = i;
+ edge_vec[i * nb_right + j].v = nb_left + j;
+ }
+ }
+
+ for i in 0..edge_vec.len() {
+ //We add the old matchings
+ if old_match[edge_vec[i].u].contains(&(edge_vec[i].v - nb_left)) {
+ edge_vec[i].w *= -1;
+ }
+ //We add the new matchings
+ if new_match[edge_vec[i].u].contains(&(edge_vec[i].v - nb_left)) {
+ (edge_vec[i].u, edge_vec[i].v) = (edge_vec[i].v, edge_vec[i].u);
+ edge_vec[i].w *= -1;
+ }
+ }
+ //Now edge_vec is a graph where edges are oriented LR if we
+ //can add them to new_match, and RL otherwise. If
+ //adding/removing them makes the matching closer to old_match
+ //they have weight 1; and -1 otherwise.
+
+ //We shuffle the edge list so that there is no bias depending in
+ //partitions/zone label in the triplet dispersion
+ let mut rng = rand::thread_rng();
+ edge_vec.shuffle(&mut rng);
+
+ //Discovering and flipping a cycle with positive weight in this
+ //graph will make the matching closer to old_match.
+ //We use Bellman Ford algorithm to discover positive cycles
+ loop {
+ if let Some(cycle) = positive_cycle(&edge_vec, nb_left, nb_right) {
+ for i in cycle {
+ //We flip the edges of the cycle.
+ (edge_vec[i].u, edge_vec[i].v) = (edge_vec[i].v, edge_vec[i].u);
+ edge_vec[i].w *= -1;
+ }
+ } else {
+ //If there is no cycle, we return the optimal matching.
+ break;
+ }
+ }
+
+ //The optimal matching is build from the graph structure.
+ let mut matching = vec![Vec::<usize>::new(); nb_left];
+ for e in edge_vec {
+ if e.u > e.v {
+ matching[e.v].push(e.u - nb_left);
+ }
+ }
+ matching
}
//This function finds a positive cycle in a bipartite wieghted graph.
-fn positive_cycle( edge_vec : &Vec<WeightedEdge>, nb_left : usize,
- nb_right : usize) -> Option<Vec<usize>> {
- let nb_side_min = min(nb_left, nb_right);
- let nb_vertices = nb_left+nb_right;
- let weight_lowerbound = -((nb_left +nb_right) as i32) -1;
- let mut accessed = vec![false ; nb_left];
-
- //We try to find a positive cycle accessible from the left
- //vertex i.
- for i in 0..nb_left{
- if accessed[i] {
- continue;
- }
- let mut weight =vec![weight_lowerbound ; nb_vertices];
- let mut prev =vec![ edge_vec.len() ; nb_vertices];
- weight[i] = 0;
- //We compute largest weighted paths from i.
- //Since the graph is bipartite, any simple cycle has length
- //at most 2*nb_side_min. In the general Bellman-Ford
- //algorithm, the bound here is the number of vertices. Since
- //the number of partitions can be much larger than the
- //number of nodes, we optimize that.
- for _ in 0..(2*nb_side_min) {
- for j in 0..edge_vec.len() {
- let e = edge_vec[j];
- if weight[e.v] < weight[e.u]+e.w {
- weight[e.v] = weight[e.u]+e.w;
- prev[e.v] = j;
- }
- }
- }
- //We update the accessed table
- for i in 0..nb_left {
- if weight[i] > weight_lowerbound {
- accessed[i] = true;
- }
- }
- //We detect positive cycle
- for e in edge_vec {
- if weight[e.v] < weight[e.u]+e.w {
- //it means e is on a path branching from a positive cycle
- let mut was_seen = vec![false ; nb_vertices];
- let mut curr = e.u;
- //We track back with prev until we reach the cycle.
- while !was_seen[curr]{
- was_seen[curr] = true;
- curr = edge_vec[prev[curr]].u;
- }
- //Now curr is on the cycle. We collect the edges ids.
- let mut cycle = Vec::<usize>::new();
- cycle.push(prev[curr]);
- let mut cycle_vert = edge_vec[prev[curr]].u;
- while cycle_vert != curr {
- cycle.push(prev[cycle_vert]);
- cycle_vert = edge_vec[prev[cycle_vert]].u;
- }
-
- return Some(cycle);
- }
- }
- }
-
- None
-}
+fn positive_cycle(
+ edge_vec: &Vec<WeightedEdge>,
+ nb_left: usize,
+ nb_right: usize,
+) -> Option<Vec<usize>> {
+ let nb_side_min = min(nb_left, nb_right);
+ let nb_vertices = nb_left + nb_right;
+ let weight_lowerbound = -((nb_left + nb_right) as i32) - 1;
+ let mut accessed = vec![false; nb_left];
+ //We try to find a positive cycle accessible from the left
+ //vertex i.
+ for i in 0..nb_left {
+ if accessed[i] {
+ continue;
+ }
+ let mut weight = vec![weight_lowerbound; nb_vertices];
+ let mut prev = vec![edge_vec.len(); nb_vertices];
+ weight[i] = 0;
+ //We compute largest weighted paths from i.
+ //Since the graph is bipartite, any simple cycle has length
+ //at most 2*nb_side_min. In the general Bellman-Ford
+ //algorithm, the bound here is the number of vertices. Since
+ //the number of partitions can be much larger than the
+ //number of nodes, we optimize that.
+ for _ in 0..(2 * nb_side_min) {
+ for j in 0..edge_vec.len() {
+ let e = edge_vec[j];
+ if weight[e.v] < weight[e.u] + e.w {
+ weight[e.v] = weight[e.u] + e.w;
+ prev[e.v] = j;
+ }
+ }
+ }
+ //We update the accessed table
+ for i in 0..nb_left {
+ if weight[i] > weight_lowerbound {
+ accessed[i] = true;
+ }
+ }
+ //We detect positive cycle
+ for e in edge_vec {
+ if weight[e.v] < weight[e.u] + e.w {
+ //it means e is on a path branching from a positive cycle
+ let mut was_seen = vec![false; nb_vertices];
+ let mut curr = e.u;
+ //We track back with prev until we reach the cycle.
+ while !was_seen[curr] {
+ was_seen[curr] = true;
+ curr = edge_vec[prev[curr]].u;
+ }
+ //Now curr is on the cycle. We collect the edges ids.
+ let mut cycle = Vec::<usize>::new();
+ cycle.push(prev[curr]);
+ let mut cycle_vert = edge_vec[prev[curr]].u;
+ while cycle_vert != curr {
+ cycle.push(prev[cycle_vert]);
+ cycle_vert = edge_vec[prev[cycle_vert]].u;
+ }
-// This function takes two arrays of capacity and computes the
-// maximal matching in the complete bipartite graph such that the
+ return Some(cycle);
+ }
+ }
+ }
+
+ None
+}
+
+// This function takes two arrays of capacity and computes the
+// maximal matching in the complete bipartite graph such that the
// left vertex i is matched to left_cap_vec[i] right vertices, and
// the right vertex j is matched to right_cap_vec[j] left vertices.
// To do so, we use Dinic's maximum flow algorithm.
-pub fn dinic_compute_matching( left_cap_vec : Vec<u32>,
- right_cap_vec : Vec<u32>) -> Vec< Vec<usize> >
-{
- let mut graph = Vec::<Vec::<EdgeFlow> >::new();
- let ed = EdgeFlow{c:0,flow:0,v:0, rev:0};
-
- // 0 will be the source
- graph.push(vec![ed ; left_cap_vec.len()]);
- for i in 0..left_cap_vec.len()
- {
- graph[0][i].c = left_cap_vec[i] as i32;
- graph[0][i].v = i+2;
- graph[0][i].rev = 0;
- }
-
- //1 will be the sink
- graph.push(vec![ed ; right_cap_vec.len()]);
- for i in 0..right_cap_vec.len()
- {
- graph[1][i].c = right_cap_vec[i] as i32;
- graph[1][i].v = i+2+left_cap_vec.len();
- graph[1][i].rev = 0;
- }
-
- //we add left vertices
- for i in 0..left_cap_vec.len() {
- graph.push(vec![ed ; 1+right_cap_vec.len()]);
- graph[i+2][0].c = 0; //directed
- graph[i+2][0].v = 0;
- graph[i+2][0].rev = i;
-
- for j in 0..right_cap_vec.len() {
- graph[i+2][j+1].c = 1;
- graph[i+2][j+1].v = 2+left_cap_vec.len()+j;
- graph[i+2][j+1].rev = i+1;
- }
- }
-
- //we add right vertices
- for i in 0..right_cap_vec.len() {
- let lft_ln = left_cap_vec.len();
- graph.push(vec![ed ; 1+lft_ln]);
- graph[i+lft_ln+2][0].c = graph[1][i].c;
- graph[i+lft_ln+2][0].v = 1;
- graph[i+lft_ln+2][0].rev = i;
-
- for j in 0..left_cap_vec.len() {
- graph[i+2+lft_ln][j+1].c = 0; //directed
- graph[i+2+lft_ln][j+1].v = j+2;
- graph[i+2+lft_ln][j+1].rev = i+1;
- }
- }
-
- //To ensure the dispersion of the triplets generated by the
- //assignation, we shuffle the neighbours of the nodes. Hence,
- //left vertices do not consider the right ones in the same order.
- let mut rng = rand::thread_rng();
- for i in 0..graph.len() {
- graph[i].shuffle(&mut rng);
- //We need to update the ids of the reverse edges.
- for j in 0..graph[i].len() {
- let target_v = graph[i][j].v;
- let target_rev = graph[i][j].rev;
- graph[target_v][target_rev].rev = j;
- }
- }
-
- let nb_vertices = graph.len();
-
- //We run Dinic's max flow algorithm
- loop{
- //We build the level array from Dinic's algorithm.
- let mut level = vec![-1; nb_vertices];
-
- let mut fifo = VecDeque::new();
- fifo.push_back((0,0));
- while !fifo.is_empty() {
- if let Some((id,lvl)) = fifo.pop_front(){
- if level[id] == -1 {
- level[id] = lvl;
- for e in graph[id].iter(){
- if e.c-e.flow > 0{
- fifo.push_back((e.v,lvl+1));
- }
- }
- }
- }
- }
- if level[1] == -1 {
- //There is no residual flow
- break;
- }
-
- //Now we run DFS respecting the level array
- let mut next_nbd = vec![0; nb_vertices];
- let mut lifo = VecDeque::new();
-
- let flow_upper_bound;
- if let Some(x) = left_cap_vec.iter().max() {
- flow_upper_bound=*x as i32;
- }
- else {
- flow_upper_bound = 0;
- assert!(false);
- }
-
- lifo.push_back((0,flow_upper_bound));
-
- loop
- {
- if let Some((id_tmp, f_tmp)) = lifo.back() {
- let id = *id_tmp;
- let f = *f_tmp;
- if id == 1 {
- //The DFS reached the sink, we can add a
- //residual flow.
- lifo.pop_back();
- while !lifo.is_empty() {
- if let Some((id,_)) = lifo.pop_back(){
- let nbd=next_nbd[id];
- graph[id][nbd].flow += f;
- let id_v = graph[id][nbd].v;
- let nbd_v = graph[id][nbd].rev;
- graph[id_v][nbd_v].flow -= f;
- }
- }
- lifo.push_back((0,flow_upper_bound));
- continue;
- }
- //else we did not reach the sink
- let nbd = next_nbd[id];
- if nbd >= graph[id].len() {
- //There is nothing to explore from id anymore
- lifo.pop_back();
- if let Some((parent, _)) = lifo.back(){
- next_nbd[*parent] +=1;
- }
- continue;
- }
- //else we can try to send flow from id to its nbd
- let new_flow = min(f,graph[id][nbd].c
- - graph[id][nbd].flow);
- if level[graph[id][nbd].v] <= level[id] ||
- new_flow == 0 {
- //We cannot send flow to nbd.
- next_nbd[id] += 1;
- continue;
- }
- //otherwise, we send flow to nbd.
- lifo.push_back((graph[id][nbd].v, new_flow));
- }
- else {
- break;
- }
- }
- }
-
- //We return the association
- let assoc_table = (0..left_cap_vec.len()).map(
- |id| graph[id+2].iter()
- .filter(|e| e.flow > 0)
- .map( |e| e.v-2-left_cap_vec.len())
- .collect()).collect();
-
- //consistency check
-
- //it is a flow
- for i in 3..graph.len(){
- assert!( graph[i].iter().map(|e| e.flow).sum::<i32>() == 0);
- for e in graph[i].iter(){
- assert!(e.flow + graph[e.v][e.rev].flow == 0);
- }
- }
-
- //it solves the matching problem
- for i in 0..left_cap_vec.len(){
- assert!(left_cap_vec[i] as i32 ==
- graph[i+2].iter().map(|e| max(0,e.flow)).sum::<i32>());
- }
- for i in 0..right_cap_vec.len(){
- assert!(right_cap_vec[i] as i32 ==
- graph[i+2+left_cap_vec.len()].iter()
- .map(|e| max(0,e.flow)).sum::<i32>());
- }
-
-
- assoc_table
-}
+pub fn dinic_compute_matching(left_cap_vec: Vec<u32>, right_cap_vec: Vec<u32>) -> Vec<Vec<usize>> {
+ let mut graph = Vec::<Vec<EdgeFlow>>::new();
+ let ed = EdgeFlow {
+ c: 0,
+ flow: 0,
+ v: 0,
+ rev: 0,
+ };
+
+ // 0 will be the source
+ graph.push(vec![ed; left_cap_vec.len()]);
+ for i in 0..left_cap_vec.len() {
+ graph[0][i].c = left_cap_vec[i] as i32;
+ graph[0][i].v = i + 2;
+ graph[0][i].rev = 0;
+ }
+
+ //1 will be the sink
+ graph.push(vec![ed; right_cap_vec.len()]);
+ for i in 0..right_cap_vec.len() {
+ graph[1][i].c = right_cap_vec[i] as i32;
+ graph[1][i].v = i + 2 + left_cap_vec.len();
+ graph[1][i].rev = 0;
+ }
+
+ //we add left vertices
+ for i in 0..left_cap_vec.len() {
+ graph.push(vec![ed; 1 + right_cap_vec.len()]);
+ graph[i + 2][0].c = 0; //directed
+ graph[i + 2][0].v = 0;
+ graph[i + 2][0].rev = i;
+
+ for j in 0..right_cap_vec.len() {
+ graph[i + 2][j + 1].c = 1;
+ graph[i + 2][j + 1].v = 2 + left_cap_vec.len() + j;
+ graph[i + 2][j + 1].rev = i + 1;
+ }
+ }
+ //we add right vertices
+ for i in 0..right_cap_vec.len() {
+ let lft_ln = left_cap_vec.len();
+ graph.push(vec![ed; 1 + lft_ln]);
+ graph[i + lft_ln + 2][0].c = graph[1][i].c;
+ graph[i + lft_ln + 2][0].v = 1;
+ graph[i + lft_ln + 2][0].rev = i;
+
+ for j in 0..left_cap_vec.len() {
+ graph[i + 2 + lft_ln][j + 1].c = 0; //directed
+ graph[i + 2 + lft_ln][j + 1].v = j + 2;
+ graph[i + 2 + lft_ln][j + 1].rev = i + 1;
+ }
+ }
+
+ //To ensure the dispersion of the triplets generated by the
+ //assignation, we shuffle the neighbours of the nodes. Hence,
+ //left vertices do not consider the right ones in the same order.
+ let mut rng = rand::thread_rng();
+ for i in 0..graph.len() {
+ graph[i].shuffle(&mut rng);
+ //We need to update the ids of the reverse edges.
+ for j in 0..graph[i].len() {
+ let target_v = graph[i][j].v;
+ let target_rev = graph[i][j].rev;
+ graph[target_v][target_rev].rev = j;
+ }
+ }
+
+ let nb_vertices = graph.len();
+
+ //We run Dinic's max flow algorithm
+ loop {
+ //We build the level array from Dinic's algorithm.
+ let mut level = vec![-1; nb_vertices];
+
+ let mut fifo = VecDeque::new();
+ fifo.push_back((0, 0));
+ while !fifo.is_empty() {
+ if let Some((id, lvl)) = fifo.pop_front() {
+ if level[id] == -1 {
+ level[id] = lvl;
+ for e in graph[id].iter() {
+ if e.c - e.flow > 0 {
+ fifo.push_back((e.v, lvl + 1));
+ }
+ }
+ }
+ }
+ }
+ if level[1] == -1 {
+ //There is no residual flow
+ break;
+ }
+
+ //Now we run DFS respecting the level array
+ let mut next_nbd = vec![0; nb_vertices];
+ let mut lifo = VecDeque::new();
+
+ let flow_upper_bound;
+ if let Some(x) = left_cap_vec.iter().max() {
+ flow_upper_bound = *x as i32;
+ } else {
+ flow_upper_bound = 0;
+ assert!(false);
+ }
+
+ lifo.push_back((0, flow_upper_bound));
+
+ loop {
+ if let Some((id_tmp, f_tmp)) = lifo.back() {
+ let id = *id_tmp;
+ let f = *f_tmp;
+ if id == 1 {
+ //The DFS reached the sink, we can add a
+ //residual flow.
+ lifo.pop_back();
+ while !lifo.is_empty() {
+ if let Some((id, _)) = lifo.pop_back() {
+ let nbd = next_nbd[id];
+ graph[id][nbd].flow += f;
+ let id_v = graph[id][nbd].v;
+ let nbd_v = graph[id][nbd].rev;
+ graph[id_v][nbd_v].flow -= f;
+ }
+ }
+ lifo.push_back((0, flow_upper_bound));
+ continue;
+ }
+ //else we did not reach the sink
+ let nbd = next_nbd[id];
+ if nbd >= graph[id].len() {
+ //There is nothing to explore from id anymore
+ lifo.pop_back();
+ if let Some((parent, _)) = lifo.back() {
+ next_nbd[*parent] += 1;
+ }
+ continue;
+ }
+ //else we can try to send flow from id to its nbd
+ let new_flow = min(f, graph[id][nbd].c - graph[id][nbd].flow);
+ if level[graph[id][nbd].v] <= level[id] || new_flow == 0 {
+ //We cannot send flow to nbd.
+ next_nbd[id] += 1;
+ continue;
+ }
+ //otherwise, we send flow to nbd.
+ lifo.push_back((graph[id][nbd].v, new_flow));
+ } else {
+ break;
+ }
+ }
+ }
+
+ //We return the association
+ let assoc_table = (0..left_cap_vec.len())
+ .map(|id| {
+ graph[id + 2]
+ .iter()
+ .filter(|e| e.flow > 0)
+ .map(|e| e.v - 2 - left_cap_vec.len())
+ .collect()
+ })
+ .collect();
+
+ //consistency check
+
+ //it is a flow
+ for i in 3..graph.len() {
+ assert!(graph[i].iter().map(|e| e.flow).sum::<i32>() == 0);
+ for e in graph[i].iter() {
+ assert!(e.flow + graph[e.v][e.rev].flow == 0);
+ }
+ }
+
+ //it solves the matching problem
+ for i in 0..left_cap_vec.len() {
+ assert!(left_cap_vec[i] as i32 == graph[i + 2].iter().map(|e| max(0, e.flow)).sum::<i32>());
+ }
+ for i in 0..right_cap_vec.len() {
+ assert!(
+ right_cap_vec[i] as i32
+ == graph[i + 2 + left_cap_vec.len()]
+ .iter()
+ .map(|e| max(0, e.flow))
+ .sum::<i32>()
+ );
+ }
+
+ assoc_table
+}
#[cfg(test)]
mod tests {
- use super::*;
-
- #[test]
- fn test_flow() {
- let left_vec = vec![3;8];
- let right_vec = vec![0,4,8,4,8];
- //There are asserts in the function that computes the flow
- let _ = dinic_compute_matching(left_vec, right_vec);
- }
-
- //maybe add tests relative to the matching optilization ?
-}
+ use super::*;
+ #[test]
+ fn test_flow() {
+ let left_vec = vec![3; 8];
+ let right_vec = vec![0, 4, 8, 4, 8];
+ //There are asserts in the function that computes the flow
+ let _ = dinic_compute_matching(left_vec, right_vec);
+ }
+ //maybe add tests relative to the matching optilization ?
+}