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-rw-r--r--src/util/bipartite.rs363
-rw-r--r--src/util/lib.rs1
2 files changed, 0 insertions, 364 deletions
diff --git a/src/util/bipartite.rs b/src/util/bipartite.rs
deleted file mode 100644
index 1e1e9caa..00000000
--- a/src/util/bipartite.rs
+++ /dev/null
@@ -1,363 +0,0 @@
-/*
- * This module deals with graph algorithm in complete bipartite
- * graphs. It is used in layout.rs to build the partition to node
- * assignation.
- * */
-
-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,
-}
-
-//Graph data structure for the detection of positive cycles.
-#[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
- * 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<usize>],
- new_match: &[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
- while 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;
- }
- }
-
- //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: &[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, e) in edge_vec.iter().enumerate() {
- 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![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
-}
-
-// 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, c) in left_cap_vec.iter().enumerate() {
- graph[0][i].c = *c 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, c) in right_cap_vec.iter().enumerate() {
- graph[1][i].c = *c 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() {
- *x as i32
- } else {
- panic!();
- };
-
- lifo.push_back((0, flow_upper_bound));
-
- while 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));
- }
- }
-
- //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 ?
-}
diff --git a/src/util/lib.rs b/src/util/lib.rs
index 891549c3..e83fc2e6 100644
--- a/src/util/lib.rs
+++ b/src/util/lib.rs
@@ -4,7 +4,6 @@
extern crate tracing;
pub mod background;
-pub mod bipartite;
pub mod config;
pub mod crdt;
pub mod data;
generated by cgit v1.2.3 (git 2.25.1) at 2024-11-10 17:21:38 +0000