sebastian/maxflow-rs
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Fix residual graph generation, minor algorithm refactorings

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Sebastian
2025-03-26 14:53:35 +01:00
parent 3f93cb57d3
commit c21d648c8f
4 changed files with 12 additions and 68 deletions
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1
src/algorithms/dinic.rs
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@@ -1,4 +1,3 @@
// Dinic
use std::cmp::min;
use std::collections::VecDeque;

7
src/algorithms/edmonds_karp.rs
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@@ -1,11 +1,10 @@
// Edmonds-Karp (also Ford-Fulkerson mit BFS statt DFS),
use std::cmp::min;
use std::collections::VecDeque;
use petgraph::{stable_graph::{NodeIndex, StableGraph, EdgeReference}, visit::{EdgeRef, VisitMap, Visitable}, Direction};
fn available_capacity(edge: EdgeReference<'_, (u64, u64)>) -> u64 {
edge.weight().1 - edge.weight().0
fn available_capacity(edge: (u64, u64)) -> u64 {
edge.1 - edge.0
}
// Runs a depth Breadth First Search (BFS) and returns an augmenting path from source to destination if possible
@@ -21,7 +20,7 @@ fn bfs(graph: &StableGraph<(f32, f32), (u64, u64)>, source: NodeIndex, destinati
for edge in outgoing_edges {
let neighbor = edge.target();
if !visited.is_visited(&neighbor) && available_capacity(edge) > 0 {
if !visited.is_visited(&neighbor) && available_capacity(*edge.weight()) > 0 {
visited.visit(neighbor);
let mut new_path = path.clone();
new_path.push(neighbor);

65
src/algorithms/ford_fulkerson.rs
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@@ -1,20 +1,14 @@
// Ford-Fulkerson mit DFS zur Berechnung des flusserhöhenden Pfades,
// Edmonds-Karp (also Ford-Fulkerson mit BFS statt DFS),
// Dinic
// Goldberg-Tarjan (auch Preflow-Push oder Push-Relabel genannt).
use std::cmp::min;
use std::collections::VecDeque;
use petgraph::{stable_graph::{EdgeReference, NodeIndex, StableGraph}, visit::{EdgeRef, VisitMap, Visitable}, Direction};
//use crate::random_generator::MaxflowProblem;
//mod random_generator;
fn available_capacity(edge: EdgeReference<'_, (u64, u64)>) -> u64 {
edge.weight().1 - edge.weight().0
fn available_capacity(edge: (u64, u64)) -> u64 {
edge.1 - edge.0
}
// Runs a depth Depth First Search (DFS) and returns an augmenting path from source to destination if possible
// Runs a depth Depth First Search (DFS) which returns an augmenting path from source to destination if possible
fn dfs(graph: &StableGraph<(f32, f32), (u64, u64)>, source: NodeIndex, destination: NodeIndex) -> Option<Vec<NodeIndex>> {
let mut visited = graph.visit_map();
let mut stack = VecDeque::from([(source, vec![source])]);
@@ -24,10 +18,10 @@ fn dfs(graph: &StableGraph<(f32, f32), (u64, u64)>, source: NodeIndex, destinati
let outgoing_edges = graph.edges_directed(node, Direction::Outgoing);
visited.visit(node);
// iterate over all outgoing edges
// iterate over all outgoing edges & add neighboring nodes to the stack
for edge in outgoing_edges {
let neighbor = edge.target();
if !visited.is_visited(&neighbor) && available_capacity(edge) > 0 {
if !visited.is_visited(&neighbor) && available_capacity(*edge.weight()) > 0 {
visited.visit(neighbor);
let mut new_path = path.clone();
new_path.push(neighbor);
@@ -67,52 +61,3 @@ pub fn ford_fulkerson(mut graph: StableGraph<(f32, f32), (u64, u64)>, source: No
// return graph with augmented flows
graph
}
//pub struct FordFulkerson {
// problem: MaxflowProblem,
// flows: Graph<(), u64, Directed, u32, DefaultNodeShape, DefaultEdgeShape>,
// alertnatively, use a map from EdgeIndex to flow value
//dfs: Dfs<N, VM>,
//}
/* impl FordFulkerson {
fn new(problem: MaxflowProblem) -> S/elf {
Self { problem: problem, flows: Graph::new(StableGraph::default()) }
}
fn graph(&mut self) -> &Graph<bool, (u64, u64)> {
&self.problem.g
}
fn flows(&mut self) -> &Graph<(), u64> {
&self.flows
}
fn dfs(&mut self, ni: NodeIndex) -> Vec<Vec<EdgeIndex>>{
// set own node to visited
self.problem.g.node_mut(ni).expect("node index not found").set_visited(true);
//self.graph().node_mut(ni).expect("node index not found").set_visited(true);
let augmenting_paths: Vec<Vec<EdgeIndex>> = Vec::new();
let neighboring_edges = self.graph().edges_directed(ni, Direction::Outgoing);
for edge in neighboring_edges {
//let neighbor = self.problem.g.node_mut(edge.target()).expect("node index not found");
//if neighbor.visited() == false {
// println!("{:?}", edge.weight());
//}
}
// iterate over all unvisited! neighbors. for each:
// - check if there is capacity left
// - if neighbor = target, return path
// - else, do dfs starting from neighbor
// - if neighbor returns augmenting path add it to own list & prepend own edge
// return list of augmenting paths
augmenting_paths
}
fn step(&self) {
//self.dfs(self.problem.s);
}
} */

7
src/graph.rs
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@@ -1,5 +1,5 @@
use egui_graphs::{DefaultNodeShape, Graph, default_edge_transform, default_node_transform, to_graph_custom};
use petgraph::{stable_graph::{StableGraph, NodeIndex}, Directed};
use petgraph::{stable_graph::{NodeIndex, StableGraph}, visit::{VisitMap, Visitable}, Directed};
use egui::Pos2;
use crate::layout::CustomEdgeShape;
use egui::Color32;
@@ -19,9 +19,10 @@ impl ResidualGraph for StableGraph<(f32, f32), (u64, u64)> {
let (reverse_flow, reverse_capacity) = *res_graph.edge_weight(reverse_edge).expect("reverse edge not found");
// update the forward edge
// TODO: this seems to overflow in certain cases
res_graph.update_edge(source, target, (flow, capacity + reverse_flow - flow));
res_graph.update_edge(source, target, (flow, capacity + reverse_flow));
// update the reverse edge
res_graph.update_edge(target, source, (reverse_flow, reverse_capacity + flow - reverse_flow));
//res_graph.update_edge(target, source, (reverse_flow, reverse_capacity + flow));
} else {
// add a residual edge with a flow of 0 if the reverse edge doesn't exist
res_graph.add_edge(target, source, (0, 0));