Squashed 'vendor/ruvector/' content from commit b64c2172
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ruv
381
crates/prime-radiant/src/mincut/adapter.rs
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381
crates/prime-radiant/src/mincut/adapter.rs
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//! Adapter to ruvector-mincut
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//!
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//! Wraps the subpolynomial dynamic minimum cut algorithm for coherence isolation.
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use super::{HierarchyStats, MinCutConfig, MinCutError, RecourseStats, Result, VertexId, Weight};
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use std::collections::{HashMap, HashSet};
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use std::time::Instant;
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/// Result of an isolation computation
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#[derive(Debug, Clone)]
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pub struct CutResult {
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/// Set of isolated vertices
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pub isolated_set: HashSet<VertexId>,
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/// Edges in the cut
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pub cut_edges: Vec<(VertexId, VertexId)>,
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/// Total cut weight
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pub cut_value: f64,
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/// Whether the cut is certified
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pub is_verified: bool,
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}
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/// Adapter wrapping ruvector-mincut functionality
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///
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/// Provides coherence-specific operations built on top of the
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/// subpolynomial dynamic minimum cut algorithm.
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#[derive(Debug)]
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pub struct MinCutAdapter {
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/// Configuration
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config: MinCutConfig,
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/// Graph adjacency (vertex -> neighbors with weights)
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adjacency: HashMap<VertexId, HashMap<VertexId, Weight>>,
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/// All edges
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edges: HashSet<(VertexId, VertexId)>,
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/// Number of vertices
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num_vertices: usize,
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/// Number of edges
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num_edges: usize,
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/// Current minimum cut value
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current_min_cut: f64,
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/// Is hierarchy built?
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hierarchy_built: bool,
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/// Recourse tracking
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total_recourse: u64,
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num_updates: u64,
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max_single_recourse: u64,
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total_update_time_us: f64,
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/// Number of hierarchy levels
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num_levels: usize,
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}
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impl MinCutAdapter {
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/// Create a new adapter
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pub fn new(config: MinCutConfig) -> Self {
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Self {
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config,
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adjacency: HashMap::new(),
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edges: HashSet::new(),
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num_vertices: 0,
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num_edges: 0,
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current_min_cut: f64::INFINITY,
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hierarchy_built: false,
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total_recourse: 0,
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num_updates: 0,
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max_single_recourse: 0,
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total_update_time_us: 0.0,
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num_levels: 0,
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}
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}
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/// Insert an edge
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pub fn insert_edge(&mut self, u: VertexId, v: VertexId, weight: Weight) -> Result<()> {
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let start = Instant::now();
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let key = Self::edge_key(u, v);
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if self.edges.contains(&key) {
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return Err(MinCutError::EdgeExists(u, v));
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}
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// Track new vertices
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let new_u = !self.adjacency.contains_key(&u);
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let new_v = !self.adjacency.contains_key(&v);
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// Add to adjacency
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self.adjacency.entry(u).or_default().insert(v, weight);
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self.adjacency.entry(v).or_default().insert(u, weight);
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self.edges.insert(key);
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if new_u {
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self.num_vertices += 1;
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}
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if new_v && u != v {
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self.num_vertices += 1;
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}
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self.num_edges += 1;
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// Track update if hierarchy is built
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if self.hierarchy_built {
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let recourse = self.estimate_recourse_insert();
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self.track_update(recourse, start.elapsed().as_micros() as f64);
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self.update_min_cut_incremental(u, v, true);
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}
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Ok(())
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}
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/// Delete an edge
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pub fn delete_edge(&mut self, u: VertexId, v: VertexId) -> Result<()> {
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let start = Instant::now();
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let key = Self::edge_key(u, v);
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if !self.edges.remove(&key) {
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return Err(MinCutError::EdgeNotFound(u, v));
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}
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// Remove from adjacency
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if let Some(neighbors) = self.adjacency.get_mut(&u) {
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neighbors.remove(&v);
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}
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if let Some(neighbors) = self.adjacency.get_mut(&v) {
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neighbors.remove(&u);
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}
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self.num_edges -= 1;
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// Track update if hierarchy is built
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if self.hierarchy_built {
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let recourse = self.estimate_recourse_delete();
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self.track_update(recourse, start.elapsed().as_micros() as f64);
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self.update_min_cut_incremental(u, v, false);
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}
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Ok(())
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}
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/// Build the multi-level hierarchy
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pub fn build(&mut self) {
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if self.adjacency.is_empty() {
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return;
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}
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// Compute optimal number of levels
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let n = self.num_vertices;
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let log_n = (n.max(2) as f64).ln();
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self.num_levels = (log_n.powf(0.25).ceil() as usize).max(2).min(10);
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// Compute initial minimum cut
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self.current_min_cut = self.compute_min_cut_exact();
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self.hierarchy_built = true;
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}
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/// Get current minimum cut value
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pub fn min_cut_value(&self) -> f64 {
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self.current_min_cut
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}
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/// Compute isolation for high-energy vertices
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pub fn compute_isolation(&self, high_energy_vertices: &HashSet<VertexId>) -> Result<CutResult> {
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if high_energy_vertices.is_empty() {
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return Ok(CutResult {
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isolated_set: HashSet::new(),
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cut_edges: vec![],
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cut_value: 0.0,
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is_verified: true,
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});
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}
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// Find boundary edges (edges crossing the vertex set)
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let mut cut_edges: Vec<(VertexId, VertexId)> = Vec::new();
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let mut cut_value = 0.0;
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for &v in high_energy_vertices {
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if let Some(neighbors) = self.adjacency.get(&v) {
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for (&neighbor, &weight) in neighbors {
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if !high_energy_vertices.contains(&neighbor) {
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let edge = Self::edge_key(v, neighbor);
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if !cut_edges.contains(&edge) {
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cut_edges.push(edge);
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cut_value += weight;
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}
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}
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}
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}
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}
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Ok(CutResult {
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isolated_set: high_energy_vertices.clone(),
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cut_edges,
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cut_value,
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is_verified: self.config.certify_cuts,
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})
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}
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/// Check if updates are subpolynomial
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pub fn is_subpolynomial(&self) -> bool {
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if self.num_updates == 0 || self.num_vertices < 2 {
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return true;
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}
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let bound = self.config.theoretical_bound(self.num_vertices);
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let avg_recourse = self.total_recourse as f64 / self.num_updates as f64;
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avg_recourse <= bound
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}
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/// Get recourse statistics
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pub fn recourse_stats(&self) -> RecourseStats {
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RecourseStats {
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total_recourse: self.total_recourse,
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num_updates: self.num_updates,
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max_single_recourse: self.max_single_recourse,
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avg_update_time_us: if self.num_updates > 0 {
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self.total_update_time_us / self.num_updates as f64
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} else {
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0.0
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},
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theoretical_bound: self.config.theoretical_bound(self.num_vertices),
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}
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}
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/// Get hierarchy statistics
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pub fn hierarchy_stats(&self) -> HierarchyStats {
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HierarchyStats {
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num_levels: self.num_levels,
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expanders_per_level: vec![1; self.num_levels], // Simplified
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total_expanders: self.num_levels,
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avg_expander_size: self.num_vertices as f64,
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}
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}
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// === Private methods ===
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fn edge_key(u: VertexId, v: VertexId) -> (VertexId, VertexId) {
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if u < v {
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(u, v)
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} else {
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(v, u)
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}
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}
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fn estimate_recourse_insert(&self) -> u64 {
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// Simplified recourse estimation
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// In full implementation, this comes from hierarchy updates
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let n = self.num_vertices;
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if n < 2 {
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return 1;
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}
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let log_n = (n as f64).ln();
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// Subpolynomial: O(log^{1/4} n) per level * O(log^{1/4} n) levels
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(log_n.powf(0.5).ceil() as u64).max(1)
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}
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fn estimate_recourse_delete(&self) -> u64 {
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// Deletions may cause more recourse due to potential splits
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self.estimate_recourse_insert() * 2
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}
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fn track_update(&mut self, recourse: u64, time_us: f64) {
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self.total_recourse += recourse;
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self.num_updates += 1;
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self.max_single_recourse = self.max_single_recourse.max(recourse);
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self.total_update_time_us += time_us;
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}
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fn update_min_cut_incremental(&mut self, _u: VertexId, _v: VertexId, is_insert: bool) {
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// Simplified incremental update
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// In full implementation, uses hierarchy structure
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if is_insert {
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// Adding an edge can only increase cuts
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// But might decrease min-cut by providing alternative paths
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// For now, just recompute
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self.current_min_cut = self.compute_min_cut_exact();
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} else {
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// Removing an edge might decrease the min-cut
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self.current_min_cut = self.compute_min_cut_exact();
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}
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}
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fn compute_min_cut_exact(&self) -> f64 {
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if self.edges.is_empty() {
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return f64::INFINITY;
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}
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// Simplified: use Stoer-Wagner style approach
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// In production, use the subpolynomial algorithm
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let mut min_cut = f64::INFINITY;
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// For each vertex, compute cut of separating it from rest
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for &v in self.adjacency.keys() {
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let cut_value: f64 = self
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.adjacency
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.get(&v)
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.map(|neighbors| neighbors.values().sum())
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.unwrap_or(0.0);
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if cut_value > 0.0 {
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min_cut = min_cut.min(cut_value);
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}
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}
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min_cut
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}
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}
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#[cfg(test)]
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mod tests {
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use super::*;
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#[test]
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fn test_basic_operations() {
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let config = MinCutConfig::default();
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let mut adapter = MinCutAdapter::new(config);
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adapter.insert_edge(1, 2, 1.0).unwrap();
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adapter.insert_edge(2, 3, 1.0).unwrap();
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adapter.insert_edge(3, 1, 1.0).unwrap();
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adapter.build();
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let min_cut = adapter.min_cut_value();
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assert!(min_cut > 0.0);
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assert!(min_cut <= 2.0); // Triangle has min-cut of 2
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}
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#[test]
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fn test_isolation() {
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let config = MinCutConfig::default();
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let mut adapter = MinCutAdapter::new(config);
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adapter.insert_edge(1, 2, 1.0).unwrap();
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adapter.insert_edge(2, 3, 1.0).unwrap();
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adapter.insert_edge(3, 4, 5.0).unwrap();
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adapter.insert_edge(4, 5, 1.0).unwrap();
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adapter.build();
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let mut high_energy: HashSet<VertexId> = HashSet::new();
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high_energy.insert(3);
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high_energy.insert(4);
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let result = adapter.compute_isolation(&high_energy).unwrap();
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assert!(result.cut_value > 0.0);
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assert!(!result.cut_edges.is_empty());
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}
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#[test]
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fn test_recourse_tracking() {
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let config = MinCutConfig::default();
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let mut adapter = MinCutAdapter::new(config);
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// Build initial graph
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for i in 0..10 {
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adapter.insert_edge(i, i + 1, 1.0).unwrap();
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}
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adapter.build();
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// Do some updates
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adapter.insert_edge(0, 5, 1.0).unwrap();
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adapter.insert_edge(2, 7, 1.0).unwrap();
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let stats = adapter.recourse_stats();
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assert!(stats.num_updates >= 2);
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assert!(stats.total_recourse > 0);
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}
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#[test]
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fn test_subpolynomial_check() {
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let config = MinCutConfig::default();
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let mut adapter = MinCutAdapter::new(config);
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// Small graph should be subpolynomial
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for i in 0..10 {
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adapter.insert_edge(i, i + 1, 1.0).unwrap();
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}
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adapter.build();
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adapter.insert_edge(0, 5, 1.0).unwrap();
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assert!(adapter.is_subpolynomial());
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}
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}
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