Merge commit 'd803bfe2b1fe7f5e219e50ac20d6801a0a58ac75' as 'vendor/ruvector'

vendor/ruvector/crates/ruvector-attn-mincut/src/graph.rs

@@ -0,0 +1,73 @@
+use serde::{Deserialize, Serialize};
+
+/// A directed edge in the attention graph.
+#[derive(Debug, Clone, Serialize, Deserialize)]
+pub struct Edge {
+    pub src: usize,
+    pub dst: usize,
+    pub weight: f32,
+}
+
+/// Weighted directed graph built from attention logits.
+#[derive(Debug, Clone)]
+pub struct AttentionGraph {
+    pub nodes: usize,
+    pub edges: Vec<Edge>,
+}
+
+/// Build a weighted directed graph from flattened `seq_len x seq_len` logits.
+/// Only positive logits become edges; non-positive entries are omitted.
+pub fn graph_from_logits(logits: &[f32], seq_len: usize) -> AttentionGraph {
+    assert_eq!(
+        logits.len(),
+        seq_len * seq_len,
+        "logits length must equal seq_len^2"
+    );
+    let mut edges = Vec::new();
+    for i in 0..seq_len {
+        for j in 0..seq_len {
+            let w = logits[i * seq_len + j];
+            if w > 0.0 {
+                edges.push(Edge {
+                    src: i,
+                    dst: j,
+                    weight: w,
+                });
+            }
+        }
+    }
+    AttentionGraph {
+        nodes: seq_len,
+        edges,
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_all_positive() {
+        let g = graph_from_logits(&[1.0, 2.0, 3.0, 4.0], 2);
+        assert_eq!(g.nodes, 2);
+        assert_eq!(g.edges.len(), 4);
+    }
+
+    #[test]
+    fn test_filters_non_positive() {
+        let g = graph_from_logits(&[1.0, -0.5, 0.0, 2.0], 2);
+        assert_eq!(g.edges.len(), 2);
+    }
+
+    #[test]
+    #[should_panic(expected = "logits length must equal seq_len^2")]
+    fn test_mismatched_length() {
+        graph_from_logits(&[1.0, 2.0], 3);
+    }
+
+    #[test]
+    fn test_empty_graph() {
+        let g = graph_from_logits(&[-1.0; 9], 3);
+        assert!(g.edges.is_empty());
+    }
+}