refactor(rust): simplify name_to_index handling in GraphSession

- Removed RefCell from name_to_index, allowing direct access to the HashMap for improved performance and clarity.
- Updated methods to reflect the change, ensuring name_to_index is built and accessed without unnecessary borrowing.
- Replaced HashSet with FxHashSet for edge pair tracking to enhance performance.

Author: frederikfabriciusbjerre

src/rust/src/graph/session.rs

@@ -17,8 +17,8 @@ use super::CaugiGraph;
 use super::RegistrySnapshot;
 use crate::edges::{EdgeRegistry, EdgeSpec};
 use crate::graph::NeighborMode;
-use std::cell::RefCell;
-use std::collections::{HashMap, HashSet};
+use rustc_hash::FxHashSet;
+use std::collections::HashMap;
 use std::sync::Arc;
 
 /// The target graph class for typed view construction.
@@ -141,8 +141,7 @@ pub struct GraphSession {
     edges: EdgeBuffer,
     names: Vec<String>,
     /// Maps node names to their 0-based indices for fast lookup.
-    /// Built lazily for sessions constructed from known index inputs.
-    name_to_index: RefCell<Option<HashMap<String, u32>>>,
+    name_to_index: HashMap<String, u32>,
 
     // ═══════════════════════════════════════════════════════════════════════════
     // VALIDITY FLAGS
@@ -175,7 +174,7 @@ impl GraphSession {
         let snapshot = Arc::new(RegistrySnapshot::from_specs(specs, registry.len() as u32));
 
         let names: Vec<String> = (0..n).map(|i| format!("{}", i)).collect();
-        let name_to_index = Some(Self::build_name_to_index(&names));
+        let name_to_index = Self::build_name_to_index(&names);
 
         Self {
             n,
@@ -184,7 +183,7 @@ impl GraphSession {
             registry: snapshot,
             edges: EdgeBuffer::new(),
             names,
-            name_to_index: RefCell::new(name_to_index),
+            name_to_index,
 
             core_valid: false,
             view_valid: false,
@@ -203,7 +202,7 @@ impl GraphSession {
         class: GraphClass,
     ) -> Self {
         let names: Vec<String> = (0..n).map(|i| format!("{}", i)).collect();
-        let name_to_index = Some(Self::build_name_to_index(&names));
+        let name_to_index = Self::build_name_to_index(&names);
 
         Self {
             n,
@@ -212,7 +211,7 @@ impl GraphSession {
             registry,
             edges: EdgeBuffer::new(),
             names,
-            name_to_index: RefCell::new(name_to_index),
+            name_to_index,
 
             core_valid: false,
             view_valid: false,
@@ -233,14 +232,15 @@ impl GraphSession {
         names: Vec<String>,
     ) -> Self {
         let n = names.len() as u32;
+        let name_to_index = Self::build_name_to_index(&names);
         Self {
             n,
             simple,
             graph_class: class,
             registry,
             edges,
             names,
-            name_to_index: RefCell::new(None),
+            name_to_index,
             core_valid: false,
             view_valid: false,
             edges_trusted: true,
@@ -271,14 +271,15 @@ impl GraphSession {
             }
         }
 
+        let name_to_index = Self::build_name_to_index(&names);
         Self {
             n,
             simple,
             graph_class: class,
             registry,
             edges,
             names,
-            name_to_index: RefCell::new(None),
+            name_to_index,
             core_valid: true,
             view_valid: false,
             edges_trusted: true,
@@ -299,7 +300,7 @@ impl GraphSession {
             registry: Arc::clone(&self.registry),
             edges: self.edges.clone(),
             names: self.names.clone(),
-            name_to_index: RefCell::new(self.name_to_index.borrow().as_ref().cloned()),
+            name_to_index: self.name_to_index.clone(),
 
             // Invalidate all declarations in the clone
             core_valid: false,
@@ -350,7 +351,7 @@ impl GraphSession {
     }
 
     pub fn replace_edges_for_pairs(&mut self, new_edges: EdgeBuffer) {
-        let mut remove_pairs: HashSet<(u32, u32)> = HashSet::with_capacity(new_edges.len());
+        let mut remove_pairs: FxHashSet<(u32, u32)> = FxHashSet::with_capacity_and_hasher(new_edges.len(), Default::default());
         if self.simple {
             for i in 0..new_edges.len() {
                 let u = new_edges.from[i];
@@ -365,8 +366,8 @@ impl GraphSession {
         }
 
         let mut kept = EdgeBuffer::with_capacity(self.edges.len() + new_edges.len());
-        let mut seen: HashSet<(u32, u32, u8)> =
-            HashSet::with_capacity(self.edges.len() + new_edges.len());
+        let mut seen: FxHashSet<(u32, u32, u8)> =
+            FxHashSet::with_capacity_and_hasher(self.edges.len() + new_edges.len(), Default::default());
 
         for i in 0..self.edges.len() {
             let u = self.edges.from[i];
@@ -409,7 +410,7 @@ impl GraphSession {
     }
 
     pub fn set_names(&mut self, names: Vec<String>) {
-        *self.name_to_index.get_mut() = Some(Self::build_name_to_index(&names));
+        self.name_to_index = Self::build_name_to_index(&names);
         self.names = names;
         // No invalidation - names are metadata
     }
@@ -434,7 +435,7 @@ impl GraphSession {
         self.graph_class = class;
         self.registry = registry;
         self.edges = edges;
-        *self.name_to_index.get_mut() = Some(Self::build_name_to_index(&names));
+        self.name_to_index = Self::build_name_to_index(&names);
         self.names = names;
         self.invalidate_core();
     }
@@ -897,32 +898,15 @@ impl GraphSession {
     /// Look up the 0-based index of a node by name.
     /// Returns `None` if the name is not found.
     pub fn index_of(&self, name: &str) -> Option<u32> {
-        if let Some(map) = self.name_to_index.borrow().as_ref() {
-            return map.get(name).copied();
-        }
-
-        let built = Self::build_name_to_index(&self.names);
-        let out = built.get(name).copied();
-        *self.name_to_index.borrow_mut() = Some(built);
-        out
+        self.name_to_index.get(name).copied()
     }
 
     /// Look up the 0-based indices of multiple nodes by name.
     /// Returns an error if any name is not found.
     pub fn indices_of(&self, names: &[String]) -> Result<Vec<u32>, String> {
-        if self.name_to_index.borrow().is_none() {
-            let built = Self::build_name_to_index(&self.names);
-            *self.name_to_index.borrow_mut() = Some(built);
-        }
-
-        let map_ref = self.name_to_index.borrow();
-        let map = map_ref
-            .as_ref()
-            .expect("name_to_index must be initialized before lookup");
-
         let mut result = Vec::with_capacity(names.len());
         for name in names {
-            match map.get(name) {
+            match self.name_to_index.get(name) {
                 Some(&idx) => result.push(idx),
                 None => return Err(format!("Non-existent node name: {}", name)),
             }