perf: improve {Dict, Set}::hash

erg-lang · Oct 3, 2024 · e7ff9f4 · e7ff9f4
1 parent f862a3f
commit e7ff9f4
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Showing 2 changed files with 23 additions and 11 deletions.
diff --git a/crates/erg_common/dict.rs b/crates/erg_common/dict.rs
@@ -36,14 +36,23 @@ impl<K: Hash + Eq + Immutable, V: Hash + Eq> Eq for Dict<K, V> {}
 
 impl<K: Hash, V: Hash> Hash for Dict<K, V> {
     fn hash<H: Hasher>(&self, state: &mut H) {
-        let mut v = self
-            .iter()
-            .map(|(key, val)| (get_hash(key), key, val))
-            .collect::<Vec<_>>();
-        v.sort_by_key(|(h, _, _)| *h);
-        for (_, key, val) in v.iter() {
-            key.hash(state);
-            val.hash(state);
+        let len = self.len();
+        len.hash(state);
+        if len <= 1 {
+            for (key, val) in self.iter() {
+                key.hash(state);
+                val.hash(state);
+            }
+        } else {
+            let mut v = self
+                .iter()
+                .map(|(key, val)| (get_hash(key), val))
+                .collect::<Vec<_>>();
+            v.sort_unstable_by_key(|(h, _)| *h);
+            for (h, val) in v.iter() {
+                state.write_usize(*h);
+                val.hash(state);
+            }
         }
     }
 }

diff --git a/crates/erg_common/set.rs b/crates/erg_common/set.rs
@@ -63,9 +63,12 @@ impl<T> Default for Set<T> {
 
 impl<T: Hash> Hash for Set<T> {
     fn hash<H: Hasher>(&self, state: &mut H) {
-        let mut v = self.iter().map(get_hash).collect::<Vec<_>>();
-        v.sort();
-        v.hash(state);
+        self.len().hash(state);
+        let sum = self
+            .iter()
+            .map(get_hash)
+            .fold(0usize, |acc, x| acc.wrapping_add(x));
+        sum.hash(state);
     }
 }