Merge #61 #62

61: Improve worst-case performance of HashSet.is_subset r=Amanieu a=Amanieu

Ported from rust-lang/rust#59665

62: Remove incorrect debug_assert r=Amanieu a=Amanieu

Fixes #60 

Co-authored-by: Amanieu d'Antras <[email protected]>

Author: bors[bot]

src/external_trait_impls/rayon/set.rs

@@ -256,7 +256,11 @@ where
     ///
     /// This method runs in a potentially parallel fashion.
     pub fn par_is_subset(&self, other: &Self) -> bool {
-        self.into_par_iter().all(|x| other.contains(x))
+        if self.len() <= other.len() {
+            self.into_par_iter().all(|x| other.contains(x))
+        } else {
+            false
+        }
     }
 
     /// Returns `true` if the set is a superset of another,

src/raw/mod.rs

@@ -118,11 +118,8 @@ fn special_is_empty(ctrl: u8) -> bool {
 #[inline]
 #[allow(clippy::cast_possible_truncation)]
 fn h1(hash: u64) -> usize {
-    #[cfg(target_pointer_width = "32")]
-    {
-        debug_assert!(hash <= u64::from(u32::max_value()));
-    }
-    hash as usize // truncation
+    // On 32-bit platforms we simply ignore the higher hash bits.
+    hash as usize
 }
 
 /// Secondary hash function, saved in the low 7 bits of the control byte.

src/set.rs

@@ -640,7 +640,11 @@ where
     /// assert_eq!(set.is_subset(&sup), false);
     /// ```
     pub fn is_subset(&self, other: &Self) -> bool {
-        self.iter().all(|v| other.contains(v))
+        if self.len() <= other.len() {
+            self.iter().all(|v| other.contains(v))
+        } else {
+            false
+        }
     }
 
     /// Returns `true` if the set is a superset of another,