Update.

src/lib.rs

@@ -1,3 +1,4 @@
+extern crate ordermap;
 extern crate rayon;
 extern crate serde;
 extern crate unreachable;
@@ -8,6 +9,7 @@ use std::iter::{FromIterator, IntoIterator, Iterator};
 use std::default::Default;
 use std::collections::{HashMap, LinkedList};
 
+use ordermap::OrderMap;
 use rayon::iter::{FromParallelIterator, IntoParallelIterator, ParallelExtend, ParallelIterator};
 
 use serde::{Deserialize, Deserializer, Serialize, Serializer};
@@ -22,6 +24,7 @@ const BITS: u64 = 64;
 
 type Block = u64;
 type Storage = HashMap<u64, Block, BitBuildHasher>;
+// type Storage = OrderMap<u64, Block, BitBuildHasher>;
 
 pub type BitHashMap<V> = HashMap<u64, V, BitBuildHasher>;
 
@@ -64,7 +67,7 @@ impl BitSet {
 
     pub fn shrink_to_fit(&mut self) {
         self.blocks.retain(|_, block| *block != 0);
-        self.blocks.shrink_to_fit()
+        // self.blocks.shrink_to_fit();
     }
 
     pub fn iter(&self) -> Iter {
@@ -246,6 +249,27 @@ impl<'a> ops::BitOr<&'a Self> for BitSet {
     }
 }
 
+impl<'a> ops::BitOr<&'a BitSet> for &'a BitSet {
+    type Output = BitSet;
+
+    #[inline]
+    fn bitor(self, rhs: &'a BitSet) -> BitSet {
+        let mut set = self.clone();
+
+        for (key, value) in &rhs.blocks {
+            let block = set.blocks.entry(*key).or_insert(0);
+
+            let n = block.count_ones();
+
+            *block |= value;
+
+            set.nbits += (block.count_ones() - n) as usize;
+        }
+
+        set
+    }
+}
+
 impl<'a> ops::Sub<&'a BitSet> for &'a BitSet {
     type Output = BitSet;
 
@@ -269,6 +293,7 @@ impl<'a> ops::Sub<&'a BitSet> for &'a BitSet {
 
 pub struct Iter<'a> {
     iter: std::collections::hash_map::Iter<'a, u64, u64>,
+    // iter: ordermap::Iter<'a, u64, u64>,
     block: u64,
     bits: u64,
     bit: u64,
@@ -276,6 +301,7 @@ pub struct Iter<'a> {
 
 pub struct IntoIter {
     iter: std::collections::hash_map::IntoIter<u64, u64>,
+    // iter: ordermap::IntoIter<u64, u64>,
     block: u64,
     bits: u64,
     bit: u64,