CASLike no longer requires that state is total ordered (#22)

Author: davidchuyaya

hydro_optimize_examples/src/compare_and_swap/cas.rs

@@ -16,7 +16,7 @@ pub struct CAS<'a, 'b> {
 
 impl<'a, 'b, State, Sender> CASLike<'a, State, Sender> for CAS<'a, 'b>
 where
-    State: Clone + Serialize + for<'de> Deserialize<'de> + Ord + 'a,
+    State: Clone + Serialize + for<'de> Deserialize<'de> + PartialOrd + 'a,
     Sender: Clone + Serialize + for<'de> Deserialize<'de> + Eq + Hash + 'a,
 {
     fn build(

hydro_optimize_examples/src/compare_and_swap/cas_distributed.rs

@@ -247,7 +247,7 @@ impl<'a, 'b> DistributedCAS<'a, 'b> {
 /// 2. Each client subscribes at most once. (Doesn't break correctness but will duplicate messages).
 impl<'a, 'b, State, Sender> CASLike<'a, State, Sender> for DistributedCAS<'a, 'b>
 where
-    State: Clone + Debug + Serialize + for<'de> Deserialize<'de> + Ord + 'a,
+    State: Clone + Debug + Serialize + for<'de> Deserialize<'de> + PartialOrd + Eq + 'a,
     Sender: Clone + Debug + Serialize + for<'de> Deserialize<'de> + Eq + Hash + 'a,
 {
     fn build(
@@ -380,7 +380,12 @@ where
                 .clone()
                 .map(q!(|(response, _all_agree)| (response.max_ballot, response.state)))
                 .chain(committed_state.into_stream())
-                .max();
+                .reduce(q!(|(ballot, state), (new_ballot, new_state)| {
+                    if new_ballot >= *ballot {
+                        *ballot = new_ballot;
+                        *state = new_state;
+                    }
+                }, commutative = manual_proof!(/** Max is commutative. If the new ballot is the same, then state can be overwritten based on order and that's ok. */)));
             // Propose a valid client write if the election is succesful and all agree
             let proposed_client_write = write_queue
                 .clone()

hydro_optimize_examples/src/compare_and_swap/cas_like.rs

@@ -43,14 +43,6 @@ impl<S: PartialOrd> PartialOrd for CASState<S> {
     }
 }
 
-impl<S: Ord> Ord for CASState<S> {
-    fn cmp(&self, other: &Self) -> std::cmp::Ordering {
-        self.version
-            .cmp(&other.version)
-            .then_with(|| self.state.cmp(&other.state))
-    }
-}
-
 #[derive(Copy, Clone, Debug, Serialize, Deserialize, PartialEq, Eq, Hash)]
 pub struct UniqueRequestId {
     pub id: u64,