Expose more helpers on ActorMesh (#452)

Summary:
Pull Request resolved: #452

Expose some additional helper methods off `ActorMeshRef`.

In particular, `iter_actor_refs()` can be used by clients using `ActorConnection`s,
as these, by definition, need to be established point-to-point.

Reviewed By: mariusae

Differential Revision: D77880648

fbshipit-source-id: 7691785f0cd6e1df2d1cb07f472081eb0cc59264

Author: andrewjcg

hyperactor_mesh/src/actor_mesh.rs

@@ -15,6 +15,8 @@ use hyperactor::Actor;
 use hyperactor::ActorId;
 use hyperactor::ActorRef;
 use hyperactor::Bind;
+use hyperactor::GangId;
+use hyperactor::GangRef;
 use hyperactor::Message;
 use hyperactor::Named;
 use hyperactor::PortHandle;
@@ -146,6 +148,13 @@ pub trait ActorMesh: Mesh {
         self.proc_mesh().world_id()
     }
 
+    /// Iterate over all `ActorRef<Self::Actor>` in this mesh.
+    fn iter_actor_refs(&self) -> impl Iterator<Item = ActorRef<Self::Actor>> {
+        let gang: GangRef<Self::Actor> =
+            GangId(self.proc_mesh().world_id().clone(), self.name().to_string()).into();
+        self.shape().slice().iter().map(move |rank| gang.rank(rank))
+    }
+
     /// Get a serializeable reference to this mesh similar to ActorHandle::bind
     fn bind(&self) -> ActorMeshRef<Self::Actor> {
         ActorMeshRef::attest(