DirectIO is working! Also a bit more cleanup.

src/mapping/cluster.rs

@@ -21,6 +21,7 @@ impl Default for Cluster {
 impl Cluster {
     /// Breaks apart into a vec of clusters,
     /// each of cluster_size, excepting last.
+    #[allow(dead_code)]
     pub fn subdivide(&mut self, cluster_len: usize) -> Vec<Cluster> {
         let domain_len = self.domain.len();
         let mut start = self.domain.start;
@@ -49,6 +50,8 @@ impl Cluster {
         clusters
     }
 
+    // This is used in unit tests at present. Ideally it probably shouldn't exist.
+    #[allow(dead_code)]
     pub fn set_stage(&mut self, stage: Stage) -> &mut Self {
         self.stage = stage;
         self