Test Rio trees

Author: polybeandip

rio/simulator/dune

@@ -1,3 +1,5 @@
+(include_subdirs unqualified)
+
 (library
  (name Simulator)
  (public_name rio.simulator)

rio/simulator/pifo.ml

@@ -0,0 +1,22 @@
+type 'a t = {
+  heap : ('a * Rank.t * int) Fheap.t;
+  counter : int; (* for breaking rank ties in FIFO order *)
+}
+
+let create () =
+  let cmp (_, a, i) (_, b, j) =
+    match Rank.cmp a b with
+    | 0 -> i - j
+    | x -> x
+  in
+  { heap = Fheap.create ~compare:cmp; counter = 0 }
+
+let size t = Fheap.length t.heap
+
+let push t v r =
+  { heap = Fheap.add t.heap (v, r, t.counter); counter = t.counter + 1 }
+
+let pop t =
+  match Fheap.pop t.heap with
+  | Some ((v, _, _), heap') -> Some (v, { t with heap = heap' })
+  | None -> None