diff --git a/tests/benchs.ml b/tests/benchs.ml
index 5c6d4e9c..041f9de3 100644
--- a/tests/benchs.ml
+++ b/tests/benchs.ml
@@ -1,6 +1,12 @@
 
 (** Benchmarking *)
 
+module IHashtbl = Hashtbl.Make(struct
+  type t = int
+  let equal i j = i - j = 0
+  let hash i = i
+end)
+
 let phashtbl_add n =
   let h = PHashtbl.create 50 in
   for i = n downto 0 do
@@ -15,10 +21,19 @@ let hashtbl_add n =
   done;
   h
 
+let ihashtbl_add n =
+  let h = IHashtbl.create 50 in
+  for i = n downto 0 do
+    IHashtbl.add h i i;
+  done;
+  h
+
 let _ =
+  Format.printf "----------------------------------------@.";
   let res = Bench.bench_n
     ["phashtbl_add", (fun n -> ignore (phashtbl_add n));
-     "hashtbl_add", (fun n -> ignore (hashtbl_add n));]
+     "hashtbl_add", (fun n -> ignore (hashtbl_add n));
+     "ihashtbl_add", (fun n -> ignore (ihashtbl_add n));]
   in
   Bench.summarize 1. res
 
@@ -42,32 +57,48 @@ let hashtbl_replace n =
   done;
   h
 
+let ihashtbl_replace n =
+  let h = IHashtbl.create 50 in
+  for i = 0 to n do
+    IHashtbl.replace h i i;
+  done;
+  for i = n downto 0 do
+    IHashtbl.replace h i i;
+  done;
+  h
+
 let _ =
+  Format.printf "----------------------------------------@.";
   let res = Bench.bench_n
     ["phashtbl_replace", (fun n -> ignore (phashtbl_replace n));
-     "hashtbl_replace", (fun n -> ignore (hashtbl_replace n));]
+     "hashtbl_replace", (fun n -> ignore (hashtbl_replace n));
+     "ihashtbl_replace", (fun n -> ignore (ihashtbl_replace n));]
   in
   Bench.summarize 1. res
 
-let phashtbl_mem h =
+let my_len = 250
+let round_n n = abs (n mod my_len)
+
+let phashtbl_find h =
   fun n ->
-    for i = 0 to n do
-      ignore (PHashtbl.find h i);
-    done
+    ignore (PHashtbl.find h (round_n n))
      
-let hashtbl_mem h =
+let hashtbl_find h =
   fun n ->
-    for i = 0 to n do
-      ignore (Hashtbl.find h i);
-    done
+    ignore (Hashtbl.find h (round_n n))
+     
+let ihashtbl_find h =
+  fun n ->
+    ignore (IHashtbl.find h (round_n n))
 
 let _ =
-  let n = 50000 in
-  let h = phashtbl_add n in
-  let h' = hashtbl_add n in
-  let res = Bench.bench_funs
-    ["phashtbl_mem", phashtbl_mem h;
-     "hashtbl_mem", hashtbl_mem h';]
-    n
+  Format.printf "----------------------------------------@.";
+  let h = phashtbl_add my_len in
+  let h' = hashtbl_add my_len in
+  let h'' = ihashtbl_add my_len in
+  let res = Bench.bench_n
+    ["phashtbl_mem", phashtbl_find h;
+     "hashtbl_mem", hashtbl_find h';
+     "ihashtbl_mem", ihashtbl_find h'';]
   in
   Bench.summarize 1. res