move uniformity tests out of CCRandom

src/core/CCRandom.ml

@@ -3,7 +3,6 @@
 
 (** {1 Random Generators} *)
 
-open CCShims_
 include Random
 
 type state = Random.State.t
@@ -208,35 +207,6 @@ let __default_state = Random.State.make_self_init ()
 
 let run ?(st=__default_state) g = g st
 
-let uniformity_test ?(size_hint=10) k rng st =
-  let histogram = Hashtbl.create size_hint in
-  let add x = let n = try Hashtbl.find histogram x with Not_found -> 0 in
-    Hashtbl.replace histogram x (n + 1) in
-  let () =
-    for _i = 0 to ( k - 1 ) do
-      add (rng st)
-    done in
-  let cardinal = float_of_int (Hashtbl.length histogram) in
-  let kf = float_of_int k in
-  (* average number of points assuming an uniform distribution *)
-  let average = kf /. cardinal in
-  (* The number of points is a sum of random variables with binomial distribution *)
-  let p = 1. /. cardinal in
-  (* The variance of a binomial distribution with average p is *)
-  let variance = p *. (1. -. p ) in
-  (* Central limit theorem: a confidence interval of 4σ provides a false positive rate
-     of 0.00634% *)
-  let confidence = 4. in
-  let std = confidence *. (sqrt (kf *. variance)) in
-  let predicate _key n acc =
-    let (<) (a : float) b = Stdlib.(<) a b in
-    acc && abs_float (average -. float_of_int n) < std in
-  Hashtbl.fold predicate histogram true
-
-(*$T split_list
-  run ~st:(QCheck_runner.random_state()) ( uniformity_test 50_000 (split_list 10 ~len:3) )
-*)
-
 (*$R
   let open Containers in
   ignore @@ List.random_choose [1;2;3] (Random.get_state())

src/core/CCRandom.mli

@@ -158,11 +158,3 @@ include CCShimsMkLet_.S with type 'a t_let := 'a t
 
 val run : ?st:state -> 'a t -> 'a
 (** Using a random state (possibly the one in argument) run a generator. *)
-
-(**/**)
-
-val uniformity_test : ?size_hint:int -> int -> 'a t -> bool t
-(** [uniformity_test k rng] tests the uniformity of the random generator [rng] using
-    [k] samples.
-    @since 0.15
-*)

src/core/tests/dune

@@ -2,12 +2,25 @@
 
 (executable
   (name check_labelled_mods)
+  (modules check_labelled_mods)
   (flags :standard -warn-error -a -w -3-33-35-27-39-50 -nolabels)
   (libraries containers))
 
+(executable
+  (name test_hash)
+  (modules test_hash)
+  (flags :standard -warn-error -a+8)
+  (libraries containers))
+
+(alias
+  (name runtest)
+  (locks ctest)
+  (package containers)
+  (action (run ./test_random.exe)))
+
 ; what matters is that it compiles
 (alias
-  (name    runtest)
+  (name runtest)
   (locks ctest)
   (package containers)
   (action  (run ./check_labelled_mods.exe)))

src/core/tests/test_random.ml

@@ -0,0 +1,32 @@
+
+open CCRandom
+
+let uniformity_test ?(size_hint=10) k rng st =
+  let histogram = Hashtbl.create size_hint in
+  let add x = let n = try Hashtbl.find histogram x with Not_found -> 0 in
+    Hashtbl.replace histogram x (n + 1) in
+  let () =
+    for _i = 0 to ( k - 1 ) do
+      add (rng st)
+    done in
+  let cardinal = float_of_int (Hashtbl.length histogram) in
+  let kf = float_of_int k in
+  (* average number of points assuming an uniform distribution *)
+  let average = kf /. cardinal in
+  (* The number of points is a sum of random variables with binomial distribution *)
+  let p = 1. /. cardinal in
+  (* The variance of a binomial distribution with average p is *)
+  let variance = p *. (1. -. p ) in
+  (* Central limit theorem: a confidence interval of 4σ provides a false positive rate
+     of 0.00634% *)
+  let confidence = 4. in
+  let std = confidence *. (sqrt (kf *. variance)) in
+  let predicate _key n acc =
+    let (<) (a : float) b = Stdlib.(<) a b in
+    acc && abs_float (average -. float_of_int n) < std in
+  Hashtbl.fold predicate histogram true
+
+let () =
+  let st = Random.State.make_self_init() in
+  let ok = run ~st ( uniformity_test 50_000 (split_list 10 ~len:3) ) in
+  if not ok then failwith "uniformity check failed"