refactored CCrandom (hide fuel, too complicated, but provide a fix operator);

bench_hash to compare hash combinators to the default hash function

.merlin

@@ -9,7 +9,7 @@ B _build/string
 B _build/tests
 B _build/examples
 PKG oUnit
-PKG bench
+PKG benchmark
 PKG threads
 PKG threads.posix
 PKG lwt

_oasis

@@ -146,6 +146,14 @@ Executable bench_batch
   MainIs: bench_batch.ml
   BuildDepends: containers,benchmark
 
+Executable bench_hash
+  Path: tests/
+  Install: false
+  CompiledObject: native
+  Build$: flag(bench) && flag(misc)
+  MainIs: bench_hash.ml
+  BuildDepends: containers,containers.misc
+
 Executable test_levenshtein
   Path: tests/
   Install: false

core/CCRandom.ml

@@ -41,112 +41,129 @@ let map f g st = f (g st)
 
 let (>|=) g f st = map f g st
 
-let choose_array a st =
+let _choose_array a st =
   if Array.length a = 0 then invalid_arg "CCRandom.choose_array";
-  a.(Random.State.int st (Array.length a)) st
+  a.(Random.State.int st (Array.length a))
 
-let choose l = choose_array (Array.of_list l)
+let choose_array a st =
+  try Some (_choose_array a st st) with Invalid_argument _ -> None
 
-let choose_return l = choose_array (Array.of_list (List.map return l))
+let choose l =
+  let a = Array.of_list l in
+  choose_array a
 
-(** {2 Fuel and Backtracking} *)
+let choose_exn l =
+  let a = Array.of_list l in
+  fun st -> _choose_array a st st
 
-module Fuel = struct
-  type fuel = int
+let choose_return l = _choose_array (Array.of_list l)
 
-  exception Backtrack
+let int i st = Random.State.int st i
 
-  (* consume [d] units of fuel and return [x] if it works *)
-  let _consume d fuel x =
-    if fuel >= d then Some (fuel-d,x) else None
+let small_int = int 100
+
+let int_range i j st = i + Random.State.int st (j-i+1)
+
+let replicate n g st =
+  let rec aux acc n =
+    if n = 0 then acc else aux (g st :: acc) (n-1)
+  in aux [] n
+
+exception SplitFail
 
 let _split i st =
-    if i < 2 then raise Backtrack
+  if i < 2 then raise SplitFail
   else
     let j = 1 + Random.State.int st (i-1) in
     (j, i-j)
 
-  let split i st = try Some (_split i st) with Backtrack -> None
+let split i st = try Some (_split i st) with SplitFail -> None
 
 (* partition of an int into [len] integers. We divide-and-conquer on
   the expected length, until it reaches 1. *)
 let split_list i ~len st =
   let rec aux i ~len acc =
-      if i < len then raise Backtrack
+    if i < len then raise SplitFail
     else if len = 1 then i::acc
     else
       (* split somewhere in the middle *)
       let len1, len2 = _split len st in
+      assert (len = len1+len2);
       if i = len
       then aux len1 ~len:len1 (aux len2 ~len:len2 acc)
       else
-          let i1, i2 = _split (i-len1-len2) st in
-          aux i1 ~len:len1 (aux i2 ~len:len2 acc)
+        let i1, i2 = _split (i-len) st in
+        aux (i1+len1) ~len:len1 (aux (i2+len2) ~len:len2 acc)
   in
-    try Some (aux i ~len []) with Backtrack -> None
+  try Some (aux i ~len []) with SplitFail -> None
 
-  (** {6 Fueled Generators} *)
-
-  type 'a t = fuel -> state -> (fuel * 'a) option
-
-  let return x fuel _st = _consume 1 fuel x
-
-  let return' fuel x fuel' _st = _consume fuel fuel' x
-
-  let flat_map f g fuel st =
-    match g fuel st with
-      | None -> None
-      | Some (fuel, x) -> f x fuel st
-
-  let (>>=) g f = flat_map f g
-
-  let map f g fuel st =
-    match g fuel st with
-    | None -> None
-    | Some (fuel, x) -> Some (fuel, f x)
-
-  let (>|=) g f = map f g
-
-  let consume fuel _st = _consume 1 fuel ()
-
-  let consume' fuel fuel' _st = _consume fuel fuel' ()
-
-  let fail _fuel _st = None
-
-  let retry ?(max=10) g fuel st =
+let retry ?(max=10) g st =
   let rec aux n =
-      match g fuel st with
+    match g st with
       | None when n=0 -> None
       | None -> aux (n-1)  (* retry *)
       | Some _ as res -> res
   in
   aux max
 
-  let rec try_successively l fuel st = match l with
+let rec try_successively l st = match l with
   | [] -> None
   | g :: l' ->
-        begin match g fuel st with
-        | None -> try_successively l' fuel st
+      begin match g st with
+      | None -> try_successively l' st
       | Some _ as res -> res
       end
 
 let (<?>) a b = try_successively [a;b]
 
-  let rec fix f fuel st = f (fix f) fuel st
+exception Backtrack
 
-  let lift g fuel st = _consume 1 fuel (g st)
+let _choose_array_call a f st =
+  try
+    f (_choose_array a st)
+  with Invalid_argument _ -> raise Backtrack
 
-  let lift' d g fuel st = _consume d fuel (g st)
+let fix ?(sub1=[]) ?(sub2=[]) ?(subn=[]) ~base fuel st =
+  let sub1 = Array.of_list sub1
+  and sub2 = Array.of_list sub2
+  and subn = Array.of_list subn in
+  (* recursive function with fuel *)
+  let rec make fuel st =
+    if fuel=0 then raise Backtrack
+    else if fuel=1 then base st
+    else
+      _try_otherwise 0
+        [| _choose_array_call sub1 (fun f -> f (make (fuel-1)) st)
+        ;  _choose_array_call sub2
+          (fun f ->
+            match split fuel st with
+            | None -> raise Backtrack
+            | Some (i,j) -> f (make i) (make j) st
+          )
+        ; _choose_array_call subn
+          (fun (len,f) ->
+            let len = len st in
+            match split_list fuel ~len st with
+            | None -> raise Backtrack
+            | Some l' ->
+                f (fun st -> List.map (fun x -> make x st) l') st
+          )
+        ; base (* base case then *)
+        |]
+  and _try_otherwise i a =
+    if i=Array.length a then raise Backtrack
+    else try
+      a.(i) st
+    with Backtrack ->
+      _try_otherwise (i+1) a
+  in
+  make (fuel st) st
 
-  let run ?(fuel=fun st -> Random.State.int st 40) f st =
-    match f (fuel st) st with
-    | None -> None
-    | Some (_fuel, x) -> Some x
+let pure x _st = x
 
-  exception GenFailure
+let (<*>) f g st = f st (g st)
+
+let __default_state = Random.State.make_self_init ()
+
+let run ?(st=__default_state) g = g st
 
-  let run_exn ?fuel f st =
-    match run ?fuel f st with
-    | None -> raise GenFailure
-    | Some x -> x
-end

core/CCRandom.mli

@@ -45,98 +45,72 @@ val map : ('a -> 'b) -> 'a t -> 'b t
 
 val (>|=) : 'a t -> ('a -> 'b) -> 'b t
 
-val choose : 'a t list -> 'a t
-(** Choose a generator within the list.
+val choose : 'a t list -> 'a option t
+(** Choose a generator within the list. *)
+
+val choose_exn : 'a t list -> 'a t
+(** Same as {!choose} but without option.
     @raise Invalid_argument if the list is empty *)
 
-val choose_array : 'a t array -> 'a t
+val choose_array : 'a t array -> 'a option t
 
 val choose_return : 'a list -> 'a t
 (** Choose among the list
     @raise Invalid_argument if the list is empty *)
 
-(** {2 Fuel and Backtracking} *)
+val replicate : int -> 'a t -> 'a list t
 
-module Fuel : sig
-  type fuel = int
-  (** The fuel is a value that represents some "resource" used by the
-      random generator. *)
+val small_int : int t
 
-  val split : fuel -> (fuel * fuel) option t
-  (** Split a (fuel) value [n] into [n1,n2] where [n = n1 + n2].
+val int : int -> int t
+
+val int_range : int -> int -> int t
+(** Inclusive range *)
+
+val split : int -> (int * int) option t
+(** Split a positive value [n] into [n1,n2] where [n = n1 + n2].
     @return [None] if the value is too small *)
 
-  val split_list : fuel -> len:int -> fuel list option t
-  (** Split a (fuel) value [n] into a list of values whose sum is [n]
+val split_list : int -> len:int -> int list option t
+(** Split a value [n] into a list of values whose sum is [n]
     and whose length is [length].
     @return [None] if the value is too small *)
 
-  (** {6 Fueled Generators} *)
-
-  type 'a t = fuel -> state -> (fuel * 'a) option
-  (** Fueled generators use some fuel to generate a value.
-      Can fail by lack of fuel. *)
-
-  val return : 'a -> 'a t
-  (** [return x] is the generator that always returns [x], and consumes one
-      fuel doing it. *)
-
-  val return' : fuel -> 'a -> 'a t
-  (** [return' f x] returns [x] but also consumes [fuel]. *)
-
-  val flat_map : ('a -> 'b t) -> 'a t -> 'b t
-
-  val (>>=) : 'a t -> ('a -> 'b t) -> 'b t
-
-  val map : ('a -> 'b) -> 'a t -> 'b t
-
-  val (>|=) : 'a t -> ('a -> 'b) -> 'b t
-
-  val consume : unit t
-  (** Consume one fuel value *)
-
-  val consume' : fuel -> unit t
-  (** Consume the given amount of fuel *)
-
-  val fail : 'a t
-  (** Always fails. *)
-
-  val retry : ?max:int -> 'a t -> 'a t
+val retry : ?max:int -> 'a option t -> 'a option t
 (** [retry g] calls [g] until it returns some value, or until the maximum
     number of retries was reached. If [g] fails,
     then it counts for one iteration, and the generator retries.
     @param max: maximum number of retries. Default [10] *)
 
-  val try_successively : 'a t list -> 'a t
+val try_successively : 'a option t list -> 'a option t
 (** [try_successively l] tries each generator of [l], one after the other.
     If some generator succeeds its result is returned, else the
     next generator is tried *)
 
-  val (<?>) : 'a t -> 'a t -> 'a t
+val (<?>) : 'a option t -> 'a option t -> 'a option t
 (** [a <?> b] is a choice operator. It first tries [a], and returns its
     result if successful. If [a] fails, then [b] is returned. *)
 
-  val fix : ('a t -> 'a t) -> 'a t
-  (** Recursion combinators, for building (fueled) recursive values *)
+val fix :
+  ?sub1:('a t -> 'a t) list ->
+  ?sub2:('a t -> 'a t -> 'a t) list ->
+  ?subn:(int t * ('a list t -> 'a t)) list ->
+  base:'a t -> int t -> 'a t
+(** Recursion combinators, for building recursive values.
+    The integer generator is used to provide fuel. The [sub_] generators
+    should use their arguments only once!
+    @param sub1 cases that recurse on one value
+    @param sub2 cases that use the recursive gen twice
+    @param subn cases that use a list of recursive cases *)
 
-  val lift : 'a random_gen -> 'a t
-  (** lifts a regular random generator into a fueled one, that consumes
-      one fuel unit *)
+(** {6 Applicative} *)
 
-  val lift' : fuel -> 'a random_gen -> 'a t
-  (** lifts a regular random generator into a fueled one, that consumes
-      one fuel unit *)
+val pure : 'a -> 'a t
 
-  (** {6 Running} *)
+val (<*>) : ('a -> 'b) t -> 'a t -> 'b t
 
-  val run : ?fuel:fuel random_gen -> 'a t -> 'a option random_gen
-  (** Run the given fueled generator with an amount of fuel
-      given by the [fuel] generator.
-      @return None if the *)
+(** {6 Run a generator} *)
 
-  exception GenFailure
+val run : ?st:state -> 'a t -> 'a
+(** Using a random state (possibly the one in argument) run a generator *)
 
-  val run_exn : ?fuel:fuel random_gen -> 'a t -> 'a random_gen
-  (** Same as {!run}, but in case of failure it raises an exception.
-      @raise GenFailure in case the generator fails *)
-end

misc/.merlin

@@ -0,0 +1,6 @@
+REC
+S ../core
+S .
+B ../_build/core/
+B ../_build/misc/
+PKG core

tests/.merlin

@@ -0,0 +1,3 @@
+S .
+B ../_build/tests/
+REC

tests/bench_hash.ml

@@ -0,0 +1,84 @@
+(** Test hash functions *)
+
+type tree =
+  | Empty
+  | Node of int * tree list
+
+let mk_node i l = Node (i,l)
+
+let random_tree =
+  CCRandom.(fix
+    ~base:(return Empty)
+    ~subn:[int 10, (fun sublist -> pure mk_node <*> small_int <*> sublist)]
+    (int_range 15 150)
+  )
+
+let random_list =
+  CCRandom.(
+    int 5 >>= fun len ->
+    CCList.random_len len random_tree
+  )
+
+let rec eq t1 t2 = match t1, t2 with
+  | Empty, Empty -> true
+  | Node(i1,l1), Node (i2,l2) -> i1=i2 && CCList.equal eq l1 l2
+  | Node _, _
+  | _, Node _ -> false
+
+let rec hash_tree t h = match t with
+  | Empty -> CCHash.string_ "empty" h
+  | Node (i, l) ->
+      h |> CCHash.string_ "node" |> CCHash.int_ i |> CCHash.list_ hash_tree l
+
+module Box = Containers_misc.PrintBox
+
+let tree2box = Box.mk_tree
+  (function
+    | Empty -> Box.empty, []
+    | Node (i,l) -> Box.line (CCPrint.sprintf "node %d" i), l
+  )
+
+let l = CCRandom.(run (CCList.random random_list))
+
+let pp_list buf l =
+  let box = Box.(frame (vlist ~bars:true (List.map tree2box l))) in
+  CCPrint.string buf (Box.to_string box)
+
+(* print some terms *)
+let () =
+  List.iter
+    (fun l -> CCPrint.printf "%a\n" pp_list l) l
+
+
+module H = Hashtbl.Make(struct
+  type t = tree
+  let equal = eq
+  let hash = CCHash.apply hash_tree
+end)
+
+let print_hashcons_stats st =
+  let open Hashtbl in
+    CCPrint.printf
+      "tbl stats: %d elements, num buckets: %d, max bucket: %d\n"
+      st.num_bindings st.num_buckets st.max_bucket_length;
+    Array.iteri
+      (fun i n -> CCPrint.printf "  %d\t buckets have length %d\n" n i)
+      st.bucket_histogram
+
+let () =
+  let st = Random.State.make_self_init () in
+  let n = 50_000 in
+  CCPrint.printf "generate %d elements...\n" n;
+  let l = CCRandom.run ~st (CCList.random_len n random_tree) in
+  (* with custom hashtable *)
+  CCPrint.printf "### custom hashtable\n";
+  let tbl = H.create 256 in
+  List.iter (fun t -> H.replace tbl t ()) l;
+  print_hashcons_stats (H.stats tbl);
+  (* with default hashtable *)
+  CCPrint.printf "### default hashtable\n";
+  let tbl' = Hashtbl.create 256 in
+  List.iter (fun t -> Hashtbl.replace tbl' t ()) l;
+  print_hashcons_stats (Hashtbl.stats tbl');
+  ()
+