1 (***************************************************************************)
2 (* Implementation for sets of positive integers implemented as deeply hash-*)
3 (* consed Patricia trees. Provide fast set operations, fast membership as *)
4 (* well as fast min and max elements. Hash consing provides O(1) equality *)
7 (***************************************************************************)
13 val intersect : t -> t -> bool
14 val is_singleton : t -> bool
15 val mem_union : t -> t -> t
18 val uncons : t -> elt*t
19 val from_list : elt list -> t
24 module Make ( H : Hcons.S ) : S with type elt = H.t =
30 | Branch of int * int * 'a * 'a
32 module rec HNode : Hcons.S with type data = Node.t = Hcons.Make (Node)
33 and Node : Hashtbl.HashedType with type t = HNode.t node =
39 | Leaf k1, Leaf k2 -> k1 == k2
40 | Branch(b1,i1,l1,r1),Branch(b2,i2,l2,r2) ->
41 b1 == b2 && i1 == i2 &&
42 (HNode.equal l1 l2) &&
47 | Leaf i -> HASHINT2(HALF_MAX_INT,H.uid i)
48 | Branch (b,i,l,r) -> HASHINT4(b,i,HNode.uid l, HNode.uid r)
57 let node _ = failwith "node"
58 let empty = HNode.make Empty
60 let is_empty s = (HNode.node s) == Empty
62 let branch p m l r = HNode.make (Branch(p,m,l,r))
64 let leaf k = HNode.make (Leaf k)
66 (* To enforce the invariant that a branch contains two non empty sub-trees *)
67 let branch_ne p m t0 t1 =
68 if (is_empty t0) then t1
69 else if is_empty t1 then t0 else branch p m t0 t1
71 (********** from here on, only use the smart constructors *************)
73 let zero_bit k m = (k land m) == 0
75 let singleton k = leaf k
78 match HNode.node n with Leaf _ -> true
83 let rec loop n = match HNode.node n with
86 | Branch (p, _, l, r) -> if kid <= p then loop l else loop r
89 let rec min_elt n = match HNode.node n with
90 | Empty -> raise Not_found
92 | Branch (_,_,s,_) -> min_elt s
94 let rec max_elt n = match HNode.node n with
95 | Empty -> raise Not_found
97 | Branch (_,_,_,t) -> max_elt t
100 let rec elements_aux acc n = match HNode.node n with
103 | Branch (_,_,l,r) -> elements_aux (elements_aux acc r) l
107 let mask k m = (k lor (m-1)) land (lnot m)
109 let naive_highest_bit x =
112 if i = 0 then 1 else if x lsr i = 1 then 1 lsl i else loop (i-1)
116 let hbit = Array.init 256 naive_highest_bit
119 let highest_bit x = let n = (x) lsr 24 in
120 if n != 0 then Array.unsafe_get hbit n lsl 24
121 else let n = (x) lsr 16 in if n != 0 then Array.unsafe_get hbit n lsl 16
122 else let n = (x) lsr 8 in if n != 0 then Array.unsafe_get hbit n lsl 8
123 else Array.unsafe_get hbit (x)
127 let highest_bit64 x =
128 let n = x lsr 32 in if n != 0 then highest_bit n lsl 32
133 let branching_bit p0 p1 = highest_bit (p0 lxor p1)
135 let join p0 t0 p1 t1 =
136 let m = branching_bit p0 p1 in
137 if zero_bit p0 m then
138 branch (mask p0 m) m t0 t1
140 branch (mask p0 m) m t1 t0
142 let match_prefix k p m = (mask k m) == p
146 let rec ins n = match HNode.node n with
148 | Leaf j -> if j == k then n else join kid (leaf k) (H.uid j) n
149 | Branch (p,m,t0,t1) ->
150 if match_prefix kid p m then
151 if zero_bit kid m then
152 branch p m (ins t0) t1
154 branch p m t0 (ins t1)
156 join kid (leaf k) p n
162 let rec rmv n = match HNode.node n with
164 | Leaf j -> if k == j then empty else n
165 | Branch (p,m,t0,t1) ->
166 if match_prefix kid p m then
167 if zero_bit kid m then
168 branch_ne p m (rmv t0) t1
170 branch_ne p m t0 (rmv t1)
176 (* should run in O(1) thanks to Hash consing *)
178 let equal a b = HNode.equal a b
180 let compare a b = (HNode.uid a) - (HNode.uid b)
183 if (equal s t) (* This is cheap thanks to hash-consing *)
186 match HNode.node s, HNode.node t with
189 | Leaf k, _ -> add k t
190 | _, Leaf k -> add k s
191 | Branch (p,m,s0,s1), Branch (q,n,t0,t1) ->
192 if m == n && match_prefix q p m then
193 branch p m (merge s0 t0) (merge s1 t1)
194 else if m > n && match_prefix q p m then
196 branch p m (merge s0 t) s1
198 branch p m s0 (merge s1 t)
199 else if m < n && match_prefix p q n then
201 branch q n (merge s t0) t1
203 branch q n t0 (merge s t1)
205 (* The prefixes disagree. *)
211 let rec subset s1 s2 = (equal s1 s2) ||
212 match (HNode.node s1,HNode.node s2) with
215 | Leaf k1, _ -> mem k1 s2
216 | Branch _, Leaf _ -> false
217 | Branch (p1,m1,l1,r1), Branch (p2,m2,l2,r2) ->
218 if m1 == m2 && p1 == p2 then
219 subset l1 l2 && subset r1 r2
220 else if m1 < m2 && match_prefix p1 p2 m2 then
221 if zero_bit p1 m2 then
222 subset l1 l2 && subset r1 l2
224 subset l1 r2 && subset r1 r2
229 let union s1 s2 = merge s1 s2
230 (* Todo replace with e Memo Module *)
231 module MemUnion = Hashtbl.Make(
235 let equal (x,y) (z,t) = (equal x z)&&(equal y t)
236 let equal a b = equal a b || equal b a
237 let hash (x,y) = (* commutative hash *)
241 if x < y then HASHINT2(x,y) else HASHINT2(y,x)
243 let h_mem = MemUnion.create MED_H_SIZE
245 let mem_union s1 s2 =
246 try MemUnion.find h_mem (s1,s2)
248 let r = merge s1 s2 in MemUnion.add h_mem (s1,s2) r;r
251 let rec inter s1 s2 =
255 match (HNode.node s1,HNode.node s2) with
258 | Leaf k1, _ -> if mem k1 s2 then s1 else empty
259 | _, Leaf k2 -> if mem k2 s1 then s2 else empty
260 | Branch (p1,m1,l1,r1), Branch (p2,m2,l2,r2) ->
261 if m1 == m2 && p1 == p2 then
262 merge (inter l1 l2) (inter r1 r2)
263 else if m1 > m2 && match_prefix p2 p1 m1 then
264 inter (if zero_bit p2 m1 then l1 else r1) s2
265 else if m1 < m2 && match_prefix p1 p2 m2 then
266 inter s1 (if zero_bit p1 m2 then l2 else r2)
274 match (HNode.node s1,HNode.node s2) with
277 | Leaf k1, _ -> if mem k1 s2 then empty else s1
278 | _, Leaf k2 -> remove k2 s1
279 | Branch (p1,m1,l1,r1), Branch (p2,m2,l2,r2) ->
280 if m1 == m2 && p1 == p2 then
281 merge (diff l1 l2) (diff r1 r2)
282 else if m1 > m2 && match_prefix p2 p1 m1 then
283 if zero_bit p2 m1 then
284 merge (diff l1 s2) r1
286 merge l1 (diff r1 s2)
287 else if m1 < m2 && match_prefix p1 p2 m2 then
288 if zero_bit p1 m2 then diff s1 l2 else diff s1 r2
293 (*s All the following operations ([cardinal], [iter], [fold], [for_all],
294 [exists], [filter], [partition], [choose], [elements]) are
295 implemented as for any other kind of binary trees. *)
297 let rec cardinal n = match HNode.node n with
300 | Branch (_,_,t0,t1) -> cardinal t0 + cardinal t1
302 let rec iter f n = match HNode.node n with
305 | Branch (_,_,t0,t1) -> iter f t0; iter f t1
307 let rec fold f s accu = match HNode.node s with
310 | Branch (_,_,t0,t1) -> fold f t0 (fold f t1 accu)
313 let rec for_all p n = match HNode.node n with
316 | Branch (_,_,t0,t1) -> for_all p t0 && for_all p t1
318 let rec exists p n = match HNode.node n with
321 | Branch (_,_,t0,t1) -> exists p t0 || exists p t1
323 let rec filter pr n = match HNode.node n with
325 | Leaf k -> if pr k then n else empty
326 | Branch (p,m,t0,t1) -> branch_ne p m (filter pr t0) (filter pr t1)
329 let rec part (t,f as acc) n = match HNode.node n with
331 | Leaf k -> if p k then (add k t, f) else (t, add k f)
332 | Branch (_,_,t0,t1) -> part (part acc t0) t1
334 part (empty, empty) s
336 let rec choose n = match HNode.node n with
337 | Empty -> raise Not_found
339 | Branch (_, _,t0,_) -> choose t0 (* we know that [t0] is non-empty *)
343 let coll k (l, b, r) =
344 if k < x then add k l, b, r
345 else if k > x then l, b, add k r
348 fold coll s (empty, false, empty)
350 (*s Additional functions w.r.t to [Set.S]. *)
352 let rec intersect s1 s2 = (equal s1 s2) ||
353 match (HNode.node s1,HNode.node s2) with
356 | Leaf k1, _ -> mem k1 s2
357 | _, Leaf k2 -> mem k2 s1
358 | Branch (p1,m1,l1,r1), Branch (p2,m2,l2,r2) ->
359 if m1 == m2 && p1 == p2 then
360 intersect l1 l2 || intersect r1 r2
361 else if m1 < m2 && match_prefix p2 p1 m1 then
362 intersect (if zero_bit p2 m1 then l1 else r1) s2
363 else if m1 > m2 && match_prefix p1 p2 m2 then
364 intersect s1 (if zero_bit p1 m2 then l2 else r2)
370 let rec uncons n = match HNode.node n with
371 | Empty -> raise Not_found
372 | Leaf k -> (k,empty)
373 | Branch (p,m,s,t) -> let h,ns = uncons s in h,branch_ne p m ns t
375 let from_list l = List.fold_left (fun acc e -> add e acc) empty l
380 module Int : S with type elt = int
382 Make ( struct type t = int
384 external hash : t -> int = "%identity"
385 external uid : t -> int = "%identity"
386 let equal : t -> t -> bool = (==)
387 external make : t -> int = "%identity"
388 external node : t -> int = "%identity"