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 (***************************************************************************)
18 | Branch of int * int * t * t
25 let hash_node = function
28 (* power of 2 +/- 1 are fast ! *)
30 (b lsl 1)+ b + i+(i lsl 4) + (l.key lsl 5)-l.key
31 + (r.key lsl 7) - r.key
32 let hash_node x = (hash_node x) land max_int
33 let equal x y = match (x.node,y.node) with
35 | Leaf k1, Leaf k2 when k1 == k2 -> true
36 | Branch(p1,m1,l1,r1), Branch(p2,m2,l2,r2) when m1==m2 && p1==p2 &&
37 (l1.id == l2.id) && (r1.id == r2.id) -> true
41 module WH =Weak.Make(Node)
43 include Hashtbl.Make(Node)
49 let pool = WH.create 4093
51 (* Neat trick thanks to Alain Frisch ! *)
53 let gen_uid () = Oo.id (object end)
55 let empty = { id = gen_uid ();
59 let _ = WH.add pool empty
61 let is_empty s = s.id==0
64 let v = { id = gen_uid ();
65 key = Node.hash_node n;
72 let branch p m l r = norm (Branch(p,m,l,r))
73 let leaf k = norm (Leaf k)
75 (* To enforce the invariant that a branch contains two non empty sub-trees *)
76 let branch_ne = function
77 | (_,_,e,t) when is_empty e -> t
78 | (_,_,t,e) when is_empty e -> t
79 | (p,m,t0,t1) -> branch p m t0 t1
81 (********** from here on, only use the smart constructors *************)
83 let zero_bit k m = (k land m) == 0
85 let singleton k = if k < 0 then failwith "singleton" else leaf k
87 let rec mem k n = match n.node with
90 | Branch (p, _, l, r) -> if k <= p then mem k l else mem k r
92 let rec min_elt n = match n.node with
93 | Empty -> raise Not_found
95 | Branch (_,_,s,_) -> min_elt s
97 let rec max_elt n = match n.node with
98 | Empty -> raise Not_found
100 | Branch (_,_,_,t) -> max_elt t
103 let rec elements_aux acc n = match n.node with
106 | Branch (_,_,l,r) -> elements_aux (elements_aux acc r) l
110 let mask k m = (k lor (m-1)) land (lnot m)
112 let naive_highest_bit x =
115 if i = 0 then 1 else if x lsr i = 1 then 1 lsl i else loop (i-1)
119 let hbit = Array.init 256 naive_highest_bit
121 let highest_bit_32 x =
122 let n = x lsr 24 in if n != 0 then Array.unsafe_get hbit n lsl 24
123 else let n = x lsr 16 in if n != 0 then Array.unsafe_get hbit n lsl 16
124 else let n = x lsr 8 in if n != 0 then Array.unsafe_get hbit n lsl 8
125 else Array.unsafe_get hbit x
127 let highest_bit_64 x =
128 let n = x lsr 32 in if n != 0 then (highest_bit_32 n) lsl 32
129 else highest_bit_32 x
131 let highest_bit = match Sys.word_size with
132 | 32 -> highest_bit_32
133 | 64 -> highest_bit_64
136 let branching_bit p0 p1 = highest_bit (p0 lxor p1)
138 let join p0 t0 p1 t1 =
139 let m = branching_bit p0 p1 in
140 if zero_bit p0 m then
141 branch (mask p0 m) m t0 t1
143 branch (mask p0 m) m t1 t0
145 let match_prefix k p m = (mask k m) == p
148 let rec ins n = match n.node with
150 | Leaf j -> if j == k then n else join k (leaf k) j n
151 | Branch (p,m,t0,t1) ->
152 if match_prefix k p m then
154 branch p m (ins t0) t1
156 branch p m t0 (ins t1)
163 let rec rmv n = match n.node with
165 | Leaf j -> if k == j then empty else n
166 | Branch (p,m,t0,t1) ->
167 if match_prefix k p m then
169 branch_ne (p, m, rmv t0, t1)
171 branch_ne (p, m, t0, rmv t1)
177 (* should run in O(1) thanks to Hash consing *)
179 let equal a b = a==b || a.id == b.id
181 let compare a b = if a == b then 0 else a.id - b.id
185 if (equal s t) (* This is cheap thanks to hash-consing *)
188 match s.node,t.node with
191 | Leaf k, _ -> add k t
192 | _, Leaf k -> add k s
193 | Branch (p,m,s0,s1), Branch (q,n,t0,t1) ->
194 if m == n && match_prefix q p m then
195 branch p m (merge s0 t0) (merge s1 t1)
196 else if m > n && match_prefix q p m then
198 branch p m (merge s0 t) s1
200 branch p m s0 (merge s1 t)
201 else if m < n && match_prefix p q n then
203 branch q n (merge s t0) t1
205 branch q n t0 (merge s t1)
207 (* The prefixes disagree. *)
212 let rec subset s1 s2 = (equal s1 s2) ||
213 match (s1.node,s2.node) with
216 | Leaf k1, _ -> mem k1 s2
217 | Branch _, Leaf _ -> false
218 | Branch (p1,m1,l1,r1), Branch (p2,m2,l2,r2) ->
219 if m1 == m2 && p1 == p2 then
220 subset l1 l2 && subset r1 r2
221 else if m1 < m2 && match_prefix p1 p2 m2 then
222 if zero_bit p1 m2 then
223 subset l1 l2 && subset r1 l2
225 subset l1 r2 && subset r1 r2
232 let rec inter s1 s2 =
236 match (s1.node,s2.node) with
239 | Leaf k1, _ -> if mem k1 s2 then s1 else empty
240 | _, Leaf k2 -> if mem k2 s1 then s2 else empty
241 | Branch (p1,m1,l1,r1), Branch (p2,m2,l2,r2) ->
242 if m1 == m2 && p1 == p2 then
243 merge (inter l1 l2) (inter r1 r2)
244 else if m1 > m2 && match_prefix p2 p1 m1 then
245 inter (if zero_bit p2 m1 then l1 else r1) s2
246 else if m1 < m2 && match_prefix p1 p2 m2 then
247 inter s1 (if zero_bit p1 m2 then l2 else r2)
255 match (s1.node,s2.node) with
258 | Leaf k1, _ -> if mem k1 s2 then empty else s1
259 | _, Leaf k2 -> remove k2 s1
260 | Branch (p1,m1,l1,r1), Branch (p2,m2,l2,r2) ->
261 if m1 == m2 && p1 == p2 then
262 merge (diff l1 l2) (diff r1 r2)
263 else if m1 > m2 && match_prefix p2 p1 m1 then
264 if zero_bit p2 m1 then
265 merge (diff l1 s2) r1
267 merge l1 (diff r1 s2)
268 else if m1 < m2 && match_prefix p1 p2 m2 then
269 if zero_bit p1 m2 then diff s1 l2 else diff s1 r2
276 (*s All the following operations ([cardinal], [iter], [fold], [for_all],
277 [exists], [filter], [partition], [choose], [elements]) are
278 implemented as for any other kind of binary trees. *)
280 let rec cardinal n = match n.node with
283 | Branch (_,_,t0,t1) -> cardinal t0 + cardinal t1
285 let rec iter f n = match n.node with
288 | Branch (_,_,t0,t1) -> iter f t0; iter f t1
290 let rec fold f s accu = match s.node with
293 | Branch (_,_,t0,t1) -> fold f t0 (fold f t1 accu)
295 let rec for_all p n = match n.node with
298 | Branch (_,_,t0,t1) -> for_all p t0 && for_all p t1
300 let rec exists p n = match n.node with
303 | Branch (_,_,t0,t1) -> exists p t0 || exists p t1
305 let rec filter pr n = match n.node with
307 | Leaf k -> if pr k then n else empty
308 | Branch (p,m,t0,t1) -> branch_ne (p, m, filter pr t0, filter pr t1)
311 let rec part (t,f as acc) n = match n.node with
313 | Leaf k -> if p k then (add k t, f) else (t, add k f)
314 | Branch (_,_,t0,t1) -> part (part acc t0) t1
316 part (empty, empty) s
318 let rec choose n = match n.node with
319 | Empty -> raise Not_found
321 | Branch (_, _,t0,_) -> choose t0 (* we know that [t0] is non-empty *)
325 let coll k (l, b, r) =
326 if k < x then add k l, b, r
327 else if k > x then l, b, add k r
330 fold coll s (empty, false, empty)
335 Printf.eprintf "{ id = %i; key = %i ; node=" n.id n.key;
337 | Empty -> Printf.eprintf "Empty; }\n"
338 | Leaf k -> Printf.eprintf "Leaf %i; }\n" k
339 | Branch (p,m,l,r) ->
340 Printf.eprintf "Branch(%i,%i,id=%i,id=%i); }\n"
346 let make l = List.fold_left (fun acc e -> add e acc ) empty l
349 (*s Additional functions w.r.t to [Set.S]. *)
351 let rec intersect s1 s2 = (equal s1 s2) ||
352 match (s1.node,s2.node) with
355 | Leaf k1, _ -> mem k1 s2
356 | _, Leaf k2 -> mem k2 s1
357 | Branch (p1,m1,l1,r1), Branch (p2,m2,l2,r2) ->
358 if m1 == m2 && p1 == p2 then
359 intersect l1 l2 || intersect r1 r2
360 else if m1 < m2 && match_prefix p2 p1 m1 then
361 intersect (if zero_bit p2 m1 then l1 else r1) s2
362 else if m1 > m2 && match_prefix p1 p2 m2 then
363 intersect s1 (if zero_bit p1 m2 then l2 else r2)
370 let from_list l = List.fold_left (fun acc i -> add i acc) empty l