2 ||M|| This file is part of HELM, an Hypertextual, Electronic
3 ||A|| Library of Mathematics, developed at the Computer Science
4 ||T|| Department, University of Bologna, Italy.
6 ||T|| HELM is free software; you can redistribute it and/or
7 ||A|| modify it under the terms of the GNU General Public License
8 \ / version 2 or (at your option) any later version.
9 \ / This software is distributed as is, NO WARRANTY.
10 V_______________________________________________________________ *)
14 type aux_comparison = XEQ | XLE | XGE | XLT | XGT | XINCOMPARABLE
20 (* This order relation should be:
21 * - stable for instantiation
22 * - total on ground terms
26 t Terms.foterm -> t Terms.foterm -> Terms.comparison
28 val compute_clause_weight : 't Terms.clause -> int
34 type weight = int * (int * int) list;;
36 let rec eq_foterm f x y =
39 | Terms.Leaf t1, Terms.Leaf t2 -> f t1 t2
40 | Terms.Var i, Terms.Var j -> i = j
41 | Terms.Node l1, Terms.Node l2 -> List.for_all2 (eq_foterm f) l1 l2
45 let string_of_weight (cw, mw) =
48 (List.map (function (m, w) -> Printf.sprintf "(%d,%d)" m w) mw)
50 Printf.sprintf "[%d; %s]" cw s
53 let weight_of_term term =
54 let vars_dict = Hashtbl.create 5 in
55 let rec aux = function
58 let oldw = Hashtbl.find vars_dict i in
59 Hashtbl.replace vars_dict i (oldw+1)
61 Hashtbl.add vars_dict i 1);
64 | Terms.Node l -> List.fold_left (+) 0 (List.map aux l)
68 Hashtbl.fold (fun meta metaw resw -> (meta, metaw)::resw) vars_dict []
72 | (m1, _), (m2, _) -> m1 - m2
74 (w, List.sort compare l) (* from the smallest meta to the bigest *)
77 let compute_literal_weight l =
78 let weight_of_polynomial w m =
80 w + factor * List.fold_left (fun acc (_,occ) -> acc+occ) 0 m
83 | Terms.Predicate t ->
84 let w, m = weight_of_term t in
85 weight_of_polynomial w m
86 | Terms.Equation (_,x,_,Terms.Lt)
87 | Terms.Equation (x,_,_,Terms.Gt) ->
88 let w, m = weight_of_term x in
89 weight_of_polynomial w m
90 | Terms.Equation (l,r,_,Terms.Eq)
91 | Terms.Equation (l,r,_,Terms.Incomparable) ->
92 let wl, ml = weight_of_term l in
93 let wr, mr = weight_of_term r in
94 weight_of_polynomial (wl+wr) (ml@mr)
97 let compute_clause_weight (_,nl,pl,_,_) =
98 List.fold_left (fun acc lit -> compute_literal_weight lit + acc) 0 (nl@pl)
100 let compute_goal_weight = compute_clause_weight;;
102 (* Riazanov: 3.1.5 pag 38 *)
103 (* Compare weights normalized in a new way :
104 * Variables should be sorted from the lowest index to the highest
105 * Variables which do not occur in the term should not be present
106 * in the normalized polynomial
108 let compare_weights (h1, w1) (h2, w2) =
109 let rec aux hdiff (lt, gt) diffs w1 w2 =
111 | ((var1, w1)::tl1) as l1, (((var2, w2)::tl2) as l2) ->
113 let diffs = (w1 - w2) + diffs in
114 let r = Pervasives.compare w1 w2 in
115 let lt = lt or (r < 0) in
116 let gt = gt or (r > 0) in
117 if lt && gt then XINCOMPARABLE else
118 aux hdiff (lt, gt) diffs tl1 tl2
119 else if var1 < var2 then
120 if lt then XINCOMPARABLE else
121 aux hdiff (false,true) (diffs+w1) tl1 l2
123 if gt then XINCOMPARABLE else
124 aux hdiff (true,false) (diffs-w2) l1 tl2
126 if gt then XINCOMPARABLE else
127 aux hdiff (true,false) (diffs-w2) [] tl2
129 if lt then XINCOMPARABLE else
130 aux hdiff (false,true) (diffs+w1) tl1 []
133 if hdiff <= 0 then XLT
134 else if (- diffs) >= hdiff then XLE else XINCOMPARABLE
136 if hdiff >= 0 then XGT
137 else if diffs >= (- hdiff) then XGE else XINCOMPARABLE
139 if hdiff < 0 then XLT
140 else if hdiff > 0 then XGT
143 aux (h1-h2) (false,false) 0 w1 w2
146 (* Riazanov: p. 40, relation >>>
147 * if head_only=true then it is not >>> but helps case 2 of 3.14 p 39 *)
148 let rec aux_ordering b_compare ?(head_only=false) t1 t2 =
150 (* We want to discard any identity equality. *
151 * If we give back XEQ, no inference rule *
152 * will be applied on this equality *)
153 | Terms.Var i, Terms.Var j when i = j ->
157 | _, Terms.Var _ -> XINCOMPARABLE
159 | Terms.Leaf a1, Terms.Leaf a2 ->
160 let cmp = b_compare a1 a2 in
161 if cmp = 0 then XEQ else if cmp < 0 then XLT else XGT
162 | Terms.Leaf _, Terms.Node _ -> XLT
163 | Terms.Node _, Terms.Leaf _ -> XGT
165 | Terms.Node l1, Terms.Node l2 ->
169 | _, [] -> (* XGT *) assert false (* hd symbols were eq *)
170 | [], _ -> (* XLT *) assert false (* hd symbols were eq *)
171 | hd1::tl1, hd2::tl2 ->
172 let o = aux_ordering b_compare ~head_only hd1 hd2 in
173 if o = XEQ && not head_only then cmp tl1 tl2 else o
178 let compare_terms o x y =
180 | XINCOMPARABLE -> Terms.Incomparable
187 module NRKBO (B : Terms.Blob) = struct
193 let eq_foterm = eq_foterm B.eq;;
195 let compute_clause_weight = compute_clause_weight;;
196 let compute_goal_weight = compute_goal_weight;;
198 (* Riazanov: p. 40, relation >_n *)
199 let nonrec_kbo t1 t2 =
200 let w1 = weight_of_term t1 in
201 let w2 = weight_of_term t2 in
202 match compare_weights w1 w2 with
203 | XLE -> (* this is .> *)
204 if aux_ordering B.compare t1 t2 = XLT then XLT else XINCOMPARABLE
206 if aux_ordering B.compare t1 t2 = XGT then XGT else XINCOMPARABLE
207 | XEQ -> aux_ordering B.compare t1 t2
211 let compare_terms = compare_terms nonrec_kbo;;
213 let profiler = HExtlib.profile ~enable:true "compare_terms(nrkbo)";;
214 let compare_terms x y =
215 profiler.HExtlib.profile (compare_terms x) y
220 module KBO (B : Terms.Blob) = struct
226 let eq_foterm = eq_foterm B.eq;;
228 let compute_clause_weight = compute_clause_weight;;
229 let compute_goal_weight = compute_goal_weight;;
231 (* Riazanov: p. 38, relation > *)
233 let aux = aux_ordering B.compare ~head_only:true in
239 | hd1::tl1, hd2::tl2 ->
240 let o = kbo hd1 hd2 in
241 if o = XEQ then cmp tl1 tl2
244 let w1 = weight_of_term t1 in
245 let w2 = weight_of_term t2 in
246 let comparison = compare_weights w1 w2 in
247 match comparison with
251 else if r = XEQ then (
253 | Terms.Node (_::tl1), Terms.Node (_::tl2) ->
254 if cmp tl1 tl2 = XLT then XLT else XINCOMPARABLE
255 | _, _ -> assert false
260 else if r = XEQ then (
262 | Terms.Node (_::tl1), Terms.Node (_::tl2) ->
263 if cmp tl1 tl2 = XGT then XGT else XINCOMPARABLE
264 | _, _ -> assert false
270 | Terms.Node (_::tl1), Terms.Node (_::tl2) -> cmp tl1 tl2
271 | _, _ -> XINCOMPARABLE
276 let compare_terms = compare_terms kbo;;
278 let profiler = HExtlib.profile ~enable:true "compare_terms(kbo)";;
279 let compare_terms x y =
280 profiler.HExtlib.profile (compare_terms x) y
285 module LPO (B : Terms.Blob) = struct
291 let eq_foterm = eq_foterm B.eq;;
293 let compute_clause_weight = compute_clause_weight;;
294 let compute_goal_weight = compute_goal_weight;;
298 | s, t when eq_foterm s t ->
300 | Terms.Var _, Terms.Var _ ->
303 if (List.mem i (Terms.vars_of_term s)) then XGT
306 if (List.mem i (Terms.vars_of_term t)) then XLT
308 | Terms.Node (hd1::tl1), Terms.Node (hd2::tl2) ->
309 let rec ge_subterm t ol = function
314 | XGT | XEQ -> (true,res::ol)
315 | o -> ge_subterm t (o::ol) tl
317 let (res, l_ol) = ge_subterm t [] tl1 in
319 else let (res, r_ol) = ge_subterm s [] tl2 in
322 let rec check_subterms t = function
325 if o = XLT then check_subterms t (ol,tl)
328 if lpo x t = XLT then check_subterms t ([],tl)
331 match aux_ordering B.compare hd1 hd2 with
332 | XGT -> if check_subterms s (r_ol,tl2) then XGT
334 | XLT -> if check_subterms t (l_ol,tl1) then XLT
337 let lex = List.fold_left2
338 (fun acc si ti -> if acc = XEQ then lpo si ti else acc)
343 if List.for_all (fun x -> lpo s x = XGT) tl2 then XGT
346 if List.for_all (fun x -> lpo x t = XLT) tl1 then XLT
349 | XINCOMPARABLE -> XINCOMPARABLE
352 | _,_ -> aux_ordering B.compare s t
356 let compare_terms = compare_terms lpo;;
358 let profiler = HExtlib.profile ~enable:true "compare_terms(lpo)";;
359 let compare_terms x y =
360 profiler.HExtlib.profile (compare_terms x) y