X-Git-Url: http://matita.cs.unibo.it/gitweb/?a=blobdiff_plain;f=helm%2Fsoftware%2Fcomponents%2Fng_paramodulation%2Fsuperposition.ml;h=5b88f90cd7a6f47b7a368102a6b5943984a645c4;hb=4ae7d510a430a2a6929f973d36b993d528772d64;hp=6b98ed5be24667a5c6be75049bab6f71ff0de53e;hpb=40ce8d1c14808ea7608ee2988bd9aba77ddf8200;p=helm.git diff --git a/helm/software/components/ng_paramodulation/superposition.ml b/helm/software/components/ng_paramodulation/superposition.ml index 6b98ed5be..5b88f90cd 100644 --- a/helm/software/components/ng_paramodulation/superposition.ml +++ b/helm/software/components/ng_paramodulation/superposition.ml @@ -19,7 +19,41 @@ module Superposition (B : Terms.Blob) = module Order = Orderings.Orderings(B) module Utils = FoUtils.Utils(B) module Pp = Pp.Pp(B) + + exception Success of B.t Terms.bag * int * B.t Terms.unit_clause + let debug s = + ()(* prerr_endline s *) + ;; + + let rec list_first f = function + | [] -> None + | x::tl -> match f x with Some _ as x -> x | _ -> list_first f tl + ;; + + let first_position pos ctx t f = + let rec aux pos ctx = function + | Terms.Leaf _ as t -> f t pos ctx + | Terms.Var _ -> None + | Terms.Node l as t-> + match f t pos ctx with + | Some _ as x -> x + | None -> + let rec first pre post = function + | [] -> None + | t :: tl -> + let newctx = fun x -> ctx (Terms.Node (pre@[x]@post)) in + match aux (List.length pre :: pos) newctx t with + | Some _ as x -> x + | None -> + if post = [] then None (* tl is also empty *) + else first (pre @ [t]) (List.tl post) tl + in + first [] (List.tl l) l + in + aux pos ctx t + ;; + let all_positions pos ctx t f = let rec aux pos ctx = function | Terms.Leaf _ as t -> f t pos ctx @@ -38,15 +72,143 @@ module Superposition (B : Terms.Blob) = in aux pos ctx t ;; + + let build_clause bag filter rule t subst vl id id2 pos dir = + let proof = Terms.Step(rule,id,id2,dir,pos,subst) in + let t = Subst.apply_subst subst t in + if filter t then + let literal = + match t with + | Terms.Node [ Terms.Leaf eq ; ty; l; r ] when B.eq B.eqP eq -> + let o = Order.compare_terms l r in + Terms.Equation (l, r, ty, o) + | t -> Terms.Predicate t + in + let bag, uc = + Utils.add_to_bag bag (0, literal, vl, proof) + in + Some (bag, uc) + else + ((*prerr_endline ("Filtering: " ^ Pp.pp_foterm t);*)None) + ;; + + + (* ============ simplification ================= *) - let superposition_right table varlist subterm pos context = + let demod table varlist subterm pos context = + let cands = IDX.DT.retrieve_generalizations table subterm in + list_first + (fun (dir, (id,lit,vl,_)) -> + match lit with + | Terms.Predicate _ -> assert false + | Terms.Equation (l,r,_,o) -> + let side, newside = if dir=Terms.Left2Right then l,r else r,l in + try + let subst, varlist = + Unif.unification (varlist@vl) varlist subterm side + in + if o = Terms.Incomparable then + let side = Subst.apply_subst subst side in + let newside = Subst.apply_subst subst newside in + let o = Order.compare_terms newside side in + (* Riazanov, pp. 45 (ii) *) + if o = Terms.Lt then + Some (context newside, subst, varlist, id, pos, dir) + else + ((*prerr_endline ("Filtering: " ^ + Pp.pp_foterm side ^ " =(< || =)" ^ + Pp.pp_foterm newside ^ " coming from " ^ + Pp.pp_unit_clause uc );*)None) + else + Some (context newside, subst, varlist, id, pos, dir) + with FoUnif.UnificationFailure _ -> None) + (IDX.ClauseSet.elements cands) + ;; + + (* XXX: possible optimization, if the literal has a "side" already + * in normal form we should not traverse it again *) + let demodulate_once bag (id, literal, vl, pr) table = + debug ("Demodulating : " ^ (Pp.pp_unit_clause (id, literal, vl, pr))); + let t = + match literal with + | Terms.Predicate t -> t + | Terms.Equation (l,r,ty,_) -> Terms.Node [ Terms.Leaf B.eqP; ty; l; r ] + in + match first_position [] (fun x -> x) t (demod table vl) with + | None -> None + | Some (newt, subst, varlist, id2, pos, dir) -> + build_clause bag (fun _ -> true) Terms.Demodulation + newt subst varlist id id2 pos dir + ;; + + let rec demodulate bag clause table = + match demodulate_once bag clause table with + | None -> bag, clause + | Some (bag, clause) -> demodulate bag clause table + ;; + + (* move away *) + let is_identity_clause = function + | _, Terms.Equation (_,_,_,Terms.Eq), _, _ -> true + | _, Terms.Predicate _, _, _ -> assert false + | _ -> false + ;; + + let is_subsumed ~unify (id, lit, vl, _) table = + match lit with + | Terms.Predicate _ -> assert false + | Terms.Equation (l,r,ty,_) -> + let retrieve = if unify then IDX.DT.retrieve_unifiables + else IDX.DT.retrieve_generalizations in + let lcands = retrieve table l in + let rcands = retrieve table r in + let f b c = + let dir, l, r, vl = + match c with + | (d, (_,Terms.Equation (l,r,ty,_),vl,_))-> d, l, r, vl + |_ -> assert false + in + let l, r = if (dir = Terms.Left2Right) = b then l,r else r,l in + Terms.Node [ Terms.Leaf B.eqP; ty; l; r ], vl + in + let cands1 = List.map (f true) (IDX.ClauseSet.elements lcands) in + let cands2 = List.map (f false) (IDX.ClauseSet.elements rcands) in + let t = Terms.Node [ Terms.Leaf B.eqP; ty; l; r ] in + let locked_vars = if unify then [] else vl in + List.exists + (fun (c, vl1) -> + try ignore(Unif.unification (vl@vl1) locked_vars c t); true + with FoUnif.UnificationFailure _ -> false) + (cands1 @ cands2) + ;; + + (* demodulate and check for subsumption *) + let forward_simplify table bag clause = + let bag, clause = demodulate bag clause table in + if is_identity_clause clause then None + else + if is_subsumed ~unify:false clause table then None + else Some (bag, clause) + ;; + + (* this is like forward_simplify but raises Success *) + let backward_simplify maxvar table bag clause = + let bag, clause = demodulate bag clause table in + if (is_identity_clause clause) || (is_subsumed ~unify:true clause table) + then raise (Success (bag, maxvar, clause)) + else bag, clause + ;; + + (* =================== inference ===================== *) + + (* this is OK for both the sup_left and sup_right inference steps *) + let superposition table varlist subterm pos context = let cands = IDX.DT.retrieve_unifiables table subterm in HExtlib.filter_map (fun (dir, (id,lit,vl,_ (*as uc*))) -> match lit with | Terms.Predicate _ -> assert false | Terms.Equation (l,r,_,o) -> - assert(o <> Terms.Eq); let side, newside = if dir=Terms.Left2Right then l,r else r,l in try let subst, varlist = @@ -70,90 +232,118 @@ module Superposition (B : Terms.Blob) = (IDX.ClauseSet.elements cands) ;; - let build_new_clause bag maxvar filter t subst vl id id2 pos dir = + let build_new_clause bag maxvar filter rule t subst vl id id2 pos dir = let maxvar, vl, relocsubst = Utils.relocate maxvar vl in let subst = Subst.concat relocsubst subst in - let proof = Terms.Step(Terms.SuperpositionRight,id,id2,dir,pos,subst) in - let t = Subst.apply_subst subst t in - if filter t then - let literal = - match t with - | Terms.Node [ Terms.Leaf eq ; ty; l; r ] when B.eq B.eqP eq -> - let o = Order.compare_terms l r in - Terms.Equation (l, r, ty, o) - | t -> Terms.Predicate t - in - let bag, uc = - Utils.add_to_bag bag (0, literal, vl, proof) - in - Some (bag, maxvar, uc) - else - ((*prerr_endline ("Filtering: " ^ Pp.pp_foterm t);*)None) + match build_clause bag filter rule t subst vl id id2 pos dir with + | Some (bag, c) -> Some ((bag, maxvar), c) + | None -> None ;; - let fold_build_new_clause bag maxvar id filter res = - let maxvar, bag, new_clauses = - List.fold_left - (fun (maxvar, bag, acc) (t,subst,vl,id2,pos,dir) -> - match build_new_clause bag maxvar filter t subst vl id id2 pos dir - with Some (bag, maxvar, uc) -> maxvar, bag, uc::acc - | None -> maxvar, bag, acc) - (maxvar, bag, []) res + + let fold_build_new_clause bag maxvar id rule filter res = + let (bag, maxvar), res = + HExtlib.filter_map_acc + (fun (bag, maxvar) (t,subst,vl,id2,pos,dir) -> + build_new_clause bag maxvar filter rule t subst vl id id2 pos dir) + (bag, maxvar) res in - bag, maxvar, new_clauses + bag, maxvar, res ;; - let superposition_right_with_table bag maxvar (id,selected,vl,_) table = + (* Superposes selected equation with equalities in table *) + let superposition_with_table bag maxvar (id,selected,vl,_) table = match selected with | Terms.Predicate _ -> assert false | Terms.Equation (l,r,ty,Terms.Lt) -> - fold_build_new_clause bag maxvar id (fun _ -> true) + fold_build_new_clause bag maxvar id Terms.Superposition + (fun _ -> true) (all_positions [3] (fun x -> Terms.Node [ Terms.Leaf B.eqP; ty; l; x ]) - r (superposition_right table vl)) + r (superposition table vl)) | Terms.Equation (l,r,ty,Terms.Gt) -> - fold_build_new_clause bag maxvar id (fun _ -> true) + fold_build_new_clause bag maxvar id Terms.Superposition + (fun _ -> true) (all_positions [2] (fun x -> Terms.Node [ Terms.Leaf B.eqP; ty; x; r ]) - l (superposition_right table vl)) + l (superposition table vl)) | Terms.Equation (l,r,ty,Terms.Incomparable) -> - fold_build_new_clause bag maxvar id + fold_build_new_clause bag maxvar id Terms.Superposition (function (* Riazanov: p.33 condition (iv) *) | Terms.Node [Terms.Leaf eq; ty; l; r ] when B.eq B.eqP eq -> Order.compare_terms l r <> Terms.Eq | _ -> assert false) ((all_positions [3] (fun x -> Terms.Node [ Terms.Leaf B.eqP; ty; l; x ]) - r (superposition_right table vl)) @ + r (superposition table vl)) @ (all_positions [2] (fun x -> Terms.Node [ Terms.Leaf B.eqP; ty; x; r ]) - l (superposition_right table vl))) + l (superposition table vl))) | _ -> assert false ;; (* the current equation is normal w.r.t. demodulation with atable * (and is not the identity) *) - let superposition_right bag maxvar current (alist,atable) = + let infer_right bag maxvar current (alist,atable) = + (* We demodulate actives clause with current *) let ctable = IDX.index_unit_clause IDX.DT.empty current in + let bag, (alist, atable) = + let bag, alist = + HExtlib.filter_map_acc (forward_simplify ctable) bag alist + in + bag, (alist, List.fold_left IDX.index_unit_clause IDX.DT.empty alist) + in + debug "Simplified active clauses with fact"; + (* We superpose active clauses with current *) let bag, maxvar, new_clauses = List.fold_left (fun (bag, maxvar, acc) active -> let bag, maxvar, newc = - superposition_right_with_table bag maxvar active ctable + superposition_with_table bag maxvar active ctable in bag, maxvar, newc @ acc) (bag, maxvar, []) alist in + debug "First superpositions"; + (* We add current to active clauses so that it can be * + * superposed with itself *) let alist, atable = current :: alist, IDX.index_unit_clause atable current in + debug "Indexed"; let fresh_current, maxvar = Utils.fresh_unit_clause maxvar current in + (* We need to put fresh_current into the bag so that all * + * variables clauses refer to are known. *) + let bag, fresh_current = Utils.add_to_bag bag fresh_current in + (* We superpose current with active clauses *) let bag, maxvar, additional_new_clauses = - superposition_right_with_table bag maxvar fresh_current atable + superposition_with_table bag maxvar fresh_current atable + in + debug "Another superposition"; + let new_clauses = new_clauses @ additional_new_clauses in + let bag, new_clauses = + HExtlib.filter_map_acc (forward_simplify atable) bag new_clauses in - bag, maxvar, (alist, atable), new_clauses @ additional_new_clauses + debug "Demodulated new clauses"; + bag, maxvar, (alist, atable), new_clauses ;; - + + let infer_left bag maxvar goal (_alist, atable) = + (* We superpose the goal with active clauses *) + let bag, maxvar, new_goals = + superposition_with_table bag maxvar goal atable + in + (* We demodulate the goal with active clauses *) + let bag, new_goals = + List.fold_left + (fun (bag, acc) g -> + let bag, g = demodulate bag g atable in + bag, g :: acc) + (bag, []) new_goals + in + bag, maxvar, List.rev new_goals + ;; + end