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=1729919af30556c5e48f78b844bb92be93a4f03c;hpb=a99b3bf44964a6a3d56d752efbdc2c962ce24d08;p=helm.git diff --git a/helm/software/components/ng_paramodulation/superposition.ml b/helm/software/components/ng_paramodulation/superposition.ml index 1729919af..5b88f90cd 100644 --- a/helm/software/components/ng_paramodulation/superposition.ml +++ b/helm/software/components/ng_paramodulation/superposition.ml @@ -19,6 +19,12 @@ 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 @@ -104,7 +110,7 @@ module Superposition (B : Terms.Blob) = 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 side 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) @@ -121,7 +127,8 @@ module Superposition (B : Terms.Blob) = (* 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, _) table = + 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 @@ -147,12 +154,14 @@ module Superposition (B : Terms.Blob) = | _ -> false ;; - let is_subsumed (id, lit, vl, _) table = + let is_subsumed ~unify (id, lit, vl, _) table = match lit with | Terms.Predicate _ -> assert false | Terms.Equation (l,r,ty,_) -> - let lcands = IDX.DT.retrieve_generalizations table l in - let rcands = IDX.DT.retrieve_generalizations table l in + 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 @@ -165,11 +174,12 @@ module Superposition (B : Terms.Blob) = 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 - List.exists - (fun (c, vl1) -> - try ignore(Unif.unification (vl@vl1) vl c t); true - with FoUnif.UnificationFailure _ -> false) - (cands1 @ cands2) + 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 *) @@ -177,13 +187,22 @@ module Superposition (B : Terms.Blob) = let bag, clause = demodulate bag clause table in if is_identity_clause clause then None else - if is_subsumed clause table then None + 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 ===================== *) - let superposition_right table varlist subterm pos context = + (* 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*))) -> @@ -232,63 +251,99 @@ module Superposition (B : Terms.Blob) = 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 Terms.SuperpositionRight + 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 Terms.SuperpositionRight + 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 Terms.SuperpositionRight + 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 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 + 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