Active goals are now demodulated after selecting a positive clause.

[helm.git] / helm / software / components / ng_paramodulation / superposition.ml

diff --git a/helm/software/components/ng_paramodulation/superposition.ml b/helm/software/components/ng_paramodulation/superposition.ml
index 4015d4b6d4a37444ce4b0f2ec6bda3473fce8cbb..5b88f90cd7a6f47b7a368102a6b5943984a645c4 100644 (file)
--- a/helm/software/components/ng_paramodulation/superposition.ml
+++ b/helm/software/components/ng_paramodulation/superposition.ml
@@ -22,6 +22,10 @@ module Superposition (B : Terms.Blob) =
     
     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
@@ -106,7 +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)
@@ -123,7 +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
@@ -149,12 +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
@@ -167,11 +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 *)
@@ -179,14 +187,15 @@ 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 then raise (Success (bag, maxvar, clause))
+      if (is_identity_clause clause) || (is_subsumed ~unify:true clause table)
+      then raise (Success (bag, maxvar, clause))
       else bag, clause
     ;;
 
@@ -242,6 +251,7 @@ module Superposition (B : Terms.Blob) =
        bag, maxvar, res
     ;;
 
+    (* Superposes selected equation with equalities in table *)
     let superposition_with_table bag maxvar (id,selected,vl,_) table =
       match selected with 
       | Terms.Predicate _ -> assert false
@@ -275,6 +285,7 @@ module Superposition (B : Terms.Blob) =
     (* 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 = 
@@ -282,6 +293,8 @@ module Superposition (B : Terms.Blob) =
         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 ->
@@ -291,24 +304,36 @@ module Superposition (B : Terms.Blob) =
              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_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 ->