X-Git-Url: http://matita.cs.unibo.it/gitweb/?a=blobdiff_plain;f=matita%2Fcomponents%2Fng_paramodulation%2Forderings.ml;h=d24a5742eeed196035d3c97c9f181e6ab0d35054;hb=48c011f52853dd106dbf9cbbd1b9da61277fba3b;hp=b457832453dd5582b5d44c95c9c292fb68578ac0;hpb=78a7786a2263ecc0440cfcab80b646327364fe2c;p=helm.git

diff --git a/matita/components/ng_paramodulation/orderings.ml b/matita/components/ng_paramodulation/orderings.ml
index b45783245..d24a5742e 100644
--- a/matita/components/ng_paramodulation/orderings.ml
+++ b/matita/components/ng_paramodulation/orderings.ml
@@ -363,10 +363,16 @@ module LPO (B : Terms.Blob) = struct
   let compute_unit_clause_weight = compute_unit_clause_weight;;
   let compute_goal_weight = compute_goal_weight;;
 
+  (*CSC: beware! Imperative cache! *)
+  let cache = Hashtbl.create 101
+
   let rec lpo_le s t = 
     eq_foterm s t || lpo_lt s t 
   
   and lpo_lt s t =
+    try Hashtbl.find cache (s,t)
+    with
+    Not_found -> let res =
     match s,t with
       | _, Terms.Var _ -> false
       | Terms.Var i,_ ->
@@ -399,13 +405,18 @@ module LPO (B : Terms.Blob) = struct
                 compare_args tl1 tl2
             | _ -> assert false
            end
+   in
+    Hashtbl.add cache (s,t) res; res
   ;;
 
   let lpo s t =
+    let res =
     if eq_foterm s t then XEQ
     else if lpo_lt s t then XLT
     else if lpo_lt t s then XGT
     else XINCOMPARABLE
+    in
+     Hashtbl.clear cache; res
   ;;