src/HOL/Tools/Sledgehammer/sledgehammer_minimize_isar.ML

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/HOL/Tools/Sledgehammer/sledgehammer_minimize_isar.ML	Fri Jul 12 14:18:06 2013 +0200
@@ -0,0 +1,112 @@
+(*  Title:      HOL/Tools/Sledgehammer/sledgehammer_minimize_isar.ML
+    Author:     Jasmin Blanchette, TU Muenchen
+    Author:     Steffen Juilf Smolka, TU Muenchen
+
+Minimize dependencies (used facts) of Isar proof steps.
+*)
+
+signature SLEDGEHAMMER_MINIMIZE_ISAR =
+sig
+  type preplay_interface = Sledgehammer_Preplay.preplay_interface
+  type isar_proof = Sledgehammer_Proof.isar_proof
+  val minimize_dependencies_and_remove_unrefed_steps :
+    preplay_interface -> isar_proof -> isar_proof
+end
+
+
+structure Sledgehammer_Minimize_Isar : SLEDGEHAMMER_MINIMIZE_ISAR =
+struct
+
+open Sledgehammer_Util
+open Sledgehammer_Proof
+open Sledgehammer_Preplay
+
+val slack = 1.3
+
+fun min_deps_of_step (_ : preplay_interface) (step as Let _) = step
+  | min_deps_of_step {get_time, set_time, preplay_quietly, set_preplay_fail, ...}
+      (step as Prove (qs, xs, l, t, subproofs, By ((lfs, gfs), method))) =
+  (case get_time l of
+    (* don't touch steps that time out *)
+    (true, _) => (set_preplay_fail true; step)
+  | (false, time) =>
+    let
+      fun mk_step_lfs_gfs lfs gfs =
+        Prove (qs, xs, l, t, subproofs, By ((lfs, gfs), method))
+      val mk_step_gfs_lfs = curry (swap #> uncurry mk_step_lfs_gfs)
+
+      fun minimize_facts _ time min_facts [] = (time, min_facts)
+        | minimize_facts mk_step time min_facts (f :: facts) =
+          (case preplay_quietly (time_mult slack time)
+                  (mk_step (min_facts @ facts)) of
+            (true, _) => minimize_facts mk_step time (f :: min_facts) facts
+          | (false, time) => minimize_facts mk_step time min_facts facts)
+
+      val (time, min_lfs) = minimize_facts (mk_step_gfs_lfs gfs) time [] lfs
+      val (time, min_gfs) = minimize_facts (mk_step_lfs_gfs min_lfs) time [] gfs
+
+    in
+      set_time l (false, time);
+      mk_step_lfs_gfs min_lfs min_gfs
+    end)
+
+fun minimize_dependencies_and_remove_unrefed_steps (preplay_interface as
+  {set_time, set_preplay_fail, ...} : preplay_interface) proof =
+  let
+    fun cons_to xs x = x :: xs
+
+    val add_lfs = fold (Ord_List.insert label_ord)
+
+    fun do_proof (Proof (fix, assms, steps)) =
+      let
+        val (refed, steps) = do_steps steps
+      in
+        (refed, Proof (fix, assms, steps))
+      end
+
+    and do_steps steps =
+      let
+        (* the last step is always implicitly referenced *)
+        val (steps, (refed, concl)) =
+          split_last steps
+          ||> do_refed_step
+      in
+        fold_rev do_step steps (refed, [concl])
+      end
+
+    and do_step step (refed, accu) =
+      case label_of_step step of
+        NONE => (refed, step :: accu)
+      | SOME l =>
+          if Ord_List.member label_ord refed l then
+            do_refed_step step
+            |>> Ord_List.union label_ord refed
+            ||> cons_to accu
+          else
+            (set_time l zero_preplay_time; (* remove unrefed step! *)
+             (refed, accu))
+
+    and do_refed_step step =
+      min_deps_of_step preplay_interface step
+      |> do_refed_step'
+
+    and do_refed_step' (Let _) = raise Fail "Sledgehammer_Minimize_Isar"
+      | do_refed_step' (Prove (qs, xs, l, t, subproofs, By ((lfs, gfs), m))) =
+        let
+          val (refed, subproofs) =
+            map do_proof subproofs
+            |> split_list
+            |>> Ord_List.unions label_ord
+            |>> add_lfs lfs
+          val step = Prove (qs, xs, l, t, subproofs, By ((lfs, gfs), m))
+        in
+          (refed, step)
+        end
+
+  in
+    set_preplay_fail false; (* step(s) causing the failure may be removed *)
+    snd (do_proof proof)
+  end
+
+
+end