(*  Title:      HOL/Tools/Sledgehammer/sledgehammer_minimize.ML

     Author:     Philipp Meyer, TU Muenchen

     Author:     Jasmin Blanchette, TU Muenchen

 Minimization of fact list for Metis using external provers.

 *)

 signature SLEDGEHAMMER_MINIMIZE =

 sig

   type locality = ATP_Translate.locality

   type play = ATP_Reconstruct.play

   type params = Sledgehammer_Provers.params

   val binary_min_facts : int Config.T

   val minimize_facts :

     string -> params -> bool -> int -> int -> Proof.state

     -> ((string * locality) * thm list) list

     -> ((string * locality) * thm list) list option

        * ((unit -> play) * (play -> string) * string)

   val run_minimize :

     params -> int -> (Facts.ref * Attrib.src list) list -> Proof.state -> unit

 end;

 structure Sledgehammer_Minimize : SLEDGEHAMMER_MINIMIZE =

 struct

 open ATP_Util

 open ATP_Proof

 open ATP_Translate

 open ATP_Reconstruct

 open Sledgehammer_Util

 open Sledgehammer_Filter

 open Sledgehammer_Provers

 (* wrapper for calling external prover *)

 fun n_facts names =

   let val n = length names in

     string_of_int n ^ " fact" ^ plural_s n ^

     (if n > 0 then

        ": " ^ (names |> map fst |> sort_distinct string_ord

                      |> space_implode " ")

      else

        "")

   end

 fun print silent f = if silent then () else Output.urgent_message (f ())

 fun test_facts ({debug, verbose, overlord, provers, max_mono_iters,

                  max_new_mono_instances, type_enc, lam_trans, isar_proof,

                  isar_shrink_factor, preplay_timeout, ...} : params)

                silent (prover : prover) timeout i n state facts =

   let

     val _ =

       print silent (fn () =>

           "Testing " ^ n_facts (map fst facts) ^

           (if verbose then " (timeout: " ^ string_from_time timeout ^ ")"

            else "") ^ "...")

     val {goal, ...} = Proof.goal state

     val facts =

       facts |> maps (fn (n, ths) => ths |> map (Untranslated_Fact o pair n))

     val params =

       {debug = debug, verbose = verbose, overlord = overlord, blocking = true,

        provers = provers, type_enc = type_enc, sound = true,

        lam_trans = lam_trans, relevance_thresholds = (1.01, 1.01),

        max_relevant = SOME (length facts), max_mono_iters = max_mono_iters,

        max_new_mono_instances = max_new_mono_instances, isar_proof = isar_proof,

        isar_shrink_factor = isar_shrink_factor, slicing = false,

        timeout = timeout, preplay_timeout = preplay_timeout, expect = ""}

     val problem =

       {state = state, goal = goal, subgoal = i, subgoal_count = n,

        facts = facts, smt_filter = NONE}

     val result as {outcome, used_facts, run_time, ...} =

       prover params (K (K (K ""))) problem

   in

     print silent

           (fn () =>

               case outcome of

                 SOME failure => string_for_failure failure

               | NONE =>

                 "Found proof" ^

                  (if length used_facts = length facts then ""

                   else " with " ^ n_facts used_facts) ^

                  " (" ^ string_from_time run_time ^ ").");

     result

   end

 (* minimalization of facts *)

 (* Give the external prover some slack. The ATP gets further slack because the

    Sledgehammer preprocessing time is included in the estimate below but isn't

    part of the timeout. *)

 val slack_msecs = 200

 fun new_timeout timeout run_time =

   Int.min (Time.toMilliseconds timeout,

            Time.toMilliseconds run_time + slack_msecs)

   |> Time.fromMilliseconds

 (* The linear algorithm usually outperforms the binary algorithm when over 60%

    of the facts are actually needed. The binary algorithm is much more

    appropriate for provers that cannot return the list of used facts and hence

    returns all facts as used. Since we cannot know in advance how many facts are

    actually needed, we heuristically set the threshold to 10 facts. *)

 val binary_min_facts =

   Attrib.setup_config_int @{binding sledgehammer_minimize_binary_min_facts}

                           (K 20)

 fun linear_minimize test timeout result xs =

   let

     fun min _ [] p = p

       | min timeout (x :: xs) (seen, result) =

         case test timeout (xs @ seen) of

           result as {outcome = NONE, used_facts, run_time, ...}

           : prover_result =>

           min (new_timeout timeout run_time) (filter_used_facts used_facts xs)

               (filter_used_facts used_facts seen, result)

         | _ => min timeout xs (x :: seen, result)

   in min timeout xs ([], result) end

 fun binary_minimize test timeout result xs =

   let

     fun min depth (result as {run_time, ...} : prover_result) sup

             (xs as _ :: _ :: _) =

         let

           val (l0, r0) = chop (length xs div 2) xs

 (*

           val _ = warning (replicate_string depth " " ^ "{ " ^

                            "sup: " ^ n_facts (map fst sup))

           val _ = warning (replicate_string depth " " ^ "  " ^

                            "xs: " ^ n_facts (map fst xs))

           val _ = warning (replicate_string depth " " ^ "  " ^

                            "l0: " ^ n_facts (map fst l0))

           val _ = warning (replicate_string depth " " ^ "  " ^

                            "r0: " ^ n_facts (map fst r0))

 *)

           val depth = depth + 1

           val timeout = new_timeout timeout run_time

         in

           case test timeout (sup @ l0) of

             result as {outcome = NONE, used_facts, ...} =>

             min depth result (filter_used_facts used_facts sup)

                       (filter_used_facts used_facts l0)

           | _ =>

             case test timeout (sup @ r0) of

               result as {outcome = NONE, used_facts, ...} =>

               min depth result (filter_used_facts used_facts sup)

                         (filter_used_facts used_facts r0)

             | _ =>

               let

                 val (sup_r0, (l, result)) = min depth result (sup @ r0) l0

                 val (sup, r0) =

                   (sup, r0) |> pairself (filter_used_facts (map fst sup_r0))

                 val (sup_l, (r, result)) = min depth result (sup @ l) r0

                 val sup = sup |> filter_used_facts (map fst sup_l)

               in (sup, (l @ r, result)) end

         end

 (*

         |> tap (fn _ => warning (replicate_string depth " " ^ "}"))

 *)

       | min _ result sup xs = (sup, (xs, result))

   in

     case snd (min 0 result [] xs) of

       ([x], result as {run_time, ...}) =>

       (case test (new_timeout timeout run_time) [] of

          result as {outcome = NONE, ...} => ([], result)

        | _ => ([x], result))

     | p => p

   end

 fun minimize_facts prover_name (params as {timeout, ...}) silent i n state

                    facts =

   let

     val ctxt = Proof.context_of state

     val prover =

       get_prover ctxt (if silent then Auto_Minimize else Minimize) prover_name

     val _ = print silent (fn () => "Sledgehammer minimizer: " ^

                                    quote prover_name ^ ".")

     fun test timeout = test_facts params silent prover timeout i n state

   in

     (case test timeout facts of

        result as {outcome = NONE, used_facts, run_time, ...} =>

        let

          val facts = filter_used_facts used_facts facts

          val min =

            if length facts >= Config.get ctxt binary_min_facts then

              binary_minimize

            else

              linear_minimize

          val (min_facts, {preplay, message, message_tail, ...}) =

            min test (new_timeout timeout run_time) result facts

          val _ = print silent (fn () => cat_lines

            ["Minimized to " ^ n_facts (map fst min_facts)] ^

             (case length (filter (curry (op =) Chained o snd o fst) min_facts) of

                0 => ""

              | n => "\n(including " ^ string_of_int n ^ " chained)") ^ ".")

        in (SOME min_facts, (preplay, message, message_tail)) end

      | {outcome = SOME TimedOut, preplay, ...} =>

        (NONE,

         (preplay,

          fn _ => "Timeout: You can increase the time limit using the \

                  \\"timeout\" option (e.g., \"timeout = " ^

                  string_of_int (10 + Time.toMilliseconds timeout div 1000) ^

                  "\").",

          ""))

      | {preplay, message, ...} =>

        (NONE, (preplay, prefix "Prover error: " o message, "")))

     handle ERROR msg =>

            (NONE, (K (Failed_to_Play plain_metis), fn _ => "Error: " ^ msg, ""))

   end

 fun run_minimize (params as {provers, ...}) i refs state =

   let

     val ctxt = Proof.context_of state

     val reserved = reserved_isar_keyword_table ()

     val chained_ths = normalize_chained_theorems (#facts (Proof.goal state))

     val facts =

       refs

       |> maps (map (apsnd single) o fact_from_ref ctxt reserved chained_ths)

   in

     case subgoal_count state of

       0 => Output.urgent_message "No subgoal!"

     | n => case provers of

              [] => error "No prover is set."

            | prover :: _ =>

              (kill_provers ();

               minimize_facts prover params false i n state facts

               |> (fn (_, (preplay, message, message_tail)) =>

                      message (preplay ()) ^ message_tail

                      |> Output.urgent_message))

   end

 end;