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

    Author:     Jasmin Blanchette, TU Muenchen

Sledgehammer's machine-learning-based relevance filter (MaSh).

*)

signature SLEDGEHAMMER_MASH =

sig

  type stature = ATP_Problem_Generate.stature

  type fact = Sledgehammer_Fact.fact

  type fact_override = Sledgehammer_Fact.fact_override

  type params = Sledgehammer_Provers.params

  type relevance_fudge = Sledgehammer_Provers.relevance_fudge

  type prover_result = Sledgehammer_Provers.prover_result

  val trace : bool Config.T

  val MaShN : string

  val mepoN : string

  val mashN : string

  val meshN : string

  val unlearnN : string

  val learn_isarN : string

  val learn_atpN : string

  val relearn_isarN : string

  val relearn_atpN : string

  val fact_filters : string list

  val escape_meta : string -> string

  val escape_metas : string list -> string

  val unescape_meta : string -> string

  val unescape_metas : string -> string list

  val extract_query : string -> string * string list

  val nickname_of : thm -> string

  val suggested_facts : string list -> ('a * thm) list -> ('a * thm) list

  val mesh_facts :

    int -> (('a * thm) list * ('a * thm) list) list -> ('a * thm) list

  val is_likely_tautology_or_too_meta : thm -> bool

  val theory_ord : theory * theory -> order

  val thm_ord : thm * thm -> order

  val goal_of_thm : theory -> thm -> thm

  val run_prover_for_mash :

    Proof.context -> params -> string -> fact list -> thm -> prover_result

  val features_of :

    Proof.context -> string -> theory -> stature -> term list -> string list

  val isar_dependencies_of : unit Symtab.table -> thm -> string list

  val atp_dependencies_of :

    Proof.context -> params -> string -> bool -> fact list -> unit Symtab.table

    -> thm -> string list

  val mash_CLEAR : Proof.context -> unit

  val mash_ADD :

    Proof.context -> bool

    -> (string * string list * string list * string list) list -> unit

  val mash_QUERY :

    Proof.context -> bool -> int -> string list * string list -> string list

  val mash_unlearn : Proof.context -> unit

  val mash_could_suggest_facts : unit -> bool

  val mash_can_suggest_facts : Proof.context -> bool

  val mash_suggest_facts :

    Proof.context -> params -> string -> int -> term list -> term

    -> ('a * thm) list -> ('a * thm) list * ('a * thm) list

  val mash_learn_proof :

    Proof.context -> params -> string -> term -> ('a * thm) list -> thm list

    -> unit

  val mash_learn_facts :

    Proof.context -> params -> string -> bool -> bool -> Time.time -> fact list

    -> string

  val mash_learn : Proof.context -> params -> bool -> unit

  val relevant_facts :

    Proof.context -> params -> string -> int -> fact_override -> term list

    -> term -> fact list -> fact list

  val kill_learners : unit -> unit

  val running_learners : unit -> unit

end;

structure Sledgehammer_MaSh : SLEDGEHAMMER_MASH =

struct

open ATP_Util

open ATP_Problem_Generate

open Sledgehammer_Util

open Sledgehammer_Fact

open Sledgehammer_Provers

open Sledgehammer_Minimize

open Sledgehammer_MePo

val trace =

  Attrib.setup_config_bool @{binding sledgehammer_mash_trace} (K false)

fun trace_msg ctxt msg = if Config.get ctxt trace then tracing (msg ()) else ()

val MaShN = "MaSh"

val mepoN = "mepo"

val mashN = "mash"

val meshN = "mesh"

val fact_filters = [meshN, mepoN, mashN]

val unlearnN = "unlearn"

val learn_isarN = "learn_isar"

val learn_atpN = "learn_atp"

val relearn_isarN = "relearn_isar"

val relearn_atpN = "relearn_atp"

fun mash_home () = getenv "MASH_HOME"

fun mash_model_dir () =

  getenv "ISABELLE_HOME_USER" ^ "/mash"

  |> tap (Isabelle_System.mkdir o Path.explode)

val mash_state_dir = mash_model_dir

fun mash_state_path () = mash_state_dir () ^ "/state" |> Path.explode

(*** Isabelle helpers ***)

fun meta_char c =

  if Char.isAlphaNum c orelse c = #"_" orelse c = #"." orelse c = #"(" orelse

     c = #")" orelse c = #"," then

    String.str c

  else

    (* fixed width, in case more digits follow *)

    "$" ^ stringN_of_int 3 (Char.ord c)

fun unmeta_chars accum [] = String.implode (rev accum)

  | unmeta_chars accum (#"$" :: d1 :: d2 :: d3 :: cs) =

    (case Int.fromString (String.implode [d1, d2, d3]) of

       SOME n => unmeta_chars (Char.chr n :: accum) cs

     | NONE => "" (* error *))

  | unmeta_chars _ (#"$" :: _) = "" (* error *)

  | unmeta_chars accum (c :: cs) = unmeta_chars (c :: accum) cs

val escape_meta = String.translate meta_char

val escape_metas = map escape_meta #> space_implode " "

val unescape_meta = String.explode #> unmeta_chars []

val unescape_metas =

  space_explode " " #> filter_out (curry (op =) "") #> map unescape_meta

fun extract_query line =

  case space_explode ":" line of

    [goal_name, suggs] => (unescape_meta goal_name, unescape_metas suggs)

  | _ => ("", [])

fun parent_of_local_thm th =

  let

    val thy = th |> Thm.theory_of_thm

    val facts = thy |> Global_Theory.facts_of

    val space = facts |> Facts.space_of

    fun id_of s = #id (Name_Space.the_entry space s)

    fun max_id (s', _) (s, id) =

      let val id' = id_of s' in if id > id' then (s, id) else (s', id') end

  in ("", ~1) |> Facts.fold_static max_id facts |> fst end

val local_prefix = "local" ^ Long_Name.separator

fun nickname_of th =

  if Thm.has_name_hint th then

    let val hint = Thm.get_name_hint th in

      (* FIXME: There must be a better way to detect local facts. *)

      case try (unprefix local_prefix) hint of

        SOME suf =>

        parent_of_local_thm th ^ Long_Name.separator ^ Long_Name.separator ^ suf

      | NONE => hint

    end

  else

    backquote_thm th

fun suggested_facts suggs facts =

  let

    fun add_fact (fact as (_, th)) = Symtab.default (nickname_of th, fact)

    val tab = Symtab.empty |> fold add_fact facts

  in map_filter (Symtab.lookup tab) suggs end

(* Ad hoc score function roughly based on Blanchette's Ringberg 2011 data. *)

fun score x = Math.pow (1.5, 15.5 - 0.05 * Real.fromInt x) + 15.0

fun sum_sq_avg [] = 0

  | sum_sq_avg xs =

    Real.ceil (100000.0 * fold (curry (op +) o score) xs 0.0) div length xs

fun mesh_facts max_facts [(selected, unknown)] =

    take max_facts selected @ take (max_facts - length selected) unknown

  | mesh_facts max_facts mess =

    let

      val mess = mess |> map (apfst (`length))

      val fact_eq = Thm.eq_thm o pairself snd

      fun score_in fact ((sel_len, sels), unks) =

        case find_index (curry fact_eq fact) sels of

          ~1 => (case find_index (curry fact_eq fact) unks of

                   ~1 => SOME sel_len

                 | _ => NONE)

        | j => SOME j

      fun score_of fact = mess |> map_filter (score_in fact) |> sum_sq_avg

      val facts = fold (union fact_eq o take max_facts o snd o fst) mess []

    in

      facts |> map (`score_of) |> sort (int_ord o swap o pairself fst)

            |> map snd |> take max_facts

    end

val thy_feature_prefix = "y_"

val thy_feature_name_of = prefix thy_feature_prefix

val const_name_of = prefix const_prefix

val type_name_of = prefix type_const_prefix

val class_name_of = prefix class_prefix

fun is_likely_tautology_or_too_meta th =

  let

    val is_boring_const = member (op =) atp_widely_irrelevant_consts

    fun is_boring_bool t =

      not (exists_Const (not o is_boring_const o fst) t) orelse

      exists_type (exists_subtype (curry (op =) @{typ prop})) t

    fun is_boring_prop (@{const Trueprop} $ t) = is_boring_bool t

      | is_boring_prop (@{const "==>"} $ t $ u) =

        is_boring_prop t andalso is_boring_prop u

      | is_boring_prop (Const (@{const_name all}, _) $ (Abs (_, _, t)) $ u) =

        is_boring_prop t andalso is_boring_prop u

      | is_boring_prop (Const (@{const_name "=="}, _) $ t $ u) =

        is_boring_bool t andalso is_boring_bool u

      | is_boring_prop _ = true

  in

    is_boring_prop (prop_of th) andalso not (Thm.eq_thm_prop (@{thm ext}, th))

  end

fun theory_ord p =

  if Theory.eq_thy p then

    EQUAL

  else if Theory.subthy p then

    LESS

  else if Theory.subthy (swap p) then

    GREATER

  else case int_ord (pairself (length o Theory.ancestors_of) p) of

    EQUAL => string_ord (pairself Context.theory_name p)

  | order => order

val thm_ord = theory_ord o pairself theory_of_thm

val freezeT = Type.legacy_freeze_type

fun freeze (t $ u) = freeze t $ freeze u

  | freeze (Abs (s, T, t)) = Abs (s, freezeT T, freeze t)

  | freeze (Var ((s, _), T)) = Free (s, freezeT T)

  | freeze (Const (s, T)) = Const (s, freezeT T)

  | freeze (Free (s, T)) = Free (s, freezeT T)

  | freeze t = t

fun goal_of_thm thy = prop_of #> freeze #> cterm_of thy #> Goal.init

fun run_prover_for_mash ctxt params prover facts goal =

  let

    val problem =

      {state = Proof.init ctxt, goal = goal, subgoal = 1, subgoal_count = 1,

       facts = facts |> map (apfst (apfst (fn name => name ())))

                     |> map Untranslated_Fact}

  in

    get_minimizing_prover ctxt MaSh (K ()) prover params (K (K (K "")))

                          problem

  end

val bad_types = [@{type_name prop}, @{type_name bool}, @{type_name fun}]

fun interesting_terms_types_and_classes ctxt prover term_max_depth

                                        type_max_depth ts =

  let

    fun is_bad_const (x as (s, _)) args =

      member (op =) atp_logical_consts s orelse

      fst (is_built_in_const_for_prover ctxt prover x args)

    fun add_classes @{sort type} = I

      | add_classes S = union (op =) (map class_name_of S)

    fun do_add_type (Type (s, Ts)) =

        (not (member (op =) bad_types s) ? insert (op =) (type_name_of s))

        #> fold do_add_type Ts

      | do_add_type (TFree (_, S)) = add_classes S

      | do_add_type (TVar (_, S)) = add_classes S

    fun add_type T = type_max_depth >= 0 ? do_add_type T

    fun mk_app s args =

      if member (op <>) args "" then s ^ "(" ^ space_implode "," args ^ ")"

      else s

    fun patternify ~1 _ = ""

      | patternify depth t =

        case strip_comb t of

          (Const (s, _), args) =>

          mk_app (const_name_of s) (map (patternify (depth - 1)) args)

        | _ => ""

    fun add_term_patterns ~1 _ = I

      | add_term_patterns depth t =

        insert (op =) (patternify depth t)

        #> add_term_patterns (depth - 1) t

    val add_term = add_term_patterns term_max_depth

    fun add_patterns t =

      let val (head, args) = strip_comb t in

        (case head of

           Const (x as (_, T)) =>

           not (is_bad_const x args) ? (add_term t #> add_type T)

         | Free (_, T) => add_type T

         | Var (_, T) => add_type T

         | Abs (_, T, body) => add_type T #> add_patterns body

         | _ => I)

        #> fold add_patterns args

      end

  in [] |> fold add_patterns ts end

fun is_exists (s, _) = (s = @{const_name Ex} orelse s = @{const_name Ex1})

val term_max_depth = 1

val type_max_depth = 1

(* TODO: Generate type classes for types? *)

fun features_of ctxt prover thy (scope, status) ts =

  thy_feature_name_of (Context.theory_name thy) ::

  interesting_terms_types_and_classes ctxt prover term_max_depth type_max_depth

                                      ts

  |> forall is_lambda_free ts ? cons "no_lams"

  |> forall (not o exists_Const is_exists) ts ? cons "no_skos"

  |> scope <> Global ? cons "local"

  |> (case status of

        General => I

      | Induction => cons "induction"

      | Intro => cons "intro"

      | Inductive => cons "inductive"

      | Elim => cons "elim"

      | Simp => cons "simp"

      | Def => cons "def")

fun isar_dependencies_of all_facts = thms_in_proof (SOME all_facts)

val atp_dep_default_max_fact = 50

fun atp_dependencies_of ctxt (params as {verbose, max_facts, ...}) prover auto

                        facts all_names th =

  case isar_dependencies_of all_names th of

    [] => []

  | isar_deps =>

    let

      val thy = Proof_Context.theory_of ctxt

      val goal = goal_of_thm thy th

      val (_, hyp_ts, concl_t) = ATP_Util.strip_subgoal ctxt goal 1

      val facts = facts |> filter (fn (_, th') => thm_ord (th', th) = LESS)

      fun fix_name ((_, stature), th) = ((fn () => nickname_of th, stature), th)

      fun is_dep dep (_, th) = nickname_of th = dep

      fun add_isar_dep facts dep accum =

        if exists (is_dep dep) accum then

          accum

        else case find_first (is_dep dep) facts of

          SOME ((name, status), th) => accum @ [((name, status), th)]

        | NONE => accum (* shouldn't happen *)

      val facts =

        facts |> iterative_relevant_facts ctxt params prover

                     (max_facts |> the_default atp_dep_default_max_fact) NONE

                     hyp_ts concl_t

              |> fold (add_isar_dep facts) isar_deps

              |> map fix_name

    in

      if verbose andalso not auto then

        let val num_facts = length facts in

          "MaSh: " ^ quote prover ^ " on " ^ quote (nickname_of th) ^

          " with " ^ string_of_int num_facts ^ " fact" ^ plural_s num_facts ^

          "."

          |> Output.urgent_message

        end

      else

        ();

      case run_prover_for_mash ctxt params prover facts goal of

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

        (if verbose andalso not auto then

           let val num_facts = length used_facts in

             "Found proof with " ^ string_of_int num_facts ^ " fact" ^

             plural_s num_facts ^ "."

             |> Output.urgent_message

           end

         else

           ();

         used_facts |> map fst)

      | _ => isar_deps

    end

(*** Low-level communication with MaSh ***)

(* more friendly than "try o File.rm" for those who keep the files open in their

   text editor *)

fun wipe_out file = File.write file ""

fun write_file (xs, f) file =

  let val path = Path.explode file in

    wipe_out path;

    xs |> chunk_list 500

       |> List.app (File.append path o space_implode "" o map f)

  end

fun run_mash_tool ctxt overlord save max_suggs write_cmds read_suggs =

  let

    val (temp_dir, serial) =

      if overlord then (getenv "ISABELLE_HOME_USER", "")

      else (getenv "ISABELLE_TMP", serial_string ())

    val log_file = if overlord then temp_dir ^ "/mash_log" else "/dev/null"

    val err_file = temp_dir ^ "/mash_err" ^ serial

    val sugg_file = temp_dir ^ "/mash_suggs" ^ serial

    val cmd_file = temp_dir ^ "/mash_commands" ^ serial

    val core =

      "--inputFile " ^ cmd_file ^ " --predictions " ^ sugg_file ^

      " --numberOfPredictions " ^ string_of_int max_suggs ^

      (if save then " --saveModel" else "")

    val command =

      mash_home () ^ "/mash --quiet --outputDir " ^ mash_model_dir () ^

      " --log " ^ log_file ^ " " ^ core ^ " >& " ^ err_file

  in

    write_file ([], K "") sugg_file;

    write_file write_cmds cmd_file;

    trace_msg ctxt (fn () => "Running " ^ command);

    Isabelle_System.bash command;

    read_suggs (fn () => try File.read_lines (Path.explode sugg_file) |> these)

    |> tap (fn _ => trace_msg ctxt (fn () =>

           case try File.read (Path.explode err_file) of

             NONE => "Done"

           | SOME "" => "Done"

           | SOME s => "Error: " ^ elide_string 1000 s))

    |> not overlord

       ? tap (fn _ => List.app (wipe_out o Path.explode)

                               [err_file, sugg_file, cmd_file])

  end

fun str_of_update (name, parents, feats, deps) =

  "! " ^ escape_meta name ^ ": " ^ escape_metas parents ^ "; " ^

  escape_metas feats ^ "; " ^ escape_metas deps ^ "\n"

fun str_of_query (parents, feats) =

  "? " ^ escape_metas parents ^ "; " ^ escape_metas feats

fun mash_CLEAR ctxt =

  let val path = mash_model_dir () |> Path.explode in

    trace_msg ctxt (K "MaSh CLEAR");

    File.fold_dir (fn file => fn _ =>

                      try File.rm (Path.append path (Path.basic file)))

                  path NONE;

    ()

  end

fun mash_ADD _ _ [] = ()

  | mash_ADD ctxt overlord upds =

    (trace_msg ctxt (fn () => "MaSh ADD " ^

         elide_string 1000 (space_implode " " (map #1 upds)));

     run_mash_tool ctxt overlord true 0 (upds, str_of_update) (K ()))

fun mash_QUERY ctxt overlord max_suggs (query as (_, feats)) =

  (trace_msg ctxt (fn () => "MaSh QUERY " ^ space_implode " " feats);

   run_mash_tool ctxt overlord false max_suggs

       ([query], str_of_query)

       (fn suggs =>

           case suggs () of

             [] => []

           | suggs => snd (extract_query (List.last suggs)))

   handle List.Empty => [])

(*** High-level communication with MaSh ***)

fun try_graph ctxt when def f =

  f ()

  handle Graph.CYCLES (cycle :: _) =>

         (trace_msg ctxt (fn () =>

              "Cycle involving " ^ commas cycle ^ " when " ^ when); def)

       | Graph.DUP name =>

         (trace_msg ctxt (fn () =>

              "Duplicate fact " ^ quote name ^ " when " ^ when); def)

       | Graph.UNDEF name =>

         (trace_msg ctxt (fn () =>

              "Unknown fact " ^ quote name ^ " when " ^ when); def)

       | exn =>

         if Exn.is_interrupt exn then

           reraise exn

         else

           (trace_msg ctxt (fn () =>

                "Internal error when " ^ when ^ ":\n" ^

                ML_Compiler.exn_message exn); def)

type mash_state = {fact_graph : unit Graph.T}

val empty_state = {fact_graph = Graph.empty}

local

val version = "*** MaSh 0.0 ***"

fun load _ (state as (true, _)) = state

  | load ctxt _ =

    let val path = mash_state_path () in

      (true,

       case try File.read_lines path of

         SOME (version' :: fact_lines) =>

         let

           fun add_edge_to name parent =

             Graph.default_node (parent, ())

             #> Graph.add_edge (parent, name)

           fun add_fact_line line =

             case extract_query line of

               ("", _) => I (* shouldn't happen *)

             | (name, parents) =>

               Graph.default_node (name, ())

               #> fold (add_edge_to name) parents

           val fact_graph =

             try_graph ctxt "loading state" Graph.empty (fn () =>

                 Graph.empty |> version' = version

                                ? fold add_fact_line fact_lines)

         in {fact_graph = fact_graph} end

       | _ => empty_state)

    end

fun save {fact_graph} =

  let

    val path = mash_state_path ()

    fun fact_line_for name parents =

      escape_meta name ^ ": " ^ escape_metas parents

    val append_fact = File.append path o suffix "\n" oo fact_line_for

  in

    File.write path (version ^ "\n");

    Graph.fold (fn (name, ((), (parents, _))) => fn () =>

                   append_fact name (Graph.Keys.dest parents))

        fact_graph ()

  end

val global_state =

  Synchronized.var "Sledgehammer_MaSh.global_state" (false, empty_state)

in

fun mash_map ctxt f =

  Synchronized.change global_state (load ctxt ##> (f #> tap save))

fun mash_get ctxt =

  Synchronized.change_result global_state (load ctxt #> `snd)

fun mash_unlearn ctxt =

  Synchronized.change global_state (fn _ =>

      (mash_CLEAR ctxt; wipe_out (mash_state_path ()); (true, empty_state)))

end

fun mash_could_suggest_facts () = mash_home () <> ""

fun mash_can_suggest_facts ctxt =

  not (Graph.is_empty (#fact_graph (mash_get ctxt)))

fun parents_wrt_facts facts fact_graph =

  let

    val facts = [] |> fold (cons o nickname_of o snd) facts

    val tab = Symtab.empty |> fold (fn name => Symtab.update (name, ())) facts

    fun insert_not_seen seen name =

      not (member (op =) seen name) ? insert (op =) name

    fun parents_of _ parents [] = parents

      | parents_of seen parents (name :: names) =

        if Symtab.defined tab name then

          parents_of (name :: seen) (name :: parents) names

        else

          parents_of (name :: seen) parents

                     (Graph.Keys.fold (insert_not_seen seen)

                                      (Graph.imm_preds fact_graph name) names)

  in parents_of [] [] (Graph.maximals fact_graph) end

(* Generate more suggestions than requested, because some might be thrown out

   later for various reasons and "meshing" gives better results with some

   slack. *)

fun max_suggs_of max_facts = max_facts + Int.min (200, max_facts)

fun is_fact_in_graph fact_graph (_, th) =

  can (Graph.get_node fact_graph) (nickname_of th)

fun mash_suggest_facts ctxt ({overlord, ...} : params) prover max_facts hyp_ts

                       concl_t facts =

  let

    val thy = Proof_Context.theory_of ctxt

    val fact_graph = #fact_graph (mash_get ctxt)

    val parents = parents_wrt_facts facts fact_graph

    val feats = features_of ctxt prover thy (Local, General) (concl_t :: hyp_ts)

    val suggs =

      if Graph.is_empty fact_graph then []

      else mash_QUERY ctxt overlord (max_suggs_of max_facts) (parents, feats)

    val selected = facts |> suggested_facts suggs

    val unknown = facts |> filter_out (is_fact_in_graph fact_graph)

  in (selected, unknown) end

fun update_fact_graph ctxt (name, parents, feats, deps) (upds, graph) =

  let

    fun maybe_add_from from (accum as (parents, graph)) =

      try_graph ctxt "updating graph" accum (fn () =>

          (from :: parents, Graph.add_edge_acyclic (from, name) graph))

    val graph = graph |> Graph.default_node (name, ())

    val (parents, graph) = ([], graph) |> fold maybe_add_from parents

    val (deps, graph) = ([], graph) |> fold maybe_add_from deps

  in ((name, parents, feats, deps) :: upds, graph) end

val learn_timeout_slack = 2.0

fun launch_thread timeout task =

  let

    val hard_timeout = time_mult learn_timeout_slack timeout

    val birth_time = Time.now ()

    val death_time = Time.+ (birth_time, hard_timeout)

    val desc = ("machine learner for Sledgehammer", "")

  in Async_Manager.launch MaShN birth_time death_time desc task end

fun mash_learn_proof ctxt ({overlord, timeout, ...} : params) prover t facts

                     used_ths =

  if is_smt_prover ctxt prover then

    ()

  else

    launch_thread timeout

        (fn () =>

            let

              val thy = Proof_Context.theory_of ctxt

              val name = timestamp () ^ " " ^ serial_string () (* freshish *)

              val feats = features_of ctxt prover thy (Local, General) [t]

              val deps = used_ths |> map nickname_of

            in

              mash_map ctxt (fn {fact_graph} =>

                  let

                    val parents = parents_wrt_facts facts fact_graph

                    val upds = [(name, parents, feats, deps)]

                    val (upds, fact_graph) =

                      ([], fact_graph) |> fold (update_fact_graph ctxt) upds

                  in

                    mash_ADD ctxt overlord upds; {fact_graph = fact_graph}

                  end);

              (true, "")

            end)

fun sendback sub =

  Markup.markup Isabelle_Markup.sendback (sledgehammerN ^ " " ^ sub)

(* Too many dependencies is a sign that a decision procedure is at work. There

   isn't much too learn from such proofs. *)

val max_dependencies = 10

val commit_timeout = seconds 30.0

(* The timeout is understood in a very slack fashion. *)

fun mash_learn_facts ctxt (params as {debug, verbose, overlord, timeout, ...})

                     prover auto atp learn_timeout facts =

  let

    val timer = Timer.startRealTimer ()

    fun next_commit_time () =

      Time.+ (Timer.checkRealTimer timer, commit_timeout)

    val {fact_graph} = mash_get ctxt

    val new_facts =

      facts |> filter_out (is_fact_in_graph fact_graph)

            |> sort (thm_ord o pairself snd)

    val num_new_facts = length new_facts

  in

    (if not auto then

       "MaShing" ^

       (if not auto then

          " " ^ string_of_int num_new_facts ^ " fact" ^

          plural_s num_new_facts ^

          (if atp then " (ATP timeout: " ^ string_from_time timeout ^ ")"

           else "")

        else

          "") ^ "..."

     else

       "")

    |> Output.urgent_message;

    if null new_facts then

      if not auto then

        "Nothing to learn.\n\nHint: Try " ^ sendback relearn_isarN ^ " or " ^

        sendback relearn_atpN ^ "  to learn from scratch."

      else

        ""

    else

      let

        val ths = facts |> map snd

        val all_names =

          ths |> filter_out is_likely_tautology_or_too_meta

              |> map (rpair () o nickname_of)

              |> Symtab.make

        fun do_commit [] state = state

          | do_commit upds {fact_graph} =

            let

              val (upds, fact_graph) =

                ([], fact_graph) |> fold (update_fact_graph ctxt) upds

            in mash_ADD ctxt overlord (rev upds); {fact_graph = fact_graph} end

        fun trim_deps deps = if length deps > max_dependencies then [] else deps

        fun commit last upds =

          (if debug andalso not auto then Output.urgent_message "Committing..."

           else ();

           mash_map ctxt (do_commit (rev upds));

           if not last andalso not auto then

             let val num_upds = length upds in

               "Processed " ^ string_of_int num_upds ^ " fact" ^

               plural_s num_upds ^ " in the last " ^

               string_from_time commit_timeout ^ "."

               |> Output.urgent_message

             end

           else

             ())

        fun do_fact _ (accum as (_, (_, _, _, true))) = accum

          | do_fact ((_, stature), th)

                    (upds, (parents, n, next_commit, false)) =

            let

              val name = nickname_of th

              val feats =

                features_of ctxt prover (theory_of_thm th) stature [prop_of th]

              val deps =

                (if atp then atp_dependencies_of ctxt params prover auto facts

                 else isar_dependencies_of) all_names th

                |> trim_deps

              val n = n |> not (null deps) ? Integer.add 1

              val upds = (name, parents, feats, deps) :: upds

              val (upds, next_commit) =

                if Time.> (Timer.checkRealTimer timer, next_commit) then

                  (commit false upds; ([], next_commit_time ()))

                else

                  (upds, next_commit)

              val timed_out =

                Time.> (Timer.checkRealTimer timer, learn_timeout)

            in (upds, ([name], n, next_commit, timed_out)) end

        val parents = parents_wrt_facts facts fact_graph

        val (upds, (_, n, _, _)) =

          ([], (parents, 0, next_commit_time (), false))

          |> fold do_fact new_facts

      in

        commit true upds;

        if verbose orelse not auto then

          "Learned " ^ string_of_int n ^ " nontrivial proof" ^ plural_s n ^

          (if verbose then

             " in " ^ string_from_time (Timer.checkRealTimer timer)

           else

             "") ^ "."

        else

          ""

      end

  end

fun mash_learn ctxt (params as {provers, ...}) atp =

  let

    val css_table = Sledgehammer_Fact.clasimpset_rule_table_of ctxt

    val facts = all_facts_of ctxt css_table

  in

     mash_learn_facts ctxt params (hd provers) false atp infinite_timeout facts

     |> Output.urgent_message

  end

(* The threshold should be large enough so that MaSh doesn't kick in for Auto

   Sledgehammer and Try. *)

val min_secs_for_learning = 15

fun relevant_facts ctxt (params as {learn, fact_filter, timeout, ...}) prover

        max_facts ({add, only, ...} : fact_override) hyp_ts concl_t facts =

  if not (subset (op =) (the_list fact_filter, fact_filters)) then

    error ("Unknown fact filter: " ^ quote (the fact_filter) ^ ".")

  else if only then

    facts

  else if max_facts <= 0 orelse null facts then

    []

  else

    let

      fun maybe_learn () =

        if learn andalso not (Async_Manager.has_running_threads MaShN) andalso

           Time.toSeconds timeout >= min_secs_for_learning then

          let val timeout = time_mult learn_timeout_slack timeout in

            launch_thread timeout

                (fn () => (true, mash_learn_facts ctxt params prover true false

                                                  timeout facts))

          end

        else

          ()

      val fact_filter =

        case fact_filter of

          SOME ff => (() |> ff <> mepoN ? maybe_learn; ff)

        | NONE =>

          if is_smt_prover ctxt prover then mepoN

          else if mash_can_suggest_facts ctxt then (maybe_learn (); meshN)

          else if mash_could_suggest_facts () then (maybe_learn (); mepoN)

          else mepoN

      val add_ths = Attrib.eval_thms ctxt add

      fun prepend_facts ths accepts =

        ((facts |> filter (member Thm.eq_thm_prop ths o snd)) @

         (accepts |> filter_out (member Thm.eq_thm_prop ths o snd)))

        |> take max_facts

      fun iter () =

        iterative_relevant_facts ctxt params prover max_facts NONE hyp_ts

                                 concl_t facts

      fun mash () =

        mash_suggest_facts ctxt params prover max_facts hyp_ts concl_t facts

      val mess =

        [] |> (if fact_filter <> mashN then cons (iter (), []) else I)

           |> (if fact_filter <> mepoN then cons (mash ()) else I)

    in

      mesh_facts max_facts mess

      |> not (null add_ths) ? prepend_facts add_ths

    end

fun kill_learners () = Async_Manager.kill_threads MaShN "learner"

fun running_learners () = Async_Manager.running_threads MaShN "learner"

end;