better weight functions for MePo/MaSh etc.

--- a/src/HOL/Tools/Sledgehammer/sledgehammer_mash.ML	Thu Dec 20 15:51:24 2012 +0100
+++ b/src/HOL/Tools/Sledgehammer/sledgehammer_mash.ML	Thu Dec 20 15:51:27 2012 +0100
@@ -58,7 +58,7 @@
   val prover_dependencies_of :
     Proof.context -> params -> string -> int -> fact list -> string Symtab.table
     -> thm -> bool * string list option
-  val weight_mash_facts : ('a * thm) list -> (('a * thm) * real) list
+  val weight_mash_facts : 'a list -> ('a * real) list
   val find_mash_suggestions :
     int -> (Symtab.key * 'a) list -> ('b * thm) list -> ('b * thm) list
     -> ('b * thm) list -> ('b * thm) list * ('b * thm) list
@@ -727,7 +727,6 @@
 fun is_fact_in_graph fact_G (_, th) =
   can (Graph.get_node fact_G) (nickname_of th)
 
-(* use MePo weights for now *)
 val weight_raw_mash_facts = weight_mepo_facts
 val weight_mash_facts = weight_raw_mash_facts
 

--- a/src/HOL/Tools/Sledgehammer/sledgehammer_mepo.ML	Thu Dec 20 15:51:24 2012 +0100
+++ b/src/HOL/Tools/Sledgehammer/sledgehammer_mepo.ML	Thu Dec 20 15:51:27 2012 +0100
@@ -18,7 +18,7 @@
   val const_names_in_fact :
     theory -> (string * typ -> term list -> bool * term list) -> term
     -> string list
-  val weight_mepo_facts : ('a * thm) list -> (('a * thm) * real) list
+  val weight_mepo_facts : 'a list -> ('a * real) list
   val mepo_suggested_facts :
     Proof.context -> params -> string -> int -> relevance_fudge option
     -> term list -> term -> fact list -> fact list
@@ -28,6 +28,7 @@
 struct
 
 open ATP_Problem_Generate
+open Sledgehammer_Util
 open Sledgehammer_Fact
 open Sledgehammer_Provers
 
@@ -509,10 +510,9 @@
                       "Total relevant: " ^ string_of_int (length accepts)))
   end
 
-(* Ad hoc score function roughly based on Blanchette's Ringberg 2011 data. *)
 (* FUDGE *)
 fun weight_of_mepo_fact rank =
-  Math.pow (1.5, 15.5 - 0.05 * Real.fromInt rank) + 15.0
+  Math.pow (0.62, log2 (Real.fromInt (rank + 1)))
 
 fun weight_mepo_facts facts =
   facts ~~ map weight_of_mepo_fact (0 upto length facts - 1)

--- a/src/HOL/Tools/Sledgehammer/sledgehammer_util.ML	Thu Dec 20 15:51:24 2012 +0100
+++ b/src/HOL/Tools/Sledgehammer/sledgehammer_util.ML	Thu Dec 20 15:51:27 2012 +0100
@@ -7,6 +7,7 @@
 signature SLEDGEHAMMER_UTIL =
 sig
   val sledgehammerN : string
+  val log2 : real -> real
   val plural_s : int -> string
   val serial_commas : string -> string list -> string list
   val simplify_spaces : string -> string
@@ -32,6 +33,10 @@
 
 val sledgehammerN = "sledgehammer"
 
+val log10_2 = Math.log10 2.0
+
+fun log2 n = Math.log10 n / log10_2
+
 fun plural_s n = if n = 1 then "" else "s"
 
 val serial_commas = Try.serial_commas