src/HOL/Library/Sum_Of_Squares/sum_of_squares.ML

tuned header;
tuned whitespace;

(* Title:      HOL/Library/Sum_Of_Squares/sum_of_squares.ML
   Author:     Amine Chaieb, University of Cambridge
   Author:     Philipp Meyer, TU Muenchen

A tactic for proving nonlinear inequalities.
*)

signature SOS =
sig

  datatype proof_method =
    Certificate of RealArith.pss_tree
  | Prover of (string -> string)

  val sos_tac : (RealArith.pss_tree -> unit) ->
    proof_method -> Proof.context -> int -> tactic

  val debugging : bool Unsynchronized.ref;

  exception Failure of string;
end

structure Sos : SOS =
struct

val rat_0 = Rat.zero;
val rat_1 = Rat.one;
val rat_2 = Rat.two;
val rat_10 = Rat.rat_of_int 10;
val rat_1_2 = rat_1 // rat_2;
val max = curry IntInf.max;
val min = curry IntInf.min;

val denominator_rat = Rat.quotient_of_rat #> snd #> Rat.rat_of_int;
val numerator_rat = Rat.quotient_of_rat #> fst #> Rat.rat_of_int;
fun int_of_rat a =
    case Rat.quotient_of_rat a of (i,1) => i | _ => error "int_of_rat: not an int";
fun lcm_rat x y = Rat.rat_of_int (Integer.lcm (int_of_rat x) (int_of_rat y));

fun rat_pow r i =
 let fun pow r i =
   if i = 0 then rat_1 else
   let val d = pow r (i div 2)
   in d */ d */ (if i mod 2 = 0 then rat_1 else r)
   end
 in if i < 0 then pow (Rat.inv r) (~ i) else pow r i end;

fun round_rat r =
 let val (a,b) = Rat.quotient_of_rat (Rat.abs r)
     val d = a div b
     val s = if r </ rat_0 then (Rat.neg o Rat.rat_of_int) else Rat.rat_of_int
     val x2 = 2 * (a - (b * d))
 in s (if x2 >= b then d + 1 else d) end

val abs_rat = Rat.abs;
val pow2 = rat_pow rat_2;
val pow10 = rat_pow rat_10;

val debugging = Unsynchronized.ref false;

exception Sanity;

exception Unsolvable;

exception Failure of string;

datatype proof_method =
    Certificate of RealArith.pss_tree
  | Prover of (string -> string)

(* Turn a rational into a decimal string with d sig digits.                  *)

local
fun normalize y =
  if abs_rat y </ (rat_1 // rat_10) then normalize (rat_10 */ y) - 1
  else if abs_rat y >=/ rat_1 then normalize (y // rat_10) + 1
  else 0
 in
fun decimalize d x =
  if x =/ rat_0 then "0.0" else
  let
   val y = Rat.abs x
   val e = normalize y
   val z = pow10(~ e) */ y +/ rat_1
   val k = int_of_rat (round_rat(pow10 d */ z))
  in (if x </ rat_0 then "-0." else "0.") ^
     implode(tl(explode(string_of_int k))) ^
     (if e = 0 then "" else "e"^string_of_int e)
  end
end;

(* Iterations over numbers, and lists indexed by numbers.                    *)

fun itern k l f a =
  case l of
    [] => a
  | h::t => itern (k + 1) t f (f h k a);

fun iter (m,n) f a =
  if n < m then a
  else iter (m+1,n) f (f m a);

(* The main types.                                                           *)

type vector = int* Rat.rat FuncUtil.Intfunc.table;

type matrix = (int*int)*(Rat.rat FuncUtil.Intpairfunc.table);

fun iszero (k,r) = r =/ rat_0;

fun fold_rev2 f l1 l2 b =
  case (l1,l2) of
    ([],[]) => b
  | (h1::t1,h2::t2) => f h1 h2 (fold_rev2 f t1 t2 b)
  | _ => error "fold_rev2";

(* Vectors. Conventionally indexed 1..n.                                     *)

fun vector_0 n = (n,FuncUtil.Intfunc.empty):vector;

fun dim (v:vector) = fst v;

fun vector_const c n =
  if c =/ rat_0 then vector_0 n
  else (n,fold_rev (fn k => FuncUtil.Intfunc.update (k,c)) (1 upto n) FuncUtil.Intfunc.empty) :vector;

val vector_1 = vector_const rat_1;

fun vector_cmul c (v:vector) =
 let val n = dim v
 in if c =/ rat_0 then vector_0 n
    else (n,FuncUtil.Intfunc.map (fn x => c */ x) (snd v))
 end;

fun vector_neg (v:vector) = (fst v,FuncUtil.Intfunc.map Rat.neg (snd v)) :vector;

fun vector_add (v1:vector) (v2:vector) =
 let val m = dim v1
     val n = dim v2
 in if m <> n then error "vector_add: incompatible dimensions"
    else (n,FuncUtil.Intfunc.combine (curry op +/) (fn x => x =/ rat_0) (snd v1) (snd v2)) :vector
 end;

fun vector_sub v1 v2 = vector_add v1 (vector_neg v2);

fun vector_dot (v1:vector) (v2:vector) =
 let val m = dim v1
     val n = dim v2
 in if m <> n then error "vector_dot: incompatible dimensions"
    else FuncUtil.Intfunc.fold (fn (i,x) => fn a => x +/ a)
        (FuncUtil.Intfunc.combine (curry op */) (fn x => x =/ rat_0) (snd v1) (snd v2)) rat_0
 end;

fun vector_of_list l =
 let val n = length l
 in (n,fold_rev2 (curry FuncUtil.Intfunc.update) (1 upto n) l FuncUtil.Intfunc.empty) :vector
 end;

(* Matrices; again rows and columns indexed from 1.                          *)

fun matrix_0 (m,n) = ((m,n),FuncUtil.Intpairfunc.empty):matrix;

fun dimensions (m:matrix) = fst m;

fun matrix_const c (mn as (m,n)) =
  if m <> n then error "matrix_const: needs to be square"
  else if c =/ rat_0 then matrix_0 mn
  else (mn,fold_rev (fn k => FuncUtil.Intpairfunc.update ((k,k), c)) (1 upto n) FuncUtil.Intpairfunc.empty) :matrix;;

val matrix_1 = matrix_const rat_1;

fun matrix_cmul c (m:matrix) =
 let val (i,j) = dimensions m
 in if c =/ rat_0 then matrix_0 (i,j)
    else ((i,j),FuncUtil.Intpairfunc.map (fn x => c */ x) (snd m))
 end;

fun matrix_neg (m:matrix) =
  (dimensions m, FuncUtil.Intpairfunc.map Rat.neg (snd m)) :matrix;

fun matrix_add (m1:matrix) (m2:matrix) =
 let val d1 = dimensions m1
     val d2 = dimensions m2
 in if d1 <> d2
     then error "matrix_add: incompatible dimensions"
    else (d1,FuncUtil.Intpairfunc.combine (curry op +/) (fn x => x =/ rat_0) (snd m1) (snd m2)) :matrix
 end;;

fun matrix_sub m1 m2 = matrix_add m1 (matrix_neg m2);

fun row k (m:matrix) =
 let val (i,j) = dimensions m
 in (j,
   FuncUtil.Intpairfunc.fold (fn ((i,j), c) => fn a => if i = k then FuncUtil.Intfunc.update (j,c) a else a) (snd m) FuncUtil.Intfunc.empty ) : vector
 end;

fun column k (m:matrix) =
  let val (i,j) = dimensions m
  in (i,
   FuncUtil.Intpairfunc.fold (fn ((i,j), c) => fn a => if j = k then FuncUtil.Intfunc.update (i,c) a else a) (snd m)  FuncUtil.Intfunc.empty)
   : vector
 end;

fun transp (m:matrix) =
  let val (i,j) = dimensions m
  in
  ((j,i),FuncUtil.Intpairfunc.fold (fn ((i,j), c) => fn a => FuncUtil.Intpairfunc.update ((j,i), c) a) (snd m) FuncUtil.Intpairfunc.empty) :matrix
 end;

fun diagonal (v:vector) =
 let val n = dim v
 in ((n,n),FuncUtil.Intfunc.fold (fn (i, c) => fn a => FuncUtil.Intpairfunc.update ((i,i), c) a) (snd v) FuncUtil.Intpairfunc.empty) : matrix
 end;

fun matrix_of_list l =
 let val m = length l
 in if m = 0 then matrix_0 (0,0) else
   let val n = length (hd l)
   in ((m,n),itern 1 l (fn v => fn i => itern 1 v (fn c => fn j => FuncUtil.Intpairfunc.update ((i,j), c))) FuncUtil.Intpairfunc.empty)
   end
 end;

(* Monomials.                                                                *)

fun monomial_eval assig m =
  FuncUtil.Ctermfunc.fold (fn (x, k) => fn a => a */ rat_pow (FuncUtil.Ctermfunc.apply assig x) k)
        m rat_1;
val monomial_1 = FuncUtil.Ctermfunc.empty;

fun monomial_var x = FuncUtil.Ctermfunc.onefunc (x, 1);

val monomial_mul =
  FuncUtil.Ctermfunc.combine (curry op +) (K false);

fun monomial_pow m k =
  if k = 0 then monomial_1
  else FuncUtil.Ctermfunc.map (fn x => k * x) m;

fun monomial_divides m1 m2 =
  FuncUtil.Ctermfunc.fold (fn (x, k) => fn a => FuncUtil.Ctermfunc.tryapplyd m2 x 0 >= k andalso a) m1 true;;

fun monomial_div m1 m2 =
 let val m = FuncUtil.Ctermfunc.combine (curry op +)
   (fn x => x = 0) m1 (FuncUtil.Ctermfunc.map (fn x => ~ x) m2)
 in if FuncUtil.Ctermfunc.fold (fn (x, k) => fn a => k >= 0 andalso a) m true then m
  else error "monomial_div: non-divisible"
 end;

fun monomial_degree x m =
  FuncUtil.Ctermfunc.tryapplyd m x 0;;

fun monomial_lcm m1 m2 =
  fold_rev (fn x => FuncUtil.Ctermfunc.update (x, max (monomial_degree x m1) (monomial_degree x m2)))
          (gen_union (is_equal o  FuncUtil.cterm_ord) (FuncUtil.Ctermfunc.dom m1, FuncUtil.Ctermfunc.dom m2)) (FuncUtil.Ctermfunc.empty);

fun monomial_multidegree m =
 FuncUtil.Ctermfunc.fold (fn (x, k) => fn a => k + a) m 0;;

fun monomial_variables m = FuncUtil.Ctermfunc.dom m;;

(* Polynomials.                                                              *)

fun eval assig p =
  FuncUtil.Monomialfunc.fold (fn (m, c) => fn a => a +/ c */ monomial_eval assig m) p rat_0;

val poly_0 = FuncUtil.Monomialfunc.empty;

fun poly_isconst p =
  FuncUtil.Monomialfunc.fold (fn (m, c) => fn a => FuncUtil.Ctermfunc.is_empty m andalso a) p true;

fun poly_var x = FuncUtil.Monomialfunc.onefunc (monomial_var x,rat_1);

fun poly_const c =
  if c =/ rat_0 then poly_0 else FuncUtil.Monomialfunc.onefunc(monomial_1, c);

fun poly_cmul c p =
  if c =/ rat_0 then poly_0
  else FuncUtil.Monomialfunc.map (fn x => c */ x) p;

fun poly_neg p = FuncUtil.Monomialfunc.map Rat.neg p;;

fun poly_add p1 p2 =
  FuncUtil.Monomialfunc.combine (curry op +/) (fn x => x =/ rat_0) p1 p2;

fun poly_sub p1 p2 = poly_add p1 (poly_neg p2);

fun poly_cmmul (c,m) p =
 if c =/ rat_0 then poly_0
 else if FuncUtil.Ctermfunc.is_empty m
      then FuncUtil.Monomialfunc.map (fn d => c */ d) p
      else FuncUtil.Monomialfunc.fold (fn (m', d) => fn a => (FuncUtil.Monomialfunc.update (monomial_mul m m', c */ d) a)) p poly_0;

fun poly_mul p1 p2 =
  FuncUtil.Monomialfunc.fold (fn (m, c) => fn a => poly_add (poly_cmmul (c,m) p2) a) p1 poly_0;

fun poly_div p1 p2 =
 if not(poly_isconst p2)
 then error "poly_div: non-constant" else
 let val c = eval FuncUtil.Ctermfunc.empty p2
 in if c =/ rat_0 then error "poly_div: division by zero"
    else poly_cmul (Rat.inv c) p1
 end;

fun poly_square p = poly_mul p p;

fun poly_pow p k =
 if k = 0 then poly_const rat_1
 else if k = 1 then p
 else let val q = poly_square(poly_pow p (k div 2)) in
      if k mod 2 = 1 then poly_mul p q else q end;

fun poly_exp p1 p2 =
  if not(poly_isconst p2)
  then error "poly_exp: not a constant"
  else poly_pow p1 (int_of_rat (eval FuncUtil.Ctermfunc.empty p2));

fun degree x p =
 FuncUtil.Monomialfunc.fold (fn (m,c) => fn a => max (monomial_degree x m) a) p 0;

fun multidegree p =
  FuncUtil.Monomialfunc.fold (fn (m, c) => fn a => max (monomial_multidegree m) a) p 0;

fun poly_variables p =
  sort FuncUtil.cterm_ord (FuncUtil.Monomialfunc.fold_rev (fn (m, c) => curry (gen_union (is_equal o FuncUtil.cterm_ord)) (monomial_variables m)) p []);;

(* Order monomials for human presentation.                                   *)

val humanorder_varpow = prod_ord FuncUtil.cterm_ord (rev_order o int_ord);

local
 fun ord (l1,l2) = case (l1,l2) of
  (_,[]) => LESS
 | ([],_) => GREATER
 | (h1::t1,h2::t2) =>
   (case humanorder_varpow (h1, h2) of
     LESS => LESS
   | EQUAL => ord (t1,t2)
   | GREATER => GREATER)
in fun humanorder_monomial m1 m2 =
 ord (sort humanorder_varpow (FuncUtil.Ctermfunc.dest m1),
  sort humanorder_varpow (FuncUtil.Ctermfunc.dest m2))
end;

(* Conversions to strings.                                                   *)

fun string_of_vector min_size max_size (v:vector) =
 let val n_raw = dim v
 in if n_raw = 0 then "[]" else
  let
   val n = max min_size (min n_raw max_size)
   val xs = map (Rat.string_of_rat o (fn i => FuncUtil.Intfunc.tryapplyd (snd v) i rat_0)) (1 upto n)
  in "[" ^ space_implode ", " xs ^
  (if n_raw > max_size then ", ...]" else "]")
  end
 end;

fun string_of_matrix max_size (m:matrix) =
 let
  val (i_raw,j_raw) = dimensions m
  val i = min max_size i_raw
  val j = min max_size j_raw
  val rstr = map (fn k => string_of_vector j j (row k m)) (1 upto i)
 in "["^ space_implode ";\n " rstr ^
  (if j > max_size then "\n ...]" else "]")
 end;

fun string_of_term t =
 case t of
   a$b => "("^(string_of_term a)^" "^(string_of_term b)^")"
 | Abs x =>
    let val (xn, b) = Term.dest_abs x
    in "(\\"^xn^"."^(string_of_term b)^")"
    end
 | Const(s,_) => s
 | Free (s,_) => s
 | Var((s,_),_) => s
 | _ => error "string_of_term";

val string_of_cterm = string_of_term o term_of;

fun string_of_varpow x k =
  if k = 1 then string_of_cterm x
  else string_of_cterm x^"^"^string_of_int k;

fun string_of_monomial m =
 if FuncUtil.Ctermfunc.is_empty m then "1" else
 let val vps = fold_rev (fn (x,k) => fn a => string_of_varpow x k :: a)
  (sort humanorder_varpow (FuncUtil.Ctermfunc.dest m)) []
 in space_implode "*" vps
 end;

fun string_of_cmonomial (c,m) =
 if FuncUtil.Ctermfunc.is_empty m then Rat.string_of_rat c
 else if c =/ rat_1 then string_of_monomial m
 else Rat.string_of_rat c ^ "*" ^ string_of_monomial m;;

fun string_of_poly p =
 if FuncUtil.Monomialfunc.is_empty p then "<<0>>" else
 let
  val cms = sort (fn ((m1,_),(m2,_)) => humanorder_monomial m1  m2) (FuncUtil.Monomialfunc.dest p)
  val s = fold (fn (m,c) => fn a =>
             if c </ rat_0 then a ^ " - " ^ string_of_cmonomial(Rat.neg c,m)
             else a ^ " + " ^ string_of_cmonomial(c,m))
          cms ""
  val s1 = String.substring (s, 0, 3)
  val s2 = String.substring (s, 3, String.size s - 3)
 in "<<" ^(if s1 = " + " then s2 else "-"^s2)^">>"
 end;

(* Conversion from HOL term.                                                 *)

local
 val neg_tm = @{cterm "uminus :: real => _"}
 val add_tm = @{cterm "op + :: real => _"}
 val sub_tm = @{cterm "op - :: real => _"}
 val mul_tm = @{cterm "op * :: real => _"}
 val inv_tm = @{cterm "inverse :: real => _"}
 val div_tm = @{cterm "op / :: real => _"}
 val pow_tm = @{cterm "op ^ :: real => _"}
 val zero_tm = @{cterm "0:: real"}
 val is_numeral = can (HOLogic.dest_number o term_of)
 fun is_comb t = case t of _$_ => true | _ => false
 fun poly_of_term tm =
  if tm aconvc zero_tm then poly_0
  else if RealArith.is_ratconst tm
       then poly_const(RealArith.dest_ratconst tm)
  else
  (let val (lop,r) = Thm.dest_comb tm
   in if lop aconvc neg_tm then poly_neg(poly_of_term r)
      else if lop aconvc inv_tm then
       let val p = poly_of_term r
       in if poly_isconst p
          then poly_const(Rat.inv (eval FuncUtil.Ctermfunc.empty p))
          else error "poly_of_term: inverse of non-constant polyomial"
       end
   else (let val (opr,l) = Thm.dest_comb lop
         in
          if opr aconvc pow_tm andalso is_numeral r
          then poly_pow (poly_of_term l) ((snd o HOLogic.dest_number o term_of) r)
          else if opr aconvc add_tm
           then poly_add (poly_of_term l) (poly_of_term r)
          else if opr aconvc sub_tm
           then poly_sub (poly_of_term l) (poly_of_term r)
          else if opr aconvc mul_tm
           then poly_mul (poly_of_term l) (poly_of_term r)
          else if opr aconvc div_tm
           then let
                  val p = poly_of_term l
                  val q = poly_of_term r
                in if poly_isconst q then poly_cmul (Rat.inv (eval FuncUtil.Ctermfunc.empty q)) p
                   else error "poly_of_term: division by non-constant polynomial"
                end
          else poly_var tm

         end
         handle CTERM ("dest_comb",_) => poly_var tm)
   end
   handle CTERM ("dest_comb",_) => poly_var tm)
in
val poly_of_term = fn tm =>
 if type_of (term_of tm) = @{typ real} then poly_of_term tm
 else error "poly_of_term: term does not have real type"
end;

(* String of vector (just a list of space-separated numbers).                *)

fun sdpa_of_vector (v:vector) =
 let
  val n = dim v
  val strs = map (decimalize 20 o (fn i => FuncUtil.Intfunc.tryapplyd (snd v) i rat_0)) (1 upto n)
 in space_implode " " strs ^ "\n"
 end;

fun triple_int_ord ((a,b,c),(a',b',c')) =
 prod_ord int_ord (prod_ord int_ord int_ord)
    ((a,(b,c)),(a',(b',c')));
structure Inttriplefunc = FuncFun(type key = int*int*int val ord = triple_int_ord);

(* String for block diagonal matrix numbered k.                              *)

fun sdpa_of_blockdiagonal k m =
 let
  val pfx = string_of_int k ^" "
  val ents =
    Inttriplefunc.fold (fn ((b,i,j), c) => fn a => if i > j then a else ((b,i,j),c)::a) m []
  val entss = sort (triple_int_ord o pairself fst) ents
 in  fold_rev (fn ((b,i,j),c) => fn a =>
     pfx ^ string_of_int b ^ " " ^ string_of_int i ^ " " ^ string_of_int j ^
     " " ^ decimalize 20 c ^ "\n" ^ a) entss ""
 end;

(* String for a matrix numbered k, in SDPA sparse format.                    *)

fun sdpa_of_matrix k (m:matrix) =
 let
  val pfx = string_of_int k ^ " 1 "
  val ms = FuncUtil.Intpairfunc.fold (fn ((i,j), c) => fn  a => if i > j then a else ((i,j),c)::a) (snd m) []
  val mss = sort ((prod_ord int_ord int_ord) o pairself fst) ms
 in fold_rev (fn ((i,j),c) => fn a =>
     pfx ^ string_of_int i ^ " " ^ string_of_int j ^
     " " ^ decimalize 20 c ^ "\n" ^ a) mss ""
 end;;

(* ------------------------------------------------------------------------- *)
(* String in SDPA sparse format for standard SDP problem:                    *)
(*                                                                           *)
(*    X = v_1 * [M_1] + ... + v_m * [M_m] - [M_0] must be PSD                *)
(*    Minimize obj_1 * v_1 + ... obj_m * v_m                                 *)
(* ------------------------------------------------------------------------- *)

fun sdpa_of_problem obj mats =
 let
  val m = length mats - 1
  val (n,_) = dimensions (hd mats)
 in
  string_of_int m ^ "\n" ^
  "1\n" ^
  string_of_int n ^ "\n" ^
  sdpa_of_vector obj ^
  fold_rev2 (fn k => fn m => fn a => sdpa_of_matrix (k - 1) m ^ a) (1 upto length mats) mats ""
 end;

fun index_char str chr pos =
  if pos >= String.size str then ~1
  else if String.sub(str,pos) = chr then pos
  else index_char str chr (pos + 1);
fun rat_of_quotient (a,b) = if b = 0 then rat_0 else Rat.rat_of_quotient (a,b);
fun rat_of_string s =
 let val n = index_char s #"/" 0 in
  if n = ~1 then s |> IntInf.fromString |> valOf |> Rat.rat_of_int
  else
   let val SOME numer = IntInf.fromString(String.substring(s,0,n))
       val SOME den = IntInf.fromString (String.substring(s,n+1,String.size s - n - 1))
   in rat_of_quotient(numer, den)
   end
 end;

fun isspace x = x = " " ;
fun isnum x = x mem_string ["0","1","2","3","4","5","6","7","8","9"]

(* More parser basics.                                                       *)

 val word = Scan.this_string
 fun token s =
  Scan.repeat ($$ " ") |-- word s --| Scan.repeat ($$ " ")
 val numeral = Scan.one isnum
 val decimalint = Scan.bulk numeral >> (rat_of_string o implode)
 val decimalfrac = Scan.bulk numeral
    >> (fn s => rat_of_string(implode s) // pow10 (length s))
 val decimalsig =
    decimalint -- Scan.option (Scan.$$ "." |-- decimalfrac)
    >> (fn (h,NONE) => h | (h,SOME x) => h +/ x)
 fun signed prs =
       $$ "-" |-- prs >> Rat.neg
    || $$ "+" |-- prs
    || prs;

fun emptyin def xs = if null xs then (def,xs) else Scan.fail xs

 val exponent = ($$ "e" || $$ "E") |-- signed decimalint;

 val decimal = signed decimalsig -- (emptyin rat_0|| exponent)
    >> (fn (h, x) => h */ pow10 (int_of_rat x));

 fun mkparser p s =
  let val (x,rst) = p (explode s)
  in if null rst then x
     else error "mkparser: unparsed input"
  end;;

(* Parse back csdp output.                                                      *)

 fun ignore inp = ((),[])
 fun csdpoutput inp =  ((decimal -- Scan.bulk (Scan.$$ " " |-- Scan.option decimal) >> (fn (h,to) => map_filter I ((SOME h)::to))) --| ignore >> vector_of_list) inp
 val parse_csdpoutput = mkparser csdpoutput

(* Run prover on a problem in linear form.                       *)

fun run_problem prover obj mats =
  parse_csdpoutput (prover (sdpa_of_problem obj mats))

(* Try some apparently sensible scaling first. Note that this is purely to   *)
(* get a cleaner translation to floating-point, and doesn't affect any of    *)
(* the results, in principle. In practice it seems a lot better when there   *)
(* are extreme numbers in the original problem.                              *)

  (* Version for (int*int) keys *)
local
  fun max_rat x y = if x </ y then y else x
  fun common_denominator fld amat acc =
      fld (fn (m,c) => fn a => lcm_rat (denominator_rat c) a) amat acc
  fun maximal_element fld amat acc =
    fld (fn (m,c) => fn maxa => max_rat maxa (abs_rat c)) amat acc
fun float_of_rat x = let val (a,b) = Rat.quotient_of_rat x
                     in Real.fromLargeInt a / Real.fromLargeInt b end;
in

fun pi_scale_then solver (obj:vector)  mats =
 let
  val cd1 = fold_rev (common_denominator FuncUtil.Intpairfunc.fold) mats (rat_1)
  val cd2 = common_denominator FuncUtil.Intfunc.fold (snd obj)  (rat_1)
  val mats' = map (FuncUtil.Intpairfunc.map (fn x => cd1 */ x)) mats
  val obj' = vector_cmul cd2 obj
  val max1 = fold_rev (maximal_element FuncUtil.Intpairfunc.fold) mats' (rat_0)
  val max2 = maximal_element FuncUtil.Intfunc.fold (snd obj') (rat_0)
  val scal1 = pow2 (20 - trunc(Math.ln (float_of_rat max1) / Math.ln 2.0))
  val scal2 = pow2 (20 - trunc(Math.ln (float_of_rat max2) / Math.ln 2.0))
  val mats'' = map (FuncUtil.Intpairfunc.map (fn x => x */ scal1)) mats'
  val obj'' = vector_cmul scal2 obj'
 in solver obj'' mats''
  end
end;

(* Try some apparently sensible scaling first. Note that this is purely to   *)
(* get a cleaner translation to floating-point, and doesn't affect any of    *)
(* the results, in principle. In practice it seems a lot better when there   *)
(* are extreme numbers in the original problem.                              *)

  (* Version for (int*int*int) keys *)
local
  fun max_rat x y = if x </ y then y else x
  fun common_denominator fld amat acc =
      fld (fn (m,c) => fn a => lcm_rat (denominator_rat c) a) amat acc
  fun maximal_element fld amat acc =
    fld (fn (m,c) => fn maxa => max_rat maxa (abs_rat c)) amat acc
fun float_of_rat x = let val (a,b) = Rat.quotient_of_rat x
                     in Real.fromLargeInt a / Real.fromLargeInt b end;
fun int_of_float x = (trunc x handle Overflow => 0 | Domain => 0)
in

fun tri_scale_then solver (obj:vector)  mats =
 let
  val cd1 = fold_rev (common_denominator Inttriplefunc.fold) mats (rat_1)
  val cd2 = common_denominator FuncUtil.Intfunc.fold (snd obj)  (rat_1)
  val mats' = map (Inttriplefunc.map (fn x => cd1 */ x)) mats
  val obj' = vector_cmul cd2 obj
  val max1 = fold_rev (maximal_element Inttriplefunc.fold) mats' (rat_0)
  val max2 = maximal_element FuncUtil.Intfunc.fold (snd obj') (rat_0)
  val scal1 = pow2 (20 - int_of_float(Math.ln (float_of_rat max1) / Math.ln 2.0))
  val scal2 = pow2 (20 - int_of_float(Math.ln (float_of_rat max2) / Math.ln 2.0))
  val mats'' = map (Inttriplefunc.map (fn x => x */ scal1)) mats'
  val obj'' = vector_cmul scal2 obj'
 in solver obj'' mats''
  end
end;

(* Round a vector to "nice" rationals.                                       *)

fun nice_rational n x = round_rat (n */ x) // n;;
fun nice_vector n ((d,v) : vector) =
 (d, FuncUtil.Intfunc.fold (fn (i,c) => fn a =>
   let val y = nice_rational n c
   in if c =/ rat_0 then a
      else FuncUtil.Intfunc.update (i,y) a end) v FuncUtil.Intfunc.empty):vector

fun dest_ord f x = is_equal (f x);

(* Stuff for "equations" ((int*int*int)->num functions).                         *)

fun tri_equation_cmul c eq =
  if c =/ rat_0 then Inttriplefunc.empty else Inttriplefunc.map (fn d => c */ d) eq;

fun tri_equation_add eq1 eq2 = Inttriplefunc.combine (curry op +/) (fn x => x =/ rat_0) eq1 eq2;

fun tri_equation_eval assig eq =
 let fun value v = Inttriplefunc.apply assig v
 in Inttriplefunc.fold (fn (v, c) => fn a => a +/ value v */ c) eq rat_0
 end;

(* Eliminate among linear equations: return unconstrained variables and      *)
(* assignments for the others in terms of them. We give one pseudo-variable  *)
(* "one" that's used for a constant term.                                    *)

local
  fun extract_first p l = case l of  (* FIXME : use find_first instead *)
   [] => error "extract_first"
 | h::t => if p h then (h,t) else
          let val (k,s) = extract_first p t in (k,h::s) end
fun eliminate vars dun eqs = case vars of
  [] => if forall Inttriplefunc.is_empty eqs then dun
        else raise Unsolvable
 | v::vs =>
  ((let
    val (eq,oeqs) = extract_first (fn e => Inttriplefunc.defined e v) eqs
    val a = Inttriplefunc.apply eq v
    val eq' = tri_equation_cmul ((Rat.neg rat_1) // a) (Inttriplefunc.delete_safe v eq)
    fun elim e =
     let val b = Inttriplefunc.tryapplyd e v rat_0
     in if b =/ rat_0 then e else
        tri_equation_add e (tri_equation_cmul (Rat.neg b // a) eq)
     end
   in eliminate vs (Inttriplefunc.update (v,eq') (Inttriplefunc.map elim dun)) (map elim oeqs)
   end)
  handle Failure _ => eliminate vs dun eqs)
in
fun tri_eliminate_equations one vars eqs =
 let
  val assig = eliminate vars Inttriplefunc.empty eqs
  val vs = Inttriplefunc.fold (fn (x, f) => fn a => remove (dest_ord triple_int_ord) one (Inttriplefunc.dom f) @ a) assig []
  in (distinct (dest_ord triple_int_ord) vs, assig)
  end
end;

(* Eliminate all variables, in an essentially arbitrary order.               *)

fun tri_eliminate_all_equations one =
 let
  fun choose_variable eq =
   let val (v,_) = Inttriplefunc.choose eq
   in if is_equal (triple_int_ord(v,one)) then
      let val eq' = Inttriplefunc.delete_safe v eq
      in if Inttriplefunc.is_empty eq' then error "choose_variable"
         else fst (Inttriplefunc.choose eq')
      end
    else v
   end
  fun eliminate dun eqs = case eqs of
    [] => dun
  | eq::oeqs =>
    if Inttriplefunc.is_empty eq then eliminate dun oeqs else
    let val v = choose_variable eq
        val a = Inttriplefunc.apply eq v
        val eq' = tri_equation_cmul ((Rat.rat_of_int ~1) // a)
                   (Inttriplefunc.delete_safe v eq)
        fun elim e =
         let val b = Inttriplefunc.tryapplyd e v rat_0
         in if b =/ rat_0 then e
            else tri_equation_add e (tri_equation_cmul (Rat.neg b // a) eq)
         end
    in eliminate (Inttriplefunc.update(v, eq') (Inttriplefunc.map elim dun))
                 (map elim oeqs)
    end
in fn eqs =>
 let
  val assig = eliminate Inttriplefunc.empty eqs
  val vs = Inttriplefunc.fold (fn (x, f) => fn a => remove (dest_ord triple_int_ord) one (Inttriplefunc.dom f) @ a) assig []
 in (distinct (dest_ord triple_int_ord) vs,assig)
 end
end;

(* Solve equations by assigning arbitrary numbers.                           *)

fun tri_solve_equations one eqs =
 let
  val (vars,assigs) = tri_eliminate_all_equations one eqs
  val vfn = fold_rev (fn v => Inttriplefunc.update(v,rat_0)) vars
            (Inttriplefunc.onefunc(one, Rat.rat_of_int ~1))
  val ass =
    Inttriplefunc.combine (curry op +/) (K false)
    (Inttriplefunc.map (tri_equation_eval vfn) assigs) vfn
 in if forall (fn e => tri_equation_eval ass e =/ rat_0) eqs
    then Inttriplefunc.delete_safe one ass else raise Sanity
 end;

(* Multiply equation-parametrized poly by regular poly and add accumulator.  *)

fun tri_epoly_pmul p q acc =
 FuncUtil.Monomialfunc.fold (fn (m1, c) => fn a =>
  FuncUtil.Monomialfunc.fold (fn (m2,e) => fn b =>
   let val m =  monomial_mul m1 m2
       val es = FuncUtil.Monomialfunc.tryapplyd b m Inttriplefunc.empty
   in FuncUtil.Monomialfunc.update (m,tri_equation_add (tri_equation_cmul c e) es) b
   end) q a) p acc ;

(* Usual operations on equation-parametrized poly.                           *)

fun tri_epoly_cmul c l =
  if c =/ rat_0 then Inttriplefunc.empty else Inttriplefunc.map (tri_equation_cmul c) l;;

val tri_epoly_neg = tri_epoly_cmul (Rat.rat_of_int ~1);

val tri_epoly_add = Inttriplefunc.combine tri_equation_add Inttriplefunc.is_empty;

fun tri_epoly_sub p q = tri_epoly_add p (tri_epoly_neg q);;

(* Stuff for "equations" ((int*int)->num functions).                         *)

fun pi_equation_cmul c eq =
  if c =/ rat_0 then Inttriplefunc.empty else Inttriplefunc.map (fn d => c */ d) eq;

fun pi_equation_add eq1 eq2 = Inttriplefunc.combine (curry op +/) (fn x => x =/ rat_0) eq1 eq2;

fun pi_equation_eval assig eq =
 let fun value v = Inttriplefunc.apply assig v
 in Inttriplefunc.fold (fn (v, c) => fn a => a +/ value v */ c) eq rat_0
 end;

(* Eliminate among linear equations: return unconstrained variables and      *)
(* assignments for the others in terms of them. We give one pseudo-variable  *)
(* "one" that's used for a constant term.                                    *)

local
fun extract_first p l = case l of
   [] => error "extract_first"
 | h::t => if p h then (h,t) else
          let val (k,s) = extract_first p t in (k,h::s) end
fun eliminate vars dun eqs = case vars of
  [] => if forall Inttriplefunc.is_empty eqs then dun
        else raise Unsolvable
 | v::vs =>
   let
    val (eq,oeqs) = extract_first (fn e => Inttriplefunc.defined e v) eqs
    val a = Inttriplefunc.apply eq v
    val eq' = pi_equation_cmul ((Rat.neg rat_1) // a) (Inttriplefunc.delete_safe v eq)
    fun elim e =
     let val b = Inttriplefunc.tryapplyd e v rat_0
     in if b =/ rat_0 then e else
        pi_equation_add e (pi_equation_cmul (Rat.neg b // a) eq)
     end
   in eliminate vs (Inttriplefunc.update (v,eq') (Inttriplefunc.map elim dun)) (map elim oeqs)
   end
  handle Failure _ => eliminate vs dun eqs
in
fun pi_eliminate_equations one vars eqs =
 let
  val assig = eliminate vars Inttriplefunc.empty eqs
  val vs = Inttriplefunc.fold (fn (x, f) => fn a => remove (dest_ord triple_int_ord) one (Inttriplefunc.dom f) @ a) assig []
  in (distinct (dest_ord triple_int_ord) vs, assig)
  end
end;

(* Eliminate all variables, in an essentially arbitrary order.               *)

fun pi_eliminate_all_equations one =
 let
  fun choose_variable eq =
   let val (v,_) = Inttriplefunc.choose eq
   in if is_equal (triple_int_ord(v,one)) then
      let val eq' = Inttriplefunc.delete_safe v eq
      in if Inttriplefunc.is_empty eq' then error "choose_variable"
         else fst (Inttriplefunc.choose eq')
      end
    else v
   end
  fun eliminate dun eqs = case eqs of
    [] => dun
  | eq::oeqs =>
    if Inttriplefunc.is_empty eq then eliminate dun oeqs else
    let val v = choose_variable eq
        val a = Inttriplefunc.apply eq v
        val eq' = pi_equation_cmul ((Rat.rat_of_int ~1) // a)
                   (Inttriplefunc.delete_safe v eq)
        fun elim e =
         let val b = Inttriplefunc.tryapplyd e v rat_0
         in if b =/ rat_0 then e
            else pi_equation_add e (pi_equation_cmul (Rat.neg b // a) eq)
         end
    in eliminate (Inttriplefunc.update(v, eq') (Inttriplefunc.map elim dun))
                 (map elim oeqs)
    end
in fn eqs =>
 let
  val assig = eliminate Inttriplefunc.empty eqs
  val vs = Inttriplefunc.fold (fn (x, f) => fn a => remove (dest_ord triple_int_ord) one (Inttriplefunc.dom f) @ a) assig []
 in (distinct (dest_ord triple_int_ord) vs,assig)
 end
end;

(* Solve equations by assigning arbitrary numbers.                           *)

fun pi_solve_equations one eqs =
 let
  val (vars,assigs) = pi_eliminate_all_equations one eqs
  val vfn = fold_rev (fn v => Inttriplefunc.update(v,rat_0)) vars
            (Inttriplefunc.onefunc(one, Rat.rat_of_int ~1))
  val ass =
    Inttriplefunc.combine (curry op +/) (K false)
    (Inttriplefunc.map (pi_equation_eval vfn) assigs) vfn
 in if forall (fn e => pi_equation_eval ass e =/ rat_0) eqs
    then Inttriplefunc.delete_safe one ass else raise Sanity
 end;

(* Multiply equation-parametrized poly by regular poly and add accumulator.  *)

fun pi_epoly_pmul p q acc =
 FuncUtil.Monomialfunc.fold (fn (m1, c) => fn a =>
  FuncUtil.Monomialfunc.fold (fn (m2,e) => fn b =>
   let val m =  monomial_mul m1 m2
       val es = FuncUtil.Monomialfunc.tryapplyd b m Inttriplefunc.empty
   in FuncUtil.Monomialfunc.update (m,pi_equation_add (pi_equation_cmul c e) es) b
   end) q a) p acc ;

(* Usual operations on equation-parametrized poly.                           *)

fun pi_epoly_cmul c l =
  if c =/ rat_0 then Inttriplefunc.empty else Inttriplefunc.map (pi_equation_cmul c) l;;

val pi_epoly_neg = pi_epoly_cmul (Rat.rat_of_int ~1);

val pi_epoly_add = Inttriplefunc.combine pi_equation_add Inttriplefunc.is_empty;

fun pi_epoly_sub p q = pi_epoly_add p (pi_epoly_neg q);;

fun allpairs f l1 l2 =  fold_rev (fn x => (curry (op @)) (map (f x) l2)) l1 [];

(* Hence produce the "relevant" monomials: those whose squares lie in the    *)
(* Newton polytope of the monomials in the input. (This is enough according  *)
(* to Reznik: "Extremal PSD forms with few terms", Duke Math. Journal,       *)
(* vol 45, pp. 363--374, 1978.                                               *)
(*                                                                           *)
(* These are ordered in sort of decreasing degree. In particular the         *)
(* constant monomial is last; this gives an order in diagonalization of the  *)
(* quadratic form that will tend to display constants.                       *)

(* Diagonalize (Cholesky/LDU) the matrix corresponding to a quadratic form.  *)

local
fun diagonalize n i m =
 if FuncUtil.Intpairfunc.is_empty (snd m) then []
 else
  let val a11 = FuncUtil.Intpairfunc.tryapplyd (snd m) (i,i) rat_0
  in if a11 </ rat_0 then raise Failure "diagonalize: not PSD"
    else if a11 =/ rat_0 then
          if FuncUtil.Intfunc.is_empty (snd (row i m)) then diagonalize n (i + 1) m
          else raise Failure "diagonalize: not PSD ___ "
    else
     let
      val v = row i m
      val v' = (fst v, FuncUtil.Intfunc.fold (fn (i, c) => fn a =>
       let val y = c // a11
       in if y = rat_0 then a else FuncUtil.Intfunc.update (i,y) a
       end)  (snd v) FuncUtil.Intfunc.empty)
      fun upt0 x y a = if y = rat_0 then a else FuncUtil.Intpairfunc.update (x,y) a
      val m' =
      ((n,n),
      iter (i+1,n) (fn j =>
          iter (i+1,n) (fn k =>
              (upt0 (j,k) (FuncUtil.Intpairfunc.tryapplyd (snd m) (j,k) rat_0 -/ FuncUtil.Intfunc.tryapplyd (snd v) j rat_0 */ FuncUtil.Intfunc.tryapplyd (snd v') k rat_0))))
          FuncUtil.Intpairfunc.empty)
     in (a11,v')::diagonalize n (i + 1) m'
     end
  end
in
fun diag m =
 let
   val nn = dimensions m
   val n = fst nn
 in if snd nn <> n then error "diagonalize: non-square matrix"
    else diagonalize n 1 m
 end
end;

fun gcd_rat a b = Rat.rat_of_int (Integer.gcd (int_of_rat a) (int_of_rat b));

(* Adjust a diagonalization to collect rationals at the start.               *)
  (* FIXME : Potentially polymorphic keys, but here only: integers!! *)
local
 fun upd0 x y a = if y =/ rat_0 then a else FuncUtil.Intfunc.update(x,y) a;
 fun mapa f (d,v) =
  (d, FuncUtil.Intfunc.fold (fn (i,c) => fn a => upd0 i (f c) a) v FuncUtil.Intfunc.empty)
 fun adj (c,l) =
 let val a =
  FuncUtil.Intfunc.fold (fn (i,c) => fn a => lcm_rat a (denominator_rat c))
    (snd l) rat_1 //
  FuncUtil.Intfunc.fold (fn (i,c) => fn a => gcd_rat a (numerator_rat c))
    (snd l) rat_0
  in ((c // (a */ a)),mapa (fn x => a */ x) l)
  end
in
fun deration d = if null d then (rat_0,d) else
 let val d' = map adj d
     val a = fold (lcm_rat o denominator_rat o fst) d' rat_1 //
          fold (gcd_rat o numerator_rat o fst) d' rat_0
 in ((rat_1 // a),map (fn (c,l) => (a */ c,l)) d')
 end
end;

(* Enumeration of monomials with given multidegree bound.                    *)

fun enumerate_monomials d vars =
 if d < 0 then []
 else if d = 0 then [FuncUtil.Ctermfunc.empty]
 else if null vars then [monomial_1] else
 let val alts =
  map (fn k => let val oths = enumerate_monomials (d - k) (tl vars)
               in map (fn ks => if k = 0 then ks else FuncUtil.Ctermfunc.update (hd vars, k) ks) oths end) (0 upto d)
 in flat alts
 end;

(* Enumerate products of distinct input polys with degree <= d.              *)
(* We ignore any constant input polynomials.                                 *)
(* Give the output polynomial and a record of how it was derived.            *)

fun enumerate_products d pols =
if d = 0 then [(poly_const rat_1,RealArith.Rational_lt rat_1)]
else if d < 0 then [] else
case pols of
   [] => [(poly_const rat_1,RealArith.Rational_lt rat_1)]
 | (p,b)::ps =>
    let val e = multidegree p
    in if e = 0 then enumerate_products d ps else
       enumerate_products d ps @
       map (fn (q,c) => (poly_mul p q,RealArith.Product(b,c)))
         (enumerate_products (d - e) ps)
    end

(* Convert regular polynomial. Note that we treat (0,0,0) as -1.             *)

fun epoly_of_poly p =
  FuncUtil.Monomialfunc.fold (fn (m,c) => fn a => FuncUtil.Monomialfunc.update (m, Inttriplefunc.onefunc ((0,0,0), Rat.neg c)) a) p FuncUtil.Monomialfunc.empty;

(* String for block diagonal matrix numbered k.                              *)

fun sdpa_of_blockdiagonal k m =
 let
  val pfx = string_of_int k ^" "
  val ents =
    Inttriplefunc.fold
      (fn ((b,i,j),c) => fn a => if i > j then a else ((b,i,j),c)::a)
      m []
  val entss = sort (triple_int_ord o pairself fst) ents
 in fold_rev (fn ((b,i,j),c) => fn a =>
     pfx ^ string_of_int b ^ " " ^ string_of_int i ^ " " ^ string_of_int j ^
     " " ^ decimalize 20 c ^ "\n" ^ a) entss ""
 end;

(* SDPA for problem using block diagonal (i.e. multiple SDPs)                *)

fun sdpa_of_blockproblem nblocks blocksizes obj mats =
 let val m = length mats - 1
 in
  string_of_int m ^ "\n" ^
  string_of_int nblocks ^ "\n" ^
  (space_implode " " (map string_of_int blocksizes)) ^
  "\n" ^
  sdpa_of_vector obj ^
  fold_rev2 (fn k => fn m => fn a => sdpa_of_blockdiagonal (k - 1) m ^ a)
    (1 upto length mats) mats ""
 end;

(* Run prover on a problem in block diagonal form.                       *)

fun run_blockproblem prover nblocks blocksizes obj mats=
  parse_csdpoutput (prover (sdpa_of_blockproblem nblocks blocksizes obj mats))

(* 3D versions of matrix operations to consider blocks separately.           *)

val bmatrix_add = Inttriplefunc.combine (curry op +/) (fn x => x =/ rat_0);
fun bmatrix_cmul c bm =
  if c =/ rat_0 then Inttriplefunc.empty
  else Inttriplefunc.map (fn x => c */ x) bm;

val bmatrix_neg = bmatrix_cmul (Rat.rat_of_int ~1);
fun bmatrix_sub m1 m2 = bmatrix_add m1 (bmatrix_neg m2);;

(* Smash a block matrix into components.                                     *)

fun blocks blocksizes bm =
 map (fn (bs,b0) =>
      let val m = Inttriplefunc.fold
          (fn ((b,i,j),c) => fn a => if b = b0 then FuncUtil.Intpairfunc.update ((i,j),c) a else a) bm FuncUtil.Intpairfunc.empty
          val d = FuncUtil.Intpairfunc.fold (fn ((i,j),c) => fn a => max a (max i j)) m 0
      in (((bs,bs),m):matrix) end)
 (blocksizes ~~ (1 upto length blocksizes));;

(* FIXME : Get rid of this !!!*)
local
  fun tryfind_with msg f [] = raise Failure msg
    | tryfind_with msg f (x::xs) = (f x handle Failure s => tryfind_with s f xs);
in
  fun tryfind f = tryfind_with "tryfind" f
end

(* Positiv- and Nullstellensatz. Flag "linf" forces a linear representation. *)


fun real_positivnullstellensatz_general prover linf d eqs leqs pol =
let
 val vars = fold_rev (curry (gen_union (op aconvc)) o poly_variables)
              (pol::eqs @ map fst leqs) []
 val monoid = if linf then
      (poly_const rat_1,RealArith.Rational_lt rat_1)::
      (filter (fn (p,c) => multidegree p <= d) leqs)
    else enumerate_products d leqs
 val nblocks = length monoid
 fun mk_idmultiplier k p =
  let
   val e = d - multidegree p
   val mons = enumerate_monomials e vars
   val nons = mons ~~ (1 upto length mons)
  in (mons,
      fold_rev (fn (m,n) => FuncUtil.Monomialfunc.update(m,Inttriplefunc.onefunc((~k,~n,n),rat_1))) nons FuncUtil.Monomialfunc.empty)
  end

 fun mk_sqmultiplier k (p,c) =
  let
   val e = (d - multidegree p) div 2
   val mons = enumerate_monomials e vars
   val nons = mons ~~ (1 upto length mons)
  in (mons,
      fold_rev (fn (m1,n1) =>
       fold_rev (fn (m2,n2) => fn  a =>
        let val m = monomial_mul m1 m2
        in if n1 > n2 then a else
          let val c = if n1 = n2 then rat_1 else rat_2
              val e = FuncUtil.Monomialfunc.tryapplyd a m Inttriplefunc.empty
          in FuncUtil.Monomialfunc.update(m, tri_equation_add (Inttriplefunc.onefunc((k,n1,n2), c)) e) a
          end
        end)  nons)
       nons FuncUtil.Monomialfunc.empty)
  end

  val (sqmonlist,sqs) = split_list (map2 mk_sqmultiplier (1 upto length monoid) monoid)
  val (idmonlist,ids) =  split_list(map2 mk_idmultiplier (1 upto length eqs) eqs)
  val blocksizes = map length sqmonlist
  val bigsum =
    fold_rev2 (fn p => fn q => fn a => tri_epoly_pmul p q a) eqs ids
            (fold_rev2 (fn (p,c) => fn s => fn a => tri_epoly_pmul p s a) monoid sqs
                     (epoly_of_poly(poly_neg pol)))
  val eqns = FuncUtil.Monomialfunc.fold (fn (m,e) => fn a => e::a) bigsum []
  val (pvs,assig) = tri_eliminate_all_equations (0,0,0) eqns
  val qvars = (0,0,0)::pvs
  val allassig = fold_rev (fn v => Inttriplefunc.update(v,(Inttriplefunc.onefunc(v,rat_1)))) pvs assig
  fun mk_matrix v =
    Inttriplefunc.fold (fn ((b,i,j), ass) => fn m =>
        if b < 0 then m else
         let val c = Inttriplefunc.tryapplyd ass v rat_0
         in if c = rat_0 then m else
            Inttriplefunc.update ((b,j,i), c) (Inttriplefunc.update ((b,i,j), c) m)
         end)
          allassig Inttriplefunc.empty
  val diagents = Inttriplefunc.fold
    (fn ((b,i,j), e) => fn a => if b > 0 andalso i = j then tri_equation_add e a else a)
    allassig Inttriplefunc.empty

  val mats = map mk_matrix qvars
  val obj = (length pvs,
            itern 1 pvs (fn v => fn i => FuncUtil.Intfunc.updatep iszero (i,Inttriplefunc.tryapplyd diagents v rat_0))
                        FuncUtil.Intfunc.empty)
  val raw_vec = if null pvs then vector_0 0
                else tri_scale_then (run_blockproblem prover nblocks blocksizes) obj mats
  fun int_element (d,v) i = FuncUtil.Intfunc.tryapplyd v i rat_0
  fun cterm_element (d,v) i = FuncUtil.Ctermfunc.tryapplyd v i rat_0

  fun find_rounding d =
   let
    val _ = if !debugging
          then writeln ("Trying rounding with limit "^Rat.string_of_rat d ^ "\n")
          else ()
    val vec = nice_vector d raw_vec
    val blockmat = iter (1,dim vec)
     (fn i => fn a => bmatrix_add (bmatrix_cmul (int_element vec i) (nth mats i)) a)
     (bmatrix_neg (nth mats 0))
    val allmats = blocks blocksizes blockmat
   in (vec,map diag allmats)
   end
  val (vec,ratdias) =
    if null pvs then find_rounding rat_1
    else tryfind find_rounding (map Rat.rat_of_int (1 upto 31) @
                                map pow2 (5 upto 66))
  val newassigs =
    fold_rev (fn k => Inttriplefunc.update (nth pvs (k - 1), int_element vec k))
           (1 upto dim vec) (Inttriplefunc.onefunc ((0,0,0), Rat.rat_of_int ~1))
  val finalassigs =
    Inttriplefunc.fold (fn (v,e) => fn a => Inttriplefunc.update(v, tri_equation_eval newassigs e) a) allassig newassigs
  fun poly_of_epoly p =
    FuncUtil.Monomialfunc.fold (fn (v,e) => fn a => FuncUtil.Monomialfunc.updatep iszero (v,tri_equation_eval finalassigs e) a)
          p FuncUtil.Monomialfunc.empty
  fun  mk_sos mons =
   let fun mk_sq (c,m) =
    (c,fold_rev (fn k=> fn a => FuncUtil.Monomialfunc.updatep iszero (nth mons (k - 1), int_element m k) a)
                 (1 upto length mons) FuncUtil.Monomialfunc.empty)
   in map mk_sq
   end
  val sqs = map2 mk_sos sqmonlist ratdias
  val cfs = map poly_of_epoly ids
  val msq = filter (fn (a,b) => not (null b)) (map2 pair monoid sqs)
  fun eval_sq sqs = fold_rev (fn (c,q) => poly_add (poly_cmul c (poly_mul q q))) sqs poly_0
  val sanity =
    fold_rev (fn ((p,c),s) => poly_add (poly_mul p (eval_sq s))) msq
           (fold_rev2 (fn p => fn q => poly_add (poly_mul p q)) cfs eqs
                    (poly_neg pol))

in if not(FuncUtil.Monomialfunc.is_empty sanity) then raise Sanity else
  (cfs,map (fn (a,b) => (snd a,b)) msq)
 end


(* Iterative deepening.                                                      *)

fun deepen f n =
  (writeln ("Searching with depth limit " ^ string_of_int n) ; (f n handle Failure s => (writeln ("failed with message: " ^ s) ; deepen f (n+1))))


(* Map back polynomials and their composites to a positivstellensatz.        *)

fun cterm_of_sqterm (c,p) = RealArith.Product(RealArith.Rational_lt c,RealArith.Square p);

fun cterm_of_sos (pr,sqs) = if null sqs then pr
  else RealArith.Product(pr,foldr1 RealArith.Sum (map cterm_of_sqterm sqs));

(* Interface to HOL.                                                         *)
local
  open Conv
  val concl = Thm.dest_arg o cprop_of
  fun simple_cterm_ord t u = TermOrd.fast_term_ord (term_of t, term_of u) = LESS
in
  (* FIXME: Replace tryfind by get_first !! *)
fun real_nonlinear_prover proof_method ctxt =
 let
  val {add,mul,neg,pow,sub,main} =  Normalizer.semiring_normalizers_ord_wrapper ctxt
      (valOf (NormalizerData.match ctxt @{cterm "(0::real) + 1"}))
     simple_cterm_ord
  val (real_poly_add_conv,real_poly_mul_conv,real_poly_neg_conv,
       real_poly_pow_conv,real_poly_sub_conv,real_poly_conv) = (add,mul,neg,pow,sub,main)
  fun mainf cert_choice translator (eqs,les,lts) =
  let
   val eq0 = map (poly_of_term o Thm.dest_arg1 o concl) eqs
   val le0 = map (poly_of_term o Thm.dest_arg o concl) les
   val lt0 = map (poly_of_term o Thm.dest_arg o concl) lts
   val eqp0 = map (fn (t,i) => (t,RealArith.Axiom_eq i)) (eq0 ~~ (0 upto (length eq0 - 1)))
   val lep0 = map (fn (t,i) => (t,RealArith.Axiom_le i)) (le0 ~~ (0 upto (length le0 - 1)))
   val ltp0 = map (fn (t,i) => (t,RealArith.Axiom_lt i)) (lt0 ~~ (0 upto (length lt0 - 1)))
   val (keq,eq) = List.partition (fn (p,_) => multidegree p = 0) eqp0
   val (klep,lep) = List.partition (fn (p,_) => multidegree p = 0) lep0
   val (kltp,ltp) = List.partition (fn (p,_) => multidegree p = 0) ltp0
   fun trivial_axiom (p,ax) =
    case ax of
       RealArith.Axiom_eq n => if eval FuncUtil.Ctermfunc.empty p <>/ Rat.zero then nth eqs n
                     else raise Failure "trivial_axiom: Not a trivial axiom"
     | RealArith.Axiom_le n => if eval FuncUtil.Ctermfunc.empty p </ Rat.zero then nth les n
                     else raise Failure "trivial_axiom: Not a trivial axiom"
     | RealArith.Axiom_lt n => if eval FuncUtil.Ctermfunc.empty p <=/ Rat.zero then nth lts n
                     else raise Failure "trivial_axiom: Not a trivial axiom"
     | _ => error "trivial_axiom: Not a trivial axiom"
   in
  (let val th = tryfind trivial_axiom (keq @ klep @ kltp)
   in
    (fconv_rule (arg_conv (arg1_conv real_poly_conv) then_conv field_comp_conv) th, RealArith.Trivial)
   end)
   handle Failure _ =>
     (let val proof =
       (case proof_method of Certificate certs =>
         (* choose certificate *)
         let
           fun chose_cert [] (RealArith.Cert c) = c
             | chose_cert (RealArith.Left::s) (RealArith.Branch (l, _)) = chose_cert s l
             | chose_cert (RealArith.Right::s) (RealArith.Branch (_, r)) = chose_cert s r
             | chose_cert _ _ = error "certificate tree in invalid form"
         in
           chose_cert cert_choice certs
         end
       | Prover prover =>
         (* call prover *)
         let
          val pol = fold_rev poly_mul (map fst ltp) (poly_const Rat.one)
          val leq = lep @ ltp
          fun tryall d =
           let val e = multidegree pol
               val k = if e = 0 then 0 else d div e
               val eq' = map fst eq
           in tryfind (fn i => (d,i,real_positivnullstellensatz_general prover false d eq' leq
                                 (poly_neg(poly_pow pol i))))
                   (0 upto k)
           end
         val (d,i,(cert_ideal,cert_cone)) = deepen tryall 0
         val proofs_ideal =
           map2 (fn q => fn (p,ax) => RealArith.Eqmul(q,ax)) cert_ideal eq
         val proofs_cone = map cterm_of_sos cert_cone
         val proof_ne = if null ltp then RealArith.Rational_lt Rat.one else