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fix: missing preprocessing in LRA; better theory combination

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This commit is contained in:
Simon Cruanes 2021-02-22 14:01:55 -05:00
parent a8e2764e92
commit 45893e92f1
3 changed files with 48 additions and 13 deletions
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44
src/arith/lra/sidekick_arith_lra.ml
View file

@ -89,14 +89,17 @@ module Make(A : ARG) : S with module A = A = struct
module Tag = struct
type t =
| By_def
| Lit of Lit.t
| CC_eq of N.t * N.t
let pp out = function
| By_def -> Fmt.string out "by-def"
| Lit l -> Fmt.fprintf out "(@[lit %a@])" Lit.pp l
| CC_eq (n1,n2) -> Fmt.fprintf out "(@[cc-eq@ %a@ %a@])" N.pp n1 N.pp n2
let to_lits si = function
| By_def -> []
| Lit l -> [l]
| CC_eq (n1,n2) ->
SI.CC.explain_eq (SI.cc si) n1 n2
@ -196,10 +199,19 @@ module Make(A : ARG) : S with module A = A = struct
let proxy = fresh_term self ~pre (A.ty_lra self.tst) in
self.encoded_le <- Comb_map.add le_comb proxy self.encoded_le;
Log.debugf 50
(fun k->k "(@[lra.encode-le@ %a@ :into-var %a@])" LE_.Comb.pp le_comb T.pp proxy);
(fun k->k "(@[lra.encode-le@ `%a`@ :into-var %a@])" LE_.Comb.pp le_comb T.pp proxy);
(* it's actually 0 *)
if LE_.Comb.is_empty le_comb then (
Log.debug 50 "(lra.encode-le.is-trivially-0)";
SimpSolver.add_constraint self.simplex
(SimpSolver.Constraint.leq proxy Q.zero) Tag.By_def;
SimpSolver.add_constraint self.simplex
(SimpSolver.Constraint.geq proxy Q.zero) Tag.By_def;
) else (
LE_.Comb.iter (fun v _ -> SimpSolver.add_var self.simplex v) le_comb;
SimpSolver.define self.simplex proxy (LE_.Comb.to_list le_comb);
);
proxy
(* preprocess linear expressions away *)
@ -207,6 +219,12 @@ module Make(A : ARG) : S with module A = A = struct
Log.debugf 50 (fun k->k "lra.preprocess %a" T.pp t);
let tst = SI.tst si in
(* tell the CC this term exists *)
let declare_term_to_cc t =
Log.debugf 50 (fun k->k "(@[simplex2.declare-term-to-cc@ %a@])" T.pp t);
ignore (SI.CC.add_term (SI.cc si) t : SI.CC.N.t);
in
match A.view_as_lra t with
| LRA_pred ((Eq | Neq), t1, t2) ->
(* the equality side. *)
@ -219,8 +237,8 @@ module Make(A : ARG) : S with module A = A = struct
(* encode [t <=> (u1 /\ u2)] *)
let lit_t = mk_lit t in
let lit_u1 = mk_lit u1 in
let lit_u2 = mk_lit u2 in
let lit_u1 = mk_lit (recurse u1) in
let lit_u2 = mk_lit (recurse u2) in
add_clause [SI.Lit.neg lit_t; lit_u1];
add_clause [SI.Lit.neg lit_t; lit_u2];
add_clause [SI.Lit.neg lit_u1; SI.Lit.neg lit_u2; lit_t];
@ -239,6 +257,8 @@ module Make(A : ARG) : S with module A = A = struct
| None, _ ->
(* non trivial linexp, give it a fresh name in the simplex *)
let proxy = var_encoding_comb self ~pre:"_le" le_comb in
declare_term_to_cc proxy;
let new_t =
match pred with
| Eq | Neq -> assert false (* unreachable *)
@ -254,6 +274,7 @@ module Make(A : ARG) : S with module A = A = struct
| Some (coeff, v), pred ->
(* [c . v <= const] becomes a direct simplex constraint [v <= const/c] *)
let q = Q.div le_const coeff in
declare_term_to_cc v;
let op = match pred with
| Leq -> S_op.Leq
@ -266,6 +287,7 @@ module Make(A : ARG) : S with module A = A = struct
let op = if Q.(coeff < zero) then S_op.neg_sign op else op in
let new_t = A.mk_lra tst (LRA_simplex_pred (v, op, q)) in
Log.debugf 10 (fun k->k "lra.preprocess@ :%a@ :into %a" T.pp t T.pp new_t);
Some new_t
end
@ -278,6 +300,8 @@ module Make(A : ARG) : S with module A = A = struct
(* if there is no constant, define [proxy] as [proxy := le_comb] and
return [proxy] *)
let proxy = var_encoding_comb self ~pre:"_le" le_comb in
declare_term_to_cc proxy;
Some proxy
) else (
(* a bit more complicated: we cannot just define [proxy := le_comb]
@ -298,6 +322,9 @@ module Make(A : ARG) : S with module A = A = struct
(fun k->k "(@[lra.encode-le.with-offset@ %a@ :var %a@ :diff-var %a@])"
LE_.Comb.pp le_comb T.pp proxy T.pp proxy2);
declare_term_to_cc proxy;
declare_term_to_cc proxy2;
add_clause [
mk_lit (A.mk_lra tst (LRA_simplex_pred (proxy2, Leq, Q.neg le_const)))
];
@ -367,10 +394,10 @@ module Make(A : ARG) : S with module A = A = struct
if n_th_comb > 0 then (
Log.debugf 5
(fun k->k "(@[LRA.needs-th-combination@ :n-lits %d@])" n_th_comb);
);
Log.debugf 50
(fun k->k "(@[LRA.needs-th-combination@ :lits %a@])"
(fun k->k "(@[LRA.needs-th-combination@ :terms [@[%a@]]@])"
(Util.pp_iter @@ Fmt.within "`" "`" T.pp) (T.Tbl.keys self.needs_th_combination));
);
(* theory combination: for [t1,t2] terms in [self.needs_th_combination]
that have same value, but are not provably equal, push
@ -397,12 +424,12 @@ module Make(A : ARG) : S with module A = A = struct
Log.debugf 50
(fun k->k "(@[LRA.th-comb.check-pair[val=%a]@ %a@ %a@])"
Q.pp_print _q T.pp t1 T.pp t2);
assert(SI.cc_mem_term si t1);
assert(SI.cc_mem_term si t2);
(* if both [t1] and [t2] are relevant to the congruence
closure, and are not equal in it yet, add [t1=t2] as
the next decision to do *)
if SI.cc_mem_term si t1 &&
SI.cc_mem_term si t2 &&
not (SI.cc_are_equal si t1 t2) then (
if not (SI.cc_are_equal si t1 t2) then (
Log.debug 50 "LRA.th-comb.must-decide-equal";
let t = A.mk_eq (SI.tst si) t1 t2 in
let lit = SI.mk_lit si acts t in
@ -472,6 +499,7 @@ module Make(A : ARG) : S with module A = A = struct
(* look for subterms of type Real, for they will need theory combination *)
let on_subterm (self:state) _ (t:T.t) : unit =
Log.debugf 50 (fun k->k "lra: cc-on-subterm %a" T.pp t);
if A.has_ty_real t &&
not (T.Tbl.mem self.needs_th_combination t) then (
Log.debugf 5 (fun k->k "(@[lra.needs-th-combination@ %a@])" T.pp t);

5
src/cc/Sidekick_cc.ml
View file

@ -534,10 +534,13 @@ module Make (A: CC_ARG)
begin
let sub_r = find_ sub in
let old_parents = sub_r.n_parents in
if Bag.is_empty old_parents then (
(* first time it has parents: call watchers that this is a subterm *)
List.iter (fun f -> f sub u) self.on_is_subterm;
);
on_backtrack self (fun () -> sub_r.n_parents <- old_parents);
sub_r.n_parents <- Bag.cons n sub_r.n_parents;
end;
List.iter (fun f -> f sub u) self.on_is_subterm;
sub
in
let[@inline] return x = Some x in

4
src/th-data/Sidekick_th_data.ml
View file

@ -390,7 +390,11 @@ module Make(A : ARG) : S with module A = A = struct
let pp_entry out (n,node) =
Fmt.fprintf out "@[<1>@[graph_node[%a]@]@ := %a@]" N.pp n pp_node node
in
if N_tbl.length g = 0 then (
Fmt.string out "(graph ø)"
) else (
Fmt.fprintf out "(@[graph@ %a@])" (Fmt.iter pp_entry) (N_tbl.to_iter g)
)
let mk_graph (self:t) cc : graph =
let g: graph = N_tbl.create ~size:32 () in