Module Sidekick_smt_solver.Solver

Main solver type, user facing.

This is the solver a user of sidekick can see, after instantiating everything. The user can add some theories, clauses, etc. and asks the solver to check satisfiability.

Theory implementors will mostly interact with SOLVER_INTERNAL.

type t

The solver's state.

val registry : t -> Registry.t

A solver contains a registry so that theories can share data

type theory = Theory.t
val mk_theory : name:string -> create_and_setup:(id:Theory_id.t -> Solver_internal.t -> 'th) -> ?push_level:('th -> unit) -> ?pop_levels:('th -> int -> unit) -> unit -> Theory.t

Helper to create a theory.

Main API

val stats : t -> Sidekick_util.Stat.t
val tracer : t -> Tracer.t
val create : (module Sigs.ARG) -> ?stat:Sidekick_util.Stat.t -> ?size:[ `Big | `Tiny | `Small ] -> tracer:Tracer.t -> theories:Theory.t list -> Sidekick_core.Term.store -> unit -> t

Create a new solver.

It needs a term state and a type state to manipulate terms and types. All terms and types interacting with this solver will need to come from these exact states.

  • parameter store_proof

    if true, proofs from the SAT solver and theories are retained and potentially accessible after solve returns UNSAT.

  • parameter size

    influences the size of initial allocations.

  • parameter theories

    theories to load from the start. Other theories can be added using add_theory.

val create_default : ?stat:Sidekick_util.Stat.t -> ?size:[ `Big | `Tiny | `Small ] -> tracer:Tracer.t -> theories:Theory.t list -> Sidekick_core.Term.store -> unit -> t

Create a new solver with the default CC view, and where all boolean subterms are mapped to boolean atoms.

val add_theory : t -> Theory.t -> unit

Add a theory to the solver. This should be called before any call to solve or to add_clause and the likes (otherwise the theory will have a partial view of the problem).

val add_theory_p : t -> 'a Theory.p -> 'a

Add the given theory and obtain its state

val add_theory_l : t -> Theory.t list -> unit
val mk_lit_t : t -> ?sign:bool -> Sigs.term -> Sigs.lit

mk_lit_t _ ~sign t returns lit', where lit' is preprocess(lit) and lit is an internal representation of ± t.

The proof of |- lit = lit' is directly added to the solver's proof.

val add_clause : t -> Sigs.lit array -> Sidekick_proof.Pterm.delayed -> unit

add_clause solver cs adds a boolean clause to the solver. Subsequent calls to solve will need to satisfy this clause.

val add_clause_l : t -> Sigs.lit list -> Sidekick_proof.Pterm.delayed -> unit

Add a clause to the solver, given as a list.

val assert_terms : t -> Sigs.term list -> unit

Helper that turns each term into an atom, before adding disjunction of the resulting atoms to the solver as a clause assertion

val assert_term : t -> Sigs.term -> unit

Helper that turns the term into an atom, before adding the result to the solver as a unit clause assertion

val add_ty : t -> Sigs.ty -> unit
type sat_result = Check_res.sat_result = {
  1. get_value : Sidekick_core.Term.t -> value option;
    (*

    Value for this term

    *)
  2. iter_classes : (Sidekick_core.Term.t Iter.t * value) Iter.t;
    (*

    All equivalence classes in the congruence closure

    *)
  3. eval_lit : Sidekick_core.Lit.t -> bool option;
    (*

    Evaluate literal

    *)
  4. iter_true_lits : Sidekick_core.Lit.t Iter.t;
    (*

    Iterate on literals that are true in the trail

    *)
}

Satisfiable

type unsat_result = Check_res.unsat_result = {
  1. unsat_core : unit -> Sidekick_core.Lit.t Iter.t;
    (*

    Unsat core (subset of assumptions), or empty

    *)
  2. unsat_proof : unit -> Sidekick_proof.Step.id option;
    (*

    Proof step for the empty clause

    *)
}

Unsatisfiable

type res = Check_res.t =
  1. | Sat of sat_result
  2. | Unsat of unsat_result
  3. | Unknown of Unknown.t
    (*

    Unknown, obtained after a timeout, memory limit, etc.

    *)

Result of solving for the current set of clauses

val solve : ?on_exit:(unit -> unit) list -> ?on_progress:(unit -> unit) -> ?should_stop:(int -> bool) -> assumptions:Sigs.lit list -> t -> res

solve s checks the satisfiability of the clauses added so far to s.

  • parameter on_progress

    called regularly during solving.

  • parameter assumptions

    a set of atoms held to be true. The unsat core, if any, will be a subset of assumptions.

  • parameter should_stop

    a callback regularly called from within the solver. It is given a number of "steps" done since last call. The exact notion of step is not defined, but is guaranteed to increase regularly. The function should return true if it judges solving must stop (returning Unknown), false if solving can proceed.

  • parameter on_exit

    functions to be run before this returns

Comply to the abstract solver interface

val last_res : t -> res option

Last result, if any. Some operations will erase this (e.g. assert_term).

val push_assumption : t -> Sigs.lit -> unit

Pushes an assumption onto the assumption stack. It will remain there until it's pop'd by pop_assumptions.

val pop_assumptions : t -> int -> unit

pop_assumptions solver n removes n assumptions from the stack. It removes the assumptions that were the most recently added via push_assumptions. Note that check_sat_propagations_only can call this if it meets a conflict.

type propagation_result =
  1. | PR_sat
  2. | PR_conflict of {
    1. backtracked : int;
    }
  3. | PR_unsat of {
    1. unsat_core : unit -> Sigs.lit Iter.t;
    }
val check_sat_propagations_only : assumptions:Sigs.lit list -> t -> propagation_result

check_sat_propagations_only solver uses assumptions (including the assumptions parameter, and atoms previously added via push_assumptions) and boolean+theory propagation to quickly assess satisfiability. It is not complete; calling solve is required to get an accurate result.

  • returns

    one of:

    • PR_sat if the current state seems satisfiable
    • PR_conflict {backtracked=n} if a conflict was found and resolved, leading to backtracking n levels of assumptions
    • PR_unsat … if the assumptions were found to be unsatisfiable, with the given core.
val pp_stats : t CCFormat.printer

Print some statistics. What it prints exactly is unspecified.