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use log::debug;
use std::convert::TryInto;
use std::ffi::{CStr, CString};
use std::fmt;
use z3_sys::*;
use crate::{
ast::{Ast, Bool, Dynamic},
Context, Model, Optimize, Params, SatResult, Statistics, Symbol,
};
use num::{
bigint::{BigInt, BigUint, Sign},
rational::BigRational,
};
impl<'ctx> Optimize<'ctx> {
unsafe fn wrap(ctx: &'ctx Context, z3_opt: Z3_optimize) -> Optimize<'ctx> {
Z3_optimize_inc_ref(ctx.z3_ctx, z3_opt);
Optimize { ctx, z3_opt }
}
/// Create a new optimize context.
pub fn new(ctx: &'ctx Context) -> Optimize<'ctx> {
unsafe { Self::wrap(ctx, Z3_mk_optimize(ctx.z3_ctx)) }
}
/// Parse an SMT-LIB2 string with assertions, soft constraints and optimization objectives.
/// Add the parsed constraints and objectives to the optimizer.
pub fn from_string<T: Into<Vec<u8>>>(&self, source_string: T) {
let source_cstring = CString::new(source_string).unwrap();
unsafe {
Z3_optimize_from_string(self.ctx.z3_ctx, self.z3_opt, source_cstring.as_ptr());
}
}
/// Get this optimizers 's context.
pub fn get_context(&self) -> &'ctx Context {
self.ctx
}
/// Assert hard constraint to the optimization context.
///
/// # See also:
///
/// - [`Optimize::assert_soft()`]
/// - [`Optimize::maximize()`]
/// - [`Optimize::minimize()`]
pub fn assert(&self, ast: &impl Ast<'ctx>) {
unsafe { Z3_optimize_assert(self.ctx.z3_ctx, self.z3_opt, ast.get_z3_ast()) };
}
/// Assert a constraint `a` into the solver, and track it (in the
/// unsat) core using the Boolean constant `p`.
///
/// This API is an alternative to
/// [`Optimize::check()`]
/// for extracting unsat cores. Both APIs can be used in the same solver.
/// The unsat core will contain a combination of the Boolean variables
/// provided using [`Optimize::assert_and_track()`]
/// and the Boolean literals provided using
/// [`Optimize::check()`].
///
/// # See also:
///
/// - [`Optimize::assert()`]
/// - [`Optimize::assert_soft()`]
pub fn assert_and_track(&self, ast: &Bool<'ctx>, p: &Bool<'ctx>) {
debug!("assert_and_track: {ast:?}");
unsafe { Z3_optimize_assert_and_track(self.ctx.z3_ctx, self.z3_opt, ast.z3_ast, p.z3_ast) };
}
/// Assert soft constraint to the optimization context.
/// Weight is a positive, rational penalty for violating the constraint.
/// Group is an optional identifier to group soft constraints.
///
/// # See also:
///
/// - [`Optimize::assert()`]
/// - [`Optimize::maximize()`]
/// - [`Optimize::minimize()`]
pub fn assert_soft(&self, ast: &impl Ast<'ctx>, weight: impl Weight, group: Option<Symbol>) {
let weight_string = weight.to_string();
let weight_cstring = CString::new(weight_string).unwrap();
let group = group
.map(|g| g.as_z3_symbol(self.ctx))
.unwrap_or_else(std::ptr::null_mut);
unsafe {
Z3_optimize_assert_soft(
self.ctx.z3_ctx,
self.z3_opt,
ast.get_z3_ast(),
weight_cstring.as_ptr(),
group,
)
};
}
/// Add a maximization constraint.
///
/// # See also:
///
/// - [`Optimize::assert()`]
/// - [`Optimize::minimize()`]
pub fn maximize(&self, ast: &impl Ast<'ctx>) {
// https://github.com/Z3Prover/z3/blob/09f911d8a84cd91988e5b96b69485b2a9a2edba3/src/opt/opt_context.cpp#L118-L120
assert!(matches!(
ast.get_sort().kind(),
SortKind::Int | SortKind::Real | SortKind::BV
));
unsafe { Z3_optimize_maximize(self.ctx.z3_ctx, self.z3_opt, ast.get_z3_ast()) };
}
/// Add a minimization constraint.
///
/// # See also:
///
/// - [`Optimize::assert()`]
/// - [`Optimize::maximize()`]
pub fn minimize(&self, ast: &impl Ast<'ctx>) {
assert!(matches!(
ast.get_sort().kind(),
SortKind::Int | SortKind::Real | SortKind::BV
));
unsafe { Z3_optimize_minimize(self.ctx.z3_ctx, self.z3_opt, ast.get_z3_ast()) };
}
/// Return a subset of the assumptions provided to either the last
///
/// * [`Optimize::check`] call, or
/// * sequence of [`Optimize::assert_and_track`] calls followed
/// by an [`Optimize::check`] call.
///
/// These are the assumptions Z3 used in the unsatisfiability proof.
/// Assumptions are available in Z3. They are used to extract unsatisfiable
/// cores. They may be also used to "retract" assumptions. Note that,
/// assumptions are not really "soft constraints", but they can be used to
/// implement them.
///
/// By default, the unsat core will not be minimized. Generation of a minimized
/// unsat core can be enabled via the `"sat.core.minimize"` and `"smt.core.minimize"`
/// settings for SAT and SMT cores respectively. Generation of minimized unsat cores
/// will be more expensive.
///
/// # See also:
///
/// - [`Optimize::check`]
pub fn get_unsat_core(&self) -> Vec<Bool<'ctx>> {
let z3_unsat_core = unsafe { Z3_optimize_get_unsat_core(self.ctx.z3_ctx, self.z3_opt) };
if z3_unsat_core.is_null() {
return vec![];
}
let len = unsafe { Z3_ast_vector_size(self.ctx.z3_ctx, z3_unsat_core) };
let mut unsat_core = Vec::with_capacity(len as usize);
for i in 0..len {
let elem = unsafe { Z3_ast_vector_get(self.ctx.z3_ctx, z3_unsat_core, i) };
let elem = unsafe { Bool::wrap(self.ctx, elem) };
unsat_core.push(elem);
}
unsat_core
}
/// Create a backtracking point.
///
/// The optimize solver contains a set of rules, added facts and assertions.
/// The set of rules, facts and assertions are restored upon calling
/// [`Optimize::pop()`].
///
/// # See also:
///
/// - [`Optimize::pop()`]
pub fn push(&self) {
unsafe { Z3_optimize_push(self.ctx.z3_ctx, self.z3_opt) };
}
/// Backtrack one level.
///
/// # Preconditions:
///
/// - The number of calls to [`Optimize::pop`] cannot exceed the number of calls to
/// [`Optimize::push()`].
///
/// # See also:
///
/// - [`Optimize::push()`]
pub fn pop(&self) {
unsafe { Z3_optimize_pop(self.ctx.z3_ctx, self.z3_opt) };
}
/// Check consistency and produce optimal values.
///
/// # See also:
///
/// - [`Optimize::get_model()`]
pub fn check(&self, assumptions: &[Bool<'ctx>]) -> SatResult {
let assumptions: Vec<Z3_ast> = assumptions.iter().map(|a| a.z3_ast).collect();
match unsafe {
Z3_optimize_check(
self.ctx.z3_ctx,
self.z3_opt,
assumptions.len().try_into().unwrap(),
assumptions.as_ptr(),
)
} {
Z3_L_FALSE => SatResult::Unsat,
Z3_L_UNDEF => SatResult::Unknown,
Z3_L_TRUE => SatResult::Sat,
_ => unreachable!(),
}
}
/// Retrieve the model for the last [`Optimize::check()`].
///
/// The error handler is invoked if a model is not available because
/// the commands above were not invoked for the given optimization
/// solver, or if the result was [`SatResult::Unsat`].
pub fn get_model(&self) -> Option<Model<'ctx>> {
Model::of_optimize(self)
}
/// Retrieve the objectives for the last [`Optimize::check()`].
///
/// This contains maximize/minimize objectives and grouped soft constraints.
pub fn get_objectives(&self) -> Vec<Dynamic<'ctx>> {
let (z3_objectives, len) = unsafe {
let objectives = Z3_optimize_get_objectives(self.ctx.z3_ctx, self.z3_opt);
let len = Z3_ast_vector_size(self.ctx.z3_ctx, objectives);
(objectives, len)
};
let mut objectives = Vec::with_capacity(len as usize);
for i in 0..len {
let elem = unsafe { Z3_ast_vector_get(self.ctx.z3_ctx, z3_objectives, i) };
let elem = unsafe { Dynamic::wrap(self.ctx, elem) };
objectives.push(elem);
}
objectives
}
/// Retrieve a string that describes the last status returned by [`Optimize::check()`].
///
/// Use this method when [`Optimize::check()`] returns [`SatResult::Unknown`].
pub fn get_reason_unknown(&self) -> Option<String> {
let p = unsafe { Z3_optimize_get_reason_unknown(self.ctx.z3_ctx, self.z3_opt) };
if p.is_null() {
return None;
}
unsafe { CStr::from_ptr(p) }
.to_str()
.ok()
.map(|s| s.to_string())
}
/// Configure the parameters for this Optimize.
pub fn set_params(&self, params: &Params<'ctx>) {
unsafe { Z3_optimize_set_params(self.ctx.z3_ctx, self.z3_opt, params.z3_params) };
}
/// Retrieve the statistics for the last [`Optimize::check()`].
pub fn get_statistics(&self) -> Statistics<'ctx> {
unsafe {
Statistics::wrap(
self.ctx,
Z3_optimize_get_statistics(self.ctx.z3_ctx, self.z3_opt),
)
}
}
}
impl fmt::Display for Optimize<'_> {
fn fmt(&self, f: &mut fmt::Formatter) -> Result<(), fmt::Error> {
let p = unsafe { Z3_optimize_to_string(self.ctx.z3_ctx, self.z3_opt) };
if p.is_null() {
return Result::Err(fmt::Error);
}
match unsafe { CStr::from_ptr(p) }.to_str() {
Ok(s) => write!(f, "{s}"),
Err(_) => Result::Err(fmt::Error),
}
}
}
impl fmt::Debug for Optimize<'_> {
fn fmt(&self, f: &mut fmt::Formatter) -> Result<(), fmt::Error> {
<Self as fmt::Display>::fmt(self, f)
}
}
impl Drop for Optimize<'_> {
fn drop(&mut self) {
unsafe { Z3_optimize_dec_ref(self.ctx.z3_ctx, self.z3_opt) };
}
}
/// A rational non-negative weight for soft assertions.
/// This trait is sealed and cannot be implemented for types outside of
/// `z3`.
///
/// # See also:
///
/// - [`Optimize::assert_soft()`]
pub trait Weight: private::Sealed {
/// This is purposefully distinct from `ToString` to allow
/// specifying a `to_string` for tuples.
fn to_string(&self) -> String;
}
macro_rules! impl_weight {
($($ty: ty),*) => {
$(
impl Weight for $ty {
fn to_string(&self) -> String {
ToString::to_string(&self)
}
}
impl Weight for ($ty, $ty) {
fn to_string(&self) -> String {
format!("{} / {}", self.0, self.1)
}
}
)*
};
}
impl_weight! {
u8, u16, u32, u64, u128, usize, i8, i16, i32, i64, i128, isize
}
impl Weight for BigInt {
fn to_string(&self) -> String {
assert_ne!(self.sign(), Sign::Minus);
self.to_str_radix(10)
}
}
impl Weight for BigUint {
fn to_string(&self) -> String {
self.to_str_radix(10)
}
}
impl Weight for BigRational {
fn to_string(&self) -> String {
assert_ne!(self.numer().sign(), Sign::Minus);
assert_ne!(self.denom().sign(), Sign::Minus);
format!(
"{} / {}",
self.numer().to_str_radix(10),
self.denom().to_str_radix(10)
)
}
}
macro_rules! impl_sealed {
($($ty: ty),*) => {
mod private {
#[allow(unused_imports)]
use super::*;
pub trait Sealed {}
$(
impl Sealed for $ty {}
impl Sealed for ($ty, $ty) {}
)*
impl Sealed for BigInt {}
impl Sealed for BigUint {}
impl Sealed for BigRational {}
}
};
}
impl_sealed! {
u8, u16, u32, u64, u128, usize, i8, i16, i32, i64, i128, isize
}