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/// methods on clause activity
mod activity;
/// methods on binary link, namely binary clause
mod binary;
/// methods on `ClauseId`
mod cid;
/// methods on `Clause`
mod clause;
/// methods on `ClauseDB`
mod db;
/// EMA
mod ema;
/// methods for Stochastic Local Search
mod sls;
/// methods for UNSAT certification
mod unsat_certificate;
/// implementation of clause vivification
mod vivify;
/// types about watching literal
mod watch_cache;
pub use self::{
binary::{BinaryLinkDB, BinaryLinkList},
cid::ClauseIdIF,
property::*,
sls::StochasticLocalSearchIF,
unsat_certificate::CertificationStore,
vivify::VivifyIF,
};
use {
self::ema::ProgressLBD,
crate::{assign::AssignIF, types::*},
std::{
num::NonZeroU32,
ops::IndexMut,
slice::{Iter, IterMut},
},
watch_cache::*,
};
#[cfg(not(feature = "no_IO"))]
use std::path::Path;
/// API for Clause, providing literal accessors.
pub trait ClauseIF {
/// return true if it contains no literals; a clause after unit propagation.
fn is_empty(&self) -> bool;
/// return true if it contains no literals; a clause after unit propagation.
fn is_dead(&self) -> bool;
/// return 1st watch
fn lit0(&self) -> Lit;
/// return 2nd watch
fn lit1(&self) -> Lit;
/// return `true` if the clause contains the literal
fn contains(&self, lit: Lit) -> bool;
/// check clause satisfiability
fn is_satisfied_under(&self, asg: &impl AssignIF) -> bool;
/// return an iterator over its literals.
fn iter(&self) -> Iter<'_, Lit>;
/// return the number of literals.
fn len(&self) -> usize;
#[cfg(feature = "boundary_check")]
/// return timestamp.
fn timestamp(&self) -> usize;
#[cfg(feature = "boundary_check")]
fn set_birth(&mut self, time: usize);
}
/// API for clause management like [`reduce`](`crate::cdb::ClauseDBIF::reduce`), [`new_clause`](`crate::cdb::ClauseDBIF::new_clause`), [`remove_clause`](`crate::cdb::ClauseDBIF::remove_clause`), and so on.
pub trait ClauseDBIF:
Instantiate
+ IndexMut<ClauseId, Output = Clause>
+ PropertyDereference<property::Tusize, usize>
+ PropertyDereference<property::Tf64, f64>
{
/// return the length of `clause`.
fn len(&self) -> usize;
/// return true if it's empty.
fn is_empty(&self) -> bool;
/// return an iterator.
fn iter(&self) -> Iter<'_, Clause>;
/// return a mutable iterator.
fn iter_mut(&mut self) -> IterMut<'_, Clause>;
//
//## interface to binary links
//
/// return binary links: `BinaryLinkList` connected with a `Lit`.
fn binary_links(&self, l: Lit) -> &BinaryLinkList;
//
//## abstraction to watch_cache
//
// get mutable reference to a watch_cache
fn fetch_watch_cache_entry(&self, lit: Lit, index: WatchCacheProxy) -> (ClauseId, Lit);
/// replace the mutable watcher list with an empty one, and return the list
fn watch_cache_iter(&mut self, l: Lit) -> WatchCacheIterator;
/// detach the watch_cache referred by the head of a watch_cache iterator
fn detach_watch_cache(&mut self, l: Lit, iter: &mut WatchCacheIterator);
/// Merge two watch cache
fn merge_watch_cache(&mut self, l: Lit, wc: WatchCache);
/// swap the first two literals in a clause.
fn swap_watch(&mut self, cid: ClauseId);
//
//## clause transformation
//
/// push back a watch literal cache by adjusting the iterator for `lit`
fn transform_by_restoring_watch_cache(
&mut self,
l: Lit,
iter: &mut WatchCacheIterator,
p: Option<Lit>,
);
/// swap i-th watch with j-th literal then update watch caches correctly
fn transform_by_updating_watch(&mut self, cid: ClauseId, old: usize, new: usize, removed: bool);
/// allocate a new clause and return its id.
/// Note this removes an eliminated Lit `p` from a clause. This is an O(n) function!
/// This returns `true` if the clause became a unit clause.
/// And this is called only from `Eliminator::strengthen_clause`.
fn new_clause(&mut self, asg: &mut impl AssignIF, v: &mut Vec<Lit>, learnt: bool) -> RefClause;
fn new_clause_sandbox(&mut self, asg: &mut impl AssignIF, v: &mut Vec<Lit>) -> RefClause;
/// un-register a clause `cid` from clause database and make the clause dead.
fn remove_clause(&mut self, cid: ClauseId);
/// un-register a clause `cid` from clause database and make the clause dead.
fn remove_clause_sandbox(&mut self, cid: ClauseId);
/// update watches of the clause
fn transform_by_elimination(&mut self, cid: ClauseId, p: Lit) -> RefClause;
/// generic clause transformer (not in use)
fn transform_by_replacement(&mut self, cid: ClauseId, vec: &mut Vec<Lit>) -> RefClause;
/// check satisfied and nullified literals in a clause
fn transform_by_simplification(&mut self, asg: &mut impl AssignIF, cid: ClauseId) -> RefClause;
/// reduce learnt clauses
/// # CAVEAT
/// *precondition*: decision level == 0.
fn reduce(&mut self, asg: &mut impl AssignIF, setting: ReductionType);
/// remove all learnt clauses.
fn reset(&mut self);
/// update flags.
/// return `true` if it's learnt.
fn update_at_analysis(&mut self, asg: &impl AssignIF, cid: ClauseId) -> bool;
/// record an asserted literal to unsat certification.
fn certificate_add_assertion(&mut self, lit: Lit);
/// save the certification record to a file.
fn certificate_save(&mut self);
/// check the number of clauses
/// * `Err(SolverError::OutOfMemory)` -- the db size is over the limit.
/// * `Ok(true)` -- enough small
/// * `Ok(false)` -- close to the limit
fn check_size(&self) -> Result<bool, SolverError>;
/// returns None if the given assignment is a model of a problem.
/// Otherwise returns a clause which is not satisfiable under a given assignment.
/// Clauses with an unassigned literal are treated as falsified in `strict` mode.
fn validate(&self, model: &[Option<bool>], strict: bool) -> Option<ClauseId>;
/// minimize a clause.
fn minimize_with_bi_clauses(&mut self, asg: &impl AssignIF, vec: &mut Vec<Lit>);
/// complete bi-clause network
fn complete_bi_clauses(&mut self, asg: &mut impl AssignIF);
#[cfg(feature = "incremental_solver")]
/// save an eliminated permanent clause to an extra space for incremental solving.
fn make_permanent_immortal(&mut self, cid: ClauseId);
//
//## for debug
//
#[cfg(feature = "boundary_check")]
/// return true if cid is included in watching literals
fn watch_cache_contains(&self, lit: Lit, cid: ClauseId) -> bool;
#[cfg(feature = "boundary_check")]
/// return a clause's watches
fn watch_caches(&self, cid: ClauseId, message: &str) -> (Vec<Lit>, Vec<Lit>);
#[cfg(feature = "boundary_check")]
fn is_garbage_collected(&mut self, cid: ClauseId) -> Option<bool>;
#[cfg(not(feature = "no_IO"))]
/// dump all active clauses and assertions as a CNF file.
fn dump_cnf(&self, asg: &impl AssignIF, fname: &Path);
}
/// Clause identifier, or clause index, starting with one.
/// Note: ids are re-used after 'garbage collection'.
#[derive(Clone, Copy, Eq, Hash, Ord, PartialEq, PartialOrd)]
pub struct ClauseId {
/// a sequence number.
pub ordinal: NonZeroU32,
}
/// A representation of 'clause'
#[derive(Clone, Debug, Eq, PartialEq, PartialOrd)]
pub struct Clause {
/// The literals in a clause.
lits: Vec<Lit>,
/// Flags (8 bits)
flags: FlagClause,
/// A static clause evaluation criterion like LBD, NDD, or something.
pub rank: u16,
/// A record of the rank at previos stage.
pub rank_old: u16,
/// the index from which `propagate` starts searching an un-falsified literal.
/// Since it's just a hint, we don't need u32 or usize.
pub search_from: u16,
#[cfg(any(feature = "boundary_check", feature = "clause_rewarding"))]
/// the number of conflicts at which this clause was used in `conflict_analyze`
timestamp: usize,
#[cfg(feature = "clause_rewarding")]
/// A dynamic clause evaluation criterion based on the number of references.
reward: f64,
#[cfg(feature = "boundary_check")]
pub birth: usize,
#[cfg(feature = "boundary_check")]
pub moved_at: Propagate,
}
/// Clause database
///
///```
/// use crate::{splr::config::Config, splr::types::*};
/// use crate::splr::cdb::ClauseDB;
/// let cdb = ClauseDB::instantiate(&Config::default(), &CNFDescription::default());
///```
#[derive(Clone, Debug)]
pub struct ClauseDB {
/// container of clauses
clause: Vec<Clause>,
/// hashed representation of binary clauses.
///## Note
/// This means a biclause \[l0, l1\] is stored at bi_clause\[l0\] instead of bi_clause\[!l0\].
///
binary_link: BinaryLinkDB,
/// container of watch literals
watch_cache: Vec<WatchCache>,
/// collected free clause ids.
freelist: Vec<ClauseId>,
/// see unsat_certificate.rs
certification_store: CertificationStore,
/// a number of clauses to emit out-of-memory exception
soft_limit: usize,
/// 'small' clause threshold
co_lbd_bound: u16,
// not in use
// lbd_frozen_clause: usize,
// bi-clause completion
bi_clause_completion_queue: Vec<Lit>,
num_bi_clause_completion: usize,
//
//## clause rewarding
//
/// an index for counting elapsed time
#[cfg(feature = "clause_rewarding")]
tick: usize,
#[cfg(feature = "clause_rewarding")]
activity_decay: f64,
#[cfg(feature = "clause_rewarding")]
activity_anti_decay: f64,
//
//## LBD
//
/// a working buffer for LBD calculation
lbd_temp: Vec<usize>,
lbd: ProgressLBD,
//
//## statistics
//
/// the number of active (not DEAD) clauses.
num_clause: usize,
/// the number of binary clauses.
num_bi_clause: usize,
/// the number of binary learnt clauses.
num_bi_learnt: usize,
/// the number of clauses which LBDs are 2.
num_lbd2: usize,
/// the present number of learnt clauses.
num_learnt: usize,
/// the number of reductions.
num_reduction: usize,
/// the number of reregistration of a bi-clause
num_reregistration: usize,
/// Literal Block Entanglement
/// EMA of LBD of clauses used in conflict analysis (dependency graph)
lb_entanglement: Ema2,
/// cutoff value used in the last `reduce`
reduction_threshold: f64,
//
//## incremental solving
//
pub eliminated_permanent: Vec<Vec<Lit>>,
}
#[derive(Clone, Debug)]
pub enum ReductionType {
/// weight by Reverse Activity Sum over the added clauses
RASonADD(usize),
/// weight by Reverse Activito Sum over all learnt clauses
RASonALL(f64, f64),
/// weight by Literal Block Distance over the added clauses
LBDonADD(usize),
/// weight by Literal Block Distance over all learnt clauses
LBDonALL(u16, f64),
}
pub mod property {
use super::ClauseDB;
use crate::types::*;
#[derive(Clone, Copy, Debug, Eq, PartialEq)]
pub enum Tusize {
NumBiClause,
NumBiClauseCompletion,
NumBiLearnt,
NumClause,
NumLBD2,
NumLearnt,
NumReduction,
NumReRegistration,
Timestamp,
}
pub const USIZES: [Tusize; 9] = [
Tusize::NumBiClause,
Tusize::NumBiClauseCompletion,
Tusize::NumBiLearnt,
Tusize::NumClause,
Tusize::NumLBD2,
Tusize::NumLearnt,
Tusize::NumReduction,
Tusize::NumReRegistration,
Tusize::Timestamp,
];
impl PropertyDereference<Tusize, usize> for ClauseDB {
#[inline]
fn derefer(&self, k: Tusize) -> usize {
match k {
Tusize::NumClause => self.num_clause,
Tusize::NumBiClause => self.num_bi_clause,
Tusize::NumBiClauseCompletion => self.num_bi_clause_completion,
Tusize::NumBiLearnt => self.num_bi_learnt,
Tusize::NumLBD2 => self.num_lbd2,
Tusize::NumLearnt => self.num_learnt,
Tusize::NumReduction => self.num_reduction,
Tusize::NumReRegistration => self.num_reregistration,
#[cfg(feature = "clause_rewarding")]
Tusize::Timestamp => self.tick,
#[cfg(not(feature = "clause_rewarding"))]
Tusize::Timestamp => 0,
}
}
}
#[derive(Clone, Copy, Debug, Eq, PartialEq)]
pub enum Tf64 {
LiteralBlockDistance,
LiteralBlockEntanglement,
ReductionThreshold,
}
pub const F64: [Tf64; 3] = [
Tf64::LiteralBlockDistance,
Tf64::LiteralBlockEntanglement,
Tf64::ReductionThreshold,
];
impl PropertyDereference<Tf64, f64> for ClauseDB {
#[inline]
fn derefer(&self, k: Tf64) -> f64 {
match k {
Tf64::LiteralBlockDistance => self.lbd.get(),
Tf64::LiteralBlockEntanglement => self.lb_entanglement.get(),
Tf64::ReductionThreshold => self.reduction_threshold,
}
}
}
#[derive(Clone, Debug, Eq, PartialEq)]
pub enum TEma {
Entanglement,
LBD,
}
pub const EMAS: [TEma; 2] = [TEma::Entanglement, TEma::LBD];
impl PropertyReference<TEma, EmaView> for ClauseDB {
#[inline]
fn refer(&self, k: TEma) -> &EmaView {
match k {
TEma::Entanglement => self.lb_entanglement.as_view(),
TEma::LBD => self.lbd.as_view(),
}
}
}
}
#[cfg(test)]
mod tests {
use super::*;
use crate::assign::{AssignStack, PropagateIF};
fn lit(i: i32) -> Lit {
Lit::from(i)
}
#[allow(dead_code)]
fn check_watches(cdb: &ClauseDB, cid: ClauseId) {
let c = &cdb.clause[NonZeroU32::get(cid.ordinal) as usize];
if c.lits.is_empty() {
println!("skip checking watches of an empty clause");
return;
}
assert!(c.lits[0..2]
.iter()
.all(|l| cdb.watch_cache[!*l].iter().any(|(c, _)| *c == cid)));
println!("pass to check watches");
}
#[test]
fn test_clause_instantiation() {
let config = Config::default();
let cnf = CNFDescription {
num_of_variables: 4,
..CNFDescription::default()
};
let mut asg = AssignStack::instantiate(&config, &cnf);
let mut cdb = ClauseDB::instantiate(&config, &cnf);
// Now `asg.level` = [_, 1, 2, 3, 4, 5, 6].
let c0 = cdb
.new_clause(&mut asg, &mut vec![lit(1), lit(2), lit(3), lit(4)], false)
.as_cid();
assert_eq!(cdb[c0].rank, 4);
asg.assign_by_decision(lit(-2)); // at level 1
asg.assign_by_decision(lit(1)); // at level 2
// Now `asg.level` = [_, 2, 1, 3, 4, 5, 6].
let c1 = cdb
.new_clause(&mut asg, &mut vec![lit(1), lit(2), lit(3)], false)
.as_cid();
let c = &cdb[c1];
assert_eq!(c.rank, 3);
assert!(!c.is_dead());
assert!(!c.is(FlagClause::LEARNT));
#[cfg(feature = "just_used")]
assert!(!c.is(Flag::USED));
let c2 = cdb
.new_clause(&mut asg, &mut vec![lit(-1), lit(2), lit(3)], true)
.as_cid();
let c = &cdb[c2];
assert_eq!(c.rank, 3);
assert!(!c.is_dead());
assert!(c.is(FlagClause::LEARNT));
#[cfg(feature = "just_used")]
assert!(!c.is(Flag::USED));
}
#[test]
fn test_clause_equality() {
let config = Config::default();
let cnf = CNFDescription {
num_of_variables: 4,
..CNFDescription::default()
};
let mut asg = AssignStack::instantiate(&config, &cnf);
let mut cdb = ClauseDB::instantiate(&config, &cnf);
let c1 = cdb
.new_clause(&mut asg, &mut vec![lit(1), lit(2), lit(3)], false)
.as_cid();
let c2 = cdb
.new_clause(&mut asg, &mut vec![lit(-1), lit(4)], false)
.as_cid();
// cdb[c2].reward = 2.4;
assert_eq!(c1, c1);
assert_ne!(c1, c2);
// assert_eq!(cdb.activity(c2), 2.4);
}
#[test]
fn test_clause_iterator() {
let config = Config::default();
let cnf = CNFDescription {
num_of_variables: 4,
..CNFDescription::default()
};
let mut asg = AssignStack::instantiate(&config, &cnf);
let mut cdb = ClauseDB::instantiate(&config, &cnf);
let c1 = cdb
.new_clause(&mut asg, &mut vec![lit(1), lit(2), lit(3)], false)
.as_cid();
assert_eq!(cdb[c1][0..].iter().map(|l| i32::from(*l)).sum::<i32>(), 6);
let mut iter = cdb[c1][0..].iter();
assert_eq!(iter.next(), Some(&lit(1)));
assert_eq!(iter.next(), Some(&lit(2)));
assert_eq!(iter.next(), Some(&lit(3)));
assert_eq!(iter.next(), None);
}
}