head_aggregate.hh

#pragma once
 
#include <clingo/ground/literal.hh>
#include <clingo/ground/matcher.hh>
#include <clingo/ground/statement.hh>
 
#include <clingo/util/small_vector.hh>
 
#include <memory_resource>
#include <ostream>
 
namespace CppClingo::Ground {
 
// Outline:
// - A :- B.
//   - atoms A are gathered in the aggregate domain
//     (on lower priority than the elements)
//   - there is no need to enqueue the aggregate
//     - propagation only derives heads
//     - element accumulation is independent
// - accu :- A, E.
//   - gathers aggregate elements
//   - enqueues aggregate A for propagation
// - propagate
//   - if A can be derived, propagate heads of aggregate elements
// - output
//   - it might happen that there are aggregates that have not been derived
//   - they are currently output as is but their heads are not propagated
//   - in principle, one could stop grounding if such an aggregate has a true body
// - classes
//   - AtomHdAggr    (to collect head aggregates)
//   - BaseHdAggr    (the base for grounding)
//   - StateHdAggr   (to gather state for grounding/output)
//   - StmHdAggr     (to derive atoms A)
//   - StmHdAggrElem (to accumulate elements)
//   - LitHdAggr     (to be used in StmHdAggrElem)
 
 
class AtomHdAggr {
  public:
    using Bound = std::variant<std::pair<Number, Number>, std::pair<Symbol, Symbol>>;
 
    AtomHdAggr(AggregateFunction fun) : bound_{init_(fun)} {}
 
    void accumulate(AggregateFunction fun, SymbolSpan tup, bool fact);
 
    auto propagate(GuardVec const &guards, Symbol const *vals) -> bool;
 
    auto enqueue() -> bool;
    void dequeue();
 
    void add_elem(size_t idx);
    [[nodiscard]] auto elems() const -> std::span<size_t const>;
    [[nodiscard]] auto todo() -> std::span<size_t const>;
 
    [[nodiscard]] auto uid() const -> std::optional<size_t>;
    void uid(size_t uid);
 
  private:
    static auto init_(AggregateFunction fun) -> Bound;
 
    std::vector<size_t> elems_;
    std::variant<std::pair<Number, Number>, std::pair<Symbol, Symbol>> bound_;
    size_t propagated_ = 0;
    size_t uid_ = invalid_offset;
    bool enqueued_ = false;
    bool matched_ = false;
};
 
class BaseHdAggr : public BaseImpl<Symbol const *, BaseHdAggr> {
  public:
    using BaseImpl::contains;
    using AtomMap = Util::ordered_map<Symbol const *, AtomHdAggr, Util::array_hash, Util::array_equal_to>;
 
    BaseHdAggr(size_t size) : atoms_{0, size, size} {}
 
    auto add(Symbol const *sym, AggregateFunction fun) -> std::pair<AtomMap::iterator, bool>;
 
    [[nodiscard]] auto size() const -> size_t;
 
    [[nodiscard]] auto index(Symbol const *sym) const -> size_t;
    [[nodiscard]] auto nth(size_t i) const -> AtomMap::const_iterator;
    [[nodiscard]] auto nth(size_t i) -> AtomMap::iterator;
 
    [[nodiscard]] auto atoms() -> AtomMap &;
 
  private:
    AtomMap atoms_;
};
 
// Note: this could as well be a small container class
class StmHdAggrElem;
 
class StateHdAggr : public State {
  public:
    class AtomKey;
    class ElementKey {
      private:
        struct priv_tag {};
 
      public:
        ElementKey(priv_tag tag, EvalContext const &ctx, AggregateFunction fun, size_t atom_idx, StmHdAggrElem &elem,
                   bool &res);
        ElementKey(ElementKey const &other) = delete;
        [[nodiscard]] static auto construct(auto &mbr, EvalContext const &ctx, AggregateFunction fun, size_t atom_idx,
                                            StmHdAggrElem &elem) -> bool;
 
        void mark_fact() const;
        [[nodiscard]] auto fact() const -> bool;
 
        [[nodiscard]] auto size() const -> size_t;
        [[nodiscard]] auto span() const -> SymbolSpan;
        [[nodiscard]] auto hash() const -> size_t;
        friend auto operator==(ElementKey const &a, ElementKey const &b) -> bool;
 
      private:
        // Note that these two could be combined to save a little bit of memory.
        mutable size_t n_;
        size_t atom_idx_;
        // NOLINTBEGIN
        CLINGO_IGNORE_ZERO_SIZED_ARRAY_B
        Symbol syms_[0];
        CLINGO_IGNORE_ZERO_SIZED_ARRAY_E
        // NOLINTEND
    };
 
    using AtomMap = BaseHdAggr::AtomMap;
    using ElementMap = Util::ordered_map<ElementKey *, Util::small_vector<std::tuple<Symbol, size_t, size_t>, 1>>;
 
    StateHdAggr(std::pmr::monotonic_buffer_resource &mbr, BaseVec bases, VariableVec global, GuardVec guards,
                AggregateFunction fun, size_t index, bool single_pass_body)
        : base_{global.size()}, global_{std::move(global)}, guards_{std::move(guards)}, bases_{std::move(bases)},
          mbr_{&mbr}, index_{index}, fun_{fun}, single_pass_body_{single_pass_body} {}
 
    [[nodiscard]] auto global() const -> VariableVec const &;
    [[nodiscard]] auto symbols() -> SymbolVec &;
    [[nodiscard]] auto guards() const -> GuardVec const &;
    [[nodiscard]] auto fun() const -> AggregateFunction;
    [[nodiscard]] auto single_pass_body() const -> bool;
    [[nodiscard]] auto index() const -> size_t;
    [[nodiscard]] auto indices() const -> std::vector<size_t>;
 
    void enqueue(Queue &queue);
 
    void propagate(OutputStm &out, Queue &queue);
 
    auto insert_atom(EvalContext const &ctx) -> std::optional<std::pair<AtomMap::iterator, bool>>;
 
    void insert_elem(EvalContext const &ctx, AtomMap::iterator it, StmHdAggrElem &elem);
 
    void print(std::ostream &out, bool print_index);
 
    void output(Logger &log, SymbolStore &store, OutputStm &out) override;
 
    [[nodiscard]] auto base() -> BaseHdAggr &;
 
  private:
    void enqueue_(AtomMap::iterator it);
 
    auto atom_index_(AtomMap::iterator it) -> size_t;
 
    BaseHdAggr base_;
    ElementMap tuples_;
    VariableVec global_;
    SymbolVec symbols_;
    GuardVec guards_;
    BaseVec bases_;
    std::vector<size_t> queue_;
    std::pmr::monotonic_buffer_resource *mbr_;
    AtomKey *atom_key_ = nullptr;
    size_t index_;
    AggregateFunction fun_;
    bool single_pass_body_;
};
 
class StmHdAggr : public Stm {
  public:
    StmHdAggr(StateHdAggr &state, Ground::ULitVec body, size_t priority)
        : state_{&state}, body_{std::move(body)}, priority_{priority} {}
 
  private:
    // Stm interface
    void do_print(std::ostream &out) const override;
 
    [[nodiscard]] auto do_body() const -> ULitVec const & override;
    [[nodiscard]] auto do_important() const -> VariableSet override;
 
    // InstanceCallback interface
    void do_print_head(std::ostream &out) const override;
    void do_init(size_t gen) override;
    [[nodiscard]] auto do_report(EvalContext const &ctx) -> bool override;
    void do_propagate(SymbolStore &store, OutputStm &out, Queue &queue) override;
    [[nodiscard]] auto do_priority() const -> size_t override;
 
    StateHdAggr *state_;
    ULitVec body_;
    size_t priority_;
};
 
class StmHdAggrElem : public Stm {
  public:
    StmHdAggrElem(StateHdAggr &state, std::optional<std::pair<UTerm, AtomBase *>> head, Location loc_weight,
                  UTermVec tuple, ULitVec body)
        : loc_weight_{std::move(loc_weight)}, state_{&state}, head_{head ? std::move(head->first) : nullptr},
          base_{head ? head->second : nullptr}, tuple_{std::move(tuple)}, body_{std::move(body)} {}
 
  private:
    friend class StateHdAggr;
    friend class StateHdAggr::ElementKey;
 
    [[nodiscard]] auto do_body() const -> ULitVec const & override;
    [[nodiscard]] auto do_important() const -> VariableSet override;
    void do_init(size_t gen) override;
    [[nodiscard]] auto do_report(EvalContext const &ctx) -> bool override;
    void do_propagate(SymbolStore &store, OutputStm &out, Queue &queue) override;
    [[nodiscard]] auto do_priority() const -> size_t override;
    void do_print_head(std::ostream &out) const override;
    void do_print(std::ostream &out) const override;
 
    auto get_cond_(EvalContext const &ctx) -> std::pair<size_t, bool>;
 
    Location loc_weight_;
    StateHdAggr *state_;
    StateHdAggr::ElementKey *elem_key_ = nullptr;
    UTerm head_;
    AtomBase *base_;
    UTermVec tuple_;
    ULitVec body_;
    bool logged_ = false;
};
 
class MatchHdAggr {
  public:
    using Key = Symbol const *;
 
    MatchHdAggr(StateHdAggr &state) : state_{&state} {
        eval_.reserve(state_->global().size() + state_->guards().size());
    }
 
    [[nodiscard]] auto vars() const -> VariableSet;
 
    [[nodiscard]] auto signature(VariableSet const &bound, VariableSet const &bind) const -> VariableVec;
 
    [[nodiscard]] auto match(EvalContext const &ctx, Symbol const *sym) const -> bool;
 
    [[nodiscard]] auto eval(EvalContext const &ctx) const -> std::optional<Symbol const *>;
 
    friend auto operator<<(std::ostream &out, MatchHdAggr const &m) -> std::ostream &;
 
    [[nodiscard]] auto state() const -> StateHdAggr &;
 
  private:
    std::vector<Symbol> mutable eval_;
    StateHdAggr *state_;
};
 
class LitHdAggr : public Lit, private MatchHdAggr {
  public:
    LitHdAggr(StateHdAggr &state) : MatchHdAggr{state} {}
 
  private:
    void do_vars(VariableSet &vars, VarSelectMode mode) const override;
 
    [[nodiscard]] auto do_domain() const -> bool override;
 
    [[nodiscard]] auto do_single_pass() const -> bool override;
 
    [[nodiscard]] auto do_matcher(std::pmr::monotonic_buffer_resource &mbr, MatcherType type,
                                  std::vector<bool> const &bound)
        -> std::pair<UMatcher, std::optional<size_t>> override;
 
    [[nodiscard]] auto do_score(std::vector<bool> const &bound) const -> double override;
 
    void do_print(std::ostream &out) const override;
 
    auto do_output(EvalContext const &ctx, OutputLit &out) const -> bool override;
 
    [[nodiscard]] auto do_copy() const -> ULit override;
 
    [[nodiscard]] auto do_hash() const -> size_t override;
 
    [[nodiscard]] auto do_equal_to(Lit const &other) const -> bool override;
 
    [[nodiscard]] auto do_compare_to(Lit const &other) const -> std::weak_ordering override;
 
    size_t offset_ = invalid_offset;
};
 
 
} // namespace CppClingo::Ground