139 lines
4.8 KiB
C++
139 lines
4.8 KiB
C++
// Copyright 2010-2025 Google LLC
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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#ifndef OR_TOOLS_SAT_ENFORCEMENT_H_
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#define OR_TOOLS_SAT_ENFORCEMENT_H_
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#include <cstdint>
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#include <functional>
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#include <ostream>
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#include <utility>
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#include <vector>
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#include "absl/container/inlined_vector.h"
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#include "absl/types/span.h"
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#include "ortools/base/strong_vector.h"
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#include "ortools/sat/model.h"
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#include "ortools/sat/sat_base.h"
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#include "ortools/util/rev.h"
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#include "ortools/util/strong_integers.h"
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namespace operations_research {
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namespace sat {
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DEFINE_STRONG_INDEX_TYPE(EnforcementId);
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// An enforced constraint can be in one of these 4 states.
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// Note that we rely on the integer encoding to take 2 bits for optimization.
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enum class EnforcementStatus {
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// One enforcement literal is false.
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IS_FALSE = 0,
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// More than two literals are unassigned.
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CANNOT_PROPAGATE = 1,
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// All enforcement literals are true but one.
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CAN_PROPAGATE_ENFORCEMENT = 2,
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// All enforcement literals are true.
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IS_ENFORCED = 3,
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};
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std::ostream& operator<<(std::ostream& os, const EnforcementStatus& e);
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// This is meant as an helper to deal with enforcement for any constraint.
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class EnforcementPropagator : public SatPropagator {
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public:
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explicit EnforcementPropagator(Model* model);
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// SatPropagator interface.
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bool Propagate(Trail* trail) final;
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void Untrail(const Trail& trail, int trail_index) final;
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// Adds a new constraint to the class and register a callback that will
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// be called on status change. Note that we also call the callback with the
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// initial status if different from CANNOT_PROPAGATE when added.
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//
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// It is better to not call this for empty enforcement list, but you can. A
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// negative id means the level zero status will never change, and only the
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// first call to callback() should be necessary, we don't save it.
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EnforcementId Register(
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absl::Span<const Literal> enforcement,
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std::function<void(EnforcementId, EnforcementStatus)> callback = nullptr);
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// Add the enforcement reason to the given vector.
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void AddEnforcementReason(EnforcementId id,
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std::vector<Literal>* reason) const;
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EnforcementStatus Status(EnforcementId id) const {
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if (id < 0) return EnforcementStatus::IS_ENFORCED;
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return statuses_[id];
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}
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// This recomputes the current status by scanning the given list.
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// It thus has a linear complexity and should not be used in hot loops.
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EnforcementStatus Status(absl::Span<const Literal> enforcement) const;
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// Recompute the status from the current assignment.
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// This should only used in DCHECK().
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EnforcementStatus DebugStatus(EnforcementId id);
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// Returns the enforcement literals of the given id.
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absl::Span<const Literal> GetEnforcementLiterals(EnforcementId id) const {
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if (id < 0) return {};
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return GetSpan(id);
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}
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private:
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absl::Span<Literal> GetSpan(EnforcementId id);
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absl::Span<const Literal> GetSpan(EnforcementId id) const;
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void ChangeStatus(EnforcementId id, EnforcementStatus new_status);
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// Returns kNoLiteralIndex if nothing need to change or a new literal to
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// watch. This also calls the registered callback.
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LiteralIndex ProcessIdOnTrue(Literal watched, EnforcementId id);
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// External classes.
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const Trail& trail_;
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const VariablesAssignment& assignment_;
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RevRepository<int> rev_int_repository_;
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// All enforcement will be copied there, and we will create Span out of this.
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// Note that we don't store the span so that we are not invalidated on buffer_
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// resizing.
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util_intops::StrongVector<EnforcementId, int> starts_;
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std::vector<Literal> buffer_;
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util_intops::StrongVector<EnforcementId, EnforcementStatus> statuses_;
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util_intops::StrongVector<
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EnforcementId, std::function<void(EnforcementId, EnforcementStatus)>>
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callbacks_;
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// Used to restore status and call callback on untrail.
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std::vector<std::pair<EnforcementId, EnforcementStatus>> untrail_stack_;
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int rev_stack_size_ = 0;
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int64_t rev_stamp_ = 0;
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// We use a two watcher scheme.
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util_intops::StrongVector<LiteralIndex, absl::InlinedVector<EnforcementId, 6>>
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watcher_;
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std::vector<Literal> temp_literals_;
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std::vector<EnforcementId> ids_to_fix_until_next_root_level_;
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friend class EnforcementHelper;
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};
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} // namespace sat
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} // namespace operations_research
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#endif // OR_TOOLS_SAT_ENFORCEMENT_H_
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