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/*
* richard-atp-engine: A saturation-based automated theorem prover for first-order logic.
* Copyright (C) 2026 Richard Qin
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program. If not, see <https://www.gnu.org/licenses/>.
*/
#include "atp/search/prover.h"
#include "atp/core/clause.h"
#include "atp/core/clause_store.h"
#include "atp/core/term_bank.h"
#include "atp/core/types.h"
#include "atp/infer/resolution.h"
#include "atp/infer/unification.h"
#include "atp/simplify/subsumption.h"
#include "atp/simplify/tautology.h"
#include <algorithm>
#include <cstddef>
#include <cstdint>
#include <optional>
#include <utility>
#include <vector>
namespace atp {
Prover::Prover(TermBank& bank, ClauseStore& store, ProverConfig config)
: bank_(bank), store_(store), config_(std::move(config)), unprocessed_(config_.comparator_) {}
void Prover::addClauses(std::vector<Clause> clauses) {
for (auto& clause : clauses) {
clause.depth_ = 0;
ClauseId const id = store_.addClause(clause);
unprocessed_.push(store_.getClause(id));
}
}
bool Prover::hitResourceLimit(size_t iterations) const {
return iterations >= config_.max_iterations_ || store_.size() >= config_.max_clauses_;
}
Clause Prover::popGivenClause() {
Clause given = unprocessed_.top();
unprocessed_.pop();
return given;
}
bool Prover::isForwardSubsumedByProcessed(const Clause& clause) const {
return std::ranges::any_of(processed_,
[&](ClauseId pid) { return subsumes(store_.getClause(pid), clause); });
}
bool Prover::shouldSkipGiven(const Clause& given) const {
return isTautology(given) || isForwardSubsumedByProcessed(given);
}
void Prover::applyBackwardSubsumption(const Clause& given) {
std::erase_if(processed_, [&](ClauseId pid) { return subsumes(given, store_.getClause(pid)); });
}
std::vector<Clause> Prover::generateNewClauses(const Clause& given) const {
std::vector<Clause> new_clauses;
const UnificationConfig uconfig{.enable_occurs_check_ = config_.enable_occurs_check_};
for (ClauseId const pid : processed_) {
const Clause& pc = store_.getClause(pid);
auto resolvents1 = allResolvents(bank_, given, pc, uconfig);
auto resolvents2 = allResolvents(bank_, pc, given, uconfig);
for (auto& r : resolvents1) {
new_clauses.push_back(std::move(r));
}
for (auto& r : resolvents2) {
new_clauses.push_back(std::move(r));
}
}
auto factors = factor(bank_, given, uconfig);
for (auto& f : factors) {
new_clauses.push_back(std::move(f));
}
return new_clauses;
}
uint16_t Prover::computeDepth(const Clause& clause) const {
uint32_t const d1 = (clause.parent1_ != kInvalidId) ? store_.getClause(clause.parent1_).depth_ : 0;
uint32_t const d2 = (clause.parent2_ != kInvalidId) ? store_.getClause(clause.parent2_).depth_ : 0;
return static_cast<uint16_t>(std::max(d1, d2) + 1);
}
std::optional<ClauseId> Prover::processNewClauses(std::vector<Clause> new_clauses) {
for (auto& nc : new_clauses) {
if (nc.isEmpty()) {
return store_.addClause(std::move(nc));
}
if (isTautology(nc)) {
continue;
}
nc.depth_ = computeDepth(nc);
ClauseId const nid = store_.addClause(nc);
const Clause& stored_nc = store_.getClause(nid);
if (isForwardSubsumedByProcessed(stored_nc)) {
continue;
}
unprocessed_.push(stored_nc);
}
return std::nullopt;
}
ProverResult Prover::prove() {
size_t iterations = 0;
while (!unprocessed_.empty()) {
if (hitResourceLimit(iterations)) {
return ProverResult::kTimeout;
}
++iterations;
Clause given = popGivenClause();
if (given.isEmpty()) {
empty_clause_id_ = given.id_;
return ProverResult::kTheorem;
}
if (shouldSkipGiven(given)) {
continue;
}
applyBackwardSubsumption(given);
std::vector<Clause> new_clauses = generateNewClauses(given);
processed_.push_back(given.id_);
const std::optional<ClauseId> derived_empty = processNewClauses(std::move(new_clauses));
if (derived_empty.has_value()) {
empty_clause_id_ = derived_empty;
return ProverResult::kTheorem;
}
}
return ProverResult::kSaturation;
}
std::optional<ClauseId> Prover::getEmptyClauseId() const {
return empty_clause_id_;
}
} // namespace atp
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