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Fix concurrent clique table publication #1775

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Fix concurrent clique table publication #1775

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10 changes: 8 additions & 2 deletions cpp/src/branch_and_bound/branch_and_bound.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -3268,6 +3268,12 @@ mip_status_t branch_and_bound_t<i_t, f_t>::solve(mip_solution_t<i_t, f_t>& solut
if ((settings_.clique_cuts != 0 || settings_.zero_half_cuts != 0) && clique_table_ == nullptr &&
omp_get_num_threads() >= CUOPT_MIP_CLIQUE_CUTS_REQUIRED_THREAD_COUNT) {
signal_extend_cliques_.store(false, std::memory_order_release);
mip::clique_config_t clique_config;
clique_table_ =
std::make_shared<mip::clique_table_t<i_t, f_t>>(2 * original_problem_.num_cols,
clique_config.min_clique_size,
clique_config.max_clique_size_for_extension);
auto* initial_clique_table = clique_table_.get();
typename mip_solver_settings_t<i_t, f_t>::tolerances_t tolerances_for_clique{};
tolerances_for_clique.presolve_absolute_tolerance = settings_.primal_tol;
tolerances_for_clique.absolute_tolerance = settings_.primal_tol;
Expand All @@ -3277,12 +3283,12 @@ mip_status_t branch_and_bound_t<i_t, f_t>::solve(mip_solution_t<i_t, f_t>& solut
tolerances_for_clique.relative_mip_gap = settings_.relative_mip_gap_tol;

#pragma omp task priority(CUOPT_DEFAULT_TASK_PRIORITY) depend(out : *clique_signal) \
firstprivate(tolerances_for_clique)
firstprivate(tolerances_for_clique, initial_clique_table)
{
user_problem_t<i_t, f_t> problem_copy = original_problem_;
timer_t timer(std::numeric_limits<double>::infinity());
mip::find_initial_cliques(
problem_copy, tolerances_for_clique, clique_table_, timer, clique_signal);
problem_copy, tolerances_for_clique, *initial_clique_table, timer, clique_signal);
}
}

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28 changes: 10 additions & 18 deletions cpp/src/mip_heuristics/presolve/conflict_graph/clique_table.cu
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Expand Up @@ -670,7 +670,7 @@ void print_clique_table(const clique_table_t<i_t, f_t>& clique_table)
template <typename i_t, typename f_t>
void find_initial_cliques(user_problem_t<i_t, f_t>& problem,
typename mip_solver_settings_t<i_t, f_t>::tolerances_t tolerances,
std::shared_ptr<clique_table_t<i_t, f_t>>& clique_table_out,
clique_table_t<i_t, f_t>& clique_table,
cuopt::timer_t& timer,
omp_atomic_t<bool>* signal_extend)
{
Expand Down Expand Up @@ -701,48 +701,40 @@ void find_initial_cliques(user_problem_t<i_t, f_t>& problem,
t_sort = stage_timer.elapsed_time();
#endif
clique_config_t clique_config;
auto clique_table =
std::make_shared<clique_table_t<i_t, f_t>>(2 * problem.num_cols,
clique_config.min_clique_size,
clique_config.max_clique_size_for_extension);
clique_table->tolerances = tolerances;
clique_table.tolerances = tolerances;
double time_limit_for_additional_cliques = timer.remaining_time() / 2;
cuopt::timer_t additional_cliques_timer(time_limit_for_additional_cliques);
double find_work_estimate = 0.0;
// Always build base cliques in full; signal_extend only gates the extension phase.
for (const auto& knapsack_constraint : knapsack_constraints) {
if (timer.check_time_limit()) { break; }
find_cliques_from_constraint(knapsack_constraint, *clique_table, additional_cliques_timer);
find_cliques_from_constraint(knapsack_constraint, clique_table, additional_cliques_timer);
find_work_estimate += knapsack_constraint.entries.size();
}
#ifdef DEBUG_CLIQUE_TABLE
t_find = stage_timer.elapsed_time();
#endif
CUOPT_LOG_DEBUG("Number of cliques: %d, additional cliques: %d, find_work=%.0f",
clique_table->first.size(),
clique_table->addtl_cliques.size(),
clique_table.first.size(),
clique_table.addtl_cliques.size(),
find_work_estimate);
remove_small_cliques(*clique_table, timer);
remove_small_cliques(clique_table, timer);
#ifdef DEBUG_CLIQUE_TABLE
t_small = stage_timer.elapsed_time();
#endif
fill_var_clique_maps(*clique_table);
fill_var_clique_maps(clique_table);
#ifdef DEBUG_CLIQUE_TABLE
t_maps = stage_timer.elapsed_time();
#endif
// Publish the base table so cut generation can start using it; the extension
// phase below keeps mutating *clique_table, so the consumer must signal this
// task to stop and join it (taskwait) before reading the table.
clique_table_out = clique_table;
double extend_work = 0.0;
i_t n_extended_cliques = extend_cliques(knapsack_constraints,
*clique_table,
clique_table,
timer,
&extend_work,
clique_config.min_extend_work,
clique_config.max_extend_work,
signal_extend);
if (n_extended_cliques > 0) { fill_var_clique_maps(*clique_table); }
if (n_extended_cliques > 0) { fill_var_clique_maps(clique_table); }
#ifdef DEBUG_CLIQUE_TABLE
t_extend = stage_timer.elapsed_time();
CUOPT_LOG_DEBUG(
Expand All @@ -765,7 +757,7 @@ void find_initial_cliques(user_problem_t<i_t, f_t>& problem,
template void find_initial_cliques<int, F_TYPE>( \
user_problem_t<int, F_TYPE> & problem, \
typename mip_solver_settings_t<int, F_TYPE>::tolerances_t tolerances, \
std::shared_ptr<clique_table_t<int, F_TYPE>> & clique_table_out, \
clique_table_t<int, F_TYPE> & clique_table, \
cuopt::timer_t & timer, \
omp_atomic_t<bool> * signal_extend); \
template void build_clique_table<int, F_TYPE>( \
Expand Down
12 changes: 5 additions & 7 deletions cpp/src/mip_heuristics/presolve/conflict_graph/clique_table.cuh
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Expand Up @@ -201,16 +201,14 @@ struct clique_table_t {
typename mip_solver_settings_t<i_t, f_t>::tolerances_t tolerances;
};

// Builds the conflict-graph clique table for `problem`. The base cliques are
// published to `clique_table_out` before the (optional, signal-gated) extension
// phase begins, so cut generation can pick up the table while extension keeps
// running concurrently. Consumers MUST set `*signal_extend` and join the
// producing task before reading the table (see prepare_fractional_sub_conflict_graph), since
// the extension phase keeps mutating the same object after it is published.
// Builds the conflict-graph clique table for `problem`. Consumers MUST set
// `*signal_extend` and join the producing task before reading the table (see
// prepare_fractional_sub_conflict_graph), since the extension phase keeps
// mutating the table after its base cliques are built.
template <typename i_t, typename f_t>
void find_initial_cliques(simplex::user_problem_t<i_t, f_t>& problem,
typename mip_solver_settings_t<i_t, f_t>::tolerances_t tolerances,
std::shared_ptr<clique_table_t<i_t, f_t>>& clique_table_out,
clique_table_t<i_t, f_t>& clique_table,
cuopt::timer_t& timer,
omp_atomic_t<bool>* signal_extend = nullptr);

Expand Down
22 changes: 22 additions & 0 deletions cpp/tests/mip/miplib_test.cu
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Expand Up @@ -90,6 +90,28 @@ TEST(mip_solve, low_thread_count_test)
test_variable_bounds(problem, solution.get_solution(), settings);
}

TEST(mip_solve, repeated_concurrent_initial_clique_generation)
{
mip_solver_settings_t<int, double> settings;
settings.num_cpu_threads = 8;
settings.time_limit = 30;
settings.work_limit = 1;
settings.clique_cuts = 1;
settings.zero_half_cuts = 1;

const raft::handle_t handle_{};

auto path = make_path_absolute("mip/gen-ip054.mps");
auto problem = cuopt::mathematical_optimization::io::read_mps<int, double>(path, false);
handle_.sync_stream();

constexpr int num_solves = 25;
for (int solve = 0; solve < num_solves; ++solve) {
auto solution = solve_mip(&handle_, problem, settings);
EXPECT_NE(solution.get_termination_status(), mip_termination_status_t::NoTermination);
}
}

// Verify --node-limit is respected: swath1 normally requires several thousand B&B
// nodes to prove optimality, so capping at 1000 forces the solver to stop early with
// a feasible (but not necessarily optimal) solution.
Expand Down