Replace process-wide seed_generator with per-worker RNGs in MIP heuristics

cpp/src/mip_heuristics/diversity/diversity_manager.cu

@@ -79,10 +79,16 @@ diversity_manager_t<i_t, f_t>::diversity_manager_t(mip_solver_context_t<i_t, f_t
                             context.problem_ptr->handle_ptr),
     sub_mip_recombiner(
       context, population, context.problem_ptr->n_variables, context.problem_ptr->handle_ptr),
-    rng(cuopt::seed_generator::get_seed()),
+    rng(mip_derive_seed(context.base_seed, mip_rng_component_id_t::diversity_manager, 0)),
     stats(context.stats),
-    mab_recombiner(0, cuopt::seed_generator::get_seed(), recombiner_alpha, "recombiner"),
-    mab_ls(mab_ls_config_t<i_t, f_t>::n_of_arms, cuopt::seed_generator::get_seed(), ls_alpha, "ls"),
+    mab_recombiner(0,
+                   mip_derive_seed(context.base_seed, mip_rng_component_id_t::diversity_manager, 1),
+                   recombiner_alpha,
+                   "recombiner"),
+    mab_ls(mab_ls_config_t<i_t, f_t>::n_of_arms,
+           mip_derive_seed(context.base_seed, mip_rng_component_id_t::diversity_manager, 2),
+           ls_alpha,
+           "ls"),
     ls_hash_map(*context.problem_ptr)
 {
   int max_config             = -1;
@@ -439,7 +445,7 @@ template <typename i_t, typename f_t>
 void diversity_manager_t<i_t, f_t>::run_fj_alone(solution_t<i_t, f_t>& solution)
 {
   CUOPT_LOG_INFO("Running FJ alone!");
-  solution.round_nearest();
+  solution.round_nearest(rng());
   ls.fj.settings.mode                   = fj_mode_t::EXIT_NON_IMPROVING;
   ls.fj.settings.n_of_minimums_for_exit = 20000 * 1000;
   ls.fj.settings.update_weights         = true;
@@ -693,7 +699,7 @@ solution_t<i_t, f_t> diversity_manager_t<i_t, f_t>::run_solver()
   if (ls.lp_optimal_exists) {
     solution_t<i_t, f_t> lp_rounded_sol(*problem_ptr);
     lp_rounded_sol.copy_new_assignment(lp_optimal_solution);
-    lp_rounded_sol.round_nearest();
+    lp_rounded_sol.round_nearest(rng());
     lp_rounded_sol.compute_feasibility();
     population.add_solution(std::move(lp_rounded_sol));
     ls.start_cpufj_lptopt_scratch_threads(population);

cpp/src/mip_heuristics/diversity/population.cu

@@ -14,7 +14,6 @@
 #include <mip_heuristics/utils.cuh>
 #include <pdlp/utils.cuh>
 #include <utilities/copy_helpers.hpp>
-#include <utilities/seed_generator.cuh>
 
 #include <mutex>
 
@@ -42,7 +41,7 @@ population_t<i_t, f_t>::population_t(std::string const& name_,
     max_solutions(max_solutions_),
     infeasibility_importance(infeasibility_weight_),
     weights(0, context.problem_ptr->handle_ptr),
-    rng(cuopt::seed_generator::get_seed()),
+    rng(mip_derive_seed(context.base_seed, mip_rng_component_id_t::population)),
     early_exit_primal_generation(false),
     population_hash_map(*problem_ptr),
     timer(0)

cpp/src/mip_heuristics/diversity/recombiners/bound_prop_recombiner.cuh

@@ -11,9 +11,10 @@
 
 #include <thrust/pair.h>
 #include <mip_heuristics/local_search/rounding/constraint_prop.cuh>
+#include <mip_heuristics/mip_constants.hpp>
 #include <mip_heuristics/relaxed_lp/relaxed_lp.cuh>
 #include <mip_heuristics/solution/solution.cuh>
-#include <utilities/seed_generator.cuh>
+#include <utilities/pcgenerator.hpp>
 
 namespace cuopt::mathematical_optimization::mip {
 
@@ -24,9 +25,9 @@ class bound_prop_recombiner_t : public recombiner_t<i_t, f_t> {
                           i_t n_vars,
                           constraint_prop_t<i_t, f_t>& constraint_prop_,
                           const raft::handle_t* handle_ptr)
-    : recombiner_t<i_t, f_t>(context, n_vars, handle_ptr),
+    : recombiner_t<i_t, f_t>(
+        context, n_vars, handle_ptr, mip_rng_component_id_t::recombiner_bound_prop),
       constraint_prop(constraint_prop_),
-      rng(cuopt::seed_generator::get_seed()),
       vars_to_fix(n_vars, handle_ptr->get_stream())
   {
   }
@@ -65,7 +66,7 @@ class bound_prop_recombiner_t : public recombiner_t<i_t, f_t> {
        offspring_view,
        int_tol,
        probing_values = probing_values.data(),
-       seed           = cuopt::seed_generator::get_seed()] __device__(i_t idx) {
+       seed           = this->rng.next_u64()] __device__(i_t idx) {
         f_t guiding_val = guiding_view.assignment[idx];
         f_t other_val   = other_view.assignment[idx];
         cuopt_assert(guiding_view.problem.check_variable_within_bounds(idx, guiding_val), "");
@@ -151,7 +152,7 @@ class bound_prop_recombiner_t : public recombiner_t<i_t, f_t> {
     if (n_different_vars > (i_t)bp_recombiner_config_t::max_n_of_vars_from_other) {
       fixed_from_guiding = n_vars_from_other - bp_recombiner_config_t::max_n_of_vars_from_other;
       n_vars_from_other  = bp_recombiner_config_t::max_n_of_vars_from_other;
-      thrust::default_random_engine g{(unsigned int)cuopt::seed_generator::get_seed()};
+      thrust::default_random_engine g{this->rng.next_u32()};
       thrust::shuffle(a.handle_ptr->get_thrust_policy(),
                       this->remaining_indices.data(),
                       this->remaining_indices.data() + n_different_vars,
@@ -245,7 +246,6 @@ class bound_prop_recombiner_t : public recombiner_t<i_t, f_t> {
 
   rmm::device_uvector<i_t> vars_to_fix;
   constraint_prop_t<i_t, f_t>& constraint_prop;
-  thrust::default_random_engine rng;
 };
 
 }  // namespace cuopt::mathematical_optimization::mip

cpp/src/mip_heuristics/diversity/recombiners/fp_recombiner.cuh

@@ -11,9 +11,9 @@
 
 #include <mip_heuristics/local_search/feasibility_pump/feasibility_pump.cuh>
 #include <mip_heuristics/local_search/rounding/constraint_prop.cuh>
+#include <mip_heuristics/mip_constants.hpp>
 #include <mip_heuristics/relaxed_lp/relaxed_lp.cuh>
 #include <mip_heuristics/solution/solution.cuh>
-#include <utilities/seed_generator.cuh>
 
 #include <thrust/partition.h>
 
@@ -29,7 +29,7 @@ class fp_recombiner_t : public recombiner_t<i_t, f_t> {
                   line_segment_search_t<i_t, f_t>& line_segment_search,
                   rmm::device_uvector<f_t>& lp_optimal_solution,
                   const raft::handle_t* handle_ptr)
-    : recombiner_t<i_t, f_t>(context, n_vars, handle_ptr),
+    : recombiner_t<i_t, f_t>(context, n_vars, handle_ptr, mip_rng_component_id_t::recombiner_fp),
       vars_to_fix(n_vars, handle_ptr->get_stream()),
       fp(context, fj, constraint_prop, line_segment_search, lp_optimal_solution)
   {
@@ -53,7 +53,7 @@ class fp_recombiner_t : public recombiner_t<i_t, f_t> {
     i_t n_vars_from_other = n_different_vars;
     if (n_vars_from_other > (i_t)fp_recombiner_config_t::max_n_of_vars_from_other) {
       n_vars_from_other = fp_recombiner_config_t::max_n_of_vars_from_other;
-      thrust::default_random_engine g{(unsigned int)cuopt::seed_generator::get_seed()};
+      thrust::default_random_engine g{this->rng.next_u32()};
       thrust::shuffle(a.handle_ptr->get_thrust_policy(),
                       this->remaining_indices.data(),
                       this->remaining_indices.data() + n_different_vars,
@@ -114,7 +114,7 @@ class fp_recombiner_t : public recombiner_t<i_t, f_t> {
     }
     // unfix the assignment on given result no matter if it is feasible
     offspring.unfix_variables(fixed_assignment, variable_map);
-    if (!run_fp) { offspring.round_nearest(); }
+    if (!run_fp) { offspring.round_nearest(this->rng.next_u64()); }
     cuopt_assert(offspring.test_number_all_integer(), "All must be integers after offspring");
     offspring.compute_feasibility();
     bool same_as_parents = this->check_if_offspring_is_same_as_parents(offspring, a, b);

cpp/src/mip_heuristics/diversity/recombiners/line_segment_recombiner.cuh

@@ -10,9 +10,9 @@
 #include "recombiner.cuh"
 
 #include <mip_heuristics/local_search/line_segment_search/line_segment_search.cuh>
+#include <mip_heuristics/mip_constants.hpp>
 #include <mip_heuristics/relaxed_lp/relaxed_lp.cuh>
 #include <mip_heuristics/solution/solution.cuh>
-#include <utilities/seed_generator.cuh>
 
 namespace cuopt::mathematical_optimization::mip {
 
@@ -23,7 +23,9 @@ class line_segment_recombiner_t : public recombiner_t<i_t, f_t> {
                             i_t n_vars,
                             line_segment_search_t<i_t, f_t>& line_segment_search_,
                             const raft::handle_t* handle_ptr)
-    : recombiner_t<i_t, f_t>(context, n_vars, handle_ptr), line_segment_search(line_segment_search_)
+    : recombiner_t<i_t, f_t>(
+        context, n_vars, handle_ptr, mip_rng_component_id_t::recombiner_line_segment),
+      line_segment_search(line_segment_search_)
   {
   }
 
@@ -40,7 +42,7 @@ class line_segment_recombiner_t : public recombiner_t<i_t, f_t> {
     i_t n_vars_from_other = remaining_variables;
     if (n_vars_from_other > (i_t)ls_recombiner_config_t::max_n_of_vars_from_other) {
       n_vars_from_other = ls_recombiner_config_t::max_n_of_vars_from_other;
-      thrust::default_random_engine g{(unsigned int)cuopt::seed_generator::get_seed()};
+      thrust::default_random_engine g{this->rng.next_u32()};
       thrust::shuffle(guiding_solution.handle_ptr->get_thrust_policy(),
                       this->remaining_indices.data(),
                       this->remaining_indices.data() + remaining_variables,

cpp/src/mip_heuristics/diversity/recombiners/recombiner.cuh

@@ -10,12 +10,13 @@
 #include "recombiner_configs.hpp"
 #include "recombiner_stats.hpp"
 
+#include <mip_heuristics/mip_constants.hpp>
 #include <mip_heuristics/solution/solution.cuh>
 #include <mip_heuristics/solver.cuh>
 #include <mip_heuristics/utils.cuh>
 #include <utilities/copy_helpers.hpp>
 #include <utilities/device_utils.cuh>
-#include <utilities/seed_generator.cuh>
+#include <utilities/splitmix64.hpp>
 
 #include <thrust/random.h>
 #include <thrust/set_operations.h>
@@ -65,8 +66,11 @@ class recombiner_t {
  public:
   recombiner_t(mip_solver_context_t<i_t, f_t>& context_,
                i_t n_integer_vars,
-               const raft::handle_t* handle_ptr)
+               const raft::handle_t* handle_ptr,
+               mip_rng_component_id_t component_id)
     : context(context_),
+      rng(mip_derive_seed(context.base_seed, component_id),
+          mip_derive_stream(context.base_seed, component_id)),
       remaining_indices(n_integer_vars, handle_ptr->get_stream()),
       n_remaining(handle_ptr->get_stream())
   {
@@ -119,7 +123,7 @@ class recombiner_t {
                     objective_indices.size());
     if (objective_indices.size() > 0 &&
         objective_indices_in_subproblem.size() < 0.4 * remaining_variables) {
-      std::default_random_engine rng_host(cuopt::seed_generator::get_seed());
+      std::default_random_engine rng_host(rng.next_i64());
       std::vector<i_t> objective_indices_not_in_subproblem;
       std::set_difference(objective_indices.begin(),
                           objective_indices.end(),
@@ -219,6 +223,7 @@ class recombiner_t {
   }
 
   mip_solver_context_t<i_t, f_t>& context;
+  splitmix64_t rng;
   rmm::device_uvector<i_t> remaining_indices;
   rmm::device_scalar<i_t> n_remaining;
   static std::vector<recombiner_enum_t> enabled_recombiners;

cpp/src/mip_heuristics/diversity/recombiners/sub_mip.cuh

@@ -25,7 +25,8 @@ class sub_mip_recombiner_t : public recombiner_t<i_t, f_t> {
                        population_t<i_t, f_t>& population,
                        i_t n_vars,
                        const raft::handle_t* handle_ptr)
-    : recombiner_t<i_t, f_t>(context, n_vars, handle_ptr),
+    : recombiner_t<i_t, f_t>(
+        context, n_vars, handle_ptr, mip_rng_component_id_t::recombiner_sub_mip),
       vars_to_fix(n_vars, handle_ptr->get_stream()),
       context(context),
       population(population)
@@ -57,7 +58,7 @@ class sub_mip_recombiner_t : public recombiner_t<i_t, f_t> {
     i_t n_vars_from_other = n_different_vars;
     if (n_vars_from_other > (i_t)sub_mip_recombiner_config_t::max_n_of_vars_from_other) {
       n_vars_from_other = sub_mip_recombiner_config_t::max_n_of_vars_from_other;
-      thrust::default_random_engine g{(unsigned int)cuopt::seed_generator::get_seed()};
+      thrust::default_random_engine g{this->rng.next_u32()};
       thrust::shuffle(a.handle_ptr->get_thrust_policy(),
                       this->remaining_indices.data(),
                       this->remaining_indices.data() + n_different_vars,
@@ -156,7 +157,7 @@ class sub_mip_recombiner_t : public recombiner_t<i_t, f_t> {
       offspring
         .clamp_within_bounds();  // Scaling might bring some very slight variable bound violations
     } else {
-      offspring.round_nearest();
+      offspring.round_nearest(this->rng.next_u64());
     }
     cuopt_func_call(offspring.test_variable_bounds());
     cuopt_assert(offspring.test_number_all_integer(), "All must be integers after offspring");

cpp/src/mip_heuristics/feasibility_jump/early_cpufj.cu

@@ -15,9 +15,11 @@ template <typename i_t, typename f_t>
 early_cpufj_t<i_t, f_t>::early_cpufj_t(
   const optimization_problem_t<i_t, f_t>& op_problem,
   const typename mip_solver_settings_t<i_t, f_t>::tolerances_t& tolerances,
-  early_incumbent_callback_t<f_t> incumbent_callback)
+  early_incumbent_callback_t<f_t> incumbent_callback,
+  uint64_t seed)
   : early_heuristic_t<i_t, f_t, early_cpufj_t<i_t, f_t>>(
-      op_problem, tolerances, std::move(incumbent_callback))
+      op_problem, tolerances, std::move(incumbent_callback)),
+    seed_(seed)
 {
 }
 
@@ -36,7 +38,8 @@ void early_cpufj_t<i_t, f_t>::start()
   this->preemption_flag_.store(false);
   this->start_time_ = std::chrono::steady_clock::now();
 
-  fj_cpu_ = init_fj_cpu_standalone(*this->problem_ptr_, *this->solution_ptr_, preemption_flag_);
+  fj_cpu_ =
+    init_fj_cpu_standalone(*this->problem_ptr_, *this->solution_ptr_, preemption_flag_, seed_);
 
   fj_cpu_->log_prefix = "[Early CPUFJ] ";
 

cpp/src/mip_heuristics/feasibility_jump/early_cpufj.cuh

@@ -20,7 +20,8 @@ class early_cpufj_t : public early_heuristic_t<i_t, f_t, early_cpufj_t<i_t, f_t>
  public:
   early_cpufj_t(const optimization_problem_t<i_t, f_t>& op_problem,
                 const typename mip_solver_settings_t<i_t, f_t>::tolerances_t& tolerances,
-                early_incumbent_callback_t<f_t> incumbent_callback);
+                early_incumbent_callback_t<f_t> incumbent_callback,
+                uint64_t seed);
 
   ~early_cpufj_t();
 
@@ -32,6 +33,9 @@ class early_cpufj_t : public early_heuristic_t<i_t, f_t, early_cpufj_t<i_t, f_t>
  private:
   std::unique_ptr<fj_cpu_climber_t<i_t, f_t>> fj_cpu_;
   std::atomic<bool> preemption_flag_{false};
+  // Explicit seed for this climber's FJ RNG, resolved once from the solve's base seed (see
+  // mip_solver_context_t::base_seed) since this heuristic runs before that context exists.
+  uint64_t seed_;
 };
 
 }  // namespace cuopt::mathematical_optimization::mip

cpp/src/mip_heuristics/feasibility_jump/early_gpufj.cu

@@ -51,7 +51,8 @@ void early_gpufj_t<i_t, f_t>::start()
   fj_settings.update_weights         = true;
   fj_settings.feasibility_run        = false;
 
-  fj_ptr_ = std::make_unique<fj_t<i_t, f_t>>(*context_ptr_, fj_settings);
+  fj_ptr_ = std::make_unique<fj_t<i_t, f_t>>(
+    *context_ptr_, fj_settings, mip_rng_component_id_t::early_gpufj);
 
   fj_ptr_->improvement_callback = [this](f_t user_obj, const std::vector<f_t>& h_assignment) {
     f_t solver_obj = this->problem_ptr_->get_solver_obj_from_user_obj(user_obj);

cpp/src/mip_heuristics/feasibility_jump/feasibility_jump.cu

@@ -15,7 +15,6 @@
 #include <mip_heuristics/mip_constants.hpp>
 #include <mip_heuristics/utils.cuh>
 #include <utilities/device_scalar_init.hpp>
-#include <utilities/seed_generator.cuh>
 #include <utilities/timer.hpp>
 
 #include <raft/linalg/eltwise.cuh>
@@ -43,8 +42,12 @@ static constexpr int iterations_per_graph = 50;
 #endif
 
 template <typename i_t, typename f_t>
-fj_t<i_t, f_t>::fj_t(mip_solver_context_t<i_t, f_t>& context_, fj_settings_t in_settings)
-  : context(context_),
+fj_t<i_t, f_t>::fj_t(mip_solver_context_t<i_t, f_t>& context_,
+                     fj_settings_t in_settings,
+                     mip_rng_component_id_t seed_component_id)
+  : rng(mip_derive_seed(context_.base_seed, seed_component_id),
+        mip_derive_stream(context_.base_seed, seed_component_id)),
+    context(context_),
     pb_ptr(context.problem_ptr),
     handle_ptr(const_cast<raft::handle_t*>(pb_ptr->handle_ptr)),
     settings(in_settings),
@@ -135,12 +138,12 @@ void fj_t<i_t, f_t>::reset_weights(const rmm::cuda_stream_view& climber_stream,
 template <typename i_t, typename f_t>
 void fj_t<i_t, f_t>::randomize_weights(const raft::handle_t* handle_ptr)
 {
-  std::mt19937 rng(cuopt::seed_generator::get_seed());
+  std::mt19937 host_rng(rng.next_i64());
   constexpr f_t min_weight = 10.;
   constexpr f_t max_weight = 30.;
   // generate a range of weights between 10. and 30.
   auto h_cstr_vec =
-    get_random_uniform_vector<i_t, f_t>(cstr_weights.size(), rng, min_weight, max_weight);
+    get_random_uniform_vector<i_t, f_t>(cstr_weights.size(), host_rng, min_weight, max_weight);
   f_t h_max_weight = *std::max_element(h_cstr_vec.begin(), h_cstr_vec.end());
   max_cstr_weight.set_value_async(h_max_weight, handle_ptr->get_stream());
   raft::copy(cstr_weights.data(), h_cstr_vec.data(), h_cstr_vec.size(), handle_ptr->get_stream());
@@ -672,7 +675,7 @@ void fj_t<i_t, f_t>::run_step_device(const rmm::cuda_stream_view& climber_stream
 
   auto& data    = *climbers[climber_idx];
   auto v        = data.view();
-  settings.seed = cuopt::seed_generator::get_seed();
+  settings.seed = rng.next_i64();
   // ensure an updated copy of the settings is used device-side
   raft::copy(v.settings, &settings, 1, climber_stream);
 
@@ -1128,7 +1131,7 @@ i_t fj_t<i_t, f_t>::solve(solution_t<i_t, f_t>& solution)
 
     // if time limit exceeded: round all remaining fractionals if any by nearest rounding.
     if (climbers[0]->fractional_variables.set_size.value(handle_ptr->get_stream()) > 0) {
-      solution.round_nearest();
+      solution.round_nearest(rng.next_u64());
     }
   }