Forward-merge release/26.04 into main

conda/environments/all_cuda-129_arch-aarch64.yaml

@@ -34,7 +34,7 @@ dependencies:
 - libcurand-dev
 - libcusolver-dev
 - libcusparse-dev
-- libgrpc
+- libgrpc >=1.78.0,<1.80.0a0
 - libprotobuf
 - libraft-headers==26.4.*,>=0.0.0a0
 - librmm==26.4.*,>=0.0.0a0

conda/environments/all_cuda-129_arch-x86_64.yaml

@@ -34,7 +34,7 @@ dependencies:
 - libcurand-dev
 - libcusolver-dev
 - libcusparse-dev
-- libgrpc
+- libgrpc >=1.78.0,<1.80.0a0
 - libprotobuf
 - libraft-headers==26.4.*,>=0.0.0a0
 - librmm==26.4.*,>=0.0.0a0

conda/environments/all_cuda-131_arch-aarch64.yaml

@@ -34,7 +34,7 @@ dependencies:
 - libcurand-dev
 - libcusolver-dev
 - libcusparse-dev
-- libgrpc
+- libgrpc >=1.78.0,<1.80.0a0
 - libprotobuf
 - libraft-headers==26.4.*,>=0.0.0a0
 - librmm==26.4.*,>=0.0.0a0

conda/environments/all_cuda-131_arch-x86_64.yaml

@@ -34,7 +34,7 @@ dependencies:
 - libcurand-dev
 - libcusolver-dev
 - libcusparse-dev
-- libgrpc
+- libgrpc >=1.78.0,<1.80.0a0
 - libprotobuf
 - libraft-headers==26.4.*,>=0.0.0a0
 - librmm==26.4.*,>=0.0.0a0

conda/recipes/libcuopt/recipe.yaml

@@ -93,7 +93,7 @@ cache:
       - bzip2
       - openssl
       - c-ares
-      - libgrpc
+      - libgrpc >=1.78.0,<1.80.0a0
       - libprotobuf
       - libabseil
       - re2
@@ -127,14 +127,22 @@ outputs:
         - bzip2
       ignore_run_exports:
         by_name:
+          - c-ares
           - cuda-nvtx
           - cuda-version
-          - libcurand
+          - libabseil
+          - libboost
           - libcudss
+          - libcurand
           - libcusparse
+          - libgrpc
+          - libprotobuf
           - librmm
-          - libzlib
           - libbz2
+          - libzlib
+          - openssl
+          - re2
+          - tbb
     tests:
     - package_contents:
         files:
@@ -174,10 +182,11 @@ outputs:
         - openssl
         - c-ares
         - libuuid
-        - libgrpc
+        - libgrpc >=1.78.0,<1.80.0a0
         - libprotobuf
         - libabseil
         - re2
+        - tbb-devel
       run:
         - ${{ pin_compatible("cuda-version", upper_bound="x", lower_bound="x") }}
         - ${{ pin_subpackage("libmps-parser", exact=True) }}
@@ -188,9 +197,10 @@ outputs:
         - openssl
         - c-ares
         - libuuid
-        - libgrpc
+        - libgrpc >=1.78.0,<1.80.0a0
         - libprotobuf
         - libabseil
+        - tbb
       ignore_run_exports:
         by_name:
           - cuda-nvtx
@@ -235,7 +245,7 @@ outputs:
         - libcusparse-dev
         - openssl
         - c-ares
-        - libgrpc
+        - libgrpc >=1.78.0,<1.80.0a0
         - libprotobuf
         - libabseil
       run:

cpp/include/cuopt/linear_programming/mip/solver_solution.hpp

@@ -75,6 +75,7 @@ class mip_solution_t : public base_solution_t {
   const std::vector<std::string>& get_variable_names() const;
   const std::vector<rmm::device_uvector<f_t>>& get_solution_pool() const;
   void write_to_sol_file(std::string_view filename, rmm::cuda_stream_view stream_view) const;
+  void log_detailed_summary() const;
   void log_summary() const;
 
  private:

cpp/src/branch_and_bound/branch_and_bound.cpp

@@ -313,6 +313,12 @@ f_t branch_and_bound_t<i_t, f_t>::get_lower_bound()
   }
 }
 
+template <typename i_t, typename f_t>
+void branch_and_bound_t<i_t, f_t>::set_initial_upper_bound(f_t bound)
+{
+  upper_bound_ = bound;
+}
+
 template <typename i_t, typename f_t>
 void branch_and_bound_t<i_t, f_t>::report_heuristic(f_t obj)
 {
@@ -469,10 +475,7 @@ void branch_and_bound_t<i_t, f_t>::set_new_solution(const std::vector<f_t>& solu
   mutex_original_lp_.unlock();
   bool is_feasible    = false;
   bool attempt_repair = false;
-  mutex_upper_.lock();
-  f_t current_upper_bound = upper_bound_;
-  mutex_upper_.unlock();
-  if (obj < current_upper_bound) {
+  if (!incumbent_.has_incumbent || obj < incumbent_.objective) {
     f_t primal_err;
     f_t bound_err;
     i_t num_fractional;
@@ -487,8 +490,8 @@ void branch_and_bound_t<i_t, f_t>::set_new_solution(const std::vector<f_t>& solu
       original_lp_, settings_, var_types_, crushed_solution, primal_err, bound_err, num_fractional);
     mutex_original_lp_.unlock();
     mutex_upper_.lock();
-    if (is_feasible && obj < upper_bound_) {
-      upper_bound_ = obj;
+    if (is_feasible && improves_incumbent(obj)) {
+      upper_bound_ = std::min(upper_bound_.load(), obj);
       incumbent_.set_incumbent_solution(obj, crushed_solution);
     } else {
       attempt_repair         = true;
@@ -648,8 +651,8 @@ void branch_and_bound_t<i_t, f_t>::repair_heuristic_solutions()
       if (is_feasible) {
         mutex_upper_.lock();
 
-        if (repaired_obj < upper_bound_) {
-          upper_bound_ = repaired_obj;
+        if (improves_incumbent(repaired_obj)) {
+          upper_bound_ = std::min(upper_bound_.load(), repaired_obj);
           incumbent_.set_incumbent_solution(repaired_obj, repaired_solution);
           report_heuristic(repaired_obj);
 
@@ -735,7 +738,9 @@ void branch_and_bound_t<i_t, f_t>::set_final_solution(mip_solution_t<i_t, f_t>&
   if (gap <= settings_.absolute_mip_gap_tol || gap_rel <= settings_.relative_mip_gap_tol) {
     solver_status_ = mip_status_t::OPTIMAL;
 #ifdef CHECK_CUTS_AGAINST_SAVED_SOLUTION
-    if (settings_.sub_mip == 0) { write_solution_for_cut_verification(original_lp_, incumbent_.x); }
+    if (settings_.sub_mip == 0 && has_solver_space_incumbent()) {
+      write_solution_for_cut_verification(original_lp_, incumbent_.x);
+    }
 #endif
     if (gap > 0 && gap <= settings_.absolute_mip_gap_tol) {
       settings_.log.printf("Optimal solution found within absolute MIP gap tolerance (%.1e)\n",
@@ -762,11 +767,10 @@ void branch_and_bound_t<i_t, f_t>::set_final_solution(mip_solution_t<i_t, f_t>&
     }
   }
 
-  if (upper_bound_ != inf) {
-    assert(incumbent_.has_incumbent);
+  if (has_solver_space_incumbent()) {
     uncrush_primal_solution(original_problem_, original_lp_, incumbent_.x, solution.x);
+    solution.objective = incumbent_.objective;
   }
-  solution.objective          = incumbent_.objective;
   solution.lower_bound        = lower_bound;
   solution.nodes_explored     = exploration_stats_.nodes_explored;
   solution.simplex_iterations = exploration_stats_.total_lp_iters;
@@ -785,17 +789,17 @@ void branch_and_bound_t<i_t, f_t>::add_feasible_solution(f_t leaf_objective,
                       compute_user_objective(original_lp_, leaf_objective));
 
   mutex_upper_.lock();
-  if (leaf_objective < upper_bound_) {
+  if (improves_incumbent(leaf_objective)) {
     incumbent_.set_incumbent_solution(leaf_objective, leaf_solution);
-    upper_bound_ = leaf_objective;
+    upper_bound_ = std::min(upper_bound_.load(), leaf_objective);
     report(feasible_solution_symbol(thread_type), leaf_objective, get_lower_bound(), leaf_depth, 0);
     send_solution = true;
   }
 
   if (send_solution && settings_.solution_callback != nullptr) {
     std::vector<f_t> original_x;
     uncrush_primal_solution(original_problem_, original_lp_, incumbent_.x, original_x);
-    settings_.solution_callback(original_x, upper_bound_);
+    settings_.solution_callback(original_x, leaf_objective);
   }
   mutex_upper_.unlock();
 }
@@ -921,7 +925,7 @@ struct nondeterministic_policy_t : tree_update_policy_t<i_t, f_t> {
   {
   }
 
-  f_t upper_bound() const override { return bnb.get_cutoff(); }
+  f_t upper_bound() const override { return bnb.get_upper_bound(); }
 
   void update_pseudo_costs(mip_node_t<i_t, f_t>* node, f_t leaf_obj) override
   {
@@ -1339,7 +1343,7 @@ dual::status_t branch_and_bound_t<i_t, f_t>::solve_node_lp(
   simplex_solver_settings_t lp_settings = settings_;
   lp_settings.concurrent_halt           = &node_concurrent_halt_;
   lp_settings.set_log(false);
-  f_t cutoff = get_cutoff();
+  f_t cutoff = upper_bound_.load();
   if (original_lp_.objective_is_integral) {
     lp_settings.cut_off = std::ceil(cutoff - settings_.integer_tol) + settings_.dual_tol;
   } else {
@@ -1452,7 +1456,7 @@ void branch_and_bound_t<i_t, f_t>::plunge_with(branch_and_bound_worker_t<i_t, f_
     // - The lower bound of the parent is lower or equal to its children
     worker->lower_bound = node_ptr->lower_bound;
 
-    if (node_ptr->lower_bound > get_cutoff()) {
+    if (node_ptr->lower_bound > upper_bound_.load()) {
       search_tree_.graphviz_node(settings_.log, node_ptr, "cutoff", node_ptr->lower_bound);
       search_tree_.update(node_ptr, node_status_t::FATHOMED);
       worker->recompute_basis  = true;
@@ -1590,7 +1594,7 @@ void branch_and_bound_t<i_t, f_t>::dive_with(branch_and_bound_worker_t<i_t, f_t>
 
     worker->lower_bound = node_ptr->lower_bound;
 
-    if (node_ptr->lower_bound > get_cutoff()) {
+    if (node_ptr->lower_bound > upper_bound_.load()) {
       worker->recompute_basis  = true;
       worker->recompute_bounds = true;
       continue;
@@ -1649,7 +1653,7 @@ void branch_and_bound_t<i_t, f_t>::run_scheduler()
   diving_heuristics_settings_t<i_t, f_t> diving_settings = settings_.diving_settings;
   const i_t num_workers                                  = 2 * settings_.num_threads;
 
-  if (!std::isfinite(upper_bound_)) { diving_settings.guided_diving = false; }
+  if (!has_solver_space_incumbent()) { diving_settings.guided_diving = false; }
   std::vector<search_strategy_t> strategies = get_search_strategies(diving_settings);
   std::array<i_t, num_search_strategies> max_num_workers_per_type =
     get_max_workers(num_workers, strategies);
@@ -1682,7 +1686,7 @@ void branch_and_bound_t<i_t, f_t>::run_scheduler()
     // If the guided diving was disabled previously due to the lack of an incumbent solution,
     // re-enable as soon as a new incumbent is found.
     if (settings_.diving_settings.guided_diving != diving_settings.guided_diving) {
-      if (std::isfinite(upper_bound_)) {
+      if (has_solver_space_incumbent()) {
         diving_settings.guided_diving = settings_.diving_settings.guided_diving;
         strategies                    = get_search_strategies(diving_settings);
         max_num_workers_per_type      = get_max_workers(num_workers, strategies);
@@ -1733,7 +1737,7 @@ void branch_and_bound_t<i_t, f_t>::run_scheduler()
         std::optional<mip_node_t<i_t, f_t>*> start_node = node_queue_.pop_best_first();
 
         if (!start_node.has_value()) { continue; }
-        if (get_cutoff() < start_node.value()->lower_bound) {
+        if (upper_bound_.load() < start_node.value()->lower_bound) {
           // This node was put on the heap earlier but its lower bound is now greater than the
           // current upper bound
           search_tree_.graphviz_node(
@@ -1757,7 +1761,7 @@ void branch_and_bound_t<i_t, f_t>::run_scheduler()
         std::optional<mip_node_t<i_t, f_t>*> start_node = node_queue_.pop_diving();
 
         if (!start_node.has_value()) { continue; }
-        if (get_cutoff() < start_node.value()->lower_bound ||
+        if (upper_bound_.load() < start_node.value()->lower_bound ||
             start_node.value()->depth < diving_settings.min_node_depth) {
           continue;
         }
@@ -1831,7 +1835,7 @@ void branch_and_bound_t<i_t, f_t>::single_threaded_solve()
     std::optional<mip_node_t<i_t, f_t>*> start_node = node_queue_.pop_best_first();
 
     if (!start_node.has_value()) { continue; }
-    if (get_cutoff() < start_node.value()->lower_bound) {
+    if (upper_bound_.load() < start_node.value()->lower_bound) {
       // This node was put on the heap earlier but its lower bound is now greater than the
       // current upper bound
       search_tree_.graphviz_node(
@@ -2331,12 +2335,12 @@ mip_status_t branch_and_bound_t<i_t, f_t>::solve(mip_solution_t<i_t, f_t>& solut
         return mip_status_t::NUMERICAL;
       }
 
-      if (settings_.reduced_cost_strengthening >= 1 && get_cutoff() < last_upper_bound) {
+      if (settings_.reduced_cost_strengthening >= 1 && upper_bound_.load() < last_upper_bound) {
         mutex_upper_.lock();
-        last_upper_bound = get_cutoff();
+        last_upper_bound = upper_bound_.load();
         std::vector<f_t> lower_bounds;
         std::vector<f_t> upper_bounds;
-        find_reduced_cost_fixings(get_cutoff(), lower_bounds, upper_bounds);
+        find_reduced_cost_fixings(upper_bound_.load(), lower_bounds, upper_bounds);
         mutex_upper_.unlock();
         mutex_original_lp_.lock();
         original_lp_.lower = lower_bounds;
@@ -2468,7 +2472,7 @@ mip_status_t branch_and_bound_t<i_t, f_t>::solve(mip_solution_t<i_t, f_t>& solut
       f_t rel_gap = user_relative_gap(original_lp_, upper_bound_.load(), root_objective_);
       f_t abs_gap = compute_user_abs_gap(original_lp_, upper_bound_.load(), root_objective_);
       if (rel_gap < settings_.relative_mip_gap_tol || abs_gap < settings_.absolute_mip_gap_tol) {
-        set_solution_at_root(solution, cut_info);
+        if (num_fractional == 0) { set_solution_at_root(solution, cut_info); }
         set_final_solution(solution, root_objective_);
         return mip_status_t::OPTIMAL;
       }
@@ -2528,10 +2532,10 @@ mip_status_t branch_and_bound_t<i_t, f_t>::solve(mip_solution_t<i_t, f_t>& solut
     return solver_status_;
   }
 
-  if (settings_.reduced_cost_strengthening >= 2 && get_cutoff() < last_upper_bound) {
+  if (settings_.reduced_cost_strengthening >= 2 && upper_bound_.load() < last_upper_bound) {
     std::vector<f_t> lower_bounds;
     std::vector<f_t> upper_bounds;
-    i_t num_fixed = find_reduced_cost_fixings(get_cutoff(), lower_bounds, upper_bounds);
+    i_t num_fixed = find_reduced_cost_fixings(upper_bound_.load(), lower_bounds, upper_bounds);
     if (num_fixed > 0) {
       std::vector<bool> bounds_changed(original_lp_.num_cols, true);
       std::vector<char> row_sense;
@@ -2636,7 +2640,7 @@ mip_status_t branch_and_bound_t<i_t, f_t>::solve(mip_solution_t<i_t, f_t>& solut
         std::optional<mip_node_t<i_t, f_t>*> start_node = node_queue_.pop_best_first();
 
         if (!start_node.has_value()) { continue; }
-        if (get_cutoff() < start_node.value()->lower_bound) {
+        if (upper_bound_.load() < start_node.value()->lower_bound) {
           // This node was put on the heap earlier but its lower bound is now greater than the
           // current upper bound
           search_tree_.graphviz_node(
@@ -3279,8 +3283,8 @@ void branch_and_bound_t<i_t, f_t>::deterministic_process_worker_solutions(
              deterministic_current_horizon_);
 
       bool improved = false;
-      if (sol->objective < upper_bound_) {
-        upper_bound_ = sol->objective;
+      if (improves_incumbent(sol->objective)) {
+        upper_bound_ = std::min(upper_bound_.load(), sol->objective);
         incumbent_.set_incumbent_solution(sol->objective, sol->solution);
         current_upper = sol->objective;
         improved      = true;
@@ -3442,8 +3446,8 @@ void branch_and_bound_t<i_t, f_t>::deterministic_sort_replay_events(
       // Process heuristic solution at its correct work unit timestamp position
       f_t new_upper = std::numeric_limits<f_t>::infinity();
 
-      if (hsol.objective < upper_bound_) {
-        upper_bound_ = hsol.objective;
+      if (improves_incumbent(hsol.objective)) {
+        upper_bound_ = std::min(upper_bound_.load(), hsol.objective);
         incumbent_.set_incumbent_solution(hsol.objective, hsol.solution);
         new_upper = hsol.objective;
       }
@@ -3477,7 +3481,7 @@ void branch_and_bound_t<i_t, f_t>::deterministic_sort_replay_events(
 template <typename i_t, typename f_t>
 void branch_and_bound_t<i_t, f_t>::deterministic_prune_worker_nodes_vs_incumbent()
 {
-  f_t upper_bound = get_cutoff();
+  f_t upper_bound = upper_bound_.load();
 
   for (auto& worker : *deterministic_workers_) {
     // Check nodes in plunge stack - filter in place
@@ -3613,7 +3617,7 @@ void branch_and_bound_t<i_t, f_t>::deterministic_populate_diving_heap()
   const int num_diving                  = deterministic_diving_workers_->size();
   constexpr int target_nodes_per_worker = 10;
   const int target_total                = num_diving * target_nodes_per_worker;
-  f_t cutoff                            = get_cutoff();
+  f_t cutoff                            = upper_bound_.load();
 
   // Collect candidate nodes from BFS worker backlog heaps
   std::vector<std::pair<mip_node_t<i_t, f_t>*, f_t>> candidates;