From 18769369742d71c919f330beaf1439ebe176366d Mon Sep 17 00:00:00 2001
From: Christopher Maes <cmaes@nvidia.com>
Date: Tue, 20 May 2025 15:57:22 -0700
Subject: [PATCH] Fix bug in crossover where numerical was returned instead of
 time limit

Also adds the --relaxation flag to cuopt_cli to solve the LP relaxation
of a MIP
---
 cpp/cuopt_cli.cpp                   | 11 +++++++++--
 cpp/src/dual_simplex/crossover.cpp  | 20 ++++++++++++++++++--
 cpp/src/linear_programming/solve.cu |  1 +
 3 files changed, 28 insertions(+), 4 deletions(-)

diff --git a/cpp/cuopt_cli.cpp b/cpp/cuopt_cli.cpp
index afb59d58b4..a81804a70a 100644
--- a/cpp/cuopt_cli.cpp
+++ b/cpp/cuopt_cli.cpp
@@ -81,6 +81,7 @@ inline auto make_async() { return std::make_shared<rmm::mr::cuda_async_memory_re
  */
 int run_single_file(const std::string& file_path,
                     const std::string& initial_solution_file,
+                    bool solve_relaxation,
                     const std::map<std::string, std::string>& settings_strings)
 {
   const raft::handle_t handle_{};
@@ -131,7 +132,7 @@ int run_single_file(const std::string& file_path,
           initial_solution_file, mps_data_model.get_variable_names());
 
   try {
-    if (is_mip) {
+    if (is_mip && !solve_relaxation) {
       auto& mip_settings = settings.get_mip_settings();
       if (initial_solution.size() > 0) {
         mip_settings.set_initial_solution(initial_solution.data(), initial_solution.size());
@@ -191,6 +192,11 @@ int main(int argc, char* argv[])
     .help("path to the initial solution .sol file")
     .default_value("");
 
+  program.add_argument("--relaxation")
+    .help("solve the LP relaxation of the MIP")
+    .default_value(false)
+    .implicit_value(true);
+
   std::map<std::string, std::string> arg_name_to_param_name;
   {
     // Add all solver settings as arguments
@@ -257,8 +263,9 @@ int main(int argc, char* argv[])
   std::string file_name = program.get<std::string>("filename");
 
   const auto initial_solution_file = program.get<std::string>("--initial-solution");
+  const auto solve_relaxation      = program.get<bool>("--relaxation");
 
   auto memory_resource = make_async();
   rmm::mr::set_current_device_resource(memory_resource.get());
-  return run_single_file(file_name, initial_solution_file, settings_strings);
+  return run_single_file(file_name, initial_solution_file, solve_relaxation, settings_strings);
 }
diff --git a/cpp/src/dual_simplex/crossover.cpp b/cpp/src/dual_simplex/crossover.cpp
index 37a67fc385..957b8d2ca5 100644
--- a/cpp/src/dual_simplex/crossover.cpp
+++ b/cpp/src/dual_simplex/crossover.cpp
@@ -1217,6 +1217,15 @@ crossover_status_t crossover(const lp_problem_t<i_t, f_t>& lp,
     std::vector<f_t> edge_norms;
     dual::status_t status =
       dual_phase2(2, 0, start_time, lp, settings, vstatus, solution, dual_iter, edge_norms);
+    if (toc(start_time) > settings.time_limit) {
+      settings.log.printf("Time limit exceeded\n");
+      return crossover_status_t::TIME_LIMIT;
+    }
+    if (settings.concurrent_halt != nullptr &&
+        settings.concurrent_halt->load(std::memory_order_acquire) == 1) {
+      settings.log.printf("Concurrent halt\n");
+      return crossover_status_t::CONCURRENT_LIMIT;
+    }
     primal_infeas = primal_infeasibility(lp, settings, vstatus, solution.x);
     dual_infeas   = dual_infeasibility(lp, settings, vstatus, solution.z);
     primal_res    = primal_residual(lp, solution);
@@ -1337,6 +1346,15 @@ crossover_status_t crossover(const lp_problem_t<i_t, f_t>& lp,
       std::vector<f_t> edge_norms;
       dual::status_t status = dual_phase2(
         2, iter == 0 ? 1 : 0, start_time, lp, settings, vstatus, solution, iter, edge_norms);
+      if (toc(start_time) > settings.time_limit) {
+        settings.log.printf("Time limit exceeded\n");
+        return crossover_status_t::TIME_LIMIT;
+      }
+      if (settings.concurrent_halt != nullptr &&
+          settings.concurrent_halt->load(std::memory_order_acquire) == 1) {
+        settings.log.printf("Concurrent halt\n");
+        return crossover_status_t::CONCURRENT_LIMIT;
+      }
       solution.iterations += iter;
       primal_infeas = primal_infeasibility(lp, settings, vstatus, solution.x);
       dual_infeas   = dual_infeasibility(lp, settings, vstatus, solution.z);
@@ -1345,7 +1363,6 @@ crossover_status_t crossover(const lp_problem_t<i_t, f_t>& lp,
       if (status != dual::status_t::OPTIMAL) {
         print_crossover_info(lp, settings, vstatus, solution, "Dual phase 2 complete");
       }
-
       primal_feasible = primal_infeas <= primal_tol && primal_res <= primal_tol;
       dual_feasible   = dual_infeas <= dual_tol && dual_res <= dual_tol;
     } else {
@@ -1355,7 +1372,6 @@ crossover_status_t crossover(const lp_problem_t<i_t, f_t>& lp,
 
   settings.log.printf("Crossover time %.2f seconds\n", toc(crossover_start));
   settings.log.printf("Total time %.2f seconds\n", toc(start_time));
-  settings.log.printf("\n");
 
   crossover_status_t status = crossover_status_t::NUMERICAL_ISSUES;
   if (dual_feasible) { status = crossover_status_t::DUAL_FEASIBLE; }
diff --git a/cpp/src/linear_programming/solve.cu b/cpp/src/linear_programming/solve.cu
index 8cca939158..0ab3d848df 100644
--- a/cpp/src/linear_programming/solve.cu
+++ b/cpp/src/linear_programming/solve.cu
@@ -396,6 +396,7 @@ optimization_problem_solution_t<i_t, f_t> run_pdlp(detail::problem_t<i_t, f_t>&
                                                                    info,
                                                                    termination_status);
     sol.copy_from(problem.handle_ptr, sol_crossover);
+    CUOPT_LOG_INFO("Crossover status %s", sol.get_termination_status_string().c_str());
   }
   if (crossover_info == 0 && settings.concurrent_halt != nullptr) {
     // We finished. Tell dual simplex to stop if it is still running.