From 646e9d472e3b7bf8f890de641bb2946e229f6d8f Mon Sep 17 00:00:00 2001
From: adityasinghz <adityasingh246810@gmail.com>
Date: Mon, 24 Nov 2025 13:31:05 +0530
Subject: [PATCH 1/2] Add message when optimal solution is found during
 presolve

---
 cpp/src/mip/solve.cu  | 1 +
 cpp/src/mip/solver.cu | 2 ++
 2 files changed, 3 insertions(+)

diff --git a/cpp/src/mip/solve.cu b/cpp/src/mip/solve.cu
index 16227c431..0227907d6 100644
--- a/cpp/src/mip/solve.cu
+++ b/cpp/src/mip/solve.cu
@@ -70,6 +70,7 @@ mip_solution_t<i_t, f_t> run_mip(detail::problem_t<i_t, f_t>& problem,
   pdlp_hyper_params::update_step_size_on_initial_solution     = true;
   // if the input problem is empty: early exit
   if (problem.empty) {
+    CUOPT_LOG_INFO("Optimal solution found during presolve");
     detail::solution_t<i_t, f_t> solution(problem);
     problem.preprocess_problem();
     thrust::for_each(problem.handle_ptr->get_thrust_policy(),
diff --git a/cpp/src/mip/solver.cu b/cpp/src/mip/solver.cu
index 28659cccd..91da23125 100644
--- a/cpp/src/mip/solver.cu
+++ b/cpp/src/mip/solver.cu
@@ -100,6 +100,7 @@ solution_t<i_t, f_t> mip_solver_t<i_t, f_t>::run_solver()
                 "preprocess_problem should be called before running the solver");
 
   if (context.problem_ptr->empty) {
+    CUOPT_LOG_INFO("Optimal solution found during presolve");
     CUOPT_LOG_INFO("Problem fully reduced in presolve");
     solution_t<i_t, f_t> sol(*context.problem_ptr);
     sol.set_problem_fully_reduced();
@@ -118,6 +119,7 @@ solution_t<i_t, f_t> mip_solver_t<i_t, f_t>::run_solver()
     return sol;
   }
   if (context.problem_ptr->empty) {
+    CUOPT_LOG_INFO("Optimal solution found during presolve");
     CUOPT_LOG_INFO("Problem full reduced in presolve");
     solution_t<i_t, f_t> sol(*context.problem_ptr);
     sol.set_problem_fully_reduced();

From 527cd6023f1c3dabbe2868d9a2d2d78283c648cc Mon Sep 17 00:00:00 2001
From: adityasinghz <adityasingh246810@gmail.com>
Date: Mon, 24 Nov 2025 20:02:55 +0530
Subject: [PATCH 2/2] Move optimal solution message to presolve function

Move the 'Optimal solution found during presolve' message to the
presolve function itself (third_party_presolve.cpp) where we can
accurately detect when presolve finds the optimal solution. This
ensures the message only appears when presolve actually found the
solution, not when the problem is empty for other reasons.

Removed the message from generic empty problem checks in:
- cpp/src/mip/solve.cu (run_mip function)
- cpp/src/mip/solver.cu (run_solver function - both locations)
---
 cpp/src/mip/presolve/third_party_presolve.cpp | 5 +++++
 cpp/src/mip/solve.cu                          | 1 -
 cpp/src/mip/solver.cu                         | 2 --
 3 files changed, 5 insertions(+), 3 deletions(-)

diff --git a/cpp/src/mip/presolve/third_party_presolve.cpp b/cpp/src/mip/presolve/third_party_presolve.cpp
index 22827c6e2..3439801ce 100644
--- a/cpp/src/mip/presolve/third_party_presolve.cpp
+++ b/cpp/src/mip/presolve/third_party_presolve.cpp
@@ -425,6 +425,11 @@ std::optional<third_party_presolve_result_t<i_t, f_t>> third_party_presolve_t<i_
                  papilo_problem.getNCols(),
                  papilo_problem.getConstraintMatrix().getNnz());
 
+  // Check if presolve found the optimal solution (problem fully reduced)
+  if (papilo_problem.getNRows() == 0 && papilo_problem.getNCols() == 0) {
+    CUOPT_LOG_INFO("Optimal solution found during presolve");
+  }
+
   auto opt_problem =
     build_optimization_problem<i_t, f_t>(papilo_problem, op_problem.get_handle_ptr());
   auto col_flags = papilo_problem.getColFlags();
diff --git a/cpp/src/mip/solve.cu b/cpp/src/mip/solve.cu
index 0227907d6..16227c431 100644
--- a/cpp/src/mip/solve.cu
+++ b/cpp/src/mip/solve.cu
@@ -70,7 +70,6 @@ mip_solution_t<i_t, f_t> run_mip(detail::problem_t<i_t, f_t>& problem,
   pdlp_hyper_params::update_step_size_on_initial_solution     = true;
   // if the input problem is empty: early exit
   if (problem.empty) {
-    CUOPT_LOG_INFO("Optimal solution found during presolve");
     detail::solution_t<i_t, f_t> solution(problem);
     problem.preprocess_problem();
     thrust::for_each(problem.handle_ptr->get_thrust_policy(),
diff --git a/cpp/src/mip/solver.cu b/cpp/src/mip/solver.cu
index 91da23125..28659cccd 100644
--- a/cpp/src/mip/solver.cu
+++ b/cpp/src/mip/solver.cu
@@ -100,7 +100,6 @@ solution_t<i_t, f_t> mip_solver_t<i_t, f_t>::run_solver()
                 "preprocess_problem should be called before running the solver");
 
   if (context.problem_ptr->empty) {
-    CUOPT_LOG_INFO("Optimal solution found during presolve");
     CUOPT_LOG_INFO("Problem fully reduced in presolve");
     solution_t<i_t, f_t> sol(*context.problem_ptr);
     sol.set_problem_fully_reduced();
@@ -119,7 +118,6 @@ solution_t<i_t, f_t> mip_solver_t<i_t, f_t>::run_solver()
     return sol;
   }
   if (context.problem_ptr->empty) {
-    CUOPT_LOG_INFO("Optimal solution found during presolve");
     CUOPT_LOG_INFO("Problem full reduced in presolve");
     solution_t<i_t, f_t> sol(*context.problem_ptr);
     sol.set_problem_fully_reduced();