Fixed early termination in CMS750_4 + Fixed hard-coded number of threads

[nguidotti]

• Fixed early termination in CMS750_4 due to an incorrect root objective from the PDLP. It provides an objective in user space and B&B expects the objective in the solver space.
• Fixed setting the number of threads to a fixed value when running cuopt_cli. Now the number of threads in the probing cache can be controlled by the bounds_update::settings_t.
• Inverted loop order in probing cache to avoid creating and deleting the OpenMP thread pool each iteration.
• Silence the logs from the concurrent mode when running inside MIP.

Checklist

• I am familiar with the Contributing Guidelines.
• Testing
  • New or existing tests cover these changes
  • Added tests
  • Created an issue to follow-up
  • NA
• Documentation
  • The documentation is up to date with these changes
  • Added new documentation
  • NA

Summary by CodeRabbit

• New Features
  • Added configurable per-run threading and a bidirectional solver↔user objective conversion.
• Optimizations
  • More consistent, configurable threading for preprocessing to improve performance stability.
• Bug Fixes
  • Safer handling to avoid unwanted state updates during active solves.
• Behavior Changes
  • Objective-value handling adjusted for more accurate solver/user consistency.
• Quality of Life
  • Reduced verbose logging during mixed-mode solves for clearer output.

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[coderabbitai]

📝 Walkthrough

Walkthrough

Reads PDLP objective as solver-space and derives user-space for callbacks; adds user→solver objective conversion API; makes presolve thread count configurable with OpenMP and binds per-thread pools to that count; guards B&B root assignment during runs; conditionally suppresses LP solver logs during MIP solves.

Changes

Cohort / File(s)	Summary
Objective conversion API cpp/src/mip/problem/problem.cuh, cpp/src/mip/problem/problem.cu	Adds get_solver_obj_from_user_obj(f_t user_obj) const to problem_t to convert user-space objective → solver-space.
Diversity manager objective handling cpp/src/mip/diversity/diversity_manager.cu	Reads PDLP objective as solver-space (lp_result.get_objective_value()), computes user-space objective, and updates root-relaxation callback call to (solver_obj, user_obj, reduction_costs, iters); adds clarifying comments about solver/user semantics.
Presolve threading / probing cache cpp/src/mip/presolve/probing_cache.cu, cpp/src/mip/presolve/bounds_presolve.cuh	Introduces configurable num_threads from bound_presolve_t::settings_t (adds i_t num_threads = -1), includes <omp.h>, sizes per-thread pools by num_threads, and uses #pragma omp parallel num_threads(num_threads) with a subsequent #pragma omp for.
Dual simplex / B&B guard cpp/src/dual_simplex/branch_and_bound.hpp	Adds guard in set_root_relaxation_solution to only assign root crossover and related fields when is_running is false.
LP solver logging cpp/src/linear_programming/solve.cu	Adds CUOPT_LP_SOLVER_LOG_INFO macro to suppress verbose logs when settings.inside_mip is true; replaces multiple CUOPT_LOG_INFO calls with the macro; updates copyright year.

Estimated code review effort

🎯 3 (Moderate) | ⏱️ ~25 minutes

🚥 Pre-merge checks | ✅ 2 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 12.50% which is insufficient. The required threshold is 80.00%.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (2 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title references two specific bug fixes (early termination in CMS750_4 and hard-coded thread count), both of which are substantive changes present in the changeset addressing objective mapping and thread configuration issues.

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✨ Finishing touches

• 📝 Generate docstrings

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[rg20]

Is this uniform across the solvers? Or just PDLP behaves differently than others? We need to standardize this.

[coderabbitai]

Actionable comments posted: 0

Caution

Some comments are outside the diff and can’t be posted inline due to platform limitations.

⚠️ Outside diff range comments (1)

cpp/src/mip/presolve/probing_cache.cu (1)

859-910: Add defensive validation for num_threads before pool sizing and parallel launch

The code assumes settings.num_threads is always positive, but since settings_t is a public struct, external code can set num_threads to 0 (or modify it between initialization and use). If 0 is assigned:

• modification_vector_pool and substitution_vector_pool would have size 0
• #pragma omp parallel num_threads(0) produces undefined behavior (OpenMP spec)
• If threads spawn despite 0, thread_idx from omp_get_thread_num() will exceed pool bounds, causing out-of-bounds access

Add a defensive clamp before sizing the pools:

Proposed fix

-  const size_t num_threads = bound_presolve.settings.num_threads;
+  const i_t requested_threads = bound_presolve.settings.num_threads;
+  size_t num_threads =
+    requested_threads > 0 ? static_cast<size_t>(requested_threads)
+                          : static_cast<size_t>(omp_get_max_threads());
+  if (num_threads == 0) { num_threads = 1; }

Aligns with multithreading safety guidelines to prevent resource exhaustion and thread safety violations.