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Release Notes

Release Notes 26.02

New Features (26.02)

  • New parallel reliability branching inside MIP solver
  • Mixed Integer Gomory, Mixed Integer Rounding, Knapsack and Strong Chvatal Gomory cuts are now added at root node
  • Added an option to use batch PDLP when running strong branching at the root. Based on Batched First-Order Methods for Parallel LP Solving in MIP (Nicolas Blin, Stefano Gualandi, Christopher Maes, Andrea Lodi, Bartolomeo Stellato)
  • Quadratic programming (QP) solver is now generally available (previously beta)
  • New infeasibility detection option for PDLP's default solver mode Stable3
  • Solutions callbacks added to C API. Users can now retrieve the dual bound and pass in user data
  • Multiple new diving techniques added for finding integer feasible solutions
  • The PSLP presolver is enabled by default for LP problems. Use the presolve option to select Papilo or disable
  • Added a batch solve for routing to boost throughput for many similar instances
  • Added experimental support for determinism in the parallel branch-and-bound solver. GPU heuristics are not supported yet in this mode

Breaking Changes (26.02)

  • The signatures of the solution callbacks have changed for the Python API
  • To use PDLP warm start, presolve must now be explicitly disabled by setting CUOPT_PRESOLVE=0. Previously, presolve was disabled automatically

Improvements (26.02)

  • Improved primal/dual warm start for PDLP's default solver mode Stable3
  • Quadratic objectives can now be constructed via a matrix in Python API
  • QP barrier now updates and solves augmented system on the GPU
  • Improved performance for LP folding
  • Probing implications and better variable ordering to strengthen presolve and branching
  • Replace deprecated cuDF Column/Buffer APIs with pylibcudf and public cuDF interfaces
  • Modernize dependency pinnings; make CUDA runtime linkage static for portability
  • Build/tooling: add --split-compile, --jobserver, Clang host build, ThreadSanitizer, improved container scripts, and branch/commit metadata in images
  • Use explicit cudaStream_t with cub::DeviceTransform and non-blocking streams for GPU control
  • Enable barrier LP tests, add regression testing, and add SonarQube static analysis
  • Added parameter for specifying the random seed used by the solver

Bug Fixes (26.02)

  • Fixed an issue with incorrect signs of dual variables and reduced costs on maximization problems
  • Fix out-of-bounds in dense-column detection in barrier
  • Correct infeasible-list handling to avoid incorrect infeasibility reports in dual simplex
  • Fix race conditions found via Clang host build + ThreadSanitizer
  • Resolve CUDA–Numba version mismatches with cuDF
  • Fix device code to include required trailing return types
  • Fix issue in crossover after dualization in barrier
  • Repair container build and test failures
  • Miscellaneous additional fixes and stability improvements

Documentation (26.02)

  • Update README and top-level docs for current build and usage
  • Document new repository branching strategies and release-cycle details in README and CONTRIBUTING
  • Add best practices for batch solving

Release Notes 25.12

New Features (25.12)

  • New quadratic programming solver using the barrier method (currently in beta).
  • Support for quadratic objectives added to the C and Python modeling APIs.
  • LP concurrent mode now supports multiple GPUs. PDLP and barrier can now be run on separate GPUs.
  • MIP root relaxation solves now use concurrent mode: PDLP, barrier, and dual simplex.

Improvements (25.12)

  • RINS heuristic adds a new improvement strategy in the MIP solver.
  • Basis factorizations are now reused in the branch and bound tree.
  • Improvement in propagating bounds from parent to child nodes in the branch and bound tree.
  • GMRES with Cholesky/LDL preconditioning is now used for iterative refinement on QPs.
  • Improved numerical stability of dual simplex when the basis is ill-conditioned.
  • Improved robustness in barrier and PDLP: fixed cuSPARSE related leaks and added RAII-style wrappers for cuSPARSE structures.
  • Papilo-based presolve carries over implied integer information from reductions, improving consistency of integrality handling.
  • Build and CI workflows improved through assertion-default changes, better handling of git-hash rebuilds, and fixes to the nightly build matrix.
  • Reduced package sizes by adjusting build outputs and test-only library linkage, and the TSP dataset download logic disables unneeded downloads.

Bug Fixes (25.12)

  • A crash in the incumbent test is resolved.
  • Fixed memory leaks in Barrier and PDLP's cuSPARSE usage.
  • The explored nodes in the MIP log now correctly reflects the actual nodes examined.
  • A compilation issue in the solve_MIP benchmarking executable is fixed, restoring benchmark builds.
  • A logger bug when log_to_console is false is fixed.
  • Routing fixes improve TSP behavior when order locations are set.
  • Nightly container testing and CI handling fix issues in the nightly container test suite and build jobs.
  • A cuDF build_column deprecation issue fixed to keep compatibility with newer cuDF versions.

Documentation (25.12)

  • Missing parameters added to the documentation for LP and MILP.
  • Release notes added to the main repository for easy access.
  • Examples in the documentation improved.
  • The openapi spec for the service showed the 'status' value for LP/MILP results as an int but it is actually a string.

Release Notes 25.10

New Features (25.10)

  • New barrier method for solving LPs. Uses cuDSS for sparse Cholesky / LDT.
  • Concurrent mode for LPs now uses PDLP, dual simplex, and barrier
  • New PDLP solver mode Stable3.
  • MIP presolve using Papilo (enabled by default). LP presolve using Papilo (optional).
  • Parallel branch and bound on the CPU: multiple best-first search and diving threads

Breaking Changes (25.10)

  • New PDLP Solver mode Stable3 is the default

Improvements (25.10)

  • Add setting "CUOPT_BARRIER_DUAL_INITIAL_POINT" to change the dual initial point used by barrier
  • CPUFJ for local search + simple rounding
  • FP as a local search
  • Sub-MIP recombiner and B&B global variable changes
  • Implement GF(2) presolve reduction
  • Implement node presolve
  • CUDA 13/12.9 support
  • Build and test with CUDA 13.0.0
  • Add read/write MPS and relaxation to python API
  • Decompression for .mps.gz and .mps.bz2 files
  • Enable parallelism for root node presolve
  • Enable singleton stuffing and use Papilo default params
  • Make infeasibility checks consistent between the main solver and presolver
  • Add maximization support for root node presolve
  • Performance improvement in dual simplex's right-looking LU factorization
  • Fix high GPU memory usage
  • Print cuOpt version / machine info before solving
  • cuopt-server: update dependencies (drop httpx, add psutil)
  • Add nightly testing of cuOpt jump interface
  • Compression tests are not run when compression is disabled
  • Add sanitizer build option- Heuristic Improvements: balance between generation and improvement heuristics
  • Loosen presolve tolerance and update timers to report cumulative presolve/solve time
  • Warn in case a dependent library is not found in libcuopt load
  • Combined variable bounds
  • Add Commit Sha to container for reference
  • use GCC 14, consolidate dependency groups, update pre-commit hooks
  • Add support for nightly cuopt-examples notebook testing
  • Reduce hard-coded version usage in repo
  • Container to work on all different users including root
  • Changes to download LP and MILP datasets, and also disable cvxpy testing for 3.10
  • Faster engine compile time
  • Fix pre-commit for trailing whitespace and end of file
  • Merge update version and fix version format bugs
  • This library now supports the QPS format, which is an extension of the standard MPS format for representing quadratic programming problems.

Bug Fixes (25.10)

  • Fix variables out of bounds caused by CPUFJ LP scratch thread
  • Fix the maybe-uninitialized compilation error
  • Fix linking errors in the test suite when disabling C adaptor
  • Compute relative gap with respect to user objectives
  • Add http timeout values for general, send, and receive to client
  • Fix bug in fixed_problem_computation
  • Remove limiting_resource_adaptor leftover
  • Add support for cuda13 container and fix cuda13 lib issues in wheel
  • Return Infeasible if the user problem contains crossing bounds
  • Fix out-of-bound access in clean_up_infeasibilities
  • Empty columns with infinite bounds are not removed

Documentation (25.10)

  • Add tutorial video links to Decompression
  • Add warmstart, model update, update docs
  • add docs on CI workflow inputs
  • Add name to drop-down for video link
  • Add video link to the docs and to the Readme
  • Add documentation on nightly installation commands
  • Fix version in version tab, change log, and fix typos
  • Doc update for container version update, and add nvidia-cuda-runtime as a dependency

Release Notes 25.08

New Features (25.08)

  • Added Python API for LP and MILP (#223)

Breaking Changes (25.08)

  • Fixed versioning for nightly and release package (#175)

Improvements (25.08)

  • New heuristic improvements (#178)
  • Add helm chart for cuOpt service (#224)
  • Add nightly container support (#180)
  • Adding deb package support as a beta feature (#190)
  • Use cusparsespmv_preprocess() now that Raft implements it (#120)
  • Create a bash script to run MPS files in parallel (#87)
  • Several fixes needed to compile cuOpt with LLVM (#121)
  • Small fixes for corner cases (#130)
  • Small improvements on how paths are handled in tests (#129)
  • Update cxxopts to v3.3.1 (#128)
  • Bump actions/checkout in nightly.yaml to v4 (#230)
  • Remove CUDA 11 specific changes from repo (#222)
  • Heuristic improvements with solution hash, MAB and simplex root solution (#216)
  • Various typos in comments and strings, note on result dir (#200)
  • Split very large tests into smaller individual test cases (#152)
  • Fix compile error when using clang with C++20 (#145)
  • Relax pinnings on several dependencies, remove nvidia channel (#125)
  • Fix compile error when building with clang (#119)
  • cuOpt service add healthcheck for / (#114)
  • refactor(shellcheck): fix all remaining shellcheck errors/warnings (#99)
  • Add CTK 12.9 fatbin flags to maintain existing binary sizes (#58)

Bug Fixes (25.08)

  • Fixed a segfault on bnatt500 due to small mu leading to inf/nan (#254)
  • Fixed a bug in basis repair. Recover from numerical issues in primal update (#249)
  • Unset NDEBUG in cmake in assert mode (#248)
  • Manual cuda graph creation in load balanced bounds presolve (#242)
  • Fixed bug on initial solution size in the check and cuda set device order (#226)
  • Disable cuda graph in batched PDLP (#225)
  • Fix logging levels format with timestamps (#201)
  • Fix bug in scaling of dual slacks and sign of dual variables for >= constraints (#191)
  • Fix inversion crossover bug with PDP and prize collection (#179)
  • Fix a bug in extract_best_per_route kernel (#156)
  • Fix several bugs appeared in unit testing of JuMP interface (#149)
  • Fix incorrect reported solving time (#131)
  • Fix max offset (#113)
  • Fix batch graph capture issue caused by pinned memory allocator (#110)
  • Fix bug in optimization_problem_solution_t::copy_from (#109)
  • Fix issue when problem has an empty problem in PDLP (#107)
  • Fix crash on models with variables but no constraints (#105)
  • Fix inversion of constraint bounds in conditional bounds presolve (#75)
  • Fix data initialization in create depot node for max travel time feature (#74)

Documentation (25.08)

  • Added more pre-commit checks to ensure coding standards (#213)
  • Mention GAMS and GAMSPy in third-party modeling languages page in documentation (#206)
  • Enable doc build workflow and build script for PR and Nightly (#203)
  • Fix the link to Python docs in README (#118)
  • Add link checker for doc build and test (#229)

Release Notes 25.05

New Features (25.05)

  • Added concurrent mode that runs PDLP and Dual Simplex together
  • Added crossover from PDLP to Dual Simplex
  • Added a C API for LP and MILP
  • PDLP: Faster iterations and new more robust default PDLPSolverMode Stable2
  • Added support for writing out mps file containing user problem. Useful for debugging

Breaking Changes (25.05)

  • NoTermination is now a NumericalError
  • Split cuOpt as libcuopt and cuopt wheel

Improvements (25.05)

  • Hook up MILP Gap parameters and add info about number of nodes explored and simplex iterations
  • FJ bug fixes, tests and improvements
  • Allow no time limit in MILP
  • Refactor routing
  • Probing cache optimization
  • Diversity improvements for routing
  • Enable more compile warnings and faster compile by bypassing rapids fetch
  • Constraint prop based on load balanced bounds update
  • Logger file handling and bug fixes on MILP
  • Add shellcheck to pre-commit and fix warnings

Bug Fixes (25.05)

  • In the solution, termination_status should be cast to correct enum.
  • Fixed a bug using vehicle IDs in construct feasible solution algorithm.
  • FP recombiner probing bug fix.
  • Fix concurrent LP crashes.
  • Fix print relative dual residual.
  • Handle empty problems gracefully.
  • Improve breaks to allow dimensions at arbitrary places in the route.
  • Free var elimination with a substitute variable for each free variable.
  • Fixed race condition when resetting vehicle IDs in heterogenous mode.
  • cuOpt self-hosted client, some MILPs do not have all fields in lp_stats.
  • Fixed RAPIDS logger usage.
  • Handle LP state more cleanly, per solution.
  • Fixed routing solver intermittent failures.
  • Gracefully exit when the problem is infeasible after presolve.
  • Fixed bug on dual resizing.
  • Fix occasional incorrect solution bound on maximization problems
  • Fix inversion of constraint bounds in conditional bounds presolve
  • Pdlp fix batch cuda graph
  • Fix obj constant on max. Fix undefined memory access at root
  • Allow long client version in service version check, this fixes the issue in case version is of the format 25.05.00.dev0

Documentation (25.05)

  • Restructure documentation to accommodate new APIs