Platforms

• Add Debian-10 support (#3209)
• Add Ubuntu 22.04 LTS support (#3276)
  • note: won't have .Net 3.1 support (see: dotnet/core#7038 (comment))
• Remove Ubuntu 21.10 LTS support

Misc

• Split archive by languages and add CMake config to the C++ one (#3200)

Graph

Split ortools.graph.pywrapgraph into:

• ortools.graph.python.linear_sum_assignment
• ortools.graph.python.max_flow
• ortools.graph.python.min_cost_flow

This allows using numpy to speed up the setup of the problems.

CP-SAT

Some improvement on:

• scheduling (propagation, cuts, lower bounds)
• MaxSAT (presolve, core based heuristics)
• MIP performance (presolve, cuts)

Platform changes

• Drop Debian-10 support
• Drop Ubuntu-16.04 support
• Drop .NET Framework 4.5.2

Dependencies Update

• Add Eigen 3.4.0.
• Add Google re2 2021-11-01.
• Protobuf 3.19.1 -> 3.19.4.
• SCIP 7.0.1 -> v800

Python

• Add pybind11.

Features

• Add PDLP as experimental
• Add MathOpt as experimental.

CP-SAT

• renamed few API for consistency
  e.g. LinearExpr.ScalProd -> LinearExpr.WeightedSum.
• Add AddAtLeastOne/AddAtMostOne/AddExactlyOne methods.
• Add AddMultiplicationConstraint(z, x, y) in all languages.
• AddMultipleCircuit() in all languages

C++

• explicit ctor IntVar(BoolVar)
• remove LinearExpr::Add*and replaced them by operator e.g. LinearExpr +=
• Add arithmetic operators on linear expression
• removed LinearExpr::BooleanSum/BooleanScalProd, use Sum/WeightedSum
• Add CpModelBuilder::FixVariable() which overwrite the domain of the variable to a single value

Java

• Rewrite LinearExpr, add a incremental builder class: LinearExpr.newBuilder().add(x).addSum(<array of variables).build()
• Follow C++ API: Circuit, MultipleCircuit, Cumulative, Reservoir, AllowedAssignment and ForbiddenAssignment now return a specialized class with incremental API to add new variables, terms, demands…

C#

• Document all methods
• Follow C++ API: Circuit, MultipleCircuit, Cumulative, Reservoir, AllowedAssignment and ForbiddenAssignment now return a specialized class with incremental API to add new variables, terms, demands…
• Add LinearExprBuilder class to build expression incrementally.

Build System

CMake

• Require at least CMake >= 3.18

Make

• Now use the CMake based build internally.

Platform changes

• Add support for Ubuntu 21:10 (last rolling release).

Dependencies Update

• .Net TFM update net5.0 -> net6.0 (need .Net SDK 6.0 LTS and .Net SDK 3.1 LTS).
• abseil-cpp 20210324.2 -> 20211102.0.
• Protobuf 3.18.0 -> 3.19.1.
• Googletest 1.10.0 -> 1.11.0.
• Python: add numpy >= 1.13.3.
• On MacOS compile Coin-OR in -O1 to avoid crash in runners.

Routing

• Improvement on filters.
• Improve first solution heuristics.
• Improve time break placements.

CP-SAT

• Breaking changes:
  • The underlying protocol buffer is incompatible with previous versions. Any stored protocol buffer will have to be re-generated with the updated builder APIs (in C++, Python, Java, and .NET)
  • In particular, the interval protobuf was clean as we removed the old fields (start, size, and end) and renamed the new ones (using _view) to use the name of the removed fields.
  • AddProductEquality has been removed. Please use AddMultiplicationEquality.
  • Now that we have floating point coefficients for the objective, we have removed ScaleObjectiveBy which had a problematic semantics.
• New features:
  • The all_different, reservoir, modulo, multiplication and division constraints accept affine expressions (a * var + b) everywhere it required integer variables.
  • The objective accepts floating point coefficients (See the DoubleLinearExpr class in C++/Java/.NET. See the knapsack_2d_sat.py example in Python).
  • The no_overlap_2d constraint supports optional intervals.
  • The C++ API implements + and * operators to build expressions.
• Improvements:
  • Improved presolve code.
  • Tighter model checker.
  • Rework reservoir constraint.
  • Add energetic cuts for the no_overlap_2d constraint.
  • Improved linear relaxation of encoding constraints (literal implies var == value).
• Deprecated and removed methods
  • Deprecated C++ BooleanSum and BooleanScalProd. Just use Sum and ScalProd.
  • Removed C++ AddLinMinEquality and AddLinMaxEquality. Just use AddMinEquality and AddMaxEquality.
• Future incompatibilities
  • At some point in the future, we will rewrite the Java modelling layer to be closer to the C++ layer.
  • In the C++ modelling layer, we will make the IntVar(BoolVar var) ctor explicit.
  • We are contemplating making the python API PEP 8 compliant (using snake_case names). If this happen, we will provide a sed file to port the code.

Build System

Bazel

• Fix Windows build.

CMake

• Add FETCH_PYTHON_DEPS option (default ON).
• Add optional support for GPLK solver (default -DUSE_GLPK=OFF).

Python

• Support numpy integers in most of the CP-SAT API.
• Fix missing __version__.

Platform changes

• Ubuntu 16.04 LTS is deprecated (actions/runner-images#3287).
• Add support for Debian 11 (Bullseye).
• Add support for Fedora 34.
• python: use manylinux2014 image (PEP 599).
• python: add support for aarch64 linux using manylinux2014_aarch64 image.
• .Net: add .Net5 support.

Dependencies Update

• abseil-cpp 20210324.1 -> 20210324.2.
• Protobuf 3.15.8 -> 3.18.0.
• SCIP 7.0.1 -> master.
• Googletest 1.8.0 -> 1.10.0.
• python: use of warning in cp_model.py (#2530).
• python: absl-py 0.11 -> 0.13.

CMake

• Bump minimum version required 3.14 -> 3.15 (#2528).
• python: bump minimum required version 3.14 -> 3.18 (#2774).

Make

• Make based build is deprecated please migrate to Bazel or CMake

Java

• Improve robustness of the native library loader (#2742).
• Fix jvm GC crash when routing model or the constraint solver were disposed (#2091, #2466).
• Fix CP-SAT logging callback crash when using multiple workers (#2775).

CP-SAT

• Improve robustness of the LNS code (see #2525).
• Improve scheduling code: new factory methods to create fixed size intervals,
  new search heuristics, improved presolve and new linear cuts.
• Improve routing code: new dedicated LNS.
• Improve model checker. It is now more pedantic, especially w.r.t. potential overflows.
• Improve MIP code: better presolve and multiple improvements to the linear relaxation of MIP
  and CP models.
• Improve search diversity. When using more than 12 workers, add workers dedicated to
  improving the lower bound of the objective.
• Change to the parallelism code: by default, the solver will now use all available cores.
  Use the num_search_parameters to specify the level of parallelism.
• Deprecate SearchAllSolutions and SolveWithSolutionCallback.
• Python API: more pedantic checks when using var == ... or var != ... outside a model.Add() call.

Platform changes

• Added support for Centos-7 (#2498)

Dependencies Update

• abseil-cpp 20200923.3 -> 20210324.1 (#2523)
• Protobuf 3.15.3 -> 3.15.8 (#2524)
• Java: jna-platform 5.5.0 -> 5.8.0 (#252)

Features/Fix

• Improve multi-threading when using CP-SAT solver (#1588)
• Add logger access support in Python, Java and .Net (#2245)
• C++: Replace Google type [u]int(16|32|64) by cstdint ones (e.g. uint64_t)
• Python: Fix std::vector<std::string> support (#2453)

Makefile

• Rework CPLEX support (#2470)

Dependency Updates

• abseil-cpp 20200923.2 -> 20200923.3
• Protobuf 3.14.0 -> 3.15.3

Routing

• Expose new APIs:
  • int RegisterUnaryTransitVector(std::vector<int64>) and
  • int RegisterTransitMatrix(std::vector<std::vector<int64>>)
• Change return of AddVectorDimension() and AddMatrixDimension() to std::pair<int, bool> whose int is the transit evaluator id.

Dependency Updates

• abseil-cpp 20200923 -> 20200923.2
• Protobuf 3.13.0 -> 3.14.0
• Add support for Gurobi 9.1.0
• drop Glog dependency (replaced by a custom implementation depending on abseil-cpp flags)
• drop Gflag dependency (replaced by abseil-cpp flags component)

Bug Fixes

• Fix double counting of Gurobi floating license (#2227)
• Fix windows build (#2200)

Dependency updates

• abseil-cpp 20200225.2 -> 20200923
• Protobuf 3.12.2 -> 3.13.0

Platform changes

• Added support for Python3.9 (#2187)
• Dropped support for Python3.5 (#2186)
• Added support for Ubuntu 20.10 (#2188)
• Dropped support for Ubuntu 16.04 LTS and Ubuntu 19.10 (#2188)

Known Breaking Change

• Since last synchronization with Google internal code base, now Routing and SAT (i.e. OR-Tools) use some C++17.
  WARNING: If you provide your own version of abseil-cpp please verify it is built against C++17 too.
• The MPSolver::CreateSolver signature has been changed. The model name argument has been dropped.

CMake

• Fix disabling SCIP support when using -DUSE_SCIP=OFF (#2129)
• Integrate samples and examples to the CMake build system.
  note: can be disable by using -DBUILD_SAMPLES=OFF and -DBUILD_EXAMPLES=OFF.
  note: can be disable for a specific language using -DBUILD_<LANG>_SAMPLES=OFF or
  -DBUILD_<LANG>_EXAMPLES=OFF (with <LANG> among CXX, PYTHON, JAVA and DOTNET).

Make

• Require Make >= 4.3 (use of Make eval function).
• Require CMake >= 3.14 (use of CMake --verbose option).
• Add option to disable SCIP support using USE_SCIP=OFF (#2134)
• Add option to disable CLP and CBC support using USE_COINOR=OFF

Java

• OR-Tools now generate maven packages (#202).

Bug fixes

• Fix C++ and Python build on FreeBSD (#2126).
• Fix build in debug on windows (#2077).
• Fix long standing crash in parallel on CP-SAT on Windows (#2001, #2019).

Dependency updates

• Gurobi 9.0.2 is now pre-integrated in prebuilt binaries. It will search for the gurobi 90 shared library in the default install path of the Gurobi installers on MAC OS X and Windows, or in the GUROBI_HOME directory.
• SCIP 7.0.1 is now integrated in prebuilt binaries.Please ensure compliance with the SCIP license before using it.
• Added support for optional Xpress Solver 8.9.0.

Linear Solver

• Added a static LinearSolver::CreateSolver() method to simplify checking support for integrated linear solver backends. It works in all languages.

CMake

• Fix and add support for FreeBSD (#2105)
• Use of FetchContent() to build dependencies
• Use of CMP0091 to control Runtime Library on Windows

Bazel

• Cleanup protobuf usage.

Bug fixes

• CP-SAT: Fix sorting in cumulative cut generation.
• Linear Solver: Fix leak in .Net wrapper when using CreateSolver().

Dependency updates

• Abseil-cpp 20200225 -> 20200225.2
• Protobuf 3.11.4 -> 3.12.2
• bazel-skylib 0.8.0 -> 1.0.2 (for bazel based build)
• Fix optional SCIP 7.0 support

CP-SAT Update

• Now, the solver returns Optimal instead of Feasible in a satisfiability model (i.e. without objective)
• Fix multi-threading crash (#2005)
• Improve feasibility pump

CMake

• Add maven package generation (#202)
• Fix Windows build