Release of or-tools : January 2017.

New Features

Installing

• Introduced simpler procedures for installing or-tools, either from binary distributions or from source code. See Installing or-tools for more information.

Routing

• Implemented an algorithm to compute the Held-Karp lower bound for symmetric Traveling Salesman Problems. This enables you to compute an upper bound to the gap between the cost of a potentially non-optimal solution and the cost of the optimal solution.
• Added a new method to the vehicle routing library, RoutingModel::SetBreakIntervalsOfVehicle, which lets you add break intervals — time periods when a vehicle cannot perform any tasks (such as traveling or visiting a node). For an example that uses this option, see
  https://github.com/google/or-tools/blob/master/examples/cpp/cvrptw_with_breaks.cc.

Scheduling

• Added support for more data formats in the parser for the Project Scheduling Library.

Sat solver

• The Sat solver's cumulative constraint now accepts optional intervals, created with the NewOptionalInterval method. For an example, see
  https://github.com/google/or-tools/blob/master/examples/cpp/rcpsp_sat.cc.
• You can now solve a maximum satisfiability problem by specifying the objective as a weighted sum of literals. It is no longer necessary to create an intermediate integer variable.

Performance improvements

• Sat solver — Improved performance of the Sat solver, particularly for the cumulative constraint.
• Glop solver— Improved numerical robustness of the Glop solver, which now returns even more accurate solutions to hard numerical problems.
• Flatzinc solver
• Greatly improved performance of the Sat backend for the flatzinc interpreter.
• Simplified the C# flatzinc interface. For an example of the new interface, see
  https://github.com/google/or-tools/blob/master/examples/csharp/csfz.cs.

Bug Fixes

• Using the PathCheapestArc heuristic on routing models with a single vehicle and side constraints would sometimes cause the solver to run for an excessively long time. This has been fixed by properly taking into account side-constraints.
• In Java, the routing solver would sometimes crash when solving vehicle routing problems. This has been fixed in the latest release.

Release of or-tools. November 2016

November 2016

Running examples

• Introduced language specific targets to compile and run the examples. Please check this page for more details.

Sat

• Added support for constraint programming.
• Implemented the diffn, cumulative , circuit and subcircuit constraints.
• Implemented the overlode checker on the basis of Max Energy Filtering Algorithm for Discrete Cumulative Constraint.
• Implemented the all different bound consistent propagator which implements better propagation for the AllDifferent constraint.

FlatZinc

• Implemented a SAT solver for FlatZinc problems.

Constraint Solver

• Implemented the following constraints :
• atMost: Sets an upper bound to the count of variables that are equal to a given value.
• MakePathPrecedenceConstraint and MakePathTransitPrecedenceConstraint: Implement the precedence constraint for a set of pairs.

Routing

• Implemented AddAtSolutionCallback, which is a callback called each time a solution is found during the search.
• Removed the RoutingModel depot-less constructors. Specifying at least one depot in the routing model is now mandatory.

Release of or-tools. September 2016

• Sat
  • Extended scheduling API and modified examples (weighted_tardiness_sat, and jobshop_sat) to use it.
• Graph
  • Added iterator traits to Graph classes.
• Or-tools distribution
  • Nuget package is supported again.

Release of or-tools. August 2016

Constraint solver

• solver
  • Implemented NotBetween method to constrain a variable to be
    outside a given interval.
• routing
  • Added a parse of the model to check existing NotMember constraints as shown in this example, and use them in local search filters.
  • Added local search profiling.
  • Fix for local moves.

Linear solver

• Fixed SCIP status reporting.

Sat

• Implemented [SolveWithPresolve](https://github.com/google/or-tools/blob/master/src/sat/simplification.h### L373) method to simplify the usage of the SAT presolver.
• Regrouped search utils in src/sat/util.h|cc.
• Implemented SMT (Lazy Clause Generation) scheduling constraints: see jobshop_sat.cc and weighted_tardiness_sat.cc.

Glop

• Improved performance by exploiting sparsity in more stages of computation.

Flatzinc

• Fixed bugs found by minizinc challenge.

Lp_data

• Continued simplification of templates in iterators.

Or-tools distribution

• C# assemblies are now strongly named by default.
• Upgraded to Protobuf3.0.0.
• Added a Python script to check or-tools archive dependencies.

Release of or-tools. July 2016

We’re happy to announce the release of July 2016 version of or-tools. Here's what's new with this release:

Constraint solver:

• Routing
  • A disjunction can now be defined with a cardinality, which is the maximum number of nodes that can be active within this disjunction. For example, if you add a disjunction with n nodes and a cardinality of k, then k nodes among the n nodes are allowed to be active. You can use the new definition of AddDisjunction to do this.
  • Added support for multiple disjunctions per node. For example, you can now add a node, N1, to many disjunctions (D1..Dm). This increases its chance of being active within any one of them.
    Introduced a faster routing search algorithm for problems related to disjunct time windows.
  • Added constraint solver parameters to routing model parameters and log_search to routing search parameters.
  • Local search algorithm is faster with resolving problems with disjoint time windows. Please see cvrp_disjoint_tw.cc example.

Glop (linear optimization):

• Introduced a faster Simplex Algorithm.

Or-tools distribution:

• One archive per platform, rather than individual archives for each of C++, Java, and C#. Python archives are still hosted on pypi.
• On pypi, we have switched to wheel (.whl) modules on Mac OS X and Windows.
  Introduced a MAJOR.MINOR numbering schema. These numbers are used the archive names, the version stored in Mac OS X shared libraries, python modules, .NET assemblies. The first version we are releasing is with this schema is v4.2

v2016-06

Examples:

• c++: getting rid of filelinereader in examples
• data: Add single machine scheduling problems

Sat:

• Remove unused core method (Resolution nodes)
• Added drat writer to checks proofs on unsatisfiability
• Add preprocessor

Documentation:

• Lots of cleanup in the header files.
• Please check the new documentation at https://developers.google.com/optimization/

Bop:

• Add new neighborhoods

Constraint Solver:

• Removed most of the instances of the callbacks (src/base/callback.h) from the CP library
• Added NotMemberCt (variable cannot belong to a set of intervals)

Routing library:

• INCOMPATIBLE CHANGE: To specify the capacity of vehicles in the AddDimensionWithVehicleCapacity, you now need to pass an array (vector in c++) instead of a callback.

GLOP:

• Change internal representation of sparse matrix
• performance improvements

Graph:

• Added A* contributed code
• Rewrite Dijkstra and Bellman-Ford algorithms to replace callbacks by std::function (C++)
• Change API of different graph implementation when iterating over arcs and nodes.

v2016-04

Main changes:

• Use protobuf instead of flags in the Constraint Programming and routing libraries.
• See http://or-tools.blogspot.fr/2016/02/heads-up-upcoming-incompatibility-in.html for details.

December 2015 binary and source archives for or-tools

Changelog:

• Broke compatibility on the Large Neighborhood Search in the CP solver
  (see examples/cpp/ls_api.cc, examples/python/pyls_api.py, examples/csharp/csls_api.cs, and
  examples/com/google/ortools/sample/LsApi.java to see the new API).
• Cleaned the the python wrapping. Support custom decision in the CP solver (see examples/test/test_cp_api.py to see the API in action).
• Various improvements and bug fixes.

September 2015 release

Release of OR-Tools
September 2015

What's new:

• First release on github. Files will be stored there from now on.
• Added binary archives for the flatzinc interpreter (see www.minizinc.org)
• Contains a few fixes over the version used in the challenge