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.