package ortools

OCaml interface to Google OR-Tools

Currently only a subset of CP-SAT is supported.

Pull requests providing the missing features are welcome, but please pay attention to documentation and tests.

This project provides two packages:

• ortools is an OCaml interface for building CP-SAT models. It does not require an installation of OR-Tools as it simply works with the protocol buffer format. See utils/sat_solve_pb.{c,py} for examples of interfacing with the CP-SAT solver.
• ortools_solvers builds on ortools to provide a simple OCaml interface for calling CP-SAT. Building and installing it requires an OR-Tools installation (see below).

Building with Google OR-Tools

Ensure that libortools.9.dylib (macOS) or libortools.so.9 (Linux), and the other runtime libraries, are accessible by your compiler and loader.

For example, on macOS, set the LIBRARY_PATH (for compilation) and DYLD_LIBRARY_PATH (for execution) environment variables.

On Linux, set the LD_LIBRARY_PATH (for compilation and execution) environment variable.

There are several options for obtaining the runtime libraries.

• Download or build from source following the official instructions (see the C++ section).
• Install the Python libraires with pip. The OR-Tools runtime can be found in site-packages/ortools/.libs.
• From the or-tools releases on github, download Google.OrTools.runtime.<os>-<arch>.9.<minor>.<patch>.nupkg where os ∈ { linux, osx, win } and arch ∈ { arm64, x64 } and unzip it. The required files are in runtimes/*/native.

I would have liked all this to be automatic, but:

• There do not seem to be suitable brew/linux packages that could be linked from opam;
• Vendoring the source in the opam package and building it on install is error-prone and resource-intensive;
• Including several binary versions in the opam package is tedious to maintain and wasteful to download; and
• Dynamically downloading the library on build is prevented by opam sandboxing (see the download branch for a prototype).

Protocol Buffer Interfaces

The Protocol Buffers interfaces have been generated with ocaml-protc (with pull/263).

If required, they can be regenerated as follows.

git clone git@github.com:google/or-tools.git
cd or-tools
git checkout v9.14      % TODO: update with required version
opam install ocaml-protoc
ocaml-protoc --binary --pp --make --ml_out src/model \
    <path-to-or-tools>/ortools/sat/cp_model.proto
ocaml-protoc --binary --pp --make --ml_out src/model \
    <path-to-or-tools>/ortools/sat/sat_parameters.proto