Sonnet

Sonnet is a modelling API and wrapper for COIN-OR mixed integer linear programming classes for the Microsoft .NET on Windows platforms.

Sonnet uses a wrapper to make the COIN-OR C++ classes available in .NET.
COIN-OR projects included in the wrapper: Cbc,
Cgl, Clp, CoinUtils
Osi.

The Sonnet API allows for code like this:

using Sonnet;  

Model model = new Model();
Variable x = new Variable();
Variable y = new Variable();
model.Add(2 * x + 3 * y <= 10);

var expr = new Expression(); // Useful in for-loops
expr.Add(3.0, x);
expr.Add(y);
model.Objective = expr; // 3*x + y

Solver solver = new Solver(model);
solver.Maximise();

You can find the latest binaries and sources from CI builds at the Sonnet-latest pre-release, or on AppVeyor (if available).

In particular, the latest binary release: https://github.com/coin-or/Sonnet/releases

Simply add the x86 or x64 libraries of Sonnet.dll and SonnetWrapper.dll to your References in Visual Studio.
Sonnet requires .NET Framework 4.8 or .NET 6.

Sonnet can only be used on Windows platforms. While, in principle, .NET 6 supports cross-platform use, this does not include the mixed C++/CLI of SonnetWrapper, where the native C++ of the COIN-OR C++ is mixed with C++/CLI.

Note: If you use the .NET 6 libraries, then also include Ijwhost.dll in your project and set this file to Always Copy to Output folder to prevent runtime errors of System.BadImageFormatException.

Building from source

Getting the source code

Option 1: Get the full src.zip asset from GitHub Sonnet-latest release

The easiest way to get started with Sonnet source code is to use the ..-src.zip asset from the Sonnet-latest pre-release assets. This zip contains the Sonnet sources as well as all the relevant COIN-OR dependencies from their master branch. Simply unzip to have all the sources in the right place.

Option 2: Get sources from GitHub

The latest Sonnet sources can be downloaded from the github repository. If you use "Download ZIP", the downloaded zip file contains the Sonnet source code and MS Visual Studio 2019 solution.

Before you can build Sonnet, the sources of the master branches of all the relevant COIN-OR dependencies are also required. See https://github.com/coin-or/Cbc#source how to get the relevant sources.

The Sonnet solution expects the COIN-OR source code to be in the same root folder. The folder structure should look like this:

├─ Cbc
├─ Cgl
├─ Clp
├─ CoinUtils
├─ Osi
└─ Sonnet

Building in Visual Studio

For Visual Studio 2022, the solution and project files can be found in Sonnet\MSVisualStudio\v17. Simply open the Sonnet solution in Sonnet\MSVisualStudio\v17\Sonnet.sln, and Build.

The Sonnet projects and solution are provided for Visual Studio 2022 (v17). The Sonnet solution refers to the project files of the relevant COIN-OR libraries.

Solution configurations for Debug, Release and ReleaseParallel are defined for the solution, each with x86 and x64 solution platforms.

Older versions of Sonnet projects and solutions files are available for Visual Studio 2019 (v16) and 2010 (v10), but these are not maintained.

Testing

The Sonnet solution also contains the SonneTest project. This builds the SonneTest.exe which will run Sonnet test and COIN-OR native tests. This can also be used with dotnet test.

Platform target (x64 or Win32/x86)

Separate builds are required for x86 or x64, in particular for SonnetWrapper.dll.
Since the C++/CLI of SonnetWraper.dll has no "AnyCPU" equivalent, it is NOT possible to use the x86 and/or x64 Sonnet.dll and SonnetWrapper.dll in an "AnyCPU" project. The project has to target x86 or x64.

Parallel version of Cbc

For Windows builds of Cbc, the standard method to build Sonnet and dependencies will build a single threaded Cbc. However, Cbc can also run with parallel threads to speed up the search. Rudimentary steps how to build a parallel version of Cbc in Windows are available in the Cbc README. Here I'll describe the steps in more detail, assuming you already have a setup where you can build Sonnet etc. in Visual Studio 2019.

Several pthread for Windows libraries are available. Sonnet was succesfully tested to work with GerHobbelt/pthread-win32. To build Sonnet with pthread, all necessary project settings are available in the respective ReleaseParallel configurations of libCbc, libCbcSolver and SonnetWrapper:

• Solution: Use the ReleaseParallel configuration.
• Define: CBC_THREAD is defined by the projects
• Include: "pthreads" include folder is expected at one level above the Sonnet root folder, so not besides Cbc, etc., but one level above.
• Linker: SonnetWrapper links to pthread_static_lib.lib that is expected in the lib\Win32 or lib\x64 folder at the root of Sonnet folder. You have to build this first, below.

Start by cloning the pthread repo, and opening the solution in VS2019. You can decide to build the pthread dll or the pthread static lib. Build the Release configurmation for either the x64 or Win32 platform, depending on your needs. Within Cbc, the only projects that actually use pthread are libCbc and libCbcSolver. Since these come together in SonnetWrapper, SonnetWrapper also links to the pthread library in the ReleaseParallel configuration.

SonnetWrapper has been configured to use the pthread_static_lib.lib, which looks for in the Sonnet/lib folder. Should you want to use pthread as a DLL instead, then copy the pthread.lib to Sonnet/lib and change the SonnetWrapper property for Linker -> Input to pthread.lib instead of pthread_static_lib.lib and ensure that the pthread.dll is copied to the output directory. Note: cbc (cbc.exe) project has been configured to use the pthread.lib and pthread.dll, but this project is not used by Sonnet.

Additional functionality

Several parts of the source code have been disabled because they require, e.g., non-standard COIN-OR code.

SONNET_LEANLOADPROBLEM (Solver.cs, see also SonnetWrapper)

Especially for CLP, this functionality loads problems more efficiently but requires non-standard osiClp code. This is really only interesting for large problems (>100K var/con).
If SONNET_LEANLOADPROBLEM is defined, then two additional member functions of SonnetWrapper's OsiClpSolverInterface are defined:

• LeanLoadProblemInit
• LeanLoadProblem

and one extra member function must be added for normal OsiClpSolverInterface

• loadCurrentProblem

SONNET_USE_SEMICONTVAR (Solver.cs)

Unfinished code for adding a variable type of SemiContinuousVariable, and automatically generate helper variable (binary) and constraint.

SONNET_SETWARMROWPRICE (WarmStart.cs)

Whether or not to include row price information in WarmStart