minizinc-js

JavaScript interface for MiniZinc

This package provides a JavaScript API for MiniZinc for use in web browsers using WebAssembly, or in NodeJS using a native installation of MiniZinc.

This library powers the MiniZinc Playground.

Getting started

Using a CDN (recommended)

Using ECMAScript modules:

<script type="module">
  import { Model } from 'https://cdn.jsdelivr.net/npm/minizinc/dist/minizinc.mjs';
  const model = new Model();
  model.addFile('test.mzn', 'var 1..3: x;');
  const solve = model.solve({
    options: {
      solver: 'gecode',
      'all-solutions': true,
    },
  });
  solve.on('solution', solution => {
    console.log(solution.output.json);
  });
  solve.then(result => {
    console.log(result.status);
  });
</script>

Using a traditional script:

<script src="https://cdn.jsdelivr.net/npm/minizinc/dist/minizinc.js"></script>
<script>
  const model = new MiniZinc.Model();
  model.addFile('test.mzn', 'var 1..3: x;');
  const solve = model.solve({
    options: {
      solver: 'gecode',
      'all-solutions': true,
    },
  });
  solve.on('solution', solution => {
    console.log(solution.output.json);
  });
  solve.then(result => {
    console.log(result.status);
  });
</script>

Self-hosting WebAssembly files

If you’re using a bundler, you can add the library to your project:

npm install minizinc

Then import it with:

import * as MiniZinc from 'minizinc';

These three files need to be served by your webserver (found in node_modules/minizinc/dist):

• minizinc-worker.js
• minizinc.wasm
• minizinc.data

If you place them alongside your bundled script, they should be found automatically. Otherwise, their URLs can be specified during initialisation.

In NodeJS

This requires an existing installation of MiniZinc.

Add the library with:

npm install minizinc

Then import it with:

// If using ESM
import * as MiniZinc from 'minizinc';
// If using CommonJS
const MiniZinc = require('minizinc');

If you have added MiniZinc to your PATH, it will be found automatically. Otherwise, you can specify the executable path during initialisation.

Usage

Initialisation

Initialisation happens automatically when the library is used, or by calling init(...). This can be used to ensure that the WebAssembly files start loading immediately, or to specify a different URL for the worker (or path to the MiniZinc executable if using NodeJS).

In the browser:

MiniZinc.init({
  // If omitted, searches for minizinc-worker.js next to the minizinc library script
  workerURL: 'http://localhost:3000/path/to/my-own-worker.js',
  // If these are omitted, searches next to the worker script
  wasmURL: 'http://localhost:3000/path/to/minizinc.wasm',
  dataURL: 'http://localhost:3000/path/to/minizinc.data',
}).then(() => {
  console.log('Ready');
});

In NodeJS:

MiniZinc.init({
  // Executable name
  minizinc: 'minizinc',
  // Search paths (can omit to use PATH)
  minizincPaths: ['/home/me/.local/bin', '/usr/local/bin'],
});

By default, the NodeJS version tries to find MiniZinc on your PATH.

Creating Models

The main entrypoint for using the library is through the Model class:

const model = new MiniZinc.Model();
// Add a file with a given name and string contents
model.addFile('test.mzn', 'var 1..3: x; int: y;');
// If you're using NodeJS, you can add files from the filesystem directly
model.addFile('test.mzn');
// Add model code from a string
model.addString('int: z;');
// Add data in DZN format
model.addDznString('y = 1;');
// Add data from a JSON object
model.addJson({ z: 2 });

Solving

Solving is done using the Model.solve(...) method, which takes an object with options in .mpc format.

const solve = model.solve({
  options: {
    solver: 'gecode',
    'time-limit': 10000,
    statistics: true,
  },
});
// You can listen for events
solve.on('solution', solution => console.log(solution.output.json));
solve.on('statistics', stats => console.log(stats.statistics));
// And/or wait until complete
solve.then(result => {
  console.log(result.solution.output.json);
  console.log(result.statistics);
});

During solving, MiniZinc emits events which can be subscribed to/unsubscribed from using the SolveProgress.on / SolveProgress.off methods. The events are those which appear in Machine-readable JSON output format, with the addition of the exit event, which can be used to detect when solving finishes (if you do not wish to await the SolveProgress object).

By default, --output-mode json is used, allowing you to retrieve the model variable values directly from the solution objects. Use Model.solve({ jsonOutput: false, ...}) (and optionally specify a different output-mode in the options) to disable this behaviour.

Documentation

For more detailed documentation of all available options and functionality, visit the API documentation.

Building

Compiling MiniZinc for WebAssembly

CI downloads minizinc-compiler-only-wasm32-emscripten.tar.gz from libminizinc’s releases (edge for the development version) rather than building it, which is also the easiest way to get one locally.

To build it yourself you need Emscripten, at the version pinned as emsdk in libminizinc’s vendor.lock: the solver archives are built with it, and mixing emscripten versions across static archives is not safe.

# Clone MiniZinc
git clone https://github.com/MiniZinc/libminizinc minizinc
cd minizinc

# Download the solvers built for wasm (requires the gh CLI, authenticated)
scripts/fetch_vendor.sh wasm32-emscripten gecode cbc chuffed highs

# Configure and build, exactly as CI does
ROOT="$PWD" CMAKE_WRAPPER=emcmake CMAKE_FIND_ROOT_PATH=/ \
  CMAKE_GENERATOR="Unix Makefiles" EXPECT_DEPS="gecode cbc chuffed highs" \
  bash scripts/build.sh

This installs into minizinc/ (bin/minizinc.js, .wasm and .data).

Building MiniZinc JS

1. Run npm install to install dependencies.
2. Place the bin/ folder of the WebAssembly build of MiniZinc inside this directory. Alternatively set the MZN_WASM_DIR environment variable to the installation directory of the WebAssembly build of MiniZinc.
3. Run npm run build to build the package. The built files are in the dist/ directory.
4. Run npm run docs to build the documentation. The output files are in the docs/ directory.

Testing

When testing, the web-worker library is used to emulate Web Worker support in NodeJS. This allows us to test both the browser version using WebAssembly, as well as the native version.

Run npm test to run tests using Jest.

License

This library is distributed under the Mozilla Public License Version 2.0. See LICENSE for more information.