incremental-cycle-detect

Lets you add edges to a directed acyclic graph and be told whether this edge introduces a cycle. If it would, it is not added. Useful when trying to build an acyclic graph.

Based on the paper:

A Dynamic Topological Sort Algorithm for Directed Acyclic Graphs
   DAVID J. PEARCE / PAUL H. J. KELLY
   Journal of Experimental Algorithmics (JEA)
   Volume 11, 2006, Article No. 1.7
   ACM New York, NY, USA

Documentation

See here for documentation

Install

The drill:

npm install --save incremental-cycle-detect

Typings for Typescript are available (this is written in typescript!).

Use the dist.js or dist.min.js for browser usage if you must.

Exposes a global object window.IncrementalCycleDetect with the same methods you can when importing this lib:

import * as IncrementalCycleDetect from "incremental-cycle-detect";

Usage

The main purpose of this library is to add edges to a directed acyclic graph and be told when that make the graph cyclic.

const { GenericGraphAdapter } = require("incremental-cycle-detect");
const graph = new GenericGraphAdapter();
graph.addEdge(0, 1) // => true
graph.addEdge(1, 2) // => true
graph.addEdge(2, 3) // => true
graph.addEdge(3, 0) // => false because this edge introduces a cycle
// The edge (3,0) was not added.

graph.deleteEdge(2, 3);
graph.addEdge(3, 0) // => true, no cycle because we deleted edge (2,3)

The main algorithm is implemented by CycleDetectorImpl. To allow for this lib to work with different graph data structures, it is subclassed. The subclass is called ...Adapter responsible for storing the vertex and edge data. For convenience, the following adapters are provided and all implement CommonAdapter

• GenericGraphAdapter: Uses Maps to associate data with a vertex, allowing any type of vertex. In the above example, you could use strings, booleans, objects etc. instead of numbers. Seems to perform pretty well.
• GraphlibAdapter: For the npm module graphlib. Vertices are strings.

const { Graph } = require("graphlib");
const graph = new GraphlibAdapter({graphlib: Graph});
graph.addEdge(0, 1) // => true

You can add vertices explicitly, but it is not required. They are added if they do not exist.

See the documentation linked above for all methods available.

Performance

Incremental cycle detection performs better than checking for cycles from scratch every time you add an edge. Tests done with benchmark. Compared with running a full topological sort with graphlib (via alg.isAcyclic(graph)) each time a vertex is added. Measured time is the time that was needed for creating a new graph and adding n vertices, checking for a cycle after each edge insertion.

// 200 vertices, 15000 random (same for each algorithm) edges added
incremental-cycle-detection(insert 15000, RandomSource) x 36.51 ops/sec ±4.53% (59 runs sampled)
graphlib(insert15000, RandomSource) x 0.18 ops/sec ±2.78% (5 runs sampled)

JavaScript environment

Some parts need Map. You can either

• use this lib in an enviroment that supports these
• polyfill Map
• pass an implementation of Mapt to the constructor of the graph adapter. This way you don't have to monkey patch:

import * as Map from "core-js/es6/map";
const graph = new GenericGraphAdapter({mapConstructor: Map}):

Use your own graph data structure

You can also use the CycleDetector (implemented by PearceKellyDetector) directly and roll your own graph data structure. See the docs. Basically, you need to call the CycleDetector every time you add an edge or delete a vertex. Then it tells you whether adding an edge is allowed. You can also use an existing GraphAdapter as the starting point.

Build

May not to work on Windows.

git clone https://github.com/blutorange/js-incremental-cycle-detect
cd js-incremental-cycle-detection
npm install
npm run build

Change log

I use the following keywords:

• Added A new feature that is backwards-compatible.
• Changed A change that is not backwards-compatible.
• Fixed A bug or error that was fixed.

From newest to oldest:

• 0.1.1 Fixed package.json and dependencies (was missing tslib).
• 0.1.0 Initial version.