Orc.DependencyGraph

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Find the source at https://github.com/WildGums/Orc.DependencyGraph

Introduction

This library will help navigate a directed acyclic graph (DAG).

The goal of this library is to make it easy to:

Naming Convention

Interface

Graph

public interface IGraph<T>
	where T : IEquatable<T>
{
	INode<T> Find(T value); 

	void AddSequence(IEnumerable<T> sequence);
	void AddSequences(IEnumerable<IEnumerable<T>> sequences);

	IEnumerable<INode<T>> Nodes { get; }

	bool CanSort();
	bool CanSort(IEnumerable<T> sequence);

	int CountNodes { get; }
	int CountLevels { get; }
	IOrderedEnumerable<INode<T>> GetNodes(int level);
	IOrderedEnumerable<INode<T>> GetNodesBetween(int levelFrom, int levelTo);
	IOrderedEnumerable<INode<T>> Sort();
}

Note:

Node

public interface INode<T>
	where T: IEquatable<T>
{
	T Value { get; }
	IGraph<T> Graph { get; }
	int Level { get; }

	// relativeLevel >= relativeLevelFrom && relativeLevel <= relativeLevelTo
	IOrderedEnumerable<INode<T>> GetNeighbours(int relativeLevelFrom, int relativeLevelTo);
	// relativeLevel < 0
	IOrderedEnumerable<INode<T>> Precedents { get; }
	// relativeLevel > 0
	IOrderedEnumerable<INode<T>> Descendants { get; }
	// relativeLevel == relativeLevel - 1
	IOrderedEnumerable<INode<T>> ImmediatePrecedents { get; }
	// relativeLevel == relativeLevel + 1
	IOrderedEnumerable<INode<T>> ImmediateDescendants { get; }
	// Precedents of the node without precedents (roots)
	IOrderedEnumerable<INode<T>> TerminatingPrecedents { get; }
	// Descendants of the node without descendants (leafs)
	IOrderedEnumerable<INode<T>> TerminatingDescendants { get; }
}

Note: - All the methods return an ordered enumerable of INode. The ordering is based on the “level” of the node. (Within a level the ordering is not important.) - If possible the methods returns all the INodes lazily. - A Node object has a reference to the Graph object.

Algorithms, Time Complexity

The Dependency Graph is a static data structure. All the nodes and their relationships should be known ahead of time.

Method NamesAlgorithmsTime Complexity
AddSequence()-O(1)
AddSequences()-O(1)
Sort()Topological SortO(V+E)
CanSort()Topological SortO(V+E)
ComputeLevels()Critical Path, DFSO(E+V)
CountNodes()-O(1)
CountLevels()-O(1)
GetNodesWithLevel()DFSO(V+E)
GetNodesWithLevelBetween()DFSO(V+E)
Precedents()DFSO(V+E)
Descendants()DFSO(V+E)
ImmediatePrecedents()DFSO(V+E)
ImmediateDescendants()DFSO(V+E)
TerminatingPrecedents()DFSO(V+E)
TerminatingDescendants()DFSO(V+E)
ComputeLevels private method

ComputeLevels method performs initial pre-calculation (e.g. pre-calculate levels for nodes) Graph will be rebuild automatically on first call of any method related to node levels after a graph structure change.

  1. Find the longest path. Critical path method O(V+E)
  2. DFS from the source of the longest path, decrementing the level value for every child DFS - O(V+E)

Example

Dependency Graph

NOTE:

Create Graph Structure

new Graph(new []
{
	new[] {11, 27, 32},
	new[] {12, 27},
	// etc....
});

or

var graph = new Graph();
graph.AddRange(new []
{
	new[] {11, 27, 32},
	new[] {12, 27},
	// etc....
});

Interaction

[Test]
public void BasicOperationsTest()
{
	var graph = CreateExampleGraph();

	Assert.IsTrue(graph.CanSort());

	Assert.AreEqual(20, graph.Count);

	Assert.IsTrue(graph.CanSort());
		
	Assert.AreEqual(6, graph.CountLevels);
		
	AssertCollectionsConsistsOfNodes(new[] {31}, graph.GetNodes(4));

	AssertCollectionsConsistsOfNodes(new[] {51, 61, 62}, graph.GetNodesBetween(4, 5));

	AssertCollectionsConsistsOfNodes(new[] {11, 12, 25, 26, 27}, graph.Find(32).Precedents);

	AssertCollectionsConsistsOfNodes(new[] {51, 61, 62}, graph.Find(43).Descendants);

	AssertCollectionsConsistsOfNodes(new[] {25, 26, 27}, graph.Find(32).ImmediatePrecedents);

	AssertCollectionsConsistsOfNodes(new[] {51}, graph.Find(43).ImmediateDescendants);

	AssertCollectionsConsistsOfNodes(new[] {11, 12}, graph.Find(32).TerminatingPrecedents);

	AssertCollectionsConsistsOfNodes(new[] {61, 62}, graph.Find(43).TerminatingDescendants);
}

Things To Think About

POIs


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