## Class SparseIntUndirectedWeightedGraph

• All Implemented Interfaces:
Serializable, Graph<Integer,​Integer>

public class SparseIntUndirectedWeightedGraph
extends SparseIntUndirectedGraph
implements Serializable
Sparse undirected weighted graph.

Assuming the graph has $n$ vertices, the vertices are numbered from $0$ to $n-1$. Similarly, edges are numbered from $0$ to $m-1$ where $m$ is the total number of edges.

It stores the boolean incidence matrix of the graph (rows are vertices and columns are edges) as Compressed Sparse Rows (CSR). In order to also support constant time source and target lookups from an edge identifier we also store the transposed of the incidence matrix again in compressed sparse row format. This is a classic format for write-once read-many use cases. Thus, the graph is unmodifiable. The edge weights are maintained in an array indexed by the edge identifier.

The graph is weighted. While unmodifiable with respect to the structure of the graph, the edge weights can be changed even after the graph is constructed.

The question of whether a sparse or dense representation is more appropriate is highly dependent on various factors such as the graph, the machine running the algorithm and the algorithm itself. Wilkinson defined a matrix as "sparse" if it has enough zeros that it pays to take advantage of them. For more details see

• Wilkinson, J. H. 1971. Linear algebra; part II: the algebraic eigenvalue problem. In Handbook for Automatic Computation, J. H. Wilkinson and C. Reinsch, Eds. Vol. 2. Springer-Verlag, Berlin, New York.
Author:
Dimitrios Michail
Serialized Form
• ### Field Detail

• #### weights

protected double[] weights
The edge weights
• ### Constructor Detail

• #### SparseIntUndirectedWeightedGraph

public SparseIntUndirectedWeightedGraph​(int numVertices,
List<Triple<Integer,​Integer,​Double>> edges)
Create a new graph from an edge list
Parameters:
numVertices - number of vertices
edges - edge list with weights
• ### Method Detail

• #### getType

public GraphType getType()
Description copied from interface: Graph
Get the graph type. The graph type can be used to query for additional metadata such as whether the graph supports directed or undirected edges, self-loops, multiple (parallel) edges, weights, etc.
Specified by:
getType in interface Graph<Integer,​Integer>
Overrides:
getType in class SparseIntUndirectedGraph
Returns:
the graph type