Generic Graph
From DocR21
Creates an instance of a graph for the graph theory mathematical operations.
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Description
The concepts of vertex, edge, and graph have been implemented as the C++ classes gvertex, gedge, and generic_graph. (entity_gvertex is derived from gvertex except that it contains a pointer to an entity in the model. Such an entity could be a cell or a face.) A gvertex may be created with an optional char* name. A gedge may be created with two gvertex pointers. An empty graph may be created and edges and vertices may be added to it by calling its add_vertex and add_edge methods. Once created, a graph may be interrogated, ordered, or subsetted in a number of ways.
The generic_graph class has methods to tell if a graph is connected, a tree, linear, or a cycle. It also has methods to tell how many components the graph has and to return each of the components as a subgraph. Moreover, the components may be identified by giving an edge or vertex in them.
negate Method
Once a graph has been ordered, its ordering may be negated with this method. Negation is a special operation and returns different results for cycles and trees depending upon the start vertex. In the following figure, the graph vertex A was initially 0 in the ordering before the negation operation.
order_cyclic Method
If a graph is cyclic, then it may be ordered by the order_cyclic method. This sets a given vertex's order to zero and the other vertices in a cyclic order as shown in the following figure.
order_from Method
The order_from method of ordering a graph works well for trees and linear graphs. The two graphs show in the Ordering Graphs figure have been ordered by distance from vertex A.
order_with Method
Another way to order a graph G is to order it with respect to an ordered graph H such that G is a subgraph of H. The order_with method imposes the order of H onto G and rescales the ordering on G to remove gap. The type of ordering (cyclic or not) is inherited from the ordered graph H. If the compress option is turned on, the resulting gvertexes are numbered sequentially. In the example below, gvertexes in the uncompressed result would be numbered 124, but in the compressed result would be numbered 012.
