In this chapter we have applied BGL to answer several questions that would come up in constructing a software build system: In what order should targets be built? Are there any cyclic dependencies? How long will compilation take? In answering these questions we looked at topological ordering of a directed graph and how this can be computed via a depth-first search.
To implement the solutions we used the BGL adjacency_list to represent the file dependency graph. We wrote straightforward implementations of topological sort and cycle detection. We then identified common pieces of code and factored them out into a generic implementation of depth-first search. We used algorithm visitors to parameterize the DFS and then wrote specific visitors to implement the topological sort and the cycle detection.
We then looked at using a different variation of the adjacency_list class that allowed properties such as vertex name and compile cost to be attached to the vertices of the graph. We then further generalized the generic DFS by parameterizing the graph type and the property access method. The chapter finished with an application of the generic topological sort and DFS to compute the time it would take to compile all the targets on a parallel computer.