Graph serialization

Question

I'm looking for a simple algorithm to 'serialize' a directed graph. In particular I've got a set of files with interdependencies on their execution order, and I want to find the correct order at compile time. I know it must be a fairly common thing to do - compilers do it all the time - but my google-fu has been weak today. What's the 'go-to' algorithm for this?

Answer 1

Topological Sort (From Wikipedia):

In graph theory, a topological sort or topological ordering of a directed acyclic graph (DAG) is a linear ordering of its nodes in which each node comes before all nodes to which it has outbound edges. Every DAG has one or more topological sorts.

Pseudo code:

L ← Empty list where we put the sorted elements Q ← Set of all nodes with no incoming edges while Q is non-empty do     remove a node n from Q     insert n into L     for each node m with an edge e from n to m do         remove edge e from the graph         if m has no other incoming edges then             insert m into Q if graph has edges then     output error message (graph has a cycle) else      output message (proposed topologically sorted order: L) 

Answer 2

I would expect tools that need this simply walk the tree in a depth-first manner and when they hit a leaf, just process it (e.g. compile) and remove it from the graph (or mark it as processed, and treat nodes with all leaves processed as leaves).

As long as it's a DAG, this simple stack-based walk should be trivial.