# Deep Analysis: BreadthFirstIterator vs TopologicalOrderIterator in JGraphT (BrainzGraph Context) - JoseCanova/brainz GitHub Wiki

Deep Analysis: BreadthFirstIterator vs TopologicalOrderIterator in JGraphT (with Ironic Commentary)

1. Context: Graph Traversal—Because Who Doesn’t Love a Good Walk?

You’re using:

public BreadthFirstIterator<Class<? extends BaseEntity>, PriorityEdge>
getBreadthFirstIterator(Class<? extends BaseEntity> class1){
    return new BreadthFirstIterator<>(entityDirectedGraph, class1);
}

Breadth-first, because why not visit everything at every level before we go deeper? (After all, what could possibly go wrong with lots of neighbors...)

2. BreadthFirstIterator vs TopologicalOrderIterator: Clash of the Titans

BreadthFirstIterator

  • Visits neighbors at the current depth before going deeper.
  • Not guaranteed to respect dependency order in a DAG. (Hey, sometimes your child gets to the party before the parent.)
  • If you start BFS from every node, the order depends on the starting node and graph structure. Every run is a surprise party.
  • Implication: Results may vary! (Collect all possible outcomes for the full set.)

TopologicalOrderIterator

  • Gives you a nice, dependency-respecting sequence: for every edge u → v, u comes before v.
  • Only valid for Directed Acyclic Graphs (DAGs)—so no cheating with cycles.
  • The order is valid, not always unique, but at least your dependencies won’t riot.
  • Implication: If you want order instead of chaos, this is your friend.

3. Why is ArtistCredit Always on Top? (The “King of the Hill” Phenomenon)

Take a look at your result files: ArtistCredit is always on top. Suspicious? Or just a natural-born leader?

  • BFS Impact: If ArtistCredit is a root or highly connected, BFS will worship it as first among equals.
  • Mathematical Enigma: The universe (or at least your graph) bends toward this node. Perhaps it’s the Beyoncé of your schema.

4. Mathematical Perspective: Science, but with More Shrugs

  • BFS is Not a Topological Sort: It’s just trying its best, but sometimes it gets dependencies backward. Oops.
  • Topological Sort is a Partial Order: All valid topological orderings are a subset of possible permutations. It’s math’s way of telling you “do whatever you want, as long as you respect the rules.”
  • Multiple Valid Orders: If several entities are independent, there are many correct orders. But if one is always first, that’s destiny. Or just a really pointy graph.

5. Implications for Your Analysis: Science or Sorcery?

  • Non-Deterministic Results: Using BFS from all nodes is like running a lottery: sometimes you win, sometimes you get ArtistCredit on top (again).
  • The “Enigma”: If one node always wins, maybe it’s time for a coup. Or just admit it’s the root.
  • For Boring, Reproducible Results: Use TopologicalOrderIterator. It’s not as exciting, but your dependencies will sleep at night.

6. Recommendation: “The Academic Way (Yawn) vs The BFS Way (Party Time)”

  • Want to analyze the “enigma”? Draw the graph. Compute all topological sorts. If ArtistCredit is always first, you’ve discovered the One True Node.
  • Want robust, boring, reproducible results? Topological sort. Sorry.

7. References (Because Footnotes Make It Real)

8. Code for Future Refactoring (Because We’ll Totally Do It Someday)

public BreadthFirstIterator<Class<? extends BaseEntity>,PriorityEdge>
getBreadthFirstIterator(Class<? extends BaseEntity> class1){
    return new BreadthFirstIterator<Class<? extends BaseEntity>,PriorityEdge> (entityDirectedGraph,class1);
}

Next time: We’ll try to “take the spirit” and understand if our priorities are an “account balance” or just an existential crisis for vertices. Stay tuned!