Topological sort returns different result for similar graphs

import scalax.collection.Graph
import scalax.collection.GraphEdge.DiEdge
import scalax.collection.GraphPredef._

object MainApp extends App {

  //Creates new graph
  def graph: Graph[String, DiEdge] = Graph(
    "A" ~> "B",
    "A" ~> "C",
    "A" ~> "D",
    "B" ~> "E",
    "B" ~> "F",
    "C" ~> "G",
    "C" ~> "H",
    "D" ~> "F",
    "D" ~> "G"
  )

  val results = 1 to 20 map { _ =>
    graph.topologicalSort.mkString("")
  }

  println(results.tail.forall(_ == results.head))
}

Given the above code, I expect to get same topological sort for the similar graphs created by graph method. But this app prints false and proves the opposite. All of the results of topologicalSort call do comply to topological sort but it’s needed to have a mechanism for fixing this order for similar graphs.

Setting ordering in graph.componentTraverser(ordering = ...).topologicalSort does not fix the order for similar graphs.

[peter-empen]

The topological sort available with Version 2.10.0 fulfills this feature request. You either make the sort ordered or order the result. The latter is done by

topoOrder withLayerOrdering yourOrdering

[seveneves]

@peter-empen thank you. I’ll give it a try