Github user markhamstra commented on a diff in the pull request:
https://github.com/apache/spark/pull/12060#discussion_r58467066
--- Diff: core/src/main/scala/org/apache/spark/scheduler/DAGScheduler.scala
---
@@ -403,32 +403,47 @@ class DAGScheduler(
parents.toList
}
- /** Find ancestor shuffle dependencies that are not registered in
shuffleToMapStage yet */
- private def getAncestorShuffleDependencies(rdd: RDD[_]):
Stack[ShuffleDependency[_, _, _]] = {
- val parents = new Stack[ShuffleDependency[_, _, _]]
+ /**
+ * Find ancestor shuffle dependencies that are not registered in
shuffleToMapStage yet.
+ * This is done in topological order to create ancestor stages first to
ensure that the result
+ * stage graph is correctly built.
+ */
+ private def getAncestorShuffleDependencies(rdd: RDD[_]):
Seq[ShuffleDependency[_, _, _]] = {
+ val parents = new ArrayBuffer[ShuffleDependency[_, _, _]]
val visited = new HashSet[RDD[_]]
// We are manually maintaining a stack here to prevent
StackOverflowError
// caused by recursively visiting
val waitingForVisit = new Stack[RDD[_]]
def visit(r: RDD[_]) {
if (!visited(r)) {
- visited += r
- for (dep <- r.dependencies) {
- dep match {
- case shufDep: ShuffleDependency[_, _, _] =>
- if (!shuffleToMapStage.contains(shufDep.shuffleId)) {
- parents.push(shufDep)
- }
- case _ =>
+ val deps = r.dependencies.filter {
+ case shufDep: ShuffleDependency[_, _, _] =>
+ !shuffleToMapStage.contains(shufDep.shuffleId)
+ case _ => true
+ }
+ if (deps.forall(dep => visited(dep.rdd))) {
+ waitingForVisit.pop()
+ visited += r
+ for (dep <- deps) {
+ dep match {
+ case shufDep: ShuffleDependency[_, _, _] =>
+ parents += shufDep
+ case _ =>
+ }
+ }
+ } else {
+ for (dep <- deps if !visited(dep.rdd)) {
+ waitingForVisit.push(dep.rdd)
}
- waitingForVisit.push(dep.rdd)
}
+ } else {
+ waitingForVisit.pop()
}
}
--- End diff --
This cuts down on the repeated scanning of data structures and should
increase performance a little more (only lightly tested):
```scala
def visit(r: RDD[_]) {
if (visited(r)) {
waitingForVisit.pop()
} else {
val visitedShuffleDeps = new ArrayBuffer[ShuffleDependency[_, _, _]]
val unvisitedDeps = new ArrayBuffer[Dependency[_]]
r.dependencies.foreach {
case dep: ShuffleDependency[_, _, _] if
!shuffleToMapStage.contains(dep.shuffleId) =>
if (visited(dep.rdd)) visitedShuffleDeps += dep
else unvisitedDeps += dep
case dep if !visited(dep.rdd) => unvisitedDeps += dep
case _ =>
}
if (unvisitedDeps.isEmpty) {
waitingForVisit.pop()
visited += r
for (shufDep <- visitedShuffleDeps) { parents += shufDep }
} else {
for (dep <- unvisitedDeps) {
waitingForVisit.push(dep.rdd)
}
}
}
}
```
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