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https://issues.apache.org/jira/browse/GEARPUMP-349?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16169654#comment-16169654
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ASF GitHub Bot commented on GEARPUMP-349:
-----------------------------------------
Github user huafengw commented on a diff in the pull request:
https://github.com/apache/incubator-gearpump/pull/223#discussion_r139345072
--- Diff: core/src/main/scala/org/apache/gearpump/util/Graph.scala ---
@@ -318,12 +360,8 @@ class Graph[N, E](vertexList: List[N], edgeList:
List[(N, E, N)]) extends Serial
* http://www.drdobbs.com/database/topological-sorting/184410262
*/
def topologicalOrderWithCirclesIterator: Iterator[N] = {
- if (hasCycle()) {
- val topo = getAcyclicCopy().topologicalOrderIterator
- topo.flatMap(_.sortBy(_indexs(_)).iterator)
- } else {
- topologicalOrderIterator
- }
+ val topo = getAcyclicCopy().topologicalOrderIterator
+ topo.flatMap(_.sortBy(indexs(_)).iterator)
--- End diff --
It's not. `topo` is an `Iterator[List[N]]` so the items of topo is sorted
but the item it self is a list and it's not sorted.
> Graph#topologicalOrderIterator is slow for large graph
> ------------------------------------------------------
>
> Key: GEARPUMP-349
> URL: https://issues.apache.org/jira/browse/GEARPUMP-349
> Project: Apache Gearpump
> Issue Type: Improvement
> Components: core
> Affects Versions: 0.8.4
> Reporter: Manu Zhang
> Assignee: Huafeng Wang
> Fix For: 0.8.5
>
>
> The algorithm is as follows
> 1. find zero in-degree nodes from a copied graph.
> 2. remove nodes from the copied graph and add them to the output
> 3. repeat 1
> The issue is that step 1 traverses all remaining nodes each time, which costs
> the algorithm {{O(n^2)}} time
> {{Graph#hasCycle}} has a similar issue
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