KAFKA-15022: Detect negative cycle from one source #14696
Conversation
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Will this impact the performance? If so, do we plan to add a performance comparison? |
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| @Override | ||
| public int compare(final V o1, final V o2) { | ||
| if (o1 == null) { |
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Do we plan to have different results returned under two different null cases? If not, maybe we can do
if (o1 == null || o2 == null) {
return -1;
}
to simplify the condition.
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| private void removeDummySourceNode(final Graph<V> residualGraph) { | ||
| if (!residualGraph.isResidualGraph) { | ||
| throw new IllegalStateException("Graph should be residual graph to add dummy source node"); |
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Maybe 'Graph should be residual graph to remove dummy source node' ?
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@ex172000 , this will improve performance. Since it's obvious that we replace the loop of number of nodes to a single iteration, I'm not planning to add comparison. |
mjsax
changed the title
mjsax
changed the title
| @Override | ||
| public int compare(final V o1, final V o2) { | ||
| if (o1 == null || o2 == null) { | ||
| return -1; |
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If one of both is null, why is o1 considered smaller than o2? Would it not be better to define null as either smallest or largest globally? -- Also, should we return zero if both are null?
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Good point, if both are null, we can return 0;
| @@ -117,6 +131,8 @@ private Graph(final boolean isResidualGraph) { | |||
| } | |||
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| public void addEdge(final V u, final V v, final int capacity, final int cost, final int flow) { | |||
| Objects.requireNonNull(u); | |||
| Objects.requireNonNull(v); | |||
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null is a special node we introduced in graph as dummy source to detect negative cycle. So users can use it
Introduce a dummy node connected to every other node and run Bellman-ford from the dummy node once instead of from every node in the graph. Reviewers: Qichao Chu (@ex172000), Matthias J. Sax <[email protected]>
Introduce a dummy node connected to every other node and run Bellman-ford from the dummy node once instead of from every node in the graph. Reviewers: Qichao Chu (@ex172000), Matthias J. Sax <[email protected]>
Introduce a dummy node connected to every other node and run Bellman-ford from the dummy node once instead of from every node in the graph. Reviewers: Qichao Chu (@ex172000), Matthias J. Sax <[email protected]>
Introduce a dummy node connected to every other node and run Bellman-ford from the dummy node once instead of from every node in the graph. Reviewers: Qichao Chu (@ex172000), Matthias J. Sax <[email protected]>
Description
Introduce a dummy node connected to every other node and run Bellman-ford from the dummy node once instead of from every node in the graph.
Testing
Existing test
Committer Checklist (excluded from commit message)