> So if I understand correctly the map is only needed for bulking so quite
often is not needed.
afaik, it is only used for bulking though it's hard to characterize how
often it is used - i suppose it all depends on the types of traversals you
write and the nature of the data being traversed.
> A significant difference.
The performance numbers are interesting. You don't get a speedup in sqlg
though when bullking would be enacted though - only when bulking would have
no effect - correct?
On Fri, Oct 13, 2017 at 3:48 PM, pieter gmail <pieter.mar...@gmail.com>
wrote:
> Hi,
>
> Doing step optimizations I am noticing a rather severe performance hit in
> TraverserSet.
>
> Sqlg does a secondary optimization on steps that it can not optimize from
> the GraphStep. Before the secondary optimization these steps will execute
> at least one query for each incoming start. The optimization caches the
> incoming start traverser and the step is executed for all incoming
> traversers in one go. This has the effect of changing the semantics into a
> breath first traversal as opposed to the default depth first.
>
> So basically the replaced steps code looks like follows
>
> @Override
> protected Traverser.Admin<S> processNextStart() throws
> NoSuchElementException {
> if (this.first) {
> this.first = false;
> while (this.starts.hasNext()) {
> Traverser.Admin<S> start = this.starts.next();
> this.traversal.addStart(start);
> }
> ....
>
> The performance hit is in the this.traversal.addStart(start) which ends up
> putting the start into the TraverserSet's internal LinkedHashMap.
>
> So if I understand correctly the map is only needed for bulking so quite
> often is not needed. Replacing the map with an ArrayList improves the
> performance drastically.
>
> For the test the optimization does the following. I replace the
> TraversalFilterStep with a custom SqlTraversalFilterStep which extends from
> a custom SqlAbstractStep. The custom SqlgAbstractStep in turn replaces the
> ExpandableStepIterator with a custom SqlgExpandableStepIterator which is a
> copy of ExpandableStepIterator except for replacing TraverserSet with a
> List<Traverser.Admin<S>> traversers = new ArrayList<>();
>
> @Test
> public void testSqlgTraversalFilterStepPerformance() {
> this.sqlgGraph.tx().normalBatchModeOn();
> int count = 10000;
> for (int i = 0; i < count; i++) {
> Vertex a1 = this.sqlgGraph.addVertex(T.label, "A", "name",
> "a1");
> Vertex b1 = this.sqlgGraph.addVertex(T.label, "B", "name",
> "b1");
> a1.addEdge("ab", b1);
> }
> this.sqlgGraph.tx().commit();
>
> StopWatch stopWatch = new StopWatch();
> for (int i = 0; i < 1000; i++) {
> stopWatch.start();
> GraphTraversal<Vertex, Vertex> traversal =
> this.sqlgGraph.traversal()
> .V().hasLabel("A")
> .where(__.out().hasLabel("B"));
> List<Vertex> vertices = traversal.toList();
> Assert.assertEquals(count, vertices.size());
> stopWatch.stop();
> System.out.println(stopWatch.toString());
> stopWatch.reset();
> }
> }
>
> Without the ArrayList optimization the output is,
> 0:00:12.198
> 0:00:09.756
> 0:00:09.435
> 0:00:14.466
> 0:00:10.197
> 0:00:04.937
> 0:00:02.974
> 0:00:02.942
> 0:00:02.977
> 0:00:03.142
> 0:00:03.207
>
> With the ArrayList optimization the output is,
> 0:00:00.334
> 0:00:00.147
> 0:00:00.114
> 0:00:00.100
> ... time for jit
> 0:00:00.055
> 0:00:00.056
> 0:00:00.054
> 0:00:00.053
> 0:00:00.054
> 0:00:00.055
>
> A significant difference.
>
> For TinkerGraph this tests optimization is moot as the TraversalFilterStep
> resets the step for every step making the TraverserSet's map empty so the
> traversers equals method is never called.
>
> Not sure if there are scenarios where this optimization will be any good
> for TinkerGraph but thought I'd let you know how I am optimizing steps.
>
> A concern is that I am now replacing core steps which makes Sqlg further
> away from the reference implementation making it fragile to changes in
> TinkerPop and harder to keep up to upstream changes. Perhaps there is a way
> to make TravererSet's current behavior configurable?
>
> Cheers
> Pieter
>
>
>
>
