What I'm saying is that: one --> two (one,two) for OUTGOING
and two <-- one (two,one) for INCOMING should yield the same timing. 2011/7/24 John cyuczieekc <[email protected]> > Thanks Mattias. The way I understand what you said is, that swapping `one` > and `two` in *finder.findSinglePath( one, two );* should yield the same > timing when Direction.BOTH is used; this would be great. But I don't see > how > this is possible (due to not knowing how it's stored too) unless you know > how many rels each node has, OR even better storage is using BTree-s (?!) > Btw, is it possible/practical that neo4j could store IDs in BTrees ? > (someone said that for rels it's a double linked list instead- I'll need to > recheck) > > irrelevant stuff follows (ie. don't read) > ---- > Until then , I lame-tested something (with both neo4j and berkeleydb): > a node `one` having 1mil rels to 1million unique nodes, and one more to a > node `two`, and node `two` having 10 incoming rels from other unique nodes, > +1 the one rel which was already from `one`, trying shortestPath between > `one` and `two` (not `two` and `one`) with Direction.BOTH > output: > just created 1,000,000 rels, took=58,381 ms (1) > Path from one to two: (one)-->(two) 121,310 ms (2) > Path from one to two: (one)-->(two) timedelta=1,066 ms > Path from one to two: (one)-->(two) timedelta=795 ms > Path from one to two: (one)-->(two) timedelta=772 ms > > (1) and (2) happened in the same transaction (ie. before tx.finish()), the > others after transaction finished (an in no new transaction - since they > were only reads) - this also means some caching must've happened from > before. > Because it happened in same transaction, adding 1 mil relationships is > slower than adding them in bursts of x, I am aware of this (and I'll try to > make a bench with that). For ie. 100k nodes neo4j is actually faster. > I even got this once (but in another modified bench): > first time creating the relationships... > just created 1,000,000 rels, took=49,307 ms (cpu was 100% here, instead of > the usual 77% limit) > Exception in thread "main" java.lang.OutOfMemoryError: Java heap space > Environment is about to shut down the neo4j database > Exception in thread "Thread-0" java.lang.OutOfMemoryError: GC overhead > limit > exceeded > at java.util.logging.LogManager.reset(LogManager.java:835) > at java.util.logging.LogManager$Cleaner.run(LogManager.java:240) > Environment shutting down complete 23,962 ms > > Exception: java.lang.OutOfMemoryError thrown from the > UncaughtExceptionHandler in thread "main" > > > this is the output when running cold, (ie. the data already existed): > search started > Path from one to two: (one)-->(two) timedelta=7,934 ms > search started > Path from one to two: (one)-->(two) timedelta=2,027 ms > search started > Path from one to two: (one)-->(two) timedelta=875 ms > Environment is about to shut down the neo4j database > Environment shutting down complete 2,971 ms > > and the exact same thing when using berkeleydb (not using transactions > though): > just created 1,000,000 rels, took=29,418 ms > Path from one to two: true 0 ms > Path from one to two: true 0 ms > Path from one to two: true 0 ms > class org.bdb.BerkEnv$1 shutting down complete 0 ms (most was 10 ms here) > > and when cold: > Path from one to two: true 10 ms > Path from one to two: true 0 ms > Path from one to two: true 0 ms > class org.bdb.BerkEnv$1 shutting down complete 0 ms > (the most was 10ms on first(sometimes 0ms, 10ms, 0ms), least was 0ms on > all) > > in bdb, this is actually how bdb does the search (I don't need to make sure > I iterate or something similar, on the node `two` which has least incoming > rels), in fact I execute a search on both nodes, one after the other and > make sure one->two and two<-one (since I am using two databases), anyway, > by > using db.getSearchBoth(...) the search is done *that *fast. I hope to see > this kind of fastness with neo4j too xD (unless I'm doing it wrong) > > if I put neo4j to find shortest path on incoming on `two` then: > search started > Path from one to two: (two)<--(one) timedelta=20 ms > search started > Path from one to two: (two)<--(one) timedelta=0 ms > search started > Path from one to two: (two)<--(one) timedelta=0 ms > Environment is about to shut down the neo4j database > Environment shutting down complete 2,590 ms > (most was 20ms, least was 20ms on first) > > TestLinkage.java (both progs) were used from here: > > https://github.com/13th-floor/neo4john/commit/a9f4b274de1d6c9ec9f1ea4a338b5c42325f19a4 > > -------------- > > Here's a lame benchmark for neo4j when I added another node `three` which > is > the first rel `one`->`three`, then added 1mil `one`->(random nodes) , and > then(as before) `one`->`two` > `three` has no other relationships > Also, creating nodes 10k per transaction until 1mil are reached. > > first time creating the relationships... > just created 1,000,000 rels, took=28,889 ms (btw my cpu is limited to 77% > of its normal speed; usually!) > closed transaction > search started > (one)-->(three) 3,234 ms > search started > (one)-->(two) 661 ms > search started > (three)<--(one) 10 ms > search started > (two)<--(one) 0 ms > search started > (one)-->(three) 631 ms > search started > (one)-->(two) 913 ms > search started > (three)<--(one) 0 ms > search started > (two)<--(one) 0 ms > search started > (one)-->(three) 610 ms > search started > (one)-->(two) 773 ms > search started > (three)<--(one) 0 ms > search started > (two)<--(one) 0 ms > Environment is about to shut down the neo4j database > Environment shutting down complete 3,801 ms > > and on cold run: > search started > (one)-->(three) 8,454 ms > search started > (one)-->(two) 885 ms > search started > (three)<--(one) 0 ms > search started > (two)<--(one) 0 ms > search started > (one)-->(three) 752 ms > search started > (one)-->(two) 755 ms > search started > (three)<--(one) 0 ms > search started > (two)<--(one) 0 ms > search started > (one)-->(three) 804 ms > search started > (one)-->(two) 621 ms > search started > (three)<--(one) 0 ms > search started > (two)<--(one) 0 ms > Environment is about to shut down the neo4j database > Environment shutting down complete 3,141 ms > ===== > and same thing in berkeleydb (no transactions tho): > first time creating the relationships... > just created 1,000,000 rels, took=29,658 ms > Path from one to three: true 10 ms > Path from one to two: true 0 ms > Path from three to one: false 0 ms > Path from two to one: false 0 ms > Path from one to three: true 0 ms > Path from one to two: true 0 ms > Path from three to one: false 0 ms > Path from two to one: false 0 ms > Path from one to three: true 0 ms > Path from one to two: true 0 ms > Path from three to one: false 0 ms > Path from two to one: false 0 ms > class org.bdb.BerkEnv$1 shutting down complete 152 ms > > and on cold: > Path from one to three: true 10 ms > Path from one to two: true 10 ms > Path from three to one: false 0 ms > Path from two to one: false 0 ms > Path from one to three: true 0 ms > Path from one to two: true 0 ms > Path from three to one: false 0 ms > Path from two to one: false 0 ms > Path from one to three: true 0 ms > Path from one to two: true 0 ms > Path from three to one: false 0 ms > Path from two to one: false 0 ms > class org.bdb.BerkEnv$1 shutting down complete 0 ms > > > these progs are on: > > https://github.com/13th-floor/neo4john/commit/d2fd5b27dcde5560e6ff980fe9320aedc4421ab7 > > Cheerios, > John. > > Song of the day: Bic Runga - She Left On A Monday > PS: asserts were enable ie. vm arg "-ea" (no quotes) > > On Sat, Jul 23, 2011 at 4:31 PM, Mattias Persson > <[email protected]>wrote: > > > Hi John, > > > > the algorithm is written to dodge these kinds of pitfalls. Maybe there's > > some issue with the implementation, but in principal it should make no > > difference. I'll look at it when I get the time (I wrote that > > implementation). > > > > 2011/7/23 John cyuczieekc <[email protected]> > > > > > Hey guys, me bugging you again :) > > > > > > (This whole thing is kind of based on the lack of being able to get the > > > number of relationships a node has) > > > > > > If I have two nodes, and the first one has 1 million outgoing > > > relationships > > > of the type X to 1 million unique/different nodes, > > > and the second node has 10 incoming relationships of type X (same type) > > of > > > which one is from the first node, > > > then using GraphAlgoFactory.shortestPath (or suggest a better way?) > > > How can I tell neo4j to iterate the search on the second node's > incoming > > > rels simply because it has 10 relationships instead of 1 million, in > > order > > > to check if each relationship is in the form of firstNode-->secondNode > ? > > > > > > For the case when first node has 100,000 relationships and second node > > has > > > 10, > > > it takes *1.7 seconds* for shortestPath to find the only one link > between > > > them using: > > > > > > final PathFinder<Path> finder = GraphAlgoFactory.shortestPath( > > > Traversal.expanderForTypes( rel, Direction.OUTGOING ), 1 ); > > > final Path foundPath = finder.findSinglePath( *one, two* ); > > > > > > I can put Direction.*BOTH *and get the same amount of time > > > *Path from one to two: (one)-->(two) timedelta=1,862,726,634 ns* > > > > > > *BUT*, get this: if I swap the nodes: > > > finder.findSinglePath(* two, one*); > > > and i use either Direction.INCOMING or Direction.*BOTH *(which makes > > sense > > > for the second node ,right) then I get *20ms* the time until it > > finishes... > > > *Path from one to two: (two)<--(one) timedelta=20,830,111 ns* > > > > > > (both cases are without data being priorly cached) > > > > > > I was expecting it to act like this: (but only when using > Direction.BOTH) > > > see which node has the least number of relationships and iterate on > > those, > > > but this would work if findSinglePath would be made for depth 1 (aka > > > particular case), but as I read "Tries to find a single path between > > > startand > > > end nodes." then it makes sense to me why it works like it does... that > > is, > > > iterate on relationships from start node, rather than from end node... > > but > > > I'm not sure if it would *not *make sense to iterate on the end node > > > instead > > > of start node, when knowing that end node has less relationships, for > > make > > > the search faster (well at least if depth is one) - I didn't look into > > how > > > neo4j actually does stuff yet :D > > > > > > anyway, it's fairly clear to me that I could make a simple wrapper > method > > > to > > > make this kind of search faster, *IF* I had the ability to know how > many > > > relationships each node has, so I can call findSinglePath with the > first > > > param being the node with the least relationship count :) But as I > > > understood it, it's not possible to find how many rels a node has... > > gimme > > > feat! :)) [by not possible I mean, without having to iterate thru all > and > > > count them, which would make the use case here obsolete] > > > > > > PS: clearly all the text I wrote here would benefit from being > > represented > > > by a graph, just think about all those grouping with autohiding the ie. > > > "[]" > > > and all kinds of stuff... heh > > > _______________________________________________ > > > Neo4j mailing list > > > [email protected] > > > https://lists.neo4j.org/mailman/listinfo/user > > > > > > > > > > > -- > > Mattias Persson, [[email protected]] > > Hacker, Neo Technology > > www.neotechnology.com > > _______________________________________________ > > Neo4j mailing list > > [email protected] > > https://lists.neo4j.org/mailman/listinfo/user > > > _______________________________________________ > Neo4j mailing list > [email protected] > https://lists.neo4j.org/mailman/listinfo/user > -- Mattias Persson, [[email protected]] Hacker, Neo Technology www.neotechnology.com _______________________________________________ Neo4j mailing list [email protected] https://lists.neo4j.org/mailman/listinfo/user
