Actually, one more question: are there any disadvantages to enabling oneToAllMessaging? Is there any reason not to do it by default?
Best, Matthew El 22/10/2014 23:28, "Matthew Saltz" <sal...@gmail.com> escribió: > Lukas, > > Thank you so much for the help. By 'the first class', you mean > SendMessageToAllCache > is not used unless I set the property to true, right? Because I actually do > have giraph.oneToAllMsgSending=true, so if that means it's using > SendMessageToAllCache then everything makes much more sense. So I guess > it makes sense then that case (b) that I mentioned that would be much > faster than case (a)? I really appreciate it. And do you have any ideas > about the second question I asked? I think the answer is no but I'm kind of > hoping it's not. > > Best, > Matthew > > > > On Wed, Oct 22, 2014 at 11:16 PM, Lukas Nalezenec < > lukas.naleze...@firma.seznam.cz> wrote: > >> Hi Matthew, >> >> See class SendMessageToAllCache. Its in the same directory as >> SendMessageCache. The first class is not used by Giraph unless you set >> property giraph.oneToAllMsgSending to true. >> >> Lukas >> >> >> On 22.10.2014 20:10, Matthew Saltz wrote: >> >> Hi everyone, >> >> I have two questions: >> >> *Question 1)* I'm using release 1.1.0 and I'm really confused about the >> fact that I'm having massive performance differences in the following >> scenario. I need to send one message from each vertex to a subset of its >> neighbors (all that satisfy a certain condition). For that, I see two basic >> options: >> >> a) Loop over all edges, making a call to sendMessage(source, target) >> whenever target satisfies a condition I want, reusing the same IntWritable >> for the target vertex by calling target.set(_) >> b) Loop over all edges, building up an ArrayList (or whatever) of >> targets that satisfy the condition, and calling >> sendMessageToMultipleMessages(targets) at the end. >> >> Surprisingly, I get much, much worse performance using option (a), >> which I would think would be much faster. So I looked in the code and >> eventually found my way to SendMessageCache >> <https://github.com/apache/giraph/blob/release-1.1/giraph-core/src/main/java/org/apache/giraph/comm/SendMessageCache.java>, >> where it turns out that sendMessageToMultipleMessages -> >> sendMessageToAllRequest(Iterator, Message) actually just loops over the >> iterator, repeatedly calling sendMessageRequest (which is what I thought I >> was doing in scenario (a). I might have incorrectly traced the code though. >> Can anyone tell me what might be going on? I'm really puzzled by this. >> >> *Question 2) *Is there a good way of sending a vertex's adjacency list >> to its neighbors, without building up your own copy of an adjacency list >> and then sending that? I'm going through the Edge iterable and building an >> ArrayPrimitiveWritable of ids but it would be nice if I could somehow >> access the underlying data structure behind the iterable or just wrap the >> iterable as a writable somehow. >> >> Thanks so much for the help, >> Matthew Saltz >> >> >> >> >> >
