Hello again,
As Tom and Matthew suggested I wrote my own custom vertex value class and input
format class. I followed Matthew's example to create my own custom vertex class
but now I'm getting the following error while running the program
java.lang.IllegalStateException: newInstance: Illegal access
org.apache.giraph.examples.DeltaVertexWritable
at
org.apache.giraph.utils.ReflectionUtils.newInstance(ReflectionUtils.java:84)
at
org.apache.giraph.utils.WritableUtils.createWritable(WritableUtils.java:68)
at
org.apache.giraph.factories.DefaultVertexValueFactory.newInstance(DefaultVertexValueFactory.java:48)
at
org.apache.giraph.conf.ImmutableClassesGiraphConfiguration.createVertexValue(ImmutableClassesGiraphConfiguration.java:729)
at
org.apache.giraph.utils.VertexIterator.resetEmptyVertex(VertexIterator.java:69)
at org.apache.giraph.utils.VertexIterator.<init>(VertexIterator.java:60)
at
org.apache.giraph.comm.requests.SendWorkerVerticesRequest.doRequest(SendWorkerVerticesRequest.java:108)
at
org.apache.giraph.comm.netty.NettyWorkerClientRequestProcessor.doRequest(NettyWorkerClientRequestProcessor.java:466)
at
org.apache.giraph.comm.netty.NettyWorkerClientRequestProcessor.flush(NettyWorkerClientRequestProcessor.java:412)
at
org.apache.giraph.worker.InputSplitsCallable.call(InputSplitsCallable.java:241)
at
org.apache.giraph.worker.InputSplitsCallable.call(InputSplitsCallable.java:60)
at
org.apache.giraph.utils.LogStacktraceCallable.call(LogStacktraceCallable.java:51)
at java.util.concurrent.FutureTask.run(FutureTask.java:262)
at
java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1145)
at
java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615)
at java.lang.Thread.run(Thread.java:744)
Here is my DeltaVertexWritable class -
https://gist.github.com/sar-vivek/df09cca17cc3f6b5ac60
I tried digging a bit but I couldn't get any success [at the first place I even
didn't understand the error message!]
Thank you.
Vivek
________________________________
From: Sardeshmukh, Vivek <[email protected]>
Sent: Monday, July 21, 2014 6:06 PM
To: [email protected]
Subject: RE: Setting variable value in Compute class and using it in the next
superstep
Thank you Matthew. Now writing a custom vertex class and input format seems
doable! Thank you.
--
Vivek
________________________________
From: Matthew Saltz <[email protected]>
Sent: Monday, July 21, 2014 5:50 PM
To: [email protected]
Subject: Re: Setting variable value in Compute class and using it in the next
superstep
Yeah, that's true. Sorry I forgot that part. Luckily, it isn't too tricky
either, depending on the input format of your graph. Here's another
example<https://gist.github.com/saltzm/ab7172c57dec927061be> to get you
started, for a very simple input format for edges with no values. I basically
took the code straight from
here<http://giraph.apache.org/apidocs/org/apache/giraph/io/formats/LongLongNullTextInputFormat.html>
and modified where I needed to it to return the InputFormat that I needed for
my code. You'll probably be better off digging through some of the already
implemented InputFormat classes that come with Giraph to do something similar,
since I'm guessing your input files will be different than mine. Take a look at
the subclasses of
TextVertexInputFormat<http://giraph.apache.org/apidocs/org/apache/giraph/io/formats/TextVertexInputFormat.html>,
since they deal with a lot of common input format styles, and see if you can
modify their code to work with your custom vertex data format. Now, the example
I give you is also easy because I just use the default constructor of the
class, but if you need to load additional data from the file into your vertex
data and the default constructor isn't appropriate, you may have to do some
extra parsing and legwork for that.
Best of luck,
Matthew
On Tue, Jul 22, 2014 at 12:28 AM, Sardeshmukh, Vivek
<[email protected]<mailto:[email protected]>> wrote:
Thank you Matthew for the example link. It is helpful. I'll give it a shot.
If I have a custom vertex class isn't it necessary to change the
VertexInputFormat class too? Since this class "loads" the data into the vertex
and if vertex has a custom value field then it doesn't know how to load the
input. Am I right?
Vivek
________________________________
From: Schweiger, Tom <[email protected]<mailto:[email protected]>>
Sent: Monday, July 21, 2014 5:16 PM
To: [email protected]<mailto:[email protected]>
Subject: RE: Setting variable value in Compute class and using it in the next
superstep
For more than one flag, a custom class is necessary (unless you're able to,
say, toggle the sign bit to get double usage out or a value).
I've started a private thread with Vivek to get a better understanding of what
he was trying to solve.
And you are also correct that there isn't much to writing a custom vertex
class. The key is making sure you read and write in the same order. Likewise,
extending a vertex reader can be quite simple.
________________________________
From: Matthew Saltz [[email protected]<mailto:[email protected]>]
Sent: Monday, July 21, 2014 3:09 PM
To: [email protected]<mailto:[email protected]>
Subject: Re: Setting variable value in Compute class and using it in the next
superstep
Tom,
If it's necessary to store more than one flag though, for example, won't a
custom class be necessary? I'm a beginner too, so I apologize if I'm incorrect
about that. Just to be clarify, to keep persistent data for a vertex from one
superstep to the next, it is necessary to encapsulate it in the type used for
the 'V', right? In other words, if Vivek tries to use a normal member variable
for the Computation class, it won't work will it?
Also, just to point out, there actually isn't too much involved with writing
your own custom vertex class. Here's a quick
example<https://gist.github.com/saltzm/692fba1d3aade035ce9c> to get you
started. Within your compute() method you can access the data in this class by
doing
SampleVertexData d = vertex.getValue();
and then using d.setFlag(true) or boolean currentFlag = d.getFlag() for
example. And your computation class is now something like
public class MyComputation extends BasicComputation<IdType, SampleVertexData,
EdgeType, MessageType> {
@Override
public void compute(Vertex<IdType, SampleVertexData, EdgeType> vertex,
Iterable<MessageType> messages) {.....}
...
}
As a warning, for this class I'm using Hadoop 0.20.203 and I'm also a beginner,
so take everything I say with a grain of salt, and Tom please correct me if I'm
wrong.
Best of luck,
Matthew
On Mon, Jul 21, 2014 at 11:37 PM, Schweiger, Tom
<[email protected]<mailto:[email protected]>> wrote:
And in answer of :
This post also suggests (along with what I described above) to have a field in
the vertex value itself. For that I need to change the vertex input format and
also create my own custom vertex class. Is it really necessary?
No, you don't need a custom vertex class or vertex input format. You can
create/initialize the value at the beginning of the first superstep.
________________________________
From: Sardeshmukh, Vivek
[[email protected]<mailto:[email protected]>]
Sent: Monday, July 21, 2014 2:05 PM
To: [email protected]<mailto:[email protected]>
Subject: Setting variable value in Compute class and using it in the next
superstep
Hi, all--
In my algorithm, I need to set a flag if certain conditions hold (locally at a
vertex v). If this flag is set then execute some other block of code *only
once*, and do nothing until some other condition is hold.
My question is, can I declare a flag variable in the class where I override
compute function? I defined the flag as a public variable and setting it once
the conditions are met but it seems the value is not "carried" over to the next
superstep.
I dig a little bit in this mailing list and found this
https://www.mail-archive.com/[email protected]/msg01266.html
This post also suggests (along with what I described above) to have a field in
the vertex value itself. For that I need to change the vertex input format and
also create my own custom vertex class. Is it really necessary?
By the way, I am using Giraph 1.1.0 compiled against Hadoop 1.0.3. I was able
to run SimpleShortestPathComputation successfully.
Here are more technical details of my algorithm: I am trying to implement
Delta-stepping shortest path algorithm (
http://dl.acm.org/citation.cfm?id=740136 or
http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.46.2200 ). This was
mentioned in Pregel paper. A vertex "relax" light edges if it belongs to the
minimum bucket index (of course, aggregators!). Once a vertex is done with
relaxing light edges it relaxes heavy edges (here is where I need a flag) once.
A vertex may be "re-inserted" to a newer bucket and may have to execute all the
steps that I described here again.
Thanks.
Sincerely,
Vivek
A beginner in Giraph (and Java too!)
