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From Pascal Jäger <pas...@pascaljaeger.de>
Subject Re: push-relabel flow algorithm
Date Tue, 25 Mar 2014 17:12:33 GMT
Hey,

I think you can do both.
you can encode and decode your values to a json formatted text every time you write them to
or read them from your value classes.
I personally added some logic to my VertexValue, thus I don’t encode my data.

So for the latter you will need to write custom input formats because you now  need to create
an instance of your edge and/or vertex value class.
The input format is the place where you can do this.

Take the LongLongNullTextInputFormat in giraph.io.formats.
Replace the NullWritable with you custom EdgeValue and adjust the
protected Iterable<Edge<LongWritable, NullWritable>> getEdges(String[] tokens)

to

protected Iterable<Edge<LongWritable, CustomEdgeValue>> getEdges(String[] tokens)

and change the body to create you your custom value.

You can also look at the Okapi Files. They also provide nice implementations:
http://grafos.ml or
https://github.com/grafos-ml/okapi

Hope that helps

Pascal

Am 25.03.2014 um 17:28 schrieb Rana Althunyan <ranooonh@gmail.com<mailto:ranooonh@gmail.com>>:

Hi again Pascal
That is realy very helpful. I don’t know how can I thank you.

I have another question, do I need to create a new custom input format? I do not think so.
I can use jason format because the other edge values i will set them in compute function.
do you agree with me.

Thank you so so much
Rana
On Mar 25, 2014, at 2:42 AM, Pascal Jäger <pascal@pascaljaeger.de<mailto:pascal@pascaljaeger.de>>
wrote:

Hi Rana,

all you need to do is writing your own EdgeValue and VertexValue class by implementing the
Writable Interface.
You can use any field you like. Just make sure you write or read them in the Writeable methods.

Here’s VertexValue I use (There may be better ways for writing list, but it works just fine)

http://pastebin.com/VpMVFuuc

In your compute method get the VertexValue with vertex.getValue() and apply your changes.
That’s it.
Whatever you write into it in step one, you will be able to read or modify in step two.

Regards

Pascal


Am 25.03.2014 um 07:14 schrieb Rana Althunyan <ranooonh@gmail.com<mailto:ranooonh@gmail.com>>:

Hello Pankaj Malhotra,

Yes, I need to assign more than values to the edge. I need the edge has [flow, capacity, distinction,
source]
You says I need to create a new class type for edge, How can I pass it to json class and how
can I make json class read my new edge object.

I need to submit my code next week, so any answer or recommendation will definitely help.

thanks
Rana

On Mar 24, 2014, at 7:29 AM, Pankaj Malhotra <pankajiitdyn@gmail.com<mailto:pankajiitdyn@gmail.com>>
wrote:

If I get your point-1 right, you want to have a vertex class type other than the ones available,
for example: Text. If this is what you want, you can have a class having as many fields as
you want. Then convert the objects of that class to Json objects using Gson for example. Then,
you can use the Json string to set the fields of the Text class.


On 22 March 2014 04:50, Rana Althunyan <ranooonh@gmail.com<mailto:ranooonh@gmail.com>>
wrote:
Hello experts,
> I really need your help. I am new to Giraph. I have project on pregel paper, and I need
to implement One algorithm via Apache Giraph.The algorithm is push-relabel flow algorithm.
Actually when I started to adapt the algorithm to fit to Giraph I found some problems. I will
list them.
>
> 1- Because any type of data structure are not allowed in Giraph how can I store excess
flow and distance value for each vertex.
> 2- When the excess value becomes zero for any vertex, I wanna keep vertex flow  during
future supersteps even if the vertex received messages.
> 3- The last point, when I want to send a flow to a vertex, i need store two values of
residual graph  the remaining value from the edge capacity and the amount of flow that we
use so far.  How can I do that. How can I keep these two values for each vertex in the graph.
>
> these following questions may are easy for you ..
> 4- How can I determine the last vertex as a sink.
> 5- How can I get the number of all vertexes from the input file .
>
> I know I have written many question.I searched a lot in the Internet, but I did not find
any discussion regards to this algorithm
>
> sorry and thank you.I appreciate any help or recommendations
> Rana







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