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From Elias Daboussi <ilikebergk...@hotmail.com>
Subject Newbie problem with Giraph and the ShortestPaths Example
Date Wed, 08 Aug 2012 08:30:56 GMT









Hello everyone,
I am having some trouble understanding the shortest path example, and some basic things of
Giraph :
I am currently using the giraph-0.1-with-dependencies jar, compiled from Maven, and Hadoop
0.20.203.0


When I launch the example, with the exact same input as given in the example, with 1 worker,
here is what I have as a result :


[0,0,[[1,0]]]
[1,0,[[2,100]]]
[2,100,[[3,200]]]
[3,300,[[4,300]]]
[4,600,[[5,400]]]
[5,1000,[[6,500]]]
[6,1500,[[7,600]]]
[7,2100,[[8,700]]]
[8,2800,[[9,800]]]
[9,3600,[[10,900]]]
[10,4500,[[11,1000]]]
[11,5500,[[12,1100]]]
[12,6600,[[13,1200]]]
[13,7800,[[14,1300]]]
[14,9100,[[0,1400]]]


If I choose a source ID of, for example, 3, I get (still with one worker) :


[0,10200,[[1,0]]]
[1,10200,[[2,100]]]
[2,10300,[[3,200]]]
[3,0,[[4,300]]]
[4,300,[[5,400]]]
[5,700,[[6,500]]]
[6,1200,[[7,600]]]
[7,1800,[[8,700]]]
[8,2500,[[9,800]]]
[9,3300,[[10,900]]]
[10,4200,[[11,1000]]]
[11,5200,[[12,1100]]]
[12,6300,[[13,1200]]]
[13,7500,[[14,1300]]]
[14,8800,[[0,1400]]]


I see here that the node 3 has a 0 value on it, and thus I understand that its the starting
point. So everything is fine. 
I tried to add more edges and do the following graph :

[1,10,[[2,100]]]
[2,10,[[3,100],[1,100]]]
[3,10,[[2,100]]]


I tried to start the job from node 2, but I didnt get any output, my job gets stuck…what
am I doing wrong? I feel like when I add edges, it always gets stuck.Is there a problem in
the way I add jobs? Or in my graph?


Also I was wondering how to add my own examples : what should I do if I want to add an example
class? 
Can I do something like that :
hadoop jar giraph-0.1-jar-with-dependencies.jar myexampleclass <args>
And if I do so, where should I place my myexampleclass class? 
Another newbie question : The shortestpaths example has a main method, but some others don't.
I understood that I need to use the GiraphRunner jar, but I don't really know how to use it
: two arguments are needed : the number of workers, and the input format, then the other arguments.Can
someone tell me how I should do, for example, to run the Shortestpaths example, with the 0.2
version of Giraph (this version does not have a main method)?

Last question, why can't I use the bin/giraph command? (and what is this command made for?
Is it for running a giraph job jar? or just to run the giraph jar?) whatever I do, it says
"can't find the giraph jar"….
Thanks a lot! I hope my questions were not too silly...
I hope I was clear enough, forgive my english, I am French :) 		 	   		  
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