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From Sebastian Schelter <...@apache.org>
Subject Re: Information
Date Wed, 26 Mar 2014 13:52:33 GMT
Hi Angelo,

It very much depends on your use case. Do you want to precompute paths 
offline in batch or are you looking for a system that answers online? 
Giraph has been built for the first scenario.

--sebastian

On 03/26/2014 02:48 PM, Angelo Immediata wrote:
> hi Claudio
>
> so, if I understood correctly, it has no sense to use Giraph for shortest
> path calculation in my scenario
>
> Am I right?
>
>
> 2014-03-26 13:27 GMT+01:00 Claudio Martella <claudio.martella@gmail.com>:
>
>> It looks like you're expecting to use Giraph in an online fashion, such as
>> you would use a database to answer queries within milliseconds or seconds.
>> Giraph is an offline batch processing system.
>>
>>
>> On Wed, Mar 26, 2014 at 11:11 AM, Angelo Immediata <angeloimm@gmail.com>wrote:
>>
>>> Hi there
>>>
>>> In my project I have to implement a routing system with good performance;
>>> at the beginning this system should be able in giving routes information
>>> only for one italian region (Lombardia) but it could be used for the whole
>>> Italy (or world....)
>>> Let's stop to the Lombardia for now. By reading OSM files I can create my
>>> own graph in the best format i can use it; then I need to use Dijkstra (or
>>> any other algorithm) in order to propose to the user K possible paths from
>>> point A to point B (K becouse i need to show to the customer also the
>>> alternatives). I can't use Contraction Herarchy algorithm becouse I need to
>>> take care of external events that can modify the weights on my built graph
>>> and this implies that I should create the "contracted" graph once again and
>>> this can be a very onerous operation
>>>
>>> By my experimentations, I saw that by reading the Lombardia OSM file I
>>> should create a graph with around 1 million of vertexes and 6 million of
>>> edges and I was thinking to use Giraph to solve my issue (I saw this link
>>> http://giraph.apache.org/intro.html where you talked about shortestpaths
>>> problem
>>> I have a couple of question for you giraph/hadoop gurus
>>>
>>>     - does it make sense to use giraph for my scenario?
>>>     - must i respect some graph format to pass to the giraph algorithm in
>>>     order to have K shortest paths from point A to point B? If so....which
>>>     format should I respect?
>>>     - what would be perfomance by using giraph? I know that Dijstra
>>>     algorithm problem is that it is slow.....by using giraph will I be able in
>>>     improving its performances on very large graph?
>>>
>>> I know these can seem very basic questions, but I'm pretty new to giraph
>>> and I'm trying to understand it
>>>
>>> Thank you
>>> Angelo
>>>
>>
>>
>>
>> --
>>     Claudio Martella
>>
>>
>


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