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From Angelo Immediata <angelo...@gmail.com>
Subject Re: Information
Date Wed, 26 Mar 2014 14:18:56 GMT
hi Sebastian

OK...I got it....I was thinking I could use it for an online scenario......
Thank you

Angelo


2014-03-26 14:52 GMT+01:00 Sebastian Schelter <ssc@apache.org>:

> 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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