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.marte...@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 <angelo...@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
