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From Paolo Castagna <castagna.li...@googlemail.com>
Subject Re: Should it be possible to extend BasicVertex<I,V,E,M>?
Date Fri, 25 May 2012 17:52:30 GMT
Hi Avery,
thanks for your reply.

However, if you expect end users to extend MutableVertex, it should not have
package private methods inherited from BasicVertex and not implemented in
MutableVertex.

Such as:

  abstract void putMessages(Iterable<M> messages);
  abstract void releaseResources();

I wanted to try to extend MutableVertex because I wanted to see what it would
take to use indexes (with memory mapped files) instead of keeping everything in
RAM. I've not done much progress on that, but I needed to put my stuff in
org.apache.giraph.graph.* because of the two methods above.

Please, correct me if I am wrong.

Cheers,
Paolo

Avery Ching wrote:
> Sorry for the delayed response, but feel free to extend MutableVertex if
> the other Vertex implementations don't meet your needs.  EdgeListVertex
> is probably the most commonly used simple case, but something like
> IntIntNullIntVertex is very optimized for certain primitives (not
> general purposed).  Still, it can be nice to same more memory...
> 
> Avery
> 
> On 5/21/12 10:08 AM, Paolo Castagna wrote:
>> Benjamin Heitmann wrote:
>>> On 21 May 2012, at 17:15, Paolo Castagna wrote:
>>>> A more direct question would be: are Giraph supposed to extend
>>>> BasicVertex<I,V,E,M>  when they do not find a subclass of
>>>> BasicVertex which meets
>>>> their needs?
>>>
>>> No, they are not. However this is not explicitly documented anywhere.
>>>
>>> Or to say it more clearly: If you look in the javadoc of BasicVertex
>>> and if you search the mailing lists,
>>> then you will find that users are discouraged from using/extending
>>> BasicVertex, but you will not find any suggestion of which
>>> Vertex to extend instead. I even asked basically the same question
>>> once, and got very indirect answers.
>>> But that is okay, I figured it out by trial and error ;)
>>>
>>>
>>> Users are supposed to extend HashMapVertex or EdgeListVertex (both in
>>> org.apache.giraph.graph).
>> Hi Benjamin,
>> right, I should have seen those (this is a good sign I should stop for
>> today
>> and continue tomorrow morning). I didn't because I was thinking: "I do
>> not need
>> my vertexes to be mutable" (since, computing PageRank does not need to
>> change
>> the topology of a graph), so I was not focusing my attention on the
>> MutableVertex hierarchy of classes (my mistake).
>>
>> Now my question would be: why SimplePageRankVertex extends
>> LongDoubleFloatDoubleVertex? (But, I'll look at this tomorrow).
>>
>>> If you try to extend them, you will see that you can basically
>>> plug-in any kind of existing class in the<I,V,E,M>  signature,
>>> as long as the implement the right interfaces, which are all Writable
>>> (and WritableComparable for I).
>>> Then you just need to add your compute() method, and you are ready to
>>> go.
>>> Both HashMapVertex and EdgeListVertex provide implementations of all
>>> the housekeeping that giraph needs.
>>>
>>> Trying to work directly by extending BasicVertex will not work, as a
>>> lot of methods are only accessibly on the same package level.
>> Yep.
>>
>>> It would probably be a good idea to submit a small javadoc patch
>>> which adds documentation to BasicVertex, that users need to look at
>>> those other two classes.
>>>
>> Yep.
>>
>> Thanks again for your help and for pointing me in the right direction.
>>
>> Paolo
> 


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