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Date: Wed, 25 Jul 2012 22:23:35 +0000 (UTC)
From: "Alessandro Presta (JIRA)" <jira@apache.org>
To: giraph-dev@incubator.apache.org
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Subject: [jira] [Commented] (GIRAPH-244) Vertex API redesign
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    [ https://issues.apache.org/jira/browse/GIRAPH-244?page=3Dcom.atlassian=
.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=3D1342=
2683#comment-13422683 ]=20

Alessandro Presta commented on GIRAPH-244:
------------------------------------------

Oh no, that was bad, sorry! It's the auto-import in IDEA, it doesn't unders=
tand Munge comments...
Thanks a lot for spotting this. I think it's better if we open a separate i=
ssue. I'll do it now and assign to you :)
               =20
> Vertex API redesign
> -------------------
>
>                 Key: GIRAPH-244
>                 URL: https://issues.apache.org/jira/browse/GIRAPH-244
>             Project: Giraph
>          Issue Type: Improvement
>            Reporter: Alessandro Presta
>            Assignee: Alessandro Presta
>         Attachments: 0001-GIRAPH-244-regression-for-non-secure-Hadoop.pat=
ch, GIRAPH-244.patch, GIRAPH-244.patch, GIRAPH-244.patch, GIRAPH-244.patch,=
 GIRAPH-244.patch, GIRAPH-244.patch, GIRAPH-244.patch, GIRAPH-244.patch, GI=
RAPH-244.patch, GIRAPH-244.patch, GIRAPH-244.patch, GIRAPH-244.patch, GIRAP=
H-244.patch, GIRAPH-244.patch, GIRAPH-244.patch, GIRAPH-244.patch
>
>
> This is an effort to rationalize the Giraph API. I've put together a few =
issues that we've talked about lately. I'm focusing on making Giraph develo=
pment even more intuitive and less error-prone, and fixing a few potential =
sources of bugs.
> I'm sorry this is a big patch, but most of those issues are intertwined a=
nd I think this might be easier to review and integrate.
> Here's an account of the changes:
> Vertex API:
> - Renamed BasicVertex to Vertex (as I understand, we used to have both an=
d then Vertex was removed).
> - Switched to Iterables instead of Iterators for both edges and messages.=
 This makes code more concise for both implementors (no need to call .itera=
tor() on collections) and users (can use foreach syntax). See also GIRAPH-2=
21.
> - Added SimpleVertex and SimpleMutableVertex classes, where there are no =
edge values and the iterable to be implemented is getNeighbors(). We don=E2=
=80=99t have multiple inheritance, so the only way I could think of was to =
have SimpleVertex extend Vertex, SimpleMutableVertex extend MutableVertex, =
and duplicate the code for the edges iterables.
> Also, due to type erasure, one still has to deal with Edge objects in Sim=
pleMutableVertex#initialize. Overall I think this is still an improvement o=
ver the current situation.
> - Added id and value field to the base Vertex class. All other classes we=
re either writing the same boilerplate again and again, or using primitive =
fields and then creating Writables on the fly (inefficient; there was even =
a TODO about that). If there are any actually useful customizations here, I=
=E2=80=99ve yet to see them.
> Also removed redundant =E2=80=9CVertex=E2=80=9D from getters/setters (com=
pare vertex.getId() with vertex.getVertexId()).
> - Made halt a private field, and added a wakeUp() method to re-activate a=
 vertex. isHalted()/voteToHalt()/wakeUp() are just more semantically-charge=
d getter/setters.
> - Renamed number of vertices/edges in graph to getTotalNum*. The previous=
 naming (getNumEdges) was arguably confusing. If this one sucks too, please=
 suggest a better one.
> - Default implementations of hasEdge(), getEdgeValue(), getNumEdges(), re=
adFields(), write(), toString(): the implementor can still optimize when th=
ere is a good opportunity. Currently we are duplicating a lot of code (see =
GIRAPH-238) and potentially introducing bugs (see GIRAPH-239).
> HashMapVertex:
> - Switched representation from Map<I, Edge<I, E>> to Map<I, E> (GIRAPH-24=
2)
> - Only override methods that can be optimized.
> EdgeListVertex:
> - Switched representation from two sorted lists to one list of Edge<I, E>=
 (see GIRAPH-243). Mainly this makes iteration over edges (target id and va=
lue) linear instead of O(n log n). Mutations are still slow and should gene=
rally be discouraged.
> - Only override methods that can be optimized.
> Small nits:
> - Our code conventions say we should try to avoid abbreviations, so I eli=
minated a few (req -> request, msg -> message).
> - Unilaterally refer to the endpoint of an edge as targetVertex (before w=
e had a mix of destVertex and targetVertex).
> - You will notice some rearranged imports. That=E2=80=99s just my IDE try=
ing to be helpful (see GIRAPH-230).

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