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From "Claudio Squarcella (Commented) (JIRA)" <>
Subject [jira] [Commented] (SANDBOX-356) Generic weight types and algorithms implementations based on wighted graphes
Date Wed, 11 Jan 2012 21:53:40 GMT


Claudio Squarcella commented on SANDBOX-356:

Hi Simone,

yes, I double-checked and essentially weights are only used (so far) in the two packages {{shortestpath}}
and {{spanning}}. So let's just close the issue and keep in mind the new approach for new
algorithm implementations :)

> Generic weight types and algorithms implementations based on wighted graphes
> ----------------------------------------------------------------------------
>                 Key: SANDBOX-356
>                 URL:
>             Project: Commons Sandbox
>          Issue Type: Improvement
>          Components: Graph
>            Reporter: Claudio Squarcella
>            Assignee: Simone Tripodi
>              Labels: generic, graph, shortestpath, type, weight
>         Attachments: GenericWeightTypeAlsoForAStar.patch, GenericWeightTypesAndUpdatedShortestPathImplementations.patch,
> Hello,
> with this issue I propose quite a major improvement to the current version of Apache
Commons Graph, aimed at introducing generic types for weights (edge weights, vertex weights,
etc) and decoupling related properties and operations using external classes. The proposed
changes reflect observations and proposals that have been evaluated on the dev mailing list,
particularly in the thread with title "On graph weight type(s)".
> A new top level package {{weight}} contains a hierarchy of interfaces representing different
"families" of weights with their properties and operations: {{Zero}}, {{Semigroup}}, {{Monoid}},
{{OrderedMonoid}}. These interfaces are meant to be specified as input by different algorithms
depending on the properties needed: e.g. some only require an ordering on the weights, some
apply operations, etc. A subpackage called {{primitive}} contains two implementations, {{DoubleWeight}}
and {{IntegerWeight}}, respectively wrapping properties and operations on weights of type
{{Double}} and {{Integer}}.
> In addition, some of the implementations in the package {{shortestpath}} have been updated
to take advantage of the new generic weight types. In particular each of the three classes
{{Dijkstra}}, {{BellmannFord}} and {{FloydWarshall}} now has two public methods: a generic
one (working with any kind of weight, provided an {{OrderedMonoid}}) and a "shortcut" for
weights of type {{Double}}, which is basically identical to the current signature. Other classes
in the package were subject to minor changes to support the improvements. As an exception,
{{AStar}} is still tied to {{Double}} weights for now: as a future step that could also use
generic weights (but it needs more thinking for the heuristics).
> Further, in order to handle generic weight types, I got rid of {{Double.POSITIVE_INFINITY}}
as a way to represent unreachability between two endpoints in a graph and replaced it with
related boolean methods.
> Finally, all the tests were updated for compatibility with the new signatures, and they
all run smoothly.
> I hope this patch meets the approval of other developers/users. I am available for discussion
and clarification.
> Ciao,
> Claudio

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