Hi Simo, I guess the 5 minutes to run example would be:
ShortestPathFunction.dijkstra .makeResult(graph, EdgeWeight.forWeightedEdge, Monotonic.sumDouble) .findShortestPath(source, target); I was assuming that there would be standard pallets of all the strategies available statically in the obvious places. Actually, now I see the code written out in full like that, I'd perhaps consider renaming makeResult to `calculate` or `prepare` or some other verb. Matthew On 23 December 2011 08:47, Simone Tripodi <simonetrip...@apache.org> wrote: > Hi Matthew! > > at a first looks it is really interesting, just give me the time to > digest because at the same time I had the feeling of a little > over-engineering activity, I am worried that "5 minutes to run" users > would find it not so immediate. > > Thanks for providing stuff to learn from! > All the best, > -Simo > > http://people.apache.org/~simonetripodi/ > http://simonetripodi.livejournal.com/ > http://twitter.com/simonetripodi > http://www.99soft.org/ > > > > On Thu, Dec 22, 2011 at 6:25 PM, Matthew Pocock > <turingatemyhams...@gmail.com> wrote: > > Hi, > > > > Just thought I'd throw something out here. My experience is that I often > > take the same graph (as in the exact same data, same objects) but at > > different times want to use different weights. So, rather than having > Edge > > extend Weighted<W>, I'd factor weights out into their own interface: > > > > /** > > * An edge weight function. > > * > > * note: perhaps this should more generally just be a Function1<A, B>, if > > we have such a thing handy. > > * > > * @tparam E edge type > > * @tparam W weight type > > */ > > public interface EdgeWeight<E, W> { > > public W getWeight(E: Edge); > > } > > > > /** > > * A combination of a monoid and comparator that satisfy monotinicity of > > the addition operation with respect to the comparator. > > * > > * ∀a: m.compare(m.zero, a) <= 0 > > * ∀a,b: m.compare(a, m.append(a, b)) <= 0 > > */ > > public interface Monotonic<W> extends Monoid<W>, Comparator<W> > > > > Also, some algorithms calculate all shortest paths at once, while others > > calculate them individually and independently. It's probably even > possible > > to calculate some lazily. So, the interfaces for shortest paths should > > decouple setting up a strategy for all shortest paths from an object that > > can be used to fetch a specific shortest path. > > > > /** > > * An algorithm for finding shortest paths between vertices of a graph, > > given some edge weighting function and > > * a well-behaved combinator for edges between connected vertices. > > */ > > public interface ShortestPathFunction<V extends Vertex, E extends > Edge<E>, > > G extends DirectedGraph<V, E>, W> { > > public ShortestPathResult<V, E, W> makeResult(G graph, EdgeWeight<E, W> > > weighting, Monotonic<W> combineWith); > > } > > > > /** > > * The shortest paths between vertices in a graph. > > */ > > public interface ShortestPathResult<V extends Vertex, E extends Edge<E>, > W> > > { > > public WeightedPath<V, E, W> findShortestPath(V source, V target); > > } > > > > How does that look? You can then have standard implementations of these > > things in some static utility class or a spring-friendly resource. The > > brute-force algorithms that compute all paths at once would do all the > work > > in makeResult() and simply store this in some state within the returned > > ShortestPathResult. Those that calculate individual pairs on the fly (or > > all shortest paths from some vertex) would capture state in makeResult() > > and perform the actual computation in findShortestPath(). > > > > Matthew > > > > On 22 December 2011 16:39, Claudio Squarcella <squar...@dia.uniroma3.it > >wrote: > > > >> Hi, > >> > >> > >> I highly appreciated the last contributions (thanks guys!) but I also > >>> agree on this point, so let's start from the end. > >>> I think that, no matter what underlying structure we come up with, the > >>> user should be able to specify e.g. a weighted edge with something like > >>> > >>> public class MyEdge implements Edge, Weighted<Double> { ... } > >>> > >>> and be able to immediately use it as an input for all the algorithms, > >>> without extra steps required. So the average user is happy, while > "graph > >>> geeks" can dig into advanced capabilities and forge their personalized > >>> weights :) > >>> I hope we all agree on this as a first step. Complexity comes after. > >>> > >>> I'll take my time as well to re-think. > >>> > >> > >> I did think and code a bit more. First of all please take a look at the > >> updated code: Weighted<W> is an interface (weight W can be any type) and > >> all the algorithms require edges to implement Weighted<Double> for now > -- > >> we did not break it that much ;) > >> > >> About the "HasProperty-vs-Property" question (as in Comparable vs > >> Comparator, MonoidElement vs Monoid, etc) I would go for the second one > >> only. That is, external classes handle all operations on weights. > Downside: > >> the # of method parameters would increase linearly with the number of > >> properties, but I can live with that (how many properties would weights > >> have anyway?). On the other hand we have a neat interface for each > >> property/class (Zero, Semigroup, Monoid, Ordering or Comparator, etc) > and > >> one clean, generic implementation for each algorithm. Dijkstra's > signature > >> becomes something like: > >> > >> public static <V extends Vertex, W, WE extends WeightedEdge<W>, G > extends > >> DirectedGraph<V, WE>> WeightedPath<V, WE, W> findShortestPath( G graph, > V > >> source, V target, Monoid<W> weightMonoid, Comparator<W> > weightComparator ) > >> > >> Scary uh? But wait, default implementations for Double, Integer, etc. > are > >> way easier. E.g. Dijkstra's shortcut for Double: > >> > >> public static <V extends Vertex, WE extends WeightedEdge<Double>, G > >> extends DirectedGraph<V, WE>> WeightedPath<V, WE, Double> > findShortestPath( > >> G graph, V source, V target ) > >> { > >> return findShortestPath(graph, source, target, new DoubleMonoid(), > new > >> DoubleComparator()); > >> } > >> > >> where DoubleMonoid and DoubleComparator are part of the library. > >> > >> > >> If you guys are fine with this, I'm ready to try and patch [graph] with > a > >> Christmas gift :) > >> Claudio > >> > >> > >> -- > >> Claudio Squarcella > >> PhD student at Roma Tre University > >> E-mail address: squar...@dia.uniroma3.it > >> Phone: +39-06-57333215 > >> Fax: +39-06-57333612 > >> http://www.dia.uniroma3.it/~**squarcel< > http://www.dia.uniroma3.it/~squarcel> > >> > >> > >> > ------------------------------**------------------------------**--------- > >> To unsubscribe, e-mail: dev-unsubscribe@commons.**apache.org< > dev-unsubscr...@commons.apache.org> > >> For additional commands, e-mail: dev-h...@commons.apache.org > >> > >> > > > > > > -- > > Dr Matthew Pocock > > Integrative Bioinformatics Group, School of Computing Science, Newcastle > > University > > mailto: turingatemyhams...@gmail.com > > gchat: turingatemyhams...@gmail.com > > msn: matthew_poc...@yahoo.co.uk > > irc.freenode.net: drdozer > > skype: matthew.pocock > > tel: (0191) 2566550 > > mob: +447535664143 > > --------------------------------------------------------------------- > To unsubscribe, e-mail: dev-unsubscr...@commons.apache.org > For additional commands, e-mail: dev-h...@commons.apache.org > > -- Dr Matthew Pocock Integrative Bioinformatics Group, School of Computing Science, Newcastle University mailto: turingatemyhams...@gmail.com gchat: turingatemyhams...@gmail.com msn: matthew_poc...@yahoo.co.uk irc.freenode.net: drdozer skype: matthew.pocock tel: (0191) 2566550 mob: +447535664143
