Hi Matthew! I think that your idea is great as a foundation for implementing algorithms but I would not allow users use that APIs to resolve known problems, unless they want to implement their own solutions or contribute back to [graph] missing algorithms.
Usually algorithms (like Dijkstra) already have clear enunciates and steps are known, so we could safety expose 1 APIs that hide all that details to clients wrapping your proposals. WDYT? Thanks again!!! -Simo http://people.apache.org/~simonetripodi/ http://simonetripodi.livejournal.com/ http://twitter.com/simonetripodi http://www.99soft.org/ On Fri, Dec 23, 2011 at 10:44 AM, Matthew Pocock <turingatemyhams...@gmail.com> wrote: > 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 --------------------------------------------------------------------- To unsubscribe, e-mail: dev-unsubscr...@commons.apache.org For additional commands, e-mail: dev-h...@commons.apache.org
