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Las cosas que voy a investigar aquí.

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  1. 1. Combining several things (new and improved)Pablo García Sánchez - University of Granada(but now in Vrije Universiteit Amsterdam)
  2. 2. Outline• What I am investigating in Granada• EvAg and MultiKulti• Evolutionary Robotics • μ+1 online • μ+1 online Vs. EvAg (Robert-Jan) • Global Parent Selector or HybridEvag (Berend-Luis) • μ+EvAg • EDEA (?)• Some ideas about MultiKulti + EvAg
  4. 4. My Work• SOAP• BPEL But in my spare time...• WSDL - XSLT Evolution• JBI - Service Oriented Evolutionary Algorithms• OSGi• XPATH• XSLT• OMG!• WTF?
  5. 5. EvAg
  6. 6. EvAg Pseudo-codeSactual←Initialize Agentloop Sols←LocalSelection(NeighborsEvAg) Snew←Recombination(Sols,Pc) Snew’←Mutation(Snew,Pm) Evaluate(Snew’) if Snew better than Sactual then Sactual←Snew’ end ifend loop
  7. 7. Newscast• Is the population structure used by Juanlu• It is the cache of Neighbours. Each entry has: • Reference to the node • Time-stamp of the entry creation • Agent identifier • Specific application data (?)• Every cycle EvAgi initiates cache exchange• Selects randomly a neighbour EvAgj of its cache• Aggregation of caches. JuanLu uses: • the c freshest items. i and j share the same cache
  8. 8. Newscast pseudocode• Active mode: loop EvAgj←Uniformily random selected node from Cachei Send Cachei to EvAgj Receive Cachej from EvAgj Cachei←Aggregate(Cachei,Cachej) endloop• Pasive mode loop Wait Cachej from EvAgj Receive Cachei to EvAgj Cachei←Aggregate(Cachei,Cachej) endloop
  9. 9. EvAg (Results)• Island model: results are sensitive to the number of islands→vulnerability in dynamic environments (like P2P)• Outperforms tuned GAs• Less links (no panmictic)• C newest items of the both caches are kept (TTL). c<<N
  10. 10. MultiKulti
  11. 11. MultiKulti (results)• MK policies outperform the classic policies (send the best or the random, that never reach the optimum)• Specially with low number of individuals but larger number of islands• It is (a bit) better to send the consensus as a representation• It is better to send the most different of an elite as response• Problem: difficult to caracterize a population using a string
  12. 12. Evolutionary Robotics• Taxonomy:• When? On-Line vs. off-line• Where? On-board vs. Off-board• How? Encapsulated vs. distributed (and hybrid!)
  13. 13. μ+1 online• Local population• No migration• Mantains the μ fittest ones• Sometimes re-evaluates
  14. 14. EvAgRobot (Robert-Jan - EA2011 October)• Added genotype exchanges using newscast. Difference: last active solutions in caches, not only connections
  15. 15. Comparison μ+1 vs. EvAg• Sensibility to parameter tuning: μ+1 is reliable. EvAg is reliable when the number of robots increases• EvAg Panmictic vs EvAg newscast: the newscast performance is worst, but in a panmictic case a large number of peers could be difficult to manage in real- case scenarios• Doubt: in newscast is it the topology fixed? Only active solutions are exchanged among neighbours or also the connections? (so a peer can exchange its new cache to new neighbours)
  16. 16. HybridEvag (Berend-Luis Approach)
  17. 17. Source code: PopulationStructure.cpp PopulationMember pop; //HivemindInstance or NewscastInstance Controller[] activeSolutions //although localPopulation is a better name Controller getNextCandidate(){ currentTime++ pop->update(currentTime) if(reevaluate) return c else... parentA and B = BinaryTournament(pop) crossover, mutation... return new candidate } SetFitness(Controller candidate, double fitness){ if (reevaluated) candidate->fitness = (fitness + oldfitness)/2 else replace the worst of activeSolutions if candidate is better if (accepted || reevaluated) pop->setNews(acceptedCandidate, pos, currentTime) }
  18. 18. HiveMind.cpp static vector <vector <newsitems>> allItems; update() // not implemented setNews(Controller c, pos, currenttime){ stores the c in the static (shared) vector (of accepted solutions) }
  19. 19. NewscastInstance.cpp update(int currentTime){ delete older than “currentTime - itemTTL” from myCache neighbour = select random peer of myCache otherCache = neighbour->exchange(myCache, currentTime) //caches CLONING the objects (no shared data) } setNews(Candidate c, int currentTime){ stores the last accepted candidate (not the best!) in the cache with my timestamp } BEFORE SEND: 1) Remove older items of my cache 2) Remove duplicates AFTER RECEIVE: 1) Mantain the cacheSize freshest solution of each node. DOUBT: this timestamp is different!
  20. 20. μ+EvAg• Combining previous approaches in a parameter-based algorithm with two parameters: •μ • rangeRate (parent selection global or local) (Note: no information about newscast, or TTL, is given in the Robert’s thesis)• Change from one to another easily• Allows a whole parameter tuning
  21. 21. EDEA (Georgios)• One solution per robot• Two kinds of mating for each robot: • Eagerly: sends genome to the partner without asking • Selectively: Binary Tournament from other peers and accepted if fitness is quite good enough: if(otherF/myF*Sc <prob()) • In GECCO‘11→panmictic→Random from all robots (experiments with an small set)
  22. 22. DifferencesAlgorithm Population Migration Ellitism Type μ+1 Local population None Replace the worst Centralized EvAg 1 Solution Selection from actual Replace if better Distributed neighbors (Juanlu) EvAg 1 Active Solution + Cache swapping Replace the active Distributed?? Cache solution if better (Robert) Global (panmictic) Replace the worst (localHybridEvAg Local population parent selection survivor selection) Hybrid Previous algorithms combined using two parameters: μ (population) and μ+Evag rangeRate (parent selection global or local) Hybrid Sends eagerly, receives New solution can be EDEA One solution selectively (panmictic in worst Distributed GECCO’11)
  23. 23. Differences Few Local genomes Many Few Local genomes Many Never mU+1 Never Genome Genome exchange exchange Always Always EvAg Few Local genomes Many Few Local genomes Many Never Never Genome Genome exchange exchange mu+EvAg Always Hybrid Evag Always
  24. 24. Differences (Population)• μ+1: Local population of μ individuals• Juanlu EvAg: 1 Best Solution + Selection from the neighbours. Topology: newscast• Robert EvAg: 1 Active Solution + cache of other (less diverssity)→Finally, behaves like a whole population• HybridEvag: local population becomes global population (panmictic) for parent selector (more diversity: not only active solutions are used) and local population for replacement• All algorithms are special cases of μ+EvAg (Robert thesis)→(few or many local genomes AND never or always genome exchange from the global pool)
  25. 25. Differences (Parent Selection)• μ+1: from the local population• JuanLu EvAg: selected from current neighbours (open)• Robert EvAg: binary tournament of active solutions (obtained from the cache)• Hybrid EvAg Approach: binary tournament of ALL populations (not the active ones)
  26. 26. Differences (Ellitism)• mu+1: Replace the worst in the local population• EvAg (Robert and Juanlu): Replace the actual solution if the new is better, otherwise is dropped• HybridEvag: replaces the worst individual if better
  27. 27. Ideas (I)• Distributed Islands with MultiKulti but without EvAg (using local populations) • Which structure is better? (ring, P2P, grid, random...) • Which migration policy is better? (best, elite...) • Compare: • All islands with the tuned parameter settings (homogeneous) • All island with random parameter settings (heterogeneous) • What about robot failures?
  28. 28. Ideas (II) Combining EvAg and Multikulti?• Combine MultiKulti with EvAg (could be difficult) • EvAg: keeps one individual + exchange of several • MultiKulti: keeps several individuals + exchange of one• So, using EvAg... • Binary Tournaments from the caches but giving priority to the most different instead the most fitted? • Sending the most different individuals in cache exchange/aggregating ordered by differences, instead timestamp • Problems: • Lost of information (is not the EvAg philosophy) • Caches not too large