MULTIMODAL OPTIMIZATION MIKE PREUSS. Multimodal Optimization 1 2014-09-14 Mike Preuss 2014-09-14 Mike Preuss.
WHAT ARE WE DEALING WITH? Multimodal Optimization 2 2014-09-14 Mike Preuss.
SOME GENERAL NOTES more questions t han answers in Mult imodal Opt imizat ion (MMO) field not well defined basic t erms not well defined similarit ies t o Mult i-Obj ect ive Opt imizat ion (MOO) huge bulk of lit erat ure Evolut ionary Comput at ion (EC) people focus on EC approaches consider t his as “ request for comment s” suggest ions for fut ure work appreciated bet t er: you st art t o do int erest ing MMO st uff Multimodal Optimization 3 2014-09-14 Mike Preuss.
OUTLINE why mult imodal opt imizat ion (MMO)? abst ract ion: niching and a model EA different scenarios and t heir measures t axonomy of met hods result s/ compet it ion/ soft ware t he fut ure Multimodal Optimization 4 2014-09-14 Mike Preuss.
why multimodal optimization (MMO)? Multimodal Optimization 5 2014-09-14 Mike Preuss.
ATTEMPTING A DEFINITION In a mult imodal opt imizat ion t ask, t he main purpose is t o f ind mult iple opt imal solut ions (global and local), so t hat t he user can have a bet t er knowledge about dif f erent opt imal solut ions in t he search space and as and when needed, t he current solut ion may be swit ched t o anot her suit able opt imum solut ion. Deb, Saha: Multimodal Optimization Using a Bi-Objective Evolutionary Algorithm, ECJ, 2012 main t asks: alt ernat ive solut ions problem knowledge Multimodal Optimization 6 2014-09-14 Mike Preuss.
SEPARATION PROCESS OPTIMIZATION REAL-WORLD EXAMPLES many solutions invalid, looks like Rastrigin problem Henrich, Bouvy, Kausch, Lucas, Preuss, Rudolph, Roosen. Economic optimization of non- sharp separation sequences by means of evolutionary algorithms. In Comput ers & Chemical Engineering , Volume 32, Issue 7, pp. 1411-1432. Elsevier, 2008. Multimodal Optimization 8 2014-09-14 Mike Preuss.
LINEAR-JET OPTIMIZATION REAL-WORLD EXAMPLES Rudolph, Preuss, Quadflieg. Two-layered surrogate modeling for tuning metaheuristics. In ENBIS / EMS E Conference Design and Analysis of Comput er Experiment s, 2009 Multimodal Optimization 9 2014-09-14 Mike Preuss.
CAMERA POSITIONING REAL-WORLD EXAMPLES Preuss, Burelli, Y annakakis. Diversified Virtual Camera Composition. In EvoApplications 2012, pp. 265-274. S pringer, 2012 Multimodal Optimization 10 2014-09-14 Mike Preuss.
MAIN RESEARCH QUESTIONS in which sit uat ions are MMO met hods act ually bet t er t han “ usual” EC opt imizat ion algorit hms? problems performance measures ext ernal condit ions, e.g. runt ime among different MMO met hods, which one shall we choose? what are t he limit s for furt her improvement ? assumption : successful MMO needs dist ribut ion of solut ions int o different basins of at t raction, t his resembles t he niching idea Multimodal Optimization 11 2014-09-14 Mike Preuss.
abstraction: niching and a model EA Multimodal Optimization 12 2014-09-14 Mike Preuss.
NICHING “ Niching in EAs is a t wo-st ep procedure t hat a) concurrent ly or subsequent ly dist ribut es individuals ont o dist inct basins of at t ract ion and b) facilit at es approximat ion of t he corresponding (local) opt imizers.” (Preuss, BIOMA 2006) Multimodal Optimization 13 2014-09-14 Mike Preuss.
NICHING/SPECIATION Multimodal Optimization 14 2014-09-14 Mike Preuss.
OPTIMIZATION PHASES Redundancy for repeat ed local search and b basins (Beasley 1993) : Multimodal Optimization 15 2014-09-14 Mike Preuss.
BASIN IDENTIFICATION/BASIN RECOGNITION Multimodal Optimization 16 2014-09-14 Mike Preuss.
BASIN IDENTIFICATION Multimodal Optimization 17 2014-09-14 Mike Preuss.
BASIN RECOGNITION Multimodal Optimization 18 2014-09-14 Mike Preuss.
PROBABILISTIC IDENTIFICATION/RECOGNITION basin ident ificat ion relies on det ect ing if t wo solut ions are locat ed in t he same basin (binary) basin recognit ion: is t he basin of a cert ain solut ion known? no perfect knowledge: probabilist ic approach t hese express sensit ivit y (we do not have informat ion about unvisit ed areas) Multimodal Optimization 19 2014-09-14 Mike Preuss.
SIMULATION quest ion: how many local searches necessary t o find t he global opt imum (t 2), or or t o visit all basins at least once (t 3)? Multimodal Optimization 20 2014-09-14 Mike Preuss.
COUPON COLLECTOR‘S PROBLEM (CCP) given a set of 8 collect or’s cards, and we randomly get 3, how many it erat ions unt il we get one specific card? (2.67) or obt ain all exist ing cards? (6.58 it erat ions) Multimodal Optimization 21 2014-09-14 Mike Preuss.
EXACT RESULTS P(BI) = 1, P(BR) = 0 under t he assumpt ion of equal probabilit ies (for single cards/ basins), t his can be comput ed formula of (S tadj e. The collector’s problem with group drawings. Advances in Applied Probability, 22(4):866– 882, 1990): b = cards/ basins per drawing, c = number of cards/ basins n = desired element s of desired set , l = desired set size Multimodal Optimization 22 2014-09-14 Mike Preuss.
EXACT RESULTS Multimodal Optimization 23 2014-09-14 Mike Preuss.
THIS IS SHOCKING! under t he equal basin size assumpt ion, obt aining t he global opt imum (t 2) needs on average b local searches! so basin ident ificat ion does not make sense? but : what about basin recognit ion? equal basin sizes not realist ic we cannot know if we have reached t 2 sit uat ion changes if we want mult iple solut ions Multimodal Optimization 24 2014-09-14 Mike Preuss.
SUMMARIZING THE SIMPLE CASES we leave out perfect BR, no BI, seems unreasonable even under ideal circumst ances, not much gain for t 2 but BI/ BR help for t 3: rat ionale for mult imodal opt imizat ion more complex cases (unequal basin sizes, PBI/ PBR not 0 or 1) have to be simulat ed Multimodal Optimization 25 2014-09-14 Mike Preuss.
SIMULATION: EQUAL BASIN SIZES P(BI) = 0, P(BR) = 0 Multimodal Optimization 26 2014-09-14 Mike Preuss.
SIMULATION: EQUAL BASIN SIZES P(BI) = 0.5, P(BR) = 0 Multimodal Optimization 27 2014-09-14 Mike Preuss.
SIMULATION: EQUAL BASIN SIZES P(BI) = 1, P(BR) = 0 (t his is t he t heoret ically t ract able case, t he difference comes from inst ant st opping when reaching t 2) Multimodal Optimization 28 2014-09-14 Mike Preuss.
SIMULATION: EQUAL BASIN SIZES P(BI) = 0.5, P(BR) = 0.5 Multimodal Optimization 29 2014-09-14 Mike Preuss.
UNEQUAL BASIN SIZES? why should we care? because size differences grow exponent ially in dimensions 10D wit h 2:1 per dim makes a volume difference of 1024:1 however, basin ident ificat ion/ basin recognit ion may be very difficult wit h large size differences we simulat e abst ract 1:10 size difference Multimodal Optimization 30 2014-09-14 Mike Preuss.
SIMULATION: UNEQUAL BASIN SIZES P(BI) = 0, P(BR) = 0 Multimodal Optimization 31 2014-09-14 Mike Preuss.
SIMULATION: UNEQUAL BASIN SIZES P(BI) = 0.5, P(BR) = 0 Multimodal Optimization 32 2014-09-14 Mike Preuss.
SIMULATION: UNEQUAL BASIN SIZES P(BI) = 1, P(BR) = 0 Multimodal Optimization 33 2014-09-14 Mike Preuss.
SIMULATION: UNEQUAL BASIN SIZES P(BI) = 0.5, P(BR) = 0.5 Multimodal Optimization 34 2014-09-14 Mike Preuss.
MODEL EA FINDINGS t here are limit s t o possible improvement s for equal basin sizes, t2 cannot really be improved t 3 can be improved a lot for unequal basin sizes, t 2 and t 3 are improved by BI/ BR basin recognit ion (needs archive) is more import ant t han basin ident ificat ion Multimodal Optimization 35 2014-09-14 Mike Preuss.
different scenarios and their measures Multimodal Optimization 36 2014-09-14 Mike Preuss.
MULTIMODAL OPTIMIZATION SCENARIOS one-global: looking for t he global opt imum only all-global: find all preimages of t he global opt imum t he problems of t he CEC 2013 niching compet it ion belong here all-known: find all preimages of known opt ima, (local or global) good-subset : locat e a small subset of preimages of all opt ima t hat is well dist ribut ed over t he search space Multimodal Optimization 37 2014-09-14 Mike Preuss.
ONE-GLOBAL t he BBOB (black-box opt imizat ion benchmark) est ablished t he expect ed runt ime (ERT) MMO not really well suit ed t o one-global scenario t his could also be applied t o ot her scenarios, need t o redefine t arget s Multimodal Optimization 38 2014-09-14 Mike Preuss.
MEASURING PROCESS 2 main component s: subset select ion measuring Multimodal Optimization 39 2014-09-14 Mike Preuss.
MEASURES most ly used current ly in lit erat ure (also for CEC’ 2013): peak rat io (PR), but t his is problemat ic Multimodal Optimization 40 2014-09-14 Mike Preuss.
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