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Metod Neldera Mida metod simpleksnogo spusku metod amebi abo politopnij metod ye populyarnim chiselnim metodom sho vikoristovuyetsya dlya poshuku minimumu abo maksimumu cilovoyi funkciyi v bagatovimirnomu prostori Ce metod pryamogo poshuku na osnovi porivnyannya funkcij i chasto zastosovuyetsya do nelinijnih zadach optimizaciyi dlya yakih pohidni mozhut ne buti vidomi Prote pidhid Neldera Mida ye evristichnim metodom poshuku yakij mozhe shoditisya do nestacionarnih tochok 1 stikayuchis z problemami yaki mozhut buti rozv yazani alternativnimi metodami 2 Poslidovni simpleksi v funkciyi Neldera Mida dlya Funkciyi Rozenbroka vgori ta funkciyi Himmelblau en vnizu Minimalnij poshuk Neldera Mida funkciyi Siminesku Uporyadkuvannya simpleksnih vershin za yih znachennyam prichomu 1 maye najmenshe najkrashe znachennya Ne slid plutati z simpleks metodom Danciga dlya zadachi linijnoyi optimizaciyi Metod Neldera Mida zaproponuvali Dzhon Nelder en i Rodzher Mid en u 1965 roci 3 yak variant modifikaciyi metodu Spendli 4 Zmist 1 Zagalnij opis 2 Odin z mozhlivih variantiv algoritmu Neldera Mida 3 Pochatkovij simpleks 4 Zavershennya 5 Div takozh 6 Primitki 7 Literatura 8 PosilannyaZagalnij opis RedaguvatiU metodi vikoristovuyetsya ponyattya simpleksa yakij ye specialnim politopom n 1 vershin v n vimirah Prikladi simpleksiv vklyuchayut vidrizok na liniyi trikutnik na ploshini tetraedr u trivimirnomu prostori tosho Metod aproksimuye lokalnij optimum zadachi z n zminnimi koli cilova funkciya zminyuyetsya plavno i ye unimodalnoyu Tipovi realizaciyi minimizuyut funkciyi maksimum f x displaystyle f mathbf x nbsp mozhna znajti za dopomogoyu minimizaciyi f x displaystyle f mathbf x nbsp Napriklad inzhener pidvisnogo mosta povinen vibrati yakoyu maye buti tovshina kozhnoyi stijki kabelyu i prichalu Ci elementi vzayemozalezhni ale nelegko vizualizuvati vpliv zmini stanu bud yakogo konkretnogo elementa Modelyuvannya takih skladnih konstrukcij chasto ye nadzvichajno obchislyuvalno skladnim dlya zapusku mozhlivo tomu sho voni potrebuyut bilshe godin na vikonannya Metod Neldera Mida vimagaye u vihidnomu varianti ne bilshe dvoh ocinok na iteraciyu za vinyatkom opisanoyi piznishe operaciyi styaguvannya sho ye perevagoyu porivnyano z inshimi metodami optimizaciyi pryamogo poshuku Odnak zagalna kilkist iteracij proponovanogo optimumu mozhe buti velikoyu Metod u n vimirah zberigaye nabir n 1 testovih tochok roztashovanih yak simpleks Potim vin ekstrapolyuye povedinku cilovoyi funkciyi vimiryanoyi v kozhnij testovij tochci shob znajti novu testovu tochku i zaminiti odnu zi starih testovih tochok na novu ce skladaye osnovnij cikl metodu Najprostishij pidhid polyagaye v tomu shob zaminiti najgirshu tochku tochkoyu vidbitoyu cherez centroyid reshti n tochok Yaksho cya tochka krasha nizh krasha potochna tochka to mi mozhemo sprobuvati roztyagnuti eksponencialno po cij liniyi Z inshogo boku yaksho cya nova tochka ne ye nabagato krashoyu nizh poperednya velichina to mi perehodimo do nastupnogo znachennya tomu mi styaguyemo simpleks u krashu tochku Intuyitivne poyasnennya algoritmu predstavleno v 5 Metod spadannya simpleksa teper vikonuye ryad krokiv bilshist krokiv prosto peremishuye tochku simpleksa de funkciya nabuvaye najbilshogo znachennya najvisha tochka cherez protilezhnu storonu simpleksa do nizhnoyi tochki Ci kroki nazivayutsya vidbittyami i voni pobudovani dlya zberezhennya obsyagu simpleksa i otzhe zberezhennya jogo nevirodzhenosti Koli ce mozhe zrobiti metod rozshiryuye simpleks v tomu chi inshomu napryamku shob zrobiti veliki kroki Koli vin dosyagaye najnizhchoyi tochki metod pochinaye ruhatisya v poperechnomu napryamku i namagayetsya prosunutisya vzdovzh liniyi spadannya U situaciyi koli simpleks namagayetsya projti kriz golku to vin stiskayetsya u vsih napryamkah styaguyuchi sebe navkolo svoyeyi najnizhchoyi krashoyi tochki Na vidminu vid suchasnih metodiv optimizaciyi evristika Neldera Mida mozhe shoditisya do nestacionarnoyi tochki yaksho zadacha ne zadovolnyaye silnishim umovam nizh ce neobhidno dlya suchasnih metodiv 1 Suchasni polipshennya evristiki Neldera Mid vidomi z 1979 roku 2 Isnuye bagato variacij zalezhno vid faktichnoyi prirodi rozv yazuvanoyi problemi Zvichajnij variant vikoristovuye nevelikij simpleks postijnogo rozmiru yakij priblizno vidpovidaye napryamku gradiyenta yakij daye najshvidshij spusk Vizualizujte malenkij trikutnik na karti visoti sho perevertayetsya po dolini do najnizhchoyi tochki na miscevosti Cej metod takozh vidomij yak gnuchkij metod bagatogrannika Ce odnak maye tendenciyu do poganogo vikonannya metodu opisanogo v cij statti oskilki vin robit neveliki nepotribni kroki v oblastyah sho predstavlyayut malij interes Odin z mozhlivih variantiv algoritmu Neldera Mida Redaguvati Ce blizko do proceduri yaka opisana v originalnij statti Neldera Mida nbsp Metod Neldera Mida zastosovanij do funkciyi RozenbrokaMi namagayemosya minimizuvati funkciyu f x displaystyle f mathbf x nbsp de x R n displaystyle mathbf x in mathbb R n nbsp Nashi potochni kontrolni tochki ye x 1 x n 1 displaystyle mathbf x 1 ldots mathbf x n 1 nbsp 1 Poryadok vidpovidno do znachen u vershinah f x 1 f x 2 f x n 1 displaystyle f mathbf x 1 leq f mathbf x 2 leq cdots leq f mathbf x n 1 nbsp Perevirte chi slid zupiniti metod Divitsya Zavershennya nizhche Inodi nepravilno nazivayut zbizhnistyu 2 Rozrahujte x o displaystyle mathbf x o nbsp centroyid vsih tochok okrim x n 1 displaystyle mathbf x n 1 nbsp 3 Vidbittya Obchisliti simetrichno viddzerkalenu abo yak budemo kazati dali vidbitu tochku x r x o a x o x n 1 displaystyle mathbf x r mathbf x o alpha mathbf x o mathbf x n 1 nbsp z a gt 0 displaystyle alpha gt 0 nbsp Yaksho vidbita krasha nizh druga najgirsha ale ne krasha nizh krasha tobto f x 1 f x r lt f x n displaystyle f mathbf x 1 leq f mathbf x r lt f mathbf x n nbsp todi otrimajte novij simpleks zaminivshi najgirshu tochku x n 1 displaystyle mathbf x n 1 nbsp simetrichno viddzerkalenoyu tochkoyu x r displaystyle mathbf x r nbsp i perejdit do kroku 1 dd 4 Rozshirennya Yaksho vidbita tochka ye najkrashoyu tochkoyu dosi f x r lt f x 1 displaystyle f mathbf x r lt f mathbf x 1 nbsp potim obchisliti rozshirenu tochku x e x o g x r x o displaystyle mathbf x e mathbf x o gamma mathbf x r mathbf x o nbsp z g gt 1 displaystyle gamma gt 1 nbsp Yaksho rozshirena tochka krashe vidbitoyi tochki f x e lt f x r displaystyle f mathbf x e lt f mathbf x r nbsp otrimuyemo novij simpleks zaminyuyuchi najgirshu tochku x n 1 displaystyle mathbf x n 1 nbsp rozshirenoyu tochkoyu x e displaystyle mathbf x e nbsp i perejdit do kroku 1 inakshe otrimuyemo novij simpleks zaminyuyuchi najgirshu tochku x n 1 displaystyle mathbf x n 1 nbsp vidbitoyu tochkoyu x r displaystyle mathbf x r nbsp i perejdit do kroku 1 dd dd 5 Skorochennya Tut napevno f x r f x n displaystyle f mathbf x r geq f mathbf x n nbsp Zauvazhte sho x n displaystyle mathbf x n nbsp ce druge chi nastupne pislya najvishogo Obchisliti kontraktnu tochku do x c x o r x n 1 x o displaystyle mathbf x c mathbf x o rho mathbf x n 1 mathbf x o nbsp z 0 lt r 0 5 displaystyle 0 lt rho leq 0 5 nbsp Yaksho kontraktna tochka krasha nizh najgirsha tochka tobto f x c lt f x n 1 displaystyle f mathbf x c lt f mathbf x n 1 nbsp potim otrimuyut novij simpleks shlyahom zamini najgirshoyi tochki x n 1 displaystyle mathbf x n 1 nbsp na kontraktnu tochku x c displaystyle mathbf x c nbsp i perehodyat do kroku 1 dd 6 Styaguvannya Zaminit vsi tochki krim krashih x 1 displaystyle mathbf x 1 nbsp z x i x 1 s x i x 1 displaystyle mathbf x i mathbf x 1 sigma mathbf x i mathbf x 1 nbsp i perejdit do kroku 1 Primitka a displaystyle alpha nbsp g displaystyle gamma nbsp r displaystyle rho nbsp i s displaystyle sigma nbsp vidpovidno koeficiyenti vidbittya rozshirennya skorochennya i styaguvannya Standartnimi znachennyami a 1 displaystyle alpha 1 nbsp g 2 displaystyle gamma 2 nbsp r 1 2 displaystyle rho 1 2 nbsp ta s 1 2 displaystyle sigma 1 2 nbsp Dlya vidbittya oskilki x n 1 displaystyle mathbf x n 1 nbsp ce vershina z vishoyu asocijovanoyu velichinoyu sered vershin mozhlivo bude menshe znachennya pri vidbitti x n 1 displaystyle mathbf x n 1 nbsp u bik protilezhnij storoni utvorenij vsima vershinami x i displaystyle mathbf x i nbsp krim x n 1 displaystyle mathbf x n 1 nbsp Dlya rozshirennya yaksho tochka vidbittya x r displaystyle mathbf x r nbsp i ye novim minimumom uzdovzh vershin mozhna rozrahovuvati znajti shukani znachennya vzdovzh napryamku vid x o displaystyle mathbf x o nbsp do x r displaystyle mathbf x r nbsp Sho stosuyetsya skorochennya yaksho f x r gt f x n displaystyle f mathbf x r gt f mathbf x n nbsp to mozhna ochikuvati sho krashe znachennya bude vseredini simpleksa utvorenogo vsima vershinami x i displaystyle mathbf x i nbsp Nareshti styaguvannya obroblyaye ridkisnij vipadok koli skorochennya vid najbilshoyi tochki zbilshuye f displaystyle f nbsp sho ne mozhe trapitis dosit blizko do nesingulyarnogo minimumu U comu vipadku mi skorochuyemo u bik najnizhchoyi tochki v ochikuvanni znajti prostishu landshaft Prote Nesh zaznachaye sho arifmetika zi skinchennoyu tochnistyu inodi ne mozhe faktichno styagnuti simpleks i vikonati perevirku togo sho rozmir naspravdi zmenshivsya 6 Pochatkovij simpleks RedaguvatiPochatkovij simpleks vazhlivij Dijsno zanadto malij pochatkovij simpleks mozhe prizvesti do lokalnih poshukiv otzhe metod mozhe legshe zupinitisya Otzhe cej simpleks povinen zalezhati vid prirodi problemi A prote originalna stattya zaproponuvala simpleks de dayetsya pochatkova tochka x 1 displaystyle mathbf x 1 nbsp a inshi generuyutsya z fiksovanim krokom po kozhnomu vimiru po cherzi Takim chinom metod chutlivij do masshtabuvannya zminnih yaki skladayut x displaystyle mathbf x nbsp Zavershennya RedaguvatiKriteriyi neobhidni dlya rozrivu iteracijnogo ciklu Nelder i Mid vikoristovuvali zrazkove standartne vidhilennya znachen funkcij potochnogo simpleksa Yaksho voni opuskayutsya nizhche pevnih obmezhen to cikl zupinyayetsya i najnizhcha tochka v simpleksi vidayetsya yak zaproponovanij optimum Zauvazhimo sho duzhe ploska funkciya mozhe mati majzhe odnakovi znachennya funkcij nad velikim domenom tak sho rishennya bude chutlivim do obmezhen Nesh 6 dodaye test na usadku yak she odin kriterij pererivannya roboti Zauvazhte sho programi pripinyayutsya todi yak iteraciyi mozhut shoditisya Div takozh RedaguvatiMetod pryamogo poshuku COBYLA en NEWUOA en LINCOA en Nelinijnij spoluchenij gradiyentnij metod en Algoritm Levenberga Markvardta Brojden Fletcher Goldfarb Shano abo BFGS metod Diferencialna evolyuciya Metod Guka Dzhivsa CMA ESPrimitki Redaguvati a b Powell Michael J D 1973 On Search Directions for Minimization Algorithms Mathematical Programming 4 193 201 doi 10 1007 bf01584660 McKinnon K I M 1999 Convergence of the Nelder Mead simplex method to a non stationary point SIAM Journal on Optimization 9 148 158 doi 10 1137 S1052623496303482 Proignorovano nevidomij parametr citeseerx dovidka algorithm summary online a b Yu Wen Ci 1979 Positive basis and a class of direct search techniques Scientia Sinica Zhongguo Kexue 53 68 Yu Wen Ci 1979 The convergent property of the simplex evolutionary technique Scientia Sinica Zhongguo Kexue 69 77 Kolda Tamara G Lewis Robert Michael Torczon Virginia 2003 Optimization by direct search new perspectives on some classical and modern methods SIAM Rev 45 3 385 482 doi 10 1137 S003614450242889 Proignorovano nevidomij parametr citeseerx dovidka Lewis Robert Michael Shepherd Anne Torczon Virginia 2007 Implementing generating set search methods for linearly constrained minimization SIAM J Sci Comput 29 6 2507 2530 doi 10 1137 050635432 Proignorovano nevidomij parametr citeseerx dovidka Nelder John A R Mead 1965 A simplex method for function minimization Computer Journal 7 4 308 313 doi 10 1093 comjnl 7 4 308 Spendley W Hext GR Himsworth FR 1962 Sequential Application of Simplex Designs in Optimisation and Evolutionary Operation Technometrics 4 4 441 461 doi 10 1080 00401706 1962 10490033 Press WH Teukolsky SA Vetterling WT Flannery BP 2007 Section 10 5 Downhill Simplex Method in Multidimensions Numerical Recipes The Art of Scientific Computing vid 3rd New York Cambridge University Press ISBN 978 0 521 88068 8 a b Nash JC 1979 Compact Numerical Methods Linear Algebra and Function Minimisation Bristol Adam Hilger ISBN 978 0 85274 330 0 Literatura RedaguvatiAvriel Mordecai 2003 Nonlinear Programming Analysis and Methods Dover Publishing ISBN 978 0 486 43227 4 Coope I D Price C J 2002 Positive Bases in Numerical Optimization Computational Optimization amp Applications 21 2 169 176 doi 10 1023 A 1013760716801 Gill Philip E Murray Walter Wright Margaret H 1981 Methods for Multivariate Non Smooth Functions Practical Optimization New York Academic Press s 93 96 ISBN 978 0 12 283950 4 Kowalik J Osborne M R 1968 Methods for Unconstrained Optimization Problems New York Elsevier s 24 27 ISBN 0 444 00041 0 Swann W H 1972 Direct Search Methods U Murray W Numerical Methods for Unconstrained Optimization New York Academic Press s 13 28 ISBN 978 0 12 512250 4 Posilannya RedaguvatiNelder Mead Simplex Method Nelder Mead Downhill Simplex explanation and visualization with the Rosenbrock banana function John Burkardt Nelder Mead code in Matlab note that a variation of the Nelder Mead method is also implemented by the Matlab function fminsearch nelder mead A Python implementation of the Nelder Mead method SOVA 1 0 freeware Simplex Optimization for Various Applications 1 HillStormer a practical tool for nonlinear multivariate and linear constrained Simplex Optimization by Nelder Mead Otrimano z https uk wikipedia org w index php title Metod Neldera Mida amp oldid 40543906