Genet i cAl gor i t hms 1. I nt r oduct i on Char l esDar wi ns t at edt het heor yofnat ur alev ol ut i oni nt heor i gi nofs pec i es .Ov er s ev er algener at i ons ,bi ol ogi c alor gani s msev ol v ebas edont hepr i nc i pl eofnat ur al s el ec t i on“ s ur v i v aloft hef i t t es t ”t or eac hc er t ai nr emar kabl et as ks . I n nat ur e,an i ndi v i duali n popul at i on c ompet es wi t h eac h ot herf orv i r t ual r es our c esl i kef ood,s hel t erand s o on.Al s oi nt hes ames pec i es ,i ndi v i dual s c ompet et oat t r ac tmat esf orr epr oduc t i on. Duet ot hi ss el ec t i on,poor l yper f or mi ngi ndi v i dual shav el es sc hanc et os ur v i v e, andt hemos tadapt edor“ f i t ”i ndi v i dual spr oduc ear el at i v el yl ar genumberof of f s pr i ng’ s .I tc anal s obenot edt hatdur i ngr epr oduc t i on,ar ec ombi nat i onoft he good c har ac t er i s t i c sofeac h anc es t orc an pr oduc e“ bes tf i t ”of f s pr i ng whos e f i t nes si sgr eat ert hant hatofapar ent .Af t eraf ew gener at i ons ,s pec i esev ol v e s pont aneous l yt obec omemor eandmor eadapt edt ot hei renv i r onment . I n 1975,Hol l and dev el oped t hi si deai n hi sbook“ Adapt at i on i n nat ur aland ar t i f i c i als y s t ems ” .Hedes c r i bedhowt oappl yt hepr i nc i pl esofnat ur alev ol ut i ont o opt i mi z at i onpr obl emsandbui l tt hef i r s tGenet i cAl gor i t hms .Hol l and’ st heor yhas beenf ur t herdev el opedandnowGenet i cAl gor i t hms( GAs )s t andupasapower f ul t oolf ors ol v i ngs ear c handopt i mi z at i onpr obl ems .Genet i cal gor i t hmsar ebas ed ont hepr i nc i pl eofgenet i c sandev ol ut i on. Thepowerofmat hemat i c sl i esi nt ec hnol ogyt r ans f er :t her eex i s tc er t ai nmodel s andmet hods ,whi c hdes c r i bemanydi f f er entphenomenaands ol v ewi dev ar i et yof pr obl ems .GAsar eanex ampl eofmat hemat i c alt ec hnol ogyt r ans f er :bys i mul at i ng ev ol ut i ononec ans ol v eopt i mi z at i onpr obl emsf r om av ar i et yofs our c es .Today , GAsar eus edt or es ol v ec ompl i c at edopt i mi z at i onpr obl ems ,l i ke,t i met abl i ng,j ob s hops c hedul i ng, gamespl ay i ng. 2.ASi mpl eGenet i cAl gor i t hm Anal gor i t hm i sas er i esofs t epsf ors ol v i ngapr obl em.Agenet i cal gor i t hm i sa pr obl em s ol v i ngmet hodt hatus esgenet i c sasi t smodelofpr obl em s ol v i ng.I t ’ sa s ear c ht ec hni que t of i nd appr ox i mat es ol ut i ons t o opt i mi z at i on and s ear c h pr obl ems . Bas i c al l y ,anopt i mi z at i onpr obl em l ooksr eal l ys i mpl e. GA handl esa popul at i on ofpos s i bl es ol ut i ons .Eac hs ol ut i on i sr epr es ent ed t hr oughac hr omos ome,whi c hi sj us tanabs t r ac tr epr es ent at i on.Codi ngal lt he pos s i bl es ol ut i onsi nt oac hr omos omei st hef i r s tpar t ,butc er t ai nl ynott hemos t s t r ai ght f or war doneofaGenet i cAl gor i t hm.As etofr epr oduc t i onoper at or shast o be det er mi ned, t oo. Repr oduc t i on oper at or s ar e appl i ed di r ec t l y on t he c hr omos omes ,and ar e us ed t o per f or m mut at i ons and r ec ombi nat i on ov er s ol ut i onsoft hepr obl em.Appr opr i at er epr es ent at i onandr epr oduc t i onoper at or s ar er eal l ys omet hi ng det er mi nant ,as t he behav i oroft he GA i s ex t r emel y dependantoni t .Fr equent l y ,i tc anbeex t r emel ydi f f i c ul tt of i ndar epr es ent at i on, whi c hr es pec t st hes t r uc t ur eoft hes ear c hs pac eandr epr oduc t i onoper at or s , whi c har ec oher entandr el ev antac c or di ngt ot hepr oper t i esoft hepr obl ems . Sel ec t i oni ss uppos edt obeabl et oc ompar eeac hi ndi v i duali nt hepopul at i on. Sel ec t i oni sdonebyus i ngaf i t nes sf unc t i on.Eac hc hr omos omehasanas s oc i at ed v al uec or r es pondi ngt ot hef i t nes soft hes ol ut i oni tr epr es ent s .Thef i t nes ss houl d c or r es pondt oanev al uat i onofhow goodt hec andi dat es ol ut i oni s .Theopt i mal s ol ut i oni st heone,whi c hmax i mi z est hef i t nes sf unc t i on.Genet i cAl gor i t hmsdeal wi t ht hepr obl emst hatmax i mi z et hef i t nes sf unc t i on.But ,i ft hepr obl em c ons i s t s i nmi ni mi z i ngac os tf unc t i on,t headapt at i oni squi t eeas y .Ei t hert hec os tf unc t i on c anbet r ans f or medi nt oaf i t nes sf unc t i on,f orex ampl ebyi nv er t i ngi t ;ort he s el ec t i on c an beadapt ed i ns uc h wayt hatt heyc ons i deri ndi v i dual swi t hl ow ev al uat i on f unc t i onsasbet t er .Onc et her epr oduc t i onandt hef i t nes sf unc t i onhav ebeen pr oper l ydef i ned,aGenet i cAl gor i t hm i sev ol v edac c or di ngt ot hes amebas i c s t r uc t ur e.I ts t ar t sbygener at i ngani ni t i alpopul at i onofc hr omos omes .Thi sf i r s t popul at i onmus tof f er awi dedi v er s i t yofgenet i cmat er i al s .Thegenepools houl dbeasl ar geaspos s i bl e s ot hatanys ol ut i onoft hes ear c hs pac ec anbeengender ed.Gener al l y ,t hei ni t i al popul at i on i sgener at ed r andoml y .Then,t hegenet i cal gor i t hm l oopsov eran i t er at i onpr oc es st omaket hepopul at i onev ol v e. Eac hi t er at i onc ons i s t soft hef ol l owi ngs t eps : •SELECTI ON:Thef i r s ts t epcons i s t si ns el ect i ngi ndi vi dual sf or r epr oduct i on.Thi ss el ect i oni sdoner andoml ywi t hapr obabi l i t y dependi ngont her el at i vef i t nes soft hei ndi vi dual ss ot hatbes t onesar eof t enchos enf orr epr oduct i ont hanpoorones . •REPRODUCTI ON:I nt hes econds t ep,of f s pr i ngar ebr edbyt he s el ect edi ndi vi dual s .Forgener at i ngnewchr omos omes ,t he al gor i t hm canus ebot hr ecombi nat i onandmut at i on. •EVALUATI ON:Thent hef i t nes soft henewchr omos omesi s eval uat ed. •REPLACEMENT:Dur i ngt hel as ts t ep,i ndi vi dual sf r om t heol d popul at i onar eki l l edandr epl acedbyt henewones . Theal gor i t hm i ss t oppedwhent hepopul at i onc onv er gest owar d t heopt i mals ol ut i on. Thebas i cgenet i cal gor i t hm i sasf ol l ows : •[ s t ar t ]Genet i cr andom popul at i onofnchr omos omes( s ui t abl e s ol ut i onsf ort hepr obl em) •[ Fi t nes s ]Eval uat et hef i t nes sf ( x)ofeachchr omos omexi nt he popul at i on •Newpopul at i on]Cr eat eanewpopul at i onbyr epeat i ngf ol l owi ng s t epsunt i lt heNewpopul at i oni scompl et e -[ s el ect i on]s el ectt wopar entchr omos omesf r om apopul at i on accor di ngt ot hei rf i t nes s(t hebet t erf i t nes s ,t hebi gger chancet ogets el ect ed) . -[ cr os s over ]Wi t hacr os s overpr obabi l i t y,cr os sovert hepar ent st o f or m newof f s pr i ng(chi l dr en) .I fnocr os s overwasper f or med, of f s pr i ngi st heexactcopyofpar ent s . -[ Mut at i on]Wi t hamut at i onpr obabi l i t y,mut at enewof f s pr i ngat eachl ocus ( pos i t i oni nchr omos ome) - [ Accept i ng]Pl acenewof f s pr i ngi nt henewpopul at i on. •[ Repl ace]Us enewgener at edpopul at i onf oraf ur t hers um oft he al gor i t hm. •[ Tes t ]I ft heendcondi t i oni ss at i s f i ed,s t op,andr et ur nt hebes t s ol ut i oni ncur r entpopul at i on. - • [ Loop]Got os t ep2f orf i t nes seval uat i on. Bas edont hef or egoi ngdi s c us s i on,t hei mpor t antc r i t er i af orGAappr oac hc anbe f or mul at edasgi v enbel ow: -Compl et enes s :Anys ol ut i ons houl dhavei t sencodi ng -Nonr edundancy:Codesands ol ut i onss houl dcor r es pondonet o one -Soundnes s :Anycode( pr oducedbygenet i coper at or s )s houl d havei t scor r es pondi ngs ol ut i on Char act er i s t i cper s ever ance:Of f s pr i ngs houl di nher i tus ef ul char act er i s t i csf r om par ent s . 3. Compar i s onofGenet i cAl gor i t hm wi t hOt her Opt i mi z at i onTechni ques Genet i cal gor i t hm di f f er sf r om c onv ent i onalopt i mi z at i ont ec hni quesi nf ol l owi ng way s : 1.GAsoper at e wi t hc oded v er s i onsoft he pr obl em par amet er sr at hert han par amet er st hems el v esi . e. ,GAwor kswi t ht hec odi ngofs ol ut i ons etandnotwi t h t hes ol ut i oni t s el f . 2.Al mos tal lc onv ent i onalopt i mi z at i ont ec hni quess ear c hf r om as i ngl epoi ntbut GAs al way s oper at e on a whol e popul at i on ofpoi nt s ( s t r i ngs )i . e. ,GA us es popul at i onofs ol ut i onsr at hert hanas i ngl es ol ut i onf r os ear c hi ng.Thi spl ay sa maj orr ol et ot her obus t nes sofgenet i cal gor i t hms .I ti mpr ov est hec hanc eof r eac hi ngt hegl obal opt i mum andal s ohel psi nav oi di ngl oc als t at i onar ypoi nt . 3.GAus esf i t nes sf unc t i onf orev al uat i onr at hert hander i v at i v es .Asar es ul t ,t hey c anbeappl i edt oanyki ndofc ont i nuousordi s c r et eopt i mi z at i onpr obl em.Thekey poi ntt o beper f or med her ei st oi dent i f yand s pec i f yameani ngf uldec odi ng f unc t i on. 4.GAs us e pr obabi l i s t i ct r ans i t i on oper at es whi l ec onv ent i onalmet hods f or c ont i nuousopt i mi z at i onappl ydet er mi ni s t i ct r ans i t i onoper at esi . e. ,GAsdoesnot us edet er mi ni s t i cr ul es . 4. Appl i cat i onsofGenet i cAl gor i t hm Af ewappl i c at i onsofGAar easf ol l ows : •Nonl i neardy nami c al s y s t ems – pr edi c t i ng,dat aanal y s i s •Robott r aj ec t or ypl anni ng •Ev ol v i ngLI SPpr ogr ams( genet i cpr ogr ammi ng) •St r at egypl anni ng •Fi ndi ngs hapeofpr ot ei nmol ec ul es •TSPands equenc es c hedul i ng •Func t i onsf orc r eat i ngi mages •Cont r ol – gaspi pel i ne,pol ebal anc i ng,mi s s i l eev as i on,pur s ui t •Des i gn– s emi c onduc t orl ay out ,ai r c r af tdes i gn, key boar d c onf i gur at i on,c ommuni c at i onnet wor ks •Sc hedul i ng– manuf ac t ur i ng,f ac i l i t ys c hedul i ng,r es our c e al l oc at i on •Mac hi neLear ni ng–Des i gni ngneur al net wor ks , bot har c hi t ec t ur e andwei ght s, i mpr ov i ngc l as s i f i c at i onal gor i t hms ,c l as s i f i er s y s t ems •Si gnalPr oc es s i ng–f i l t erdes i gn •Combi nat or i alOpt i mi z at i on–s etc ov er i ng, t r av el i ngs al es man ( TSP) ,Sequenc es c hedul i ng,r out i ng,bi npac ki ng, gr aph c ol or i ngandpar t i t i oni ng
