Stigmergy in Computing

8/14/2019 Stigmergy in Computing

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Multicellular Computing

Evolution of Multicellular Computing:Parallels with Multicellular LifeSeminar, December 21, 2!"niversit# of $irmingham, "%

Steve $urbec&

evolutionofcomputing'org


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Multicellular Computing2

(hat woul) #ou )o with a MulticellularComputer*

Suppose that in 212, 11 lorries +truc&s are set to arriveat #our )ata center each carr#ing a shipping container

1 of the lorries carr# a )ata-center in a bo. +from /$M,Sun, Dell, 0P, or other ven)ors:

Each bo. contains 2, -core servers' 3hetotal for the shipment is nearl# one millionservers'

Each container re4uires 5 connections:

1 a fiber-optic )ata lin&,

2 %( of power, an)

5 6 tons of chille) water cooling'

3he 11thbo. contains a 6 ton water chiller that cancool the 1 computing containers

3ogether the eleven containers use over megawatts'

3he combine) information processing capabilit# ise4uivalent to that of a small 7ell#fish'

(hat )o #ou )o* (hat )oes it )o* 0ow )o #ou8program9 it* 0ow )o #ou &eep it from 4uic&l# becomingta&en over b# a botnet*


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Multicellular Computing3

(h# the Multicellular Metaphor*

3he 8Clou) Computing9 metaphor isnt aboutmuch of an#thing'''its basicall# a mar&eting termthat )oesnt offer useful architectural insights'

Parallel computing is about parallel algorithmsan) ma.imum ;L


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E.isting Large Multicellular Computing S#stems

>oogle

?t least ! speciali=e) t#pes of server inclu)ing crawers, a)servers, in)e.ing, spelling, )ocuments, http, search, formatting,pro.#@cache

? total of at least 1'A million servers B 116 per shippingcontainer, A containers per )ata-center warehouse, an) atleast 5A )ata centers worl)-wi)e

;aceboo&

5, servers of at least t#pes

Eba#?t least A functional t#pes of servers: Database, LD?P, (ebServers, ?pplication Servers, etwor&ing Switches an) outers

Estimate) 1A%-2% servers

en$an&

Clou) s#stems B >oogles Clou), ?ma=ons clou) +EC2,Microsofts clou), Salesforce'comSocial networ&s +e'g', M#Space, ;aceboo&, 3witter

Massivel# Multipla#er ames +e'g', (orl) of(arcraft, Everuest, Secon) Life,

/nstant messaging chat an) F


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3he ?nalog# $etween Life an) Computing

3he forces that have shape) the evolution of computing are similarto those in the evolution of life:

?s comple.it# grows, multiple levels of organi=ation orabstraction +meta-levels emerge

Subs#stems become encapsulate) to re)uce unwante) or)angerous interactions

Species co-evolve in response to each other to improvepre)ation, s#mbiosis an) other co-)epen)ent behavior'

Evolution in computing architecture occurs both )espite an)because of our attempts at 8)esign'9 3he histor# of computingprovi)es insight into the circumstances of the emergence ofcomputational meta-levels'

?s computing continues to become more comple. an) powerful, wecan an) shoul) appl# lessons learne) from 5'A $illion #ears of trialan) error biological e.perimentation'


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3he Central /ssuesEmergence of meta-levels

Emergence is &nown variousl# as self-organi=ation +%auffman,metas#stem transition +3urchin, autocatal#sis +Prigogine, increasingreturns an) path )epen)ence in economics +$rian ?rthur, an) others'

Living an) )igital s#stems cannot help but un)ergo the stepwiseemergence of multiple meta-levels

Multicellularit# is a ma7or organi=ational transition B what are its prere4uisites*

Single cells an) single computers are limite) in scope, scale an)comple.it#'

Multicellularit# offers solutions to those problems'

Get multicellular s#stems face new issues such as cooperation, protectionfrom pre)ators, an) maintenance of 8self9

Strategies that support multicellular s#stems

3he most basic are: Speciali=ation,


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"bi4uitous /nformation Processing?ll living organisms sense, process, an) act on information in their environment'

Man# single-cellorganisms sense light, vibration, temperature, an) their chemicalenvironment' 3he# respon) to changing sensor# input b# mo)if#ing their internalbehavior an)@or moving to more favorable locations'

Man# organisms +inclu)ing single cell bacteria 8signal9 others in a wa# that promotescooperative behavior' /ts calle) quorum sensingin bacteria'

Even plants cooperate' Some plants sense attac& b# insects, increase their )efensivechemistr#, an) emit pheromones that signal attac& to other nearb# plants'

(e )ont necessaril# &now what information a given organism senses, what the result ofthe processing )etermines, what time-scale it operates on, or what 8purpose9 it serves'

Digital information processing surroun)s us but is largel# invisible, even to computing professionals'

Much of what mo)ern societies an) economies )o is me)iate) b# )igital information

processing/f #ou are not a computing professional, #ou ma# not perceive or even &now abstractl# the)igital processing ta&ing place all aroun) us'

(e swim in a sea of electromagnetic ra)iation that to)a# is mostl# pro)uce) b# an)receive) b# )igital )evices of man# sorts'

(e sel)om are far awa# from wires, fiber optic cables an) wireless signals'


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E.ample of $iological /nformation Processing

Escherecia coli +E' coli is one of the simplest an) best stu)ie) bacteria' $iologists &now a great )eal abouthow it senses, processes an) respon)s to information in its environment

Sensors +#ellow provi)e information about various attractant an) repellent aspects of the environment

/n)ivi)ual sensor proteins have a 12)#namic range

$# cooperation between sensors, the patch as a whole provi)es a 1 or 1Arange

Messenger proteins +CheGp, represente) b# small re) )ots )iffuse throughout the cell an) aresimultaneousl# )ephosphor#late) +i'e', inactivate) b# comple. fee)bac& mechanisms'

Messengers bin) to an) regulate 6 - flagella with bi-)irectional motors

(hen turning countercloc&wise, the flagella bunch together to propel the bacteria forwar)

(hen turning cloc&wise, the flagella separate an) cause the cell to tumble ran)oml#

(hen attractant )ominates, forwar) runs ten) to be relativel# long, when repellents )ominatetumbles are more fre4uent

http:@@www'p)n'cam'ac'u&@groups@comp-cell@$igIbug'html


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/nformation Processing Comparison:Stan)alone Computer vs' Single Cell $ ?M +co)e an) )ata

Persistent )ata in multi->$ Dis&

0= serial processors

Deterministic an) fragile B nee)s fre4uent reboots,little tolerance for ran)omness, can be )isable) b#failure of single gates'

Poor abilit# for self organi=ation, no abilit# to replicate,)epen)ent on outsi)e power, maintenance an)support'

otoriousl# susceptible to malware attac&

Co)e si=e +D? B from AM$ +simple bacteria toJA>$ +?moeba' ote: human has K1>$

Persistent )ata enco)e) in protein structure an) D?

3housan)s to millions of %0= 8processors9 +proteinan) ? molecular machines operating in parallel

Stochastic an) robust B Cells tolerate, even e.ploit,ran)omness' obustness far e.cee)s human-engineere) re)un)anc#

Self organi=ing, self supporting, self healing, an) selfrepro)ucing

0as substantial )efenses against infection B evenbacteria have en=#me )efenses against viral infection


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Evolution of ComputingEarl# computers were a small, simple, slow collection of )iscrete logic gates

3he unit of software was the machine instruction B no abstraction whateveran) no tools other than 8co)ing sheets9

/@< consiste) of little more than panel )ispla# lights or a telet#pe'

Computing professionals alive to)a# witnesse) the following evolution

0ar)ware evolve) protecte) a))ress spaces, virtual memor#, microco)e)instruction sets, 8privilege) instructions,9 pipeline) processors, parallel an)multi-core processors, various e.ternal storage me)ia, various sorts ofph#sical memor#, etc'

8S#stems Software9 evolve) to provi)e


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Co-Evolution H Comple.it#

Co-evolution in life ma&es strangebe)fellows such as 8$ee


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Software Comple.it# +(in)ows //S

IIS call graph for serving a single HTTP page containing one image


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Comple.it# of Single Cell Protein-Protein/nteractions +Geast

Geast S' cerevisiae protein-protein interaction)iagram' $arabasi H


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"(

;amiliar Emergent Phenomena

3he 8long haul9 /nternet


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"

Emergence in $iolog# an) Computing

Comple. ph#sics begets comple. biochemistr# begets the comple. cells thatcollaborate to form comple. organisms

Comple. )igital har)ware begets comple. software which begets comple.interactions between computers, especiall# in the /nternet

3his 8begetting9 is emergent, i'e', self-organi=ing, )riven b# positive fee)bac&between interacting sets of elements

Self-reinforcing sets become elements in a meta-level s#stem

?s each meta-level emerges, its behavior is 4ualitativel# )ifferentfrom that of its constituent elements

Each new meta-level t#picall# encapsulates, or hi)es, )etails+information about the lower level phenomena

3he organi=ational structure of each new meta-level creates newinformation +i'e' structural or)er at the higher level

3he higher level behavior can often be thought of as a 8virtual machine9interface that is 8implemente)9 b# the coor)inate) action of its lower levelelements'


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Causalit# Crosses Meta-Levels/mperfectl#

Causalit# crosses almost all meta-level boun)aries, both upwar) an))ownwar), but t#picall# imperfectl# an) in wa#s )ifficult to pre)ict'

"pwar) causation is )ue to )etails of how lower level elements pla# a role inspecific autocatal#tic sets' Meta-level behavior ten)s to be robust, so lowerlevel 8causes9 ma# onl# wea&l# affect the higher-level behavior' $ut in somecases, effects at higher levels can be )ramatic:

Fer# low-level co)e can create buffer overruns in (in)ows that have/nternet-wi)e conse4uences

Pharmaceutical )rugs )irectl# affect in)ivi)ual cells that in)irectl#affect the brain, hence ps#chological states such as )epression'

Downwar) effects are usuall# )ue to in)uce) organi=ation of lower levelelements +i'e', a))e) information create) b# the upper level' E.amples:

floc&s, where visible 8floc&ness9 gui)es flight of in)ivi)ual bir)s' eal-time events act as signals

0ives, termite moun)s, )atabases, provi)e more persistentorgani=ation which ma# ma&e it easier to un)erstan) 8causes9 an)

8effects9 separatel#


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Countering "nwante) /nteractions withEncapsulation B 3he Designer Perspective

Cells evolve) man# sorts of membrane encapsulate) subunits long ago:

3he cell membrane itself which prevents most e.ternal chemicals fromentering or leaving the cell'

3he nucleus, which encapsulates the D? an) basic gene e.pressionmechanisms +comparable to


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Encapsulation in Single-Cell Geast

Electron tomogram of a complete #east cell shows man# internalmembrane enclosures that prevent unwante) interactions'

0oog NL, Schwart= C, oon ?3,


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Multicellularit#

$iofilms +training wheels for true multicellularit# consist of man#cooperating bacteria an) viruses, often of man# species, withseparate an) )iffering D?' 3he cells temporaril# form amulticellular organism b# changing their behavior when the#sense that the# are in a sufficientl# large group' 3his is calle)

84uorum sensing'9 $ecause the cooperative behavior is notgeneticall# unifie), evolution of more comple. behavior isproblematic'

Multicellular organisms, or Meta=oans, have multiplecooperating cells that share the same D?' ?s each organism

grows, cells )ifferentiate into speciali=e) cell t#pes that each useonl# part of the D?' Differentiation itself is un)er D?8program control9 so the success or failure of the wholeorganism is )etermine) both b# the success of the variousspeciali=ations an) b# the success of their orchestration'


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Placo=oa: the Simplest Meta=oan

Millimeter-scale )iscs that contain a few thousan)cells of onl# four t#pes' Dorsal cells with flagella,ventral 8glan) cells9, ventral flagellar cells, an) central8fiber cells' ;iber cells also contain s#mbioticbacteria'

Moves in coor)inate) manner using the central la#erof 8fiber cells9 that have both neuron-li&e an) muscle-

li&e function'

umber of cells an) cell-t#pescomparable to eBay


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Cni)eria B Consi)erabl# More Comple.

0#)ra

Estimate) number of cells A, -J,

?t least 1A cell t#pes

Nell#fish +Cni)eria C#anea shown here

umber of cells Q 1 million

?t least 22 cell t#pes inclu)ing neurons,sensors, muscle, en)ocrine, an)ematoc#sts +stinging cells use) forcapturing pre#'


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Multicellular Comple.it#umber of 8Cells9 vs' umber of 8Cell9 3#pes

A 1 1A 2 2A

1

2

5

A

6

J

umber of RCellR t#pes

umberof

RCells

R+Log1,

Jellyfish

Google

Hydra

Placozoa

Facebook eBay


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;our ?rchitectural Prere4uisites forMulticellularit#

Messaging B in multicellular transition, single cells forego )irectD? transfer in favor of pol#morphic protein messages'

?poptosis +or Programme) Cell Death B controlle) suici)e of

in)ivi)ual cells for the benefit or protection of the whole organism'

Differentiation B permanent speciali=ation of cells' /n humansthere are about 2A speciali=e) t#pes of cells'

Stigmerg# B organi=ation an) orchestration via a share) ph#sicalstructure that is create) b# the organisms that it helps to organi=e'


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2(

Messaging an) Pol#morphism

$acteria communicate b# 8con7ugation9 B )irecte.change of D? +thin re) threa) at left'Multicellular organisms D<


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Swarms:


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2*

Longer Lasting than Swarms:


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2+

oogle, for e.ample, mo)els the (eb

;aceboo&, twitter, etc', mo)el social networ&s

? complete Semantic et +Sowa 1!J6, 1!, 2 woul) be a worth# tas&for a serious multicellular computer B or a brain


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2,

Stigmerg# in Computing

Dis&s an) (in)ows registr# provi)e

coor)ination for in)ivi)ual computers

8$lac&boar)9 s#stems coor)inate betweenagents'

Databases serve as stigmerg# structuresfor companies an) communities'

DS +the root server an) cachingservers

>PS +the structure is a set of satellitesthat are mo)ifie) b# the >PSgroun)station an) rea) b# all >PS)evices

Linu. is a self-organi=e) stigmerg#s#stem in the /nternet

3he persistent structure isprovi)e) b# the CFS co)erepositor#


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2-

Self@on-Self in Multicellular


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3#

?poptosis +Programme) Cell Death

? message ?P/ for controlling a carefull#

choreographe) process programme) into each an) ever# cell in a multicellular organism'

?poptosis is a prere4uisite for multicellular life

?poptosis evolve) coinci)ent with

the first t#pes of multicellular life -bacterial biofilms'

/t evolve) to )eal with the sorts ofissues that plague multicellularorganisms but not single cellorganisms such as replicative D?)amage, viral infection, an) cells

8going rogue'9/t solves those issues from a multicellularperspective - sacrificing the in)ivi)ual cell for the goo)of the multicellular organism'


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3"

3he ole of ?poptosis/t is not simpl# to cause )angerous cells to suici)e in a safe wa#

/t also is use) to 8sculpt9 the )eveloping organism

/t is central to the ma7or changes in insect bo)ies as the#change from larvae to pupae to a)ult

/t is how ta)poles lose their tails

/t is how human fingers an) toes separate from each other

?n) it is crucial to the )eveloping human brain' ?bout half ofall )eveloping neurons fail to get enough positive reinforcementfrom their target neurons to avoi) apoptosis' 3hat is, twice asman# are create) than are nee)e), an) those that )ont turn

out to ma&e valuable connections commit suici)e' +a usefulmo)el for multicellular computation*

$etween A an) J billion cells )ie each )a# )ue to apoptosis in theaverage human a)ult'


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32

?poptosis in Computing

Central lessons of apoptosis3he s#stem must be architecte) so that no cell isin)ispensableEver# computer in the s#stem shoul) beresponsible for monitoring its own 8health9 an)

shutting )own or )etaching from the networ& upon)etecting its own anomalous behavior'

/f reliable apoptosis is a base part of thearchitecture, multicellular s#stems can spawnvarious speciali=e) servers safe in the &nowle)ge

that those not rewar)e) for useful wor& can be setup to recogni=e that fact an) remove themselves,ma&ing wa# for other t#pes of server +that is, as& fora new software reloa)'


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3he ;our Principles are /ntertwine)

Facilitated By Necessary Because

Specialization

Messaging

Stigmergy

Apoptosis

Cell-surface receptors arespeciali=e) b# cell t#pe'

E.portable messages surviveoutsi)e the cells an) thee.tracellular matri. provi)esattachment locations for long-

live) messages


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Last +$ut not Least the Multicellular8Sensorium9

Multicellular life increases the scale an) accurac# of sensor# input an) the scale ofeffector behavior, i'e', the effectiveness of the organisms 8awareness9 an) manipulationof its environment'

/n most cases, this is the ver# point of /nformation Processing

?n) its not a ba) )efinition of Darwinian 8;itness9 +a tric topic to be sure

Single cells have wi)e range of 8senses9 but multi-cellular organisms can coor)inateinputs from man# cells giving better )etail an) )#namic range'

3he senses available to coor)inate) in)ivi)ual computing 8cells9 +e'g', iPhones will)etermine what information can be organi=e) b# higher levels' iPhones )irectl# 8sense9,i'e', capture, te.t, au)io, image, vi)eo, location +>PS, an) +5-D acceleration'

;or e.ample, 8images9 from man# ;lic&r accounts or location information from

man# >PS )evices +cell phones can be combine) to provi)e a coor)inate)view of the worl)'

?s& #ourselves: 80ow will one multicellular computing s#stem senseanother*9


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3he Multicellular 8DesignerPerspective9

Lets return to preparing for the arrival of the shipping containers

0ow )o #ou even thin& about the problem*

(hat )o #ou want #our multicellular computer to be when it grows up*

(hat will the stigmerg# structure+s nee) to be*

(hat speciali=e) t#pes of servers will there be*

(hat messages will be acte) upon, i'e', what are the ?P/s, or the virtual machineinterface+s*

0ow will the servers recogni=e failure or infection b# viruses, worms, bac&)oors,root&its, etc'* ?n), if infecte), what will the# )o*

?n), of course, how will #ou 8program9 the various servers, loa) them with images,an) maintain them' 3hat is, what sort of software )evelopment an) maintenance tools)o #ou nee) to create*

oogle )o*


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/ts the $eginning, ot the En)

uestions an) Discussion

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Stigmergy in Computing

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