《信息科學(xué)類專業(yè)英語》課件第2章

Vocabulary(詞匯)ImportantSentences(重點句)QuestionsandAnswers(問答)Problems(問題)Lesson2ExtremeScaleComputing

(第二課超大規(guī)模計算)

Supercomputinghasbeenamajorpartofmyeducationandcareer,fromthelate1960swhenIwasdoingatomicandmolecularcalculationsasaphysicsdoctoratestudentattheUniversityofChicago,totheearly1990swhenIwasgeneralmanagerofIBM’sSP

familyofparallelsupercomputers.

Theperformanceadvancesofsupercomputersinthesepastdecadeshavebeenremarkable.ThemachinesIusedasastudentinthe1960sprobablyhadapeakperformanceofafewmillioncalculationspersecondormegaflops.Gigaflops(billions)peakspeedswereachievedin1985,teraflops(trillions)in1997,andpetaflops(a1followedbyfifteenzeros)in2008.

Thesupercomputingcommunityisnowaimingforexascalecomputing,1,000,000,000,000,000,000calculationspersecond.Thepursuitofexascale-classsystemswasahottopicattherecentSC09

supercomputingconference.

Inthequestforthefastestmachines,supercomputershavealwaysbeenattheleadingedgeofadvancesinIT,identifyingthekeybarrierstoovercomeandexperimentingwithtechnologiesandarchitecturesthatgenerallythenappearinmorecommercialproductsafewyearslater.

Throughthe1970sand1980s,thefastestsupercomputerswerebasedonvectorarchitecturesandusedhighlysophisticatedtechnologiesandliquidcoolingmethodstoremovethelargeamountsofheattheygenerated.

Bythelate1980s,thesecomplexandexpensivetechnologiesranoutofgas.Asthemicroprocessorsusedinpersonalcomputersandtechnicalworkstationswerebecomingincreasinglypowerful,youcouldnowbuildsupercomputersusingtheseCMOSmicrosandparallelarchitecturesatamuchlowerpricethanthepreviousgenerationsofvectormachines.Asimilartransitiontomicroprocessorcomponentsandparallelarchitecturestookplaceinthemainframesusedincommercialapplications.

Massivelyparallelarchitectures,usingtenstohundredsofthousandsofprocessorsfromthePCandUnixmarketshavedominatedsupercomputingoverthepasttwentyyears.Theygotusintotheterascaleandpetascaleranges.But,theywillnotgetustoexascale.AnothermassivetechnologyandarchitecturaltransitionnowloomsforsupercomputingandtheITindustryingeneral.[1]

Anticipatingthemajorchallengesinvolvedinthetransitiontoexascale,theDepartmentOfEnergy(DOE)andDARPAlaunchedaseriesofactivitiesaroundthreeyearsagotostartplanningforsuchsystems.

ThisDARPAExaScaleComputingStudyprovidesaverygoodoverviewofthekeytechnologychallenges.Thestudyidentifiedfourmajorchallengeswherecurrenttrendsareinsufficient,anddisruptivetechnologybreakthroughsareneededtomakeexascalecomputingareality.

TheEnergyandPowerChallengeispervasive,affectingeverypartofthesystem.Today’sleadingedgepetascalesystemsconsumebetween2-3Megawatts(MW)perpetaflop.Itisgenerallyagreedthatanexaflopsystemmustconsumearound20MWs,otherwisetheiroperatingcostswouldbeprohibitivelyexpensive.The1000-foldincreaseinperformancefrompetascaletoexascalemustthusbeachievedatnomorethana10-foldincreaseinpowerconsumption.

Suchstretchtargetswereactuallyachievedinthetransitionfromterascaleinthelate1990stopetascalenow.Butnoonebelievesitcanbedoneagainwithtoday’stechnologies,hencetheassumptionthatatechnologyandarchitecturaltransitionasprofoundastheonetwodecadesagoisnowrequired.

TheMemoryandStorageChallengeisamajorconsequenceofthepowerchallenge.Thecurrentlyavailablemainmemories(DRAM)anddiskdrives(HDD)thathavedominatedcomputinginthelastdecadeconsumewaytoomuchpower.Newtechnologiesareneeded.

TheConcurrencyandLocalityChallenge

isanotherconsequenceofthepowerchallenge.Overthepasttwentyyearswehavebeenabletoachieveperformanceincreasesthroughacombinationoffasterprocessesandhigherlevelsofparallelism.But,wearenolongerabletoincreasetheperformanceofasingleprocessingelementbyturninguptheclockrateduetopowerandcoolingissues.

Wenowhavetorelysolelyonincreasedconcurrency.

Thetopterascalesystemsoftenyearsagohadroughly10,000processingelements.Today’spetscalesystemisupinthelow100,000s.But,because,theonlywaytonowincreaseperformancetowardanexascalesystemismassiveparallelism,anexaflopsupercomputermighthave100sofmillionsofprocessingelementsorcores.Suchmassiveparallelismwillrequiremajorinnovationsinthearchitecture,softwareandapplicationsforexascalesystems.ThisDARPAExascaleSoftwareStudyprovidesagoodoverviewofthesoftwarebreakthroughsrequired.

Finally,wehavetheResiliencyChallenge,thatis,theabilityofasystemwithsuchhugenumberofcomponentstocontinueoperationsinthepresenceoffaults.Anexascalesystemmustbetrulyautonomicinnature,constantlyawareofitsstatus,andoptimizingandadaptingitselftorapidlychangingconditions,includingfailuresofitsindividualcomponents.TheexascaleresiliencychallengesarediscussedinthisDARPAreportonSystemResiliencyatExtremeScales.

Therearevastbusinessimplicationstosuchamassivetechnologyandarchitecturaltransition.Forone,theecosystemofthepasttwentyyears,wherePCshaveprovidedthecomponentsforparallelsupercomputers,isnowgivingwaytoanewbusinessecosystem.Consumerelectronics,mobiledevicesandembeddedsensorsarenowthenewpartnersoftheextremescalesupercomputingcommunity,becausetheysharethesamerequirementsforplentiful,powerfulandinexpensivecomponentsthatconsumelittlepower.

Thistransitiontoanewecosystemalreadystartedaboutfiveyearsago.IBM’sBlueGenefamilyusesrelativelylowpower,embeddedcoresasitsprocessingelements,andRoadrunner’shybriddesignincludestheCellprocessorsoriginallydevelopedforSony’sPlayStation3.

ThemostpowerfulsupercomputersintheUShavegenerallybeendevelopedfor,andfirstinstalledatDOE’snationallabs,eitheraspartofitsAdvancedScientificComputingResearch(ASCR)programinsupportofenergyandenvironmentalresearch,ortheAdvancedSimulationandComputingprograminsupportofnuclearweaponsresearch.TheseDOElabstypicallyworkcloselywiththevendorsintherequirementsanddesignofsuchleadingedgesupercomputers.

Tobegintounderstandtherequirementsforexascalemachines,ASCRsponsoredaseriesoftownhallmeetings,whichheldopendiscussionsonthemostcriticalandchallengingproblemsinenergy,theenvironmentandbasicscience.Thesemeetingswherethenfollowedbyaseriesoftechnicalworkshops,eachfocusingonaspecificscientificdomain.

TheDOEtownhallsandworkshopshaveidentifiedtheopportunityforexascalecomputingtorevolutionizethewayweapproachchallengesinenergyresearch,environmentalsustainabilityandnationalsecurity.Theyalsoidentifiedtheimpactofexascalecomputingonkeyscienceareaslikebiology,astrophysics,climatescienceandnuclearphysics.

Oneoftheirmostcompellingconclusionsisthatwithexascalecomputing,wearereachingatippingpointinpredictivescience,anareawithpotentiallymajorimplicationsacrossawholerangeofnew,massivelycomplexproblems.Letmeexplain.

HighendsupercomputersaregenerallydesignedforeithercapabilityorcapacitycomputingCapabilitysupercomputersdedicatethewhole(ormostofthe)machinetosolveaverylargeproblemintheshortestamountoftime.Capacitysupercomputers,ontheotherhand,supportlargenumbersofuserssolvingdifferentkindsofproblemssimultaneously.

Whilebothkindsofsupercomputingareveryimportant,initiativesdesignedtopushtheenvelope,likeDOE’sexascaleproject,tendtofocusonthedevelopmentofcapabilitymachinestoaddressGrandChallenge

problemslikethosementionedabove,thatcouldnotbesolvedinanyotherway.

Capabilitycomputinghasbeenprimarilyappliedtowhatissometimesreferredtoasheroiccomputations,wherejustaboutthewholemachineisappliedtoasingletask.And,withoutadoubt,therearequiteanumberofproblemsthatwewillbeabletoaddresswithmachines1000timesmorepowerful.

But,atleastasexciting,isthepotentialforexascalecomputingtoaddressaclassofhighlycomplexproblemsthathavebeenbeyondourreach,notjustduetotheirsheersize,butbecauseoftheirinherentuncertaintiesandunpredictability.Thewaytodealwithsuchuncertaintyistosimultaneouslyrunmultipleensemblesorcopiesofthesameapplications,usingmanydifferentcombinationsofparameters,andthusbeabletoexplorethesolutionspaceoftheseotherwiseunpredictableproblems.Thiswillletussearchforoptimalsolutionstomanyproblemsinscienceandengineering,aswellasenableustocalculatetheprobabilitiesofextremeevents.

Thisnewstyleofpredictivemodelingwillhelpusapplymorescientificmethodologiestomanykindsofproblems,fromclimatestudiestothedesignofsafenuclearreactors.Beyondscienceandengineering,therearemanydisciplinesthatwillbenefitfromsuchpredictivecapabilities,fromeconomicsandmedicinetobusinessandgovernment.

Ensemblecomputinghasattributesofbothcapabilityandcapacitycomputing.Itdevotesthewholemachinetooneproblem,butitdoessobyrunningmanycopiesoftheprobleminparallelwithdifferentinitialconditions.Innovativetechniquesarealreadyemergingtohelpdevelopersbetterprogramandmanagesuchensemble-orientedapplications.

Finally,itisimportantnottounderestimatetheimpactofexascalebreakthroughstomorecapacityorientedmachines,aswellastosmallermachinesthatsharethesametechnologies,architecture,softwareandapplications.Manyoftheinnovationthatwillenableustodevelopexascaleclasssupercomputerswillyieldrelativelyinexpensivepetascaleclasssystemsaswellassmallerones.Thewidertheaccesstosuchfamiliesofsystems,therichertheoverallecosystemincludingapplications,usersandtechnologies.

Inaddition,thesesameexascaleinnovationswillfindwideusageinthemorecommerciallyorientedcloudcomputingsystems.Thetechnologyrequirementsarequitesimilar,especiallytheneedforlowpower,lowcostcomponents.Theyalsosharesimilarrequirementsforhighlyefficient,autonomicsystemmanagement.Onecanactuallyviewcloud-basedsystemsasakindofexascaleclasssupercomputersdesignedtosupportembarrassinglyparallelworkloads,suchasmassiveinformationanalysisorhugenumbersofsensorsandmobiledevices.

InitsStrategyforAmericanInnovation,theObamaadministrationlistedexascalecomputingamongtheGrandChallenges

ofthe21stcenturyinscience,technologyandinnovation,that“willallowthenationtosetandmeetambitiousgoalsthatwillimproveourqualityoflifeandestablishthefoundationfortheindustriesandjobsofthefuture.”Itexplicitlycalledfor.[2]

“Anexascalesupercomputercapableofamilliontrillioncalculationspersecond–dramaticallyincreasingourabilitytounderstandtheworldaroundusthroughsimulationandslashingthetimeneededtodesigncomplexproductssuchastherapeutics,advancedmaterials,andhighly-efficientautosandaircraft.”[3]

Thisisatrulyexcitingandimportantchallenge.1．molecularadj.adv.n.分子狀態(tài)的;分子式;分子量。

2．remarkableadj.值得注意的；不尋常的。

3．loomn.織布機vi.隱約出現(xiàn);陰森地逼近。

4．stretchvt.&vi.n.adj.伸展;拉緊;延伸;盡力,全力以赴。

5．resiliencyn.跳回,彈性。

6．ecosystemn.?<生>生態(tài)系統(tǒng)。

7．sustainabilityn.持續(xù)性;能維持性;永續(xù)性。Vocabulary

8．compellingadj.引人入勝的;扣人心弦的;非常強烈的;不可抗拒的;令人信服的。

9．simultaneouslyadv.同時地。

10．ensemblen.系集，整體,總效果;合奏,合唱;合奏組。

11．callfor去接(某人),去取(某物);需要;要求。

12．therapeuticsn.[pl.]治療學(xué),療法。

13．FLOPS(FLoatingpointOperationsPerSecond)每秒浮點操作數(shù)，用于度量浮點計算機速度的單位，見下表。

本文中的exascale是計算機科學(xué)家又定義的一個新詞，exa來源于上面的表格中，暫且翻譯成超大規(guī)模計算。

[1]Massivelyparallelarchitectures,usingtenstohundredsofthousandsofprocessorsfromthePCandUNIXmarketshavedominatedsupercomputingoverthepasttwentyyears.Theygotusintotheterascaleandpetascaleranges.But,theywillnotgetustoexascale.AnothermassivetechnologyandarchitecturaltransitionnowloomsforsupercomputingandtheITindustryingeneral.

ImportantSentences近20年來，在PC和UNIX市場上使用幾十萬個處理器的大規(guī)模并行體系機構(gòu)占主導(dǎo)地位。這使得我們進入了萬億和千萬億計算的范圍。但是還不能使我們進入極大規(guī)模計算。對于超級計算和信息產(chǎn)業(yè)來說，其他的大規(guī)模技術(shù)和體系結(jié)構(gòu)的轉(zhuǎn)變目前還不明朗。

[2]InitsStrategyforAmericanInnovation,theObamaadministrationlistedexascalecomputingamongtheGrandChallengesofthe21stcenturyinscience,technologyandinnovation,that“willallowthenationtosetandmeetambitiousgoalsthatwillimproveourqualityoflifeandestablishthefoundationfortheindustriesandjobsofthefuture.”Itexplicitlycalledfor.

在“美國創(chuàng)新戰(zhàn)略”中，奧巴馬政府把超大規(guī)模計算作為21世紀(jì)科學(xué)、技術(shù)和創(chuàng)新的重大挑戰(zhàn)之一。他們明確號召：這將使得我們建立并達到改善生活質(zhì)量、建立未來產(chǎn)業(yè)和工作崗位的基礎(chǔ)的宏偉目標(biāo)。

[3]Anexascalesupercomputercapableofamilliontrillioncalculationspersecond–dramatically