HPCSummit,Prague
ExaFLOW
ExaFLOW
ExaFLOW–EnablingExascaleFluidDynamicsSimula>onsErwinLaure,KTH,Stockholm,SWEDEN
HPCSummit,Prague
ExaFLOW
ExaFLOW 2
ExaFLOW
àAddresscurrentalgorithmicboGleneckstoenabletheuseofaccurateCFDcodesforproblemsofprac>calengineeringinterest
HPCSummit,Prague
ExaFLOW
ExaFLOW
TheAirbusChallenge,DavidHills,2008
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AnAirbus310cruisingat250m/sat10000mTeraflopsmachine(1012Flops):8·105yearsResultinoneweek:4·1019flopsmachine(40EFlops)(basedonJohnKim’ses>mate,TSFP-9,2015)
HPCSummit,Prague
ExaFLOW
ExaFLOW
Navier–Stokesequa>ons
DatafromMira(2013),millioncorehours• Engineering/CFD 525 19%• Subsurfaceflow&reac>vetransport 80 3%
• Combus>on 100 4%• Climate 280 10%• Astrophysics 28 1%• Supernovae 105 4%
1118 40%
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(frac>onofNavier-Stokesbasedsimula>ononcurrentsupercomputers)
HPCSummit,Prague
ExaFLOW
ExaFLOW
ExaFLOWOverview
ThemaingoaloftheprojectistoaddresscurrentalgorithmicboGleneckstoenabletheuseofaccurateCFDcodesforproblemsofprac>calengineeringinterest.Thefocuswillbeondifferentsimula>onaspectsincluding:
• accurateerrorcontrolandadapJvemeshrefinementincomplexcomputa>onaldomains,
• solverefficiencyviamixeddiscon>nuousandcon>nuousGalerkinmethodsandappropriateop>misedprecondi>oners,
• strategiestoensurefaulttoleranceandresilience,• heterogeneousmodellingtoallowfordifferentsolu>onalgorithmsindifferentdomainzones,
• parallelinput/outputforextremedata,employingnoveldatareduc>onalgorithms(feature-basedin-situanalysis),
• energyawarenessofhigh-ordermethods,• 4differentcodes.
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HPCSummit,Prague
ExaFLOW
ExaFLOW
ExaFLOWPartners
• KTHStockholm,PDCandMechanics(Coordinator)• ImperialCollege,London,CFD• UniversityofSouthampton,Aerodynamics• UniversityofEdinburgh,EPCC• UniversityofStuGgart,HLRSandAerodynamics• EPFLausanne,Mathema>cs
• McLarenRacing,UK• Automo>veSimula>onCenterStuGgart
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HPCSummit,Prague
ExaFLOW
ExaFLOW
AlgorithmicDevelopment
• 3mainobjec>vestodevelopthemathema>calandalgorithmicknowledgeneededtotacklekeyobjec>vesandenableexascale-levelCFDsogware:– ObjecJve1:errorcontrolthroughadap>on,heterogeneousmodellingandresilience
– ObjecJve2:strongscalingatexascale– ObjecJve3:techniquesforI/Oatexascale
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HPCSummit,Prague
ExaFLOW
ExaFLOW
WP1:6monthprogresshighlights
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Workingimplementa>onofaspectralerrores>matortodriveah-adap>veprocessforObjec>ve1(KTH)
Ini>alformula>onofhybridCG-HDGononenodeundergoingini>altes>ngforObjec>ve2,
aimtoreducecommunica>onboGleneck(ICL)
Preprintofinves>ga>onintoresiliencemeasuresforhard/sogerrorsduringrun>meforObjec>ve1(EPFL)
HPCSummit,Prague
ExaFLOW
ExaFLOW
Powerandenergyprofilingtobuildbaselines
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• BuildingpowerandenergyprofilesofNektar++andNek5000toestablishbaselineuponwhichtomeasureimprovements.
• Usingfulltestcasestoexercisecompletecode.• Energy-to-solu>onand>me-to-solu>onasafunc>onofprocessor
frequency(leg);lookingforop>maltrade-offs.• Varia>onseenbetweenotherwiseiden>calrunsofthesamecodeand
test-case(right);lookingtoquan>fyuncertaintyinmeasurements.
HPCSummit,Prague
ExaFLOW
ExaFLOW
AddingmodernparallelI/OtoNektar++
• CodeboGleneckfoundinI/O.– Slowscheckpoint/restartandfinalresultswrites.
• Previouslymul>plefiles,perprocesswri>ng.• NowusingHDF5atopMPI-IOforparallelI/Otosinglefile.
– Non-trivialmappingofelementsoneachprocesstofile.– AllowscheckpointonXnodes,restartonZnodes;X!=Z.– Fitproblemtoavailableresources,evenwhensolu>onrequires>1jobsofdifferentlengths/widths.
• Buildsontopofworkdoneinpriorproject,nowreadytomergeintotrunk.
• Givesimplementa>ontobringtootherprojectcodesdoingsimilarI/Owithnon-trivialmappings.
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HPCSummit,Prague
ExaFLOW
ExaFLOW
l Fivecomputa>onally-demandingusecasessuitablefordemonstra>ngtheneedforexascalecapabili>eshavebeencreated:
l l -NACA4412(compressible)-Sotonl -NACA4412(incompressible)-KTHl -Jetincrossflow-KTH/StuGgartl -AutomoJve/flowpastacar-ASCSl -ImperialFrontwing–Imperial/McLarenl l SomeofthesehavealreadybeenpublishedonlineontheExaFLOWprojectwebsite.TheotherswillsoonbemadeavailableviaDeliverable3.1.
l l Quan>ta>vemeasurestoensurecorrectflowphysicsisreproducedagercodeop>misa>onshavebeendefined.
l l Computa>onalrequirementshavebeeninves>gatedandinternalevalua>onofusecasesisunderway.
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PilotCases
HPCSummit,Prague
ExaFLOW
ExaFLOW
l Vor>cesbeinggeneratedl fromaNACA4412airfoil:
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Turbulent straight pipe simulation(part of the jet in cross flow case):
Preliminary results of strong scaling from the incompressible NACA-4412 case (3.2 billion solution points):
Geometry for Imperial front wing use case:
HPCSummit,Prague
ExaFLOW
ExaFLOW
WorkPackages
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1. Algorithmicimprovementstowardsexascale(IC)2. Efficiencyimprovementstowardsexascale(UEDIN)3. Valida>on&usecases(SOTON)4. Dissemina>onandexploita>on(USTUTT)5. Management(KTH)
HPCSummit,Prague
ExaFLOW
ExaFLOW
ConclusionsandOutlook
• Fluidmechanicsisaprimeexampleforexascale• ExaFLOWwilladdresssomeoftheissueswhenitcomesto
pracJalapplicaJons– errorcontrolandadap>vemeshingforlargerandmorecomplexsimula>ondomains;capableofdynamicremeshingifnecessary.
– Heterogeneousmodelling– Resilience&faulttolerance– datahandling,complexfeatureextrac>on(in-situ)andsharingofsimula>ondata.
• Enhancingcommunitycodes(Nek5000,Nektar++,SBLI);Open-sourcedevelopmentofallcomponents
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