predicting the temporal evolution of tokamak plasma profiles … suli deliverables...
TRANSCRIPT
RESEARCH POSTER PRESENTATION DESIGN © 2012
www.PosterPresentations.com
Motivation
Background- DeepLearningviaRecurrent NeuralNetworks
JalalButt1 andEgemenKolemen2,3PredictingtheTemporalEvolutionofTokamakPlasmaProfileswithDeepLearning
ReferencesandAcknowledgements
FutureWork
PreliminaryPlasmaProfilePredictionsviaRNN
DeepLearningwithNeuralNetworks
1CentralConnecticutStateUniversity,2PrincetonUniversity,3PrincetonPlasmaPhysicsLaboratory
Modelinearlystages(lotsstilltodo):• Largertrainingshotlist(modelcurrentlytrainson~600shots– lotsmoredataavailable)• More0Ddata(powerandtorquefromeachbeam– potentiallyvaluableinfluenceonlocalspatialscales)• Comparingprofileevolutionpredictionsfordata-drivenandphysics-basedmodels• CNN-RNNhybrid- learnmoreabstractspatialpatterns• Parameterizeinput data– reducecomputationalexpense• Kinetically-constrainedplasmaprofiles• Trainmodelonplasmatransportcodes(e.g.TRANSP)
ImplementingRNNinNERSCSupercomputers
• AwardedNERSCexploratoryresourcestoupscaleproject
• ImplementingRNNmodelinCoriandEdisonSupercomputers• Necessary:increaseaccuracyàincreasecomputationalpower
• Inspiredbybiologicalneuralnetworks• Interdisciplinaryapplications(including
fusion,particularlydisruptionpredictions)• Supervisedlearningproblem(targetprofiles
known)
• Why?:RudimentaryNNpreviouslydevelopeddoesn’texplicitlyuseprevioustime-stepsandpredictionsasmodelinputs(doesn’thave“memory”)– butplasmaevolutionhasspatial+temporal dependence
• Modelgoal:predictphysicallysignificantspatio-temporalchangesinprofileswithknowledgeofpreviousplasmastate(viaprofiles)andcurrent0Dinputs
• Examplesfrompreliminaryresultsshowmodelpredictingonsetofionprofile“hollowing”
• Fusiongoal:Makenuclearfusionacommerciallyfeasibleenergysource
• Majorchallenge:plasmastability• ifwecanpredictplasmastabilityàmanipulateplasmatoavoidinstabilities/dangerousmodes
• Tokamakplasmaprofilesareinputstoplasmastabilitycodes• CanAIhelpuspredictplasma[profile]evolution?• Plasmaevolutionknowledgeà predictpotential
instabilityonsets
• 3.)LearningProcess:Minimizeloss(𝑦"# )byupdatingweightsandbiases(𝜃)usingSGDalgorithm;4.)minimizationoptimizedbyAdamoptimizer
• 2.)Amean-absolutedifferenceloss[error]functionisdefinedforlossminimization:
• [1]LongShort-TermMemory,Hochreiter etal,NeuralComputation1997• [2]Adam:AMethodforStochasticOptimization,Kingma etal,ICLR2015• [3]ABriefIntroductiontoMachineLearningforEngineers,Simeone,KCL
• ThisworkissupportedbyUSDOEgrantsDE-FC02-04ER54698,DE-AC02-09CH11466,andDE-SC0015878.
• NERSC,U.S.D.O.E.OfficeofScienceUserFacilityoperatedunderContractNo.DE-AC02-05CH11231.
• PrincetonPlasmaPhysicsLaboratory,DOEforfundingtheSummerUndergraduateLaboratoryInternship(SULI)
• PatrickVail,FlorianLaggner,andYichen Fufortheirinsighttofusionplasmas.
✓i ✓i�1 +�i
batch
X
n2batch
(r✓fn(✓)|✓=✓(i�1))
=
• Each“neuron”isitsownneuralnetwork–nodelearnsnon-linearcombinationofvaluestodeterminegates’operationforMLtask
• 1.a.)Weights(W)andbiases(b)forthemodel’srawneuronactivations(Ai+1)aredefinedas:
Rudimentaryneuralnetwork
Relevantinformation• RecurrentNeuralNetworkModel:• LSTMUnits:200;LSTMCells[layers]:4• Limitedbycomp.power
• 588[DIII-D]shots• 50-mstime-slices• BuiltusingGoogle’sTensorFlow API
Loss:measureof”error”
RNNunrolledintime- howRNNusespervioustime-slicesforprediction
f
t
= ReLU(Wf
· [Ct�1, ht�1, xt
] + b
f
)
i
t
= ReLU(Wi
· [Ct�1, ht�1, xt
] + b
i
)
o
t
= ReLU(Wo
· [Ct
, h
t�1, xt
] + b
o
)
à Forgetgateà Inputgateà Outputgate
• 1.b.)Rawneuronacts.arelinearlyactivated:
• Eachnode(LSTMunit)describedby:
ModelInputs:• Previous150-msofne,ni,Te,Ti,Rot.profiles(zipfit - OMFITmdsplus)
• 0Dtime-traces(previousandconcurrent)•NBIpower/torque,gasA/Bflowrates,ECHpower
ModelOutputs:• Future(unseen)150-msofplasmaprofiles
2
6664
Ai+11
Ai+12...
Ai+1n
3
7775=
2
66664
W 11 W 1
2 . . . W 1np
W 21
. . ....
...Wn
1 . . . Wnnp
3
77775·
2
6664
Ai1
Ai2...
Ainp
3
7775+
2
6664
b1b2...
bnp
3
7775
Tensorsareextendedbyonerankformulti-layerNN
yi isthesumofthetargetvaluesvectorand𝑦"# isthesumofthepredictedvaluesvector
ReLU(Ai+1j ) = max(0, Ai+1
j ) = x
+
Differences
:prediction:target
Anotherexampleofion-hollowingonsetprediction
x1019
x1019
x1019
loss(yi) =batchsizeX
1
���(yi � yi)
batchsize
���
𝛾": learning-rateschedule;𝜃": updatedweightsandbiases
𝑦'":parameterizedby𝑊 and𝑏