OpenMP introductionWord下载.docx

OpenMP introductionWord下载.docx

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3.WORKSHAREDirective

4.SINGLEDirective

6.CombinedParallelWork-SharingConstructs

1.PARALLELDO/parallelforDirective

2.PARALLELSECTIONSDirective

3.PARALLELWORKSHAREDirective

7.TASKConstruct

8.SynchronizationConstructs

1.MASTERDirective

2.CRITICALDirective

3.BARRIERDirective

4.TASKWAITDirective

5.ATOMICDirective

6.FLUSHDirective

7.ORDEREDDirective

9.THREADPRIVATEDirective

10.DataScopeAttributeClauses

1.PRIVATEClause

2.SHAREDClause

3.DEFAULTClause

4.FIRSTPRIVATEClause

5.LASTPRIVATEClause

6.COPYINClause

7.COPYPRIVATEClause

8.REDUCTIONClause

11.Clauses/DirectivesSummary

12.DirectiveBindingandNestingRules

5.Run-TimeLibraryRoutines

1.OMP_SET_NUM_THREADS

2.OMP_GET_NUM_THREADS

3.OMP_GET_MAX_THREADS

4.OMP_GET_THREAD_NUM

5.OMP_GET_THREAD_LIMIT

6.OMP_GET_NUM_PROCS

7.OMP_IN_PARALLEL

8.OMP_SET_DYNAMIC

9.OMP_GET_DYNAMIC

10.OMP_SET_NESTED

11.OMP_GET_NESTED

12.OMP_SET_SCHEDULE

13.OMP_GET_SCHEDULE

14.OMP_SET_MAX_ACTIVE_LEVELS

15.OMP_GET_MAX_ACTIVE_LEVELS

16.OMP_GET_LEVEL

17.OMP_GET_ANCESTOR_THREAD_NUM

18.OMP_GET_TEAM_SIZE

19.OMP_GET_ACTIVE_LEVEL

20.OMP_INIT_LOCK

21.OMP_DESTROY_LOCK

22.OMP_SET_LOCK

23.OMP_UNSET_LOCK

24.OMP_TEST_LOCK

25.OMP_INIT_NEST_LOCK

26.OMP_DESTROY_NEST_LOCK

27.OMP_SET_NEST_LOCK

28.OMP_UNSET_NEST_LOCK

29.OMP_TEST_NEST_LOCK

30.OMP_GET_WTIME

31.OMP_GET_WTICK

6.EnvironmentVariables

7.MemoryandPerformanceIssues

8.LLNLSpecificInformationandRecommendations

9.ReferencesandMoreInformation

10.Exercise

Abstract

OpenMPisanApplicationProgramInterface（API）,jointlydefinedbyagroupofmajorcomputerhardwareandsoftwarevendors.OpenMPprovidesaportable,scalablemodelfordevelopersofsharedmemoryparallelapplications.TheAPIsupportsC/C++andFortranonawidevarietyofarchitectures.ThistutorialcoversmostofthemajorfeaturesofOpenMP,includingitsvariousconstructsanddirectivesforspecifyingparallelregions,worksharing,synchronizationanddataenvironment.Runtimelibraryfunctionsandenvironmentvariablesarealsocovered.ThistutorialincludesbothCandFortranexamplecodesandalabexercise.

Level/Prerequisites:

GearedtothosewhoarenewtoparallelprogrammingwithOpenMP.BasicunderstandingofparallelprogramminginCorFortranassumed.ForthosewhoareunfamiliarwithParallelProgrammingingeneral,thematerialcoveredinEC3500:

IntroductiontoParallelComputingwouldbehelpful.

Introduction

WhatisOpenMP?

OpenMPIs:

∙AnApplicationProgramInterface（API）thatmaybeusedtoexplicitlydirectmulti-threaded,sharedmemoryparallelism

∙ComprisedofthreeprimaryAPIcomponents:

oCompilerDirectives

oRuntimeLibraryRoutines

oEnvironmentVariables

∙Portable:

oTheAPIisspecifiedforC/C++andFortran

oMostmajorplatformshavebeenimplementedincludingUnix/LinuxplatformsandWindowsNT

∙Standardized:

oJointlydefinedandendorsedbyagroupofmajorcomputerhardwareandsoftwarevendors

∙WhatdoesOpenMPstandfor?

oShortversion:

OpenMulti-Processing

oLongversion:

OpenspecificationsforMulti-Processingviacollaborativeworkbetweeninterestedpartiesfromthehardwareandsoftwareindustry,governmentandacademia.

OpenMPIsNot:

∙Meantfordistributedmemoryparallelsystems（byitself）

∙Necessarilyimplementedidenticallybyallvendors

∙Guaranteedtomakethemostefficientuseofsharedmemory

∙Requiredtocheckfordatadependencies,dataconflicts,raceconditions,ordeadlocks

∙Requiredtocheckforcodesequencesthatcauseaprogramtobeclassifiedasnon-conforming

∙Meanttocovercompiler-generatedautomaticparallelizationanddirectivestothecompilertoassistsuchparallelization

∙Designedtoguaranteethatinputoroutputtothesamefileissynchronouswhenexecutedinparallel.Theprogrammerisresponsibleforsynchronizinginputandoutput.

References:

∙OpenMPwebsite:

openmp.org

APIspecifications,FAQ,presentations,discussions,mediareleases,calendar,membershipapplicationandmore...

∙Wikipedia:

en.wikipedia.org/wiki/OpenMP

History

AncientHistory:

∙Intheearly90'

s,vendorsofshared-memorymachinessuppliedsimilar,directive-based,Fortranprogrammingextensions:

oTheuserwouldaugmentaserialFortranprogramwithdirectivesspecifyingwhichloopsweretobeparallelized

oThecompilerwouldberesponsibleforautomaticallyparallelizingsuchloopsacrosstheSMPprocessors

∙Implementationswereallfunctionallysimilar,butwerediverging（asusual）

∙FirstattemptatastandardwasthedraftforANSIX3H5in1994.Itwasneveradopted,largelyduetowaninginterestasdistributedmemorymachinesbecamepopular.

WhichLedTo...

∙TheOpenMPstandardspecificationstartedinthespringof1997,takingoverwhereANSIX3H5hadleftoff,asnewersharedmemorymachinearchitecturesstartedtobecomeprevalent.

∙LedbytheOpenMPArchitectureReviewBoard（ARB）.OriginalARBmembersincluded:

（Disclaimer:

allpartnernamesderivedfromtheOpenMPwebsite）

oCompaq/Digital

oHewlett-PackardCompany

oIntelCorporation

oInternationalBusinessMachines（IBM）

oKuck&

Associates,Inc.（KAI）

oSiliconGraphics,Inc.

oSunMicrosystems,Inc.

oU.S.DepartmentofEnergyASCIprogram

∙Othercontributorsincluded:

Endorsingapplicationdevelopers:

oADINAR&

D,Inc.

oANSYS,Inc.

oDashAssociates

oFluent,Inc.

oILOGCPLEXDivision

oLivermoreSoftwareTechnologyCorporation（LSTC）

oMECALOGSARL

oOxfordMolecularGroupPLC

oTheNumericalAlgorithmsGroupLtd.（NAG）

Endorsingsoftwarevendors:

oAbsoftCorporation

oEdinburghPortableCompilers

oGENIASSoftwareGmBH

oMyriasComputerTechnologies,Inc.

oThePortlandGroup,Inc.（PGI）

∙FormorenewsandmembershipinformationabouttheOpenMPARB,visit:

openmp.org/wp/about-openmp.

ReleaseHistory

GoalsofOpenMP

Standardization:

∙Provideastandardamongavarietyofsharedmemoryarchitectures/platforms

LeanandMean:

∙Establishasimpleandlimitedsetofdirectivesforprogrammingsharedmemorymachines.Significantparallelismcanbeimplementedbyusingjust3or4directives.

EaseofUse:

∙Providecapabilitytoincrementallyparallelizeaserialprogram,unlikemessage-passinglibrarieswhichtypicallyrequireanallornothingapproach

∙Providethecapabilitytoimplementbothcoarse-grainandfine-grainparallelism

Portability:

∙SupportsFortran（77,90,and95）,C,andC++

∙PublicforumforAPIandmembership

OpenMPProgrammingModel

SharedMemory,ThreadBasedParallelism:

∙OpenMPisbasedupontheexistenceofmultiplethreadsinthesharedmemoryprogrammingparadigm.Asharedmemoryprocessconsistsofmultiplethreads.

ExplicitParallelism:

∙OpenMPisanexplicit（notautomatic）programmingmodel,offeringtheprogrammerfullcontroloverparallelization.

Fork-JoinModel:

∙OpenMPusesthefork-joinmodelofparallelexecution:

∙AllOpenMPprogramsbeginasasingleprocess:

themasterthread.Themasterthreadexecutessequentiallyuntilthefirstparallelregionconstructisencountered.

∙FORK:

themasterthreadthencreatesateamofparallelthreads

∙Thestatementsintheprogramthatareenclosedbytheparallelregionconstructarethenexecutedinparallelamongthevariousteamthreads

∙JOIN:

Whentheteamthreadscompletethestatementsintheparallelregionconstruct,theysynchronizeandterminate,leavingonlythemasterthread

CompilerDirectiveBased:

∙MostOpenMPparallelismisspecifiedthroughtheuseofcompilerdirectiveswhichareimbeddedinC/C++orFortransourcecode.

NestedParallelismSupport:

∙TheAPIprovidesfortheplacementofparallelregionsinsideotherparallelregions.

∙Implementationsmayormaynotsupportthisfeature.

DynamicThreads:

∙TheAPIprovidesfortheruntimeenvironmenttodynamicallyalterthenumberofthreadsusedtoexecuteparallelregions.Intendedtopromotemoreefficientuseofresources,ifpossible.

I/O:

∙OpenMPspecifiesnothingaboutparallelI/O.Thisisparticularlyimportantifmultiplethreadsattempttowrite/readfromthesamefile.

∙IfeverythreadconductsI/Otoadifferentfile,theissuesarenotassignificant.

∙ItisentirelyuptotheprogrammertoinsurethatI/Oisconductedcorrectlywithinthecontextofamulti-threadedprogram.

MemoryModel:

FLUSHOften?

∙OpenMPprovidesa"

relaxed-consistency"

and"

temporary"

viewofthreadmemory（intheirwords）.Inotherwords,threadscan"

cache"

theirdataandarenotrequiredtomaintainexactconsistencywithrealmemoryallofthetime.

∙Whenitiscriticalthatallthreadsviewasharedvariableidentically,theprogrammerisresponsibleforinsuringthatthevariableisFLUSHedbyallthreadsasneeded.

∙Moreonthislater...

ExampleOpenMPCodeStructure

Fortran-GeneralCodeStructure

PROGRAMHELLO

INTEGERVAR1,VAR2,VAR3

Serialcode

.

Beginningofparallelsection.Forkateamofthreads.

Speci