Turning ESMF Components into CCA Components

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Turning ESMF Components into CCA Components

• Arlindo da Silva, NASA/GSFC Data Assimilation
  Office
• Shujia Zhou, TASC NASA ESTO CT
• Data Assimilation Office, NASA/GSFC

Components Workshop, GFDL, 14 May 2003
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Acknowledgements

• Portions adapted from CCA Forum Tutorial of 15
  Jan 2003 available from
• http//www.cca-forum.org/tutorials/
• CCA Forum Tutorial WG
• Rob Armstrong, David Bernholdt, Wael Elwasif,
  Lori Freitag, Dan Katz, Jim Kohl, Gary Kumfert,
  Lois Curfman McInnes, Boyana Norris, Craig
  Rasmussen, Jaideep Ray, Torsten Wilde
• ANL, JPL, LANL, LLNL, ORNL, SNL

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Outline

• Goals of the project
• What is Common Component Architecture (CCA)?
• Overview of key CCA concepts
• ESMF components in a nutshell
• Language interoperability issues
• Prototype simple ocean/atmosphere coupled
  system
• Next step Cane-Zebiak model

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Goals of the Project

• Given Earth system models developed under Earth
  System Modeling Framework (ESMF), explore
  interoperability with alternative architectures,
  in particular
• Common Component Architecture (CCA)
• Use CCA-compliant framework such as Ccaffeine to
  assemble climate applications based on ESMF
  components, carrying out sample simulations
• Document process of turning ESMF components into
  CCA components

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Component Architectures

• Existing component architecture standards such as
  CORBA, COM/DCOM, and JavaBeans/EJB, are widely
  used in commercial industry.
• They do not support efficient parallel
  communication channels between components
• Existing high-performance frameworks such as
  POOMA and Overture are object-oriented, but are
  not based on peer components
• Rather, components are viewed as elements in an
  inheritance hierarchy

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What is the CCA?

• A component model specifically designed for
  high-performance computing
• Support HPC languages (Babel)
• Support parallel as well as distributed execution
  models
• Minimize performance overhead
• Minimalist approach makes it easier to
  componentize existing software
• Component interactions are not merely dataflow
• Components are peers
• No particular component assumes it is in
  charge of the others.
• Allows the application developer to decide what
  is important.

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CCA Concepts Ports

FunctionPort
FunctionPort
IntegratorPort
NonlinearFunction
MidpointIntegrator

• Components interact through well-defined
  interfaces, or ports
• In OO languages, a port is a class or interface
• In Fortran, a port is a bunch of subroutines or a
  module
• Components may provide ports implement the
  class or subroutines of the port
• Components may use ports call methods or
  subroutines in the port
• Links denote a caller/callee relationship, not
  dataflow!
• e.g., FunctionPort could contain evaluate(in
  Arg, out Result)

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Components and Ports in the Integrator Example

FunctionPort
FunctionPort
IntegratorPort
NonlinearFunction

FunctionPort
MidpointIntegrator
IntegratorPort
GoPort
LinearFunction

FunctionPort
Driver
FunctionPort
IntegratorPort
PiFunction
RandomGeneratorPort

RandomGeneratorPort
MonteCarloIntegrator
RandomGenerator
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An Application Built from the Example Components

FunctionPort
FunctionPort
IntegratorPort
NonlinearFunction

FunctionPort
MidpointIntegrator
IntegratorPort
GoPort
LinearFunction

FunctionPort
Driver
FunctionPort
IntegratorPort
PiFunction
RandomGeneratorPort

RandomGeneratorPort
MonteCarloIntegrator
RandomGenerator
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Another Application

FunctionPort
FunctionPort
IntegratorPort
NonlinearFunction

FunctionPort
MidpointIntegrator
IntegratorPort
GoPort
LinearFunction

FunctionPort
Driver
FunctionPort
IntegratorPort
PiFunction
RandomGeneratorPort

RandomGeneratorPort
MonteCarloIntegrator
RandomGenerator
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And Many More
Dashed lines indicate alternate connections

FunctionPort
FunctionPort
IntegratorPort
NonlinearFunction

FunctionPort
MidpointIntegrator
IntegratorPort
GoPort
LinearFunction

FunctionPort
Driver
FunctionPort
IntegratorPort
PiFunction
RandomGeneratorPort

RandomGeneratorPort
MonteCarloIntegrator
Create different applications in "plug-and-play"
fashion
RandomGenerator
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CCA Frameworks

• The framework provides the means to hold
  components and compose them into applications
• The framework is often applications main or
  program
• Frameworks allow exchange of ports among
  components without exposing implementation
  details
• Frameworks provide a small set of standard
  services to components
• BuilderServices allow programs to compose CCA
  apps
• Frameworks may make themselves appear as
  components in order to connect to components in
  other frameworks

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The Lifecycle of a CCA Component

• User instructs framework to load and instantiate
  components
• User instructs framework to connect uses ports to
  provides ports
• Code in components uses functions provided by
  another component
• Ports may be disconnected
• Component may be destroyed

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CCA Concepts Direct Connection

• Components loaded into separate namespaces in the
  same address space (process) from shared
  libraries
• getPort call returns a pointer to the ports
  function table
• Calls between components equivalent to a C
  virtual function call lookup function location,
  invoke
• Cost equivalent of 2.8 F77 or C function calls

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ESMF Components

• ESMF Gidded Components are most likely
  implemented in F90, e.g.
• Module ATM_GridComp
• Public
• ATM_SetServices()
• Private
• ATM_Initialize()
• ATM_Run()
• ATM_Finalize()

These are saved In function pointer Table by
ATM_SetServices()
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ESMF F90 Application

• User code is called via ESMF routines of similar
  name
• Type(ESMF_GridComp) gcATM
• gcATM ESMF_GridCompCreate()
• Call ESMF_GridCompSetServices(gcATM,)
• Call ESMF_GridCompInitialize(gcATM,)
• Call ESMF_GridCompRun(gcATM,)
• Call ESMF_GridCompFinalize(gcATM,)
• C bindings exist for each ESMF_ rountine
• Therefore, a C interface automatically exists
  for any user written F90 component

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ESMF on CCA Approach

• Use ESMF language interoperability feature to
  interface to CCA in C
• No need to instrument user code with complex
  BABEL machinery (F90 not yet supported), or CHASM
• For a typical ocean-atmosphere coupled system one
  needs to write CCA wrappers for 4 components
• Gridded Components OCN, ATM
• Couplers OCNxATM, ATMxOCN

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Wrapping an ESMF Component for CCA
CCA_Comp
ESMC_Comp
FTable
CCA_Driver
ESMC_CompInitialize ESMC_CompRun ESMC_CompFinalize
ATM-gtRun()
ATM is the instance of CCA_ESMF_Comp CCA_Comp
is assembled with ESMF utilities and is
compiled as .so
User_ATM
User_ATMInitialize User_ATMRun User_ATMFinalize
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Component Relationship via CCA Wiring
ATM
OCN
Port link
Data flow