ESMF Early Adopters Tutorial Examples Chris Hill, cnhplume.mit.edu

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ESMF Early Adopters Tutorial ExamplesChris
Hill, cnh_at_plume.mit.edu
ESMF Community Meeting, Boulder, 2004

• Early Adopters (EA) group has been holding
  regular meetings at GFDL for five months. One
  focus of these meeting has been to begin to
  develop some introductory examples. For this
  afternoon look at these examples look at
  interoperability codes, user adoption activities.

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Ways someone learns about ESMF

• Background and introduction.
• General orientation.
• Application case studies.
• Interoperability experiments experience.
• Tutorial and idealized examples.
• Downloadable sample code.
• e.g flow solver demo, Early Adopters examples

this morning
this afternoon
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Recap of this morning
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Background and introduction
Platforms

• Context
• describing motivation and goals.
• Summary of ESMF architecture and 2.0
  distribution
  
• pointers to 2.0 distribution docs

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Case studies

• Describes approaches of deployment projects -
• Demonstrates approaches to ESMF adoption in large
  existing codes.

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Key ESMF concepts

• Gridded and Coupler Components.
• Import and Export States.
• Clocks.
• Fields and Grids.
• Model of underlying paralleism.
• Tutorial Examples illustrate these concepts

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Tutorial examples
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Tutorial examples

• So far from Early Adopters group
• collecting its learning experience.
• Assembling a range of examples
• simple hello world to
• useful sub-components e.g. solvers and
  interpolators
  
• Small footprint
• quick download
• build on most Unix/Linux platforms.

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Current tutorial examples center on two basic
areas

• Components (component_tutorials/)
• hello_world/
• demonstrates SetServices(), Init(), Run(),
  Final()
  
• import_and_export/
• demonstrates passing data in ESMF_States
• clock/
• demonstrates alarms and clock.
• simple_couple_1/
• demonstrates coupler components.
• combines SetServices, ESMF_State, clock in a
  simple application.

• Fields and grids (fields_and_grids_tutorials/)
• regrid/
• interpolates Levitus SST through coupler with
  regrid
  
• demonstrates regridding and transferring data
  between parallel components.
  
• laplace/
• estimates flow from 2o Topex SSH
• solves for non-divergent flow at arbitrary
  resolution.
  
• demonstrates halo(), globalsum() etc..

Gridded and paralleism.
Basic component wiring and control
Not especially gridded.
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component_tutorials/hello_world/
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Hello World App- component_tutorials/hello_world
-

• Every software project needs a Hello World
• For ESMF, Hello World demonstrates
• a single component driven from one layer above
• using SetServices() and Gridded Components in
  practice.
  

Top Layer App Driver
ESMF library code
SetServices()
Initialize()
Run()
Finalize()
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Hello World has two source files

• MyWorldGridCompMod.F90 contains the
  SetServices(), Initialize(), Run() and Finalize()
  code.
  
• hello_world_app.F90 contains the top layer app
  driver.

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Top Layer App Driver
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SetServices() and Initialize() Methods
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Run() and Finalize() Methods
Run()
Finalize()
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Compiling and executing Hello World

• MyWorldGridCompMod.F90 contains the
  SetServices(), Initialize(), Run() and Finalize()
  code.
  
• hello_world_app.F90 contains the top layer app
  driver.

Building Hello World demonstrates one way to
compile programs that use ESMF.
All the EA tutorial examples use this approach.
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Compiling Hello World - I

• Compile with make
• Need to
• use same compiler as used to build ESMF.
• use compiler options consistent with ESMF build.
• use link options consistent with ESMF build.
• specify location of ESMF 2.0 distribution library
  and Fortran module files.
  

Path names and compiler options for my laptop
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Compiling Hello World - II

• File .obj_list in each example directory
  specifies what to compile

• Shared directory example_make_files contains
  make files with fbase etc.. settings
  predefined

• To make with an example make file

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Executing Hello World

• File output.txt in each example directory
  contains reference output

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component_tutorials/clock/
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Clock- component_tutorials/clock -

• Clock
• same approach as hello_world.
• driver loops over run() stage
• run() demonstrates simple use of clock and alarm
  (at Y2K).
  

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Clock source

• top layer driver creates clock, sets initial
  time, sets alarm, advances clock.
  
• gridded component reads clock and checks alarm

• MyWorldGridCompMod.F90 contains the
  SetServices(), Initialize(), Run() and Finalize()
  code.
  
• clock_app.F90 contains the top layer app driver.

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Clock top level clock_app.F90

• like hello_world,
• creates component
• calls SetServices(), Init(), Run(), Finalize
• three extra blocks of code in top layer driver

1 - Declare clock variables and set default
calendar.
2 - Set clock and alarm
3 - Iterate, advancing clock
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Clock gridded component MyWorldGridCompMod.F90

• SetServices(), Initialize() like hello_world,
• Run() has extra logic, to print time and check
  alarm.
  
• in ESMF component interface standard CLOCK is
  passed in through Run() interface.

Top Layer App Driver
clock/ Run()
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Running Clock- component_tutorials/clock -
Iteration 1
Iteration 2
Iteration 3

• File output.txt contains reference output

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component_tutorials/import_export/
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Import Exportcomponent_tutorials/import_export

• Import Export
• single gridded component as hello_world and
  clock.
  
• demonstrates using ESMF_Array in ESMF_State to
  pass data in and out of a component
  

Top Layer App Driver
Export State
Run
Initialize
1 - Top Layer creates Export State
3 Initialize creates an ESMF Array for holding
data.
4 Initialize adds ESMF Array to Export State.
5 Export State is returned to top layer.
6 Export State is passed to Run.
7 Run adds the value 1 to the ESMF Array.
8 Export state is returned to the top layer.
9 Top layer calls run again, passing down
import and export state.
10 Run() adds 1 to the contents of the ESMF
Array in the Export State.
2 - Top Layer passes Export State to Initialize()
Export State
1
2
ESMF Array
1
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Import Export source

• top layer driver creates import and export
  states, iterates over calling run.
  
• gridded component decodes import and export
  states and 1.
  

• MyWorldGridCompMod.F90 contains the
  SetServices(), Initialize(), Run() and Finalize()
  code.
  
• import_export_app.F90 contains the top layer app
  driver.

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Import Export top level import_export_app.F90

• like hello_world,
• creates component
• calls SetServices(), Init(), Run(), Finalize
• two extra blocks of code in top layer driver

1 Setup import and export states
2 - Iterate
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Import Export gridded component
MyWorldGridCompMod.F90

• SetServices(), Initialize() like hello_world,
• Run() has extra logic, to read and write to and
  from import and export state.
  
• in ESMF component interface standard import,
  export are passed in through Run() interface.

Top Layer App Driver
import_export/ Run()

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Combining lessons

• Together hello_world, clock and import_export
  introduce key tools you need to wire examples
  like those shown
  
• the boxes are ESMF Gridded Components
• the data-flow between boxes occurs through ESMF
  import and ESMF export states
  
• time is synchronized through ESMF clocks

Questions so far?
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component_tutorials/simple_couple_1/

• ESMF supports applications with more than one
  gridded component!
  
• simple_couple_1 demonstrates multi-component
  programming under ESMF
  

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• simple_couple_1
• five gridded components (P, Q, R, S) that
  evaluate equations for an oscilloscope like
  device.
  
• a clock that sends alarms to signal components to
  update their outputs.
  
• two coupler components (PQ2R and PQ2S) that
  combine import states from multiple components
  into a single export state.
  
• also demonstrates ESMF configuration attributes
  to get runtime parameters.
  

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simple_couple_1 source

• simple_couple_1.F90 acts as top driver, creates
  mid-level driver, calls Run() methods.
  
• GridComp.F90, CplComp.F90 components.
• oscillate.F90 mid-level driver.
• e_utils.F90 convenience functions that combine
  common ESMF operations.

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what the components do
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Top level driver simple_source_1.F90
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• oscillate.F90 mid-level driver
• creates and manages components passes them
  import/export states, configuration attribute
  resource files etc
  

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• oscillate.F90
• to create the appropriate data flow we
  interconnect import and export state
  
• latch everyone to a common clock

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• GridCompP.F90 (and Q,R,S .)
• called from mid-level driver
• carry out computation, pass results out through
  export state.
  

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• Clock with multiple alarms is used at mid-level
  to
  
• schedule calls to Gridded Components.
• schedule calls to Output Component.
• e.g.

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Configuration attributes are used in getting
alarm frequency parameters and other parameters
e.g. GridCompP frequency
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Running simple_couple- component_tutorials/simple
_couple_1 -
Outputs for different resource file settings.
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simple_couple- component_tutorials/simple_couple_
1 -
Outputs for different resource file settings.
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fields_and_grids_tutorials/regrid/
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Regrid tutorial

• Regridding Levitus at 1o to 2o.
• Uses 1 component to read in data.
• A coupler component calls Regrid
• A second component writes the result.

• Can run in parallel.
• Uses VM and does lat decomp lon decomp switch.

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