The Fujin

1
The Fujin

• Development
• of
• Parallel Coupler

Takashi Arakawa arakawa_at_tokyo.rist.or.jp Research
Organization for Information Science Technology
2
General Meaning of Fujin

• A god of wind
• Inscribed in Chinese/Japanese Kanji characters

Painted by Khorin Ogata
3
God of Wind

• Very popular name in Japan
• Used in various fields

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Our Fujin

• Framework for meteorological model(s)
• Objectives
• parallel computing, domain nesting, coupling
• with minimal effort and minimal time
• Information hiding
• Modular and Layered Structure
• Fortran 90 employed

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What can you do with the Fujin?

• Parallelization
• Two Dimensional domain decomposition
• Domain Nesting
• Two way nesting
• No limitation for nesting depth
• Each coupled models can have different nesting
  depth
• Coupling
• Multi-model coupling

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Limitations of the Fujin

• Structured Grid based model only
• FEM, Spectral Model etc. are not supported
• No implementation of interpolation scheme for
  Nested Domains/Coupled Models
• interpolation scheme is meteorological issue
• not concerned problem for the Fujin
• Fujin provides only the simple interface

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Structure of the Fujin

• 25 modules, 450 procedures
• Three layers
• Parallel package layer
• parallel library package using MPI
• Data layer
• definition of data structure
• procedures for the data
• Interface layer
• Utility modules
• Error handling,logging,file management

existing model
Interface
Data Definition
Parallel Package
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Detail of the Interface Layer

• Coupler
• task control
• flux exchange
• Data Definition
• definition of the global variables
• Driver
• Initialization, Integration, Result output
• Inserting procedures of existing model

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Grid Structure

• User is required to define the location of each
  global variable in a initialization subroutine

call InitData(pot_tmp,potential temperature,
SCALAR_POINT)
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Domain Nesting (1)Time Integration Scheme

• Two way self-nesting

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Domain 1
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Domain 2
?
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Domain 3
Time
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Domain Nesting (2)Data Exchange Scheme

• Effective data exchange scheme

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Interpolation
?
?
12
CouplingTask Control Strategy

• Each model is attached to one of these tasks
• Models in the same task are computed serially
• Models in the different tasks are computed
  parallelly

Coupler
Task 1
Task 2
Task 3

• Models in the same task
• must have the same number of domain
• Having a different decomposition pattern is
  allowed

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Coupling (2)data exchange scheme

• Same as the scheme of domain nesting
• Type-D ? similar to MPCCI of GMD
• Difference from MPCCI is coupling strategy

14
Connecting the Model

• Target model is CReSS
• non-hydrostatic model developed by Nagoya Univ.
  and RIST

• Parallel Efficiency
• over 85 for 64 PEs
• Characteristic of CReSS, not the Fujin

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Connecting the Model (2)

• Domain Nesting Test
• Three dimensional mountain wave
• Three domains
• Interpolation and boundary condition?Meso-NH

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Future Plan

• Final goal
• To release the Fujin as free software
• Program structure is still complex
• Document