The Fujin Development of Parallel Coupler Takashi Arakawa Research Organization for Information Science & Technology

General Meaning of Fujin A god of wind Inscribed in Chinese/Japanese Kanji characters wind god Painted by Khorin Ogata

God of Wind Very popular name in Japan –Used in various fields

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

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

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

Parallel Package Data Definition Interface existing model 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

Detail of the Interface Layer Coupler Driver Model Routines Data definition Driver Coupler –task control –flux exchange Data Definition –definition of the global variables Driver –Initialization, Integration, Result output –Inserting procedures of existing model

Grid Structure User is required to define the location of each global variable in a initialization subroutine i_endi_start i_end+1 j_start j_end j_end+1 (1,1) (ni,nj) (ni+1,nj+1) call InitData(pot_tmp,”potential temperature”, SCALAR_POINT)

Domain Nesting (1) Time Integration Scheme Two way self-nesting ① ② ③④ ⑤ ⑥⑦ Time Domain 1 Domain 2 Domain 3

Domain Nesting (2) Data Exchange Scheme Effective data exchange scheme ① ①② ③④ ① Interpolation

Coupling Task 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 1Task 2Task 3 Model 2 Model 1 Model 3 Model 4 Models in the same task  must have the same number of domain  Having a different decomposition pattern is allowed

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 C A C A C A C O C O C O C O

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

Connecting the Model (2) Domain Nesting Test –Three dimensional mountain wave –Three domains –Interpolation and boundary condition ← Meso-NH

Future Plan Final goal –To release the Fujin as free software Program structure is still complex Document