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WRF Software Development and Performance. NCAR: W. Skamarock, J. Dudhia, D. Gill, A. Bourgeois, W. Wang, C. Deluca, R. Loft NOAA/NCEP: Tom Black, Jim Purser, S. Gopal NOAA/FSL: T. Henderson, J. Middlecoff, L.Hart U. Oklahoma: M. Xue AFWA: J. Wegiel, D. McCormick

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wrf software development and performance

WRF Software Development andPerformance

NCAR: W. Skamarock, J. Dudhia, D. Gill, A. Bourgeois, W. Wang, C. Deluca, R. Loft

NOAA/NCEP: Tom Black, Jim Purser, S. Gopal

NOAA/FSL: T. Henderson, J. Middlecoff, L.Hart

U. Oklahoma: M. Xue

AFWA: J. Wegiel, D. McCormick

C. Coats (MCNC), J. Schmidt (NRL), V. Balaji (GFDL) S. Chen (UC Davis), J. Edwards (IBM)

Acknowledgement:

Significant funding for WRF software development from DoD HPCMO CHSSI program (CWO6)

John Michalakes, NCAR

wrf software
Goals

Community Model

Good performance

Portable across a range of architectures

Flexible, maintainable, understandable

Facilitate code reuse

Multiple dynamics/ physics options

Run-time configurable

Nested

Aspects of Design

Single-source code

Fortran90 modules, dynamic memory, structures, recursion

Hierarchical software architecture

Multi-level parallelism

CASE: Registry

Package-neutral APIs

I/O, data formats

Communication

IKJ Storage Order

Vector’s not dead yet!

WRF Software

WRF Users Workshop

software architecture
Software Architecture

Driver

Driver Layer

Config

Inquiry

DM comm

I/O API

Package

Independent

Solve

Mediation Layer

OMP

Config

Module

WRF Tile-callable

Subroutines

Data formats,

Parallel I/O

Package

Dependent

Message

Passing

Threads

Model Layer

External Packages

  • Driver: I/O, communication, multi-nests, state data
  • Model routines computational, tile-callable, thread-safe
  • Mediation layer: interface between model and driver
  • Interfaces to external packages

WRF Users Workshop

wrf multi layer domain decomposition
Single version of code for efficient execution on:

Distributed-memory

Shared-memory

Clusters of SMPs

Vector and microprocessors

WRF Multi-Layer Domain Decomposition

Logical domain

1 Patch, divided into multiple tiles

Model domains are decomposed for parallelism on two-levels

  • Patch: section of model domain allocated to a distributed memory node
  • Tile: section of a patch allocated to a shared-memory processor within a node; this is also the scope of a model layer subroutine.
  • Distributed memory parallelism is over patches; shared memory parallelism is over tiles within patches

Inter-processor communication

WRF Users Workshop

i o architecture
I/O Architecture
  • Requirements of I/O Infrastructure
    • Efficiency: key concern for operations
    • Flexibility: key concern in research
    • Both types of user-institution already heavily invested in I/O infrastructure
      • Operations: GRIB, BUFR
      • Research: NetCDF, HDF
    • “Portable I/O” – adaptable to range of uses, installations without affecting WRF and other programs that use the I/O infrastructure

WRF Users Workshop

i o architecture1
I/O Architecture
  • WRF I/O API
    • Package-independent interface to NetCDF, Fast-binary, HDF (planned)
    • Random access of fields by timestamp/name
    • Full transposition to arbitrary memory order
    • Built-in support for read/write of parallel file systems (planned)
    • Data-set centric, not file-centric (planned); Grid Computing
  • Additional WRF model functionality
    • Collection/distribution of decomposed data to serial datasets
    • Fast, asynchronous, “quilt-server” I/O from NCEP Eta model

WRF Users Workshop

i o performance

5 MB/s

16 MB/s

I/O Performance

120,000,000

netcdf

100,000,000

bin

80,000,000

bytes/second

60,000,000

40,000,000

20,000,000

0

0

1

4

i/o servers

WRF Users Workshop

wrf performance
WRF Performance
  • Platforms
    • IBM SP (blackforest.ucar.edu)
      • 293 4x375 Mhz Power3 nodes
      • Peak 1500 Mflop/s/cpu
    • Compaq TCS (lemieux.psc.edu)
      • 750 4x1 GHz EV68 nodes
      • Peak 2000 Mflop/s/cpu
  • Scaling efficiency (32 to 512pe)
    • IBM: 69 %
    • Compaq: 57 %
  • Efficiency relative to peak
    • 32pes: IBM (7%), Compaq (20%)
    • 512pes: IBM (5%), Compaq (11%)
  • Sustained Performance:
    • IBM: 39 Gflop/second
    • Compaq: 110 Gflop/second
  • 12 km CONUS
    • 425x300x35
    • 4.5 million cells
    • 22 Gflop/time step
  • 48 hour forecast
    • 21 minutes on 128p
    • 8 minutes on 512p
  • I/O time not included
model performance
Model Performance
  • Efficiency with respect to other models
    • WRF about 2x cost of NCEP Eta (mid 2001)
      • Complexity: WRF 1.6 times more operations for a given period of integration
      • Code efficiency: WRF .78 of Eta
    • Scientific or forecast efficiency…?

WRF Users Workshop

summary
Summary
  • Status
    • Third release: WRFV1.2, April 2002
    • Systems: IBM, Compaq, SGI, PC/Alpha Linux
    • Nesting, 3DVAR: first implementations this Summer
  • WRF software architecture designed to support development and maintenance as a community model serving operational and research users over a range of applications, and on a variety of computing architectures
  • Additional information: http://www.wrf-model.org

WRF Users Workshop

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