David Wong

1
A Parallel Program Building Block

• David Wong
• EPA, NOAA
• Research Triangle Park, NC
• IAMA Conference
• UC Davis, December 5-7, 2007

2
Outline

• Parallel computing general background
• Stenex library
• CMAQ
• Summary and current work

3
Parallel Computing General Background

• Division of labour over a set of resources
• Various kinds of parallelism
• Hardware vector pipeline, super scalar
• Software loop, section, domain

4
Parallel Computing General Background (cont)

• Domain decomposition

5
Parallel Computing General Background (cont)

• Amdahls Law

6
Stenex Library

• It is for processor communication
• Hide nitty-gritty details
• One source code

7
Stenex Library (cont)

• Communication direction
• Data orientation

8
Stenex Library (cont)
9
Stenex Library (cont)

• Other communication types

10
CMAQ CTM (CCTM)

• Community Multiscale Air Quality - Chemistry
  Transport Model
• It was developed at EPA in the late 90s
• A similar version is used in the NOAA National
  Air Quality Forecast System
• Stenex is one of the essential libraries to
  create a parallel version of CMAQ and its
  associated process, ICON

11
CMAQ (cont)
12
Summary and Current Work

• A general parallel computing background was given
• Stenex library was introduced as a building in
  our application
• CMAQ general description and its performance were
  shown
• The same library is applied with extension to
  form a WRF-CMAQ two-ways coupling system

13
Preliminary results

• 12km grid, Eastern US
• CBIV and ae3
• 8/2/06 one-day simulation
• 1 min WRF time step
• CMAQ call frequency 4 and 1
• 16 processors

14
Preliminary results (cont)
15
Preliminary results (cont)
16
Preliminary results (cont)
17
Thank You !! Disclaimer The research
presented here was performed under the Memorandum
of Understanding between the U.S. Environmental
Protection Agency (EPA) and the U.S. Department
of Commerce's National Oceanic and Atmospheric
Administration (NOAA) and under agreement number
DW13921548. This work constitutes a contribution
to the NOAA Air Quality Program. Although it has
been reviewed by EPA and NOAA and approved for
publication, it does not necessarily reflect
their policies or views.