1. GEOS-CHEM: Platforms and Resolution 4x5 is under control, many platform options exist. 2x2.5 is a factor of 5-6 slower than 4x5, but useful. global 1x1 problematic (< 10X faster than the atmosphere)

2. How can we run faster and increase model resolution? Use high resolution windows embedded in lower resolution global calculations. Run in parallel on more processors. Shouldn’t an N processor job finish N times sooner? Wait for computers to become faster.

3. Parallel Computing: Amdahl’s Law 90% parallel -> ~5X faster on 10 processors, < 10X faster on infinite number of processors

4. What is Overhead?

5. Algebraic version

6. Least Squares Fit of

7. Implications

8. Things can get worse

9. Maybe things can get better

10. Speculation: What if transport scaled as well as chemistry?

11. For more information about parallel overhead and Beowulf systems from someone with personal experience, see Robert G. Brown’s pages at http://www.phy.duke.edu/resources/computing/brahma/index.php or visit your local computer science library. The slides in this presentation are temporarily accessible at http://www.as.harvard.edu/people/staff/jhy/GEOS-CHEM Credit