# Presentation: 219038

## SOO/STRC WRF Environmental Modeling System

- Robert Rozumalski
- National SOO Science and Training Resource CoordinatorNOAA/NWS/OCWWS/Training Division/FDTB

- Computer Resources

## Computer Resources

- How much computer power do I need?
- An often-asked question with the affirmative answer:

- 	It depends

**Notes:**

A commonly asked question

## Computer Resources

- How much computer power do I need?
- It depends if you are making real-time forecasts
- It depends if you are doing two-way nesting
- It depends upon the computational domain configuration
- It depends upon the horizontal grid spacing
- It depends on the model physics and dynamics

## Computer Resources

- Minimum requirements:
- Single CPU system 1.0GhZ or greater
- 1Gb physical memory
- 32Gb hard disk
- DVD-Rom drive
- Relatively current Linux distribution*

- * The WRF EMS version 2.1.2.2 has been tested on Fedora Core 2/3/4/5/6/7 RedHat Enterprise 3/4 and CentOS 5

## Computer Resources

- With minimum system you can run:
- The benchmark simulations
- A single, non-nested ARW or NMM core simulation
- Non real-time case and sensitivity studies with a grid spacing greater than 10km
- Real-time forecast accuracy will be degraded unless grid spacing is defined unrealistically large

## Computer Resources

- Suggested minimum system for real-time forecast purposes:
- Dual CPU (dual-core) system 2.0GhZ or greater
- INTEL Xeon (32- or 64-bit)
- AMD Opteron (32- or 64-bit)
- 1Gb physical memory per physical CPU (2Gb)
- 250Gb hard disk
- DVD-Rom drive
- Internet connection
- Relatively current Linux distribution*

- * The WRF EMS version 2.1.2.2 has been tested on Fedora Core 2/3/4/5/6/7 RedHat Enterprise 3/4 and CentOS 5

## Computer Resources

- A recommended system for real-time forecasting would include:
- Multi-CPU (quad-core+) system 2.6GhZ or greater
- INTEL Xeon (32- or 64-bit)
- AMD Opteron (32- or 64-bit)
- 1+ Gb physical memory per virtual CPU
- 2 x quad-core CPU = 8Gb+ of physical memory
- 500Gb or more of disk space
- DVD-RW drive
- Internet connection
- A current Linux distribution

## Computer Resources

- 32km

- 8km

- 4km

**A**

**B**

- For the same areal coverage:
- Grid **B** requires 4x more memory to run than **A ****(more physical memory)**
- Grid **B** requires 8x more clock time to run than **A ****(faster/more CPUs)**

## Computer Resources

- 	In order of priority when purchasing a modeling system:
- Multi-CPU (quad-core+) system
- CPU speed
- Physical memory
- More CPU cores
- More CPU speed
- More Physical Memory
- Additional disk space

## Computer Resources

- The impact of increasing the number of processors on the time to run a simulation
- The impact of running the model in a shared Vs. distributed memory environment on a multi-core system
- Any difference in scalability between the ARW and NMM cores

## Computer Resources

- Scaling of WRF EMS benchmark runs on multi-core systems

- 31min 40s

- 17min 41s

- 13min 42s

- 12min 49s

- 16min 31s

- 15min 18s

- 8min 39s

- 6min 45s

- 6min 9s

*All benchmarks executed on 2x dual core AMD Opteron 280 (2.4GhZ) system with 4Gb of memory running Fedora Core 6*

## Computer Resources

- Shared memory executables (SM) can not currently take advantage of “virtual CPUs” on multi-core systems
- Possible kernel limitation
- Set NCPUS in WRF.cshrc to number of physical CPUs for shared memory

## Computer Resources

- Limited scaling with distributed memory executables
- For distributed memory runs:
- Edit conf/wrf_run/run_DMrun.conf file
- Set “-np <procs>” where <procs> = number of CPUs x number of cores

## SOO/STRC WRF Environmental Modeling System

- The End

- Computer Resources