What many of us at Los Alamos National Labs, where high speed computing
has been near to tops in the world since the 50s, is that vector
processes are equally important in high speed computing.
Vector processes are not currently in vogue (unless things have changed
since I've retired). The problem with large numbers of processes is
keeping them busy. Ideally, you have large numbers of independent
operations. This is often possible in 3D, but not in lower dimensions.
Climate modeling is intrinsically 3D. Many physical processes
intrinsically require communication between cells (transport processes).
The problem is that the national labs in the 90s bought into cheap
parallel processors used by the gaming industry, where massive
independent operations are the name of the game. It is the gaming
industry that economically and in practice drives the computational
computing industry. Cray was the last company, perhaps in the world, to
be dedicated to scientific parallel processing.
Those that are more current can perhaps address this issue better than
Sat, 29 Aug 2009, Rich
> Climate Simulation Computer Becomes More Powerful08.24.09
> Remember the day you got a brand-new computer? Applications snapped open,
> processes that once took minutes finished in seconds, and graphics and
> animation flowed as smoothly as TV video. But several months and many new
> applications later, the bloom fell off the rose.
> Your lightning-fast computer no longer was fast. You needed more memory and
> faster processors to handle the gigabytes of new files now embedded in your
> Climate scientists can relate.
> They, too, need more powerful computers to process the sophisticated computer
> models used in climate forecasts. Such an expanded capability is now being
> developed at NASAís Goddard Space Flight Center in Greenbelt, Md.
> High-End Computing System Installed
> In August, Goddard added 4,128 new-generation Intel "Nehalem" processors to
> its Discover high-end computing system. The upgraded Discover will serve as
> the centerpiece of a new climate simulation capability at Goddard. Discover
> will host NASAís modeling contributions to the Intergovernmental Panel on
> Climate Change (IPCC), the leading scientific organization for assessing
> climate change, and other national and international climate initiatives.
> To further enhance Discoverís capabilities, Goddard will install another
> 4,128 Nehalem processors in the fall, bringing Discover to 15,160 processors.
> "We are the first high-end computing site in the United States to install
> Nehalem processors dedicated to climate research," said Phil Webster, chief
> of Goddardís Computational and Information Sciences and Technology Office
> (CISTO). "This new computing system represents a dramatic step forward in
> performance for climate simulations."
> Well-Suited for Climate Studies
> According to CISTO lead architect Dan Duffy, the Nehalem architecture is
> especially well-suited to climate studies. "Speed is an inherent advantage
> for solving complex problems, but climate models also require large memory
> and fast access to memory," he said. Each processor has 3 gigabytes of
> memory, among the highest available today. In addition, memory access is
> three to four times faster than Discoverís previous-generation processors.
> In preliminary testing of Discoverís Nehalem processors, NASA climate
> simulations performed up to twice as fast per processor compared with other
> nationally recognized high-end computing systems. The new computational
> capabilities also allowed NASA climate scientists to run high-resolution
> simulations that reproduced atmospheric features not previously seen in their
> For instance, "features such as well-defined hurricane eyewalls and
> convective cloud clusters appeared for the first time," said William Putman,
> acting lead of the Advanced Software Technology Group in Goddardís Software
> Integration and Visualization Office. "At these cloud-permitting resolutions,
> the differences are stunning."
> IPCC Simulations
> For the IPCC studies, scientists will run both longer-term and shorter-term
> climate projections using different computer models. A climate model from the
> Goddard Institute for Space Studies will perform simulations going back a
> full millennium and forward to 2100. Goddardís Global Modeling and
> Assimilation Office will use a climate model for projections of the next 30
> years and an atmospheric chemistry-climate model for short-term simulations
> of chemistry-climate feedbacks. The IPCC will use information from climate
> simulations such as these in its Fifth Assessment Report, which IPCC expects
> to publish in 2014.
> NASA climate simulation efforts also contribute to the U.S. Global Change
> Research Program, the U.S. Integrated Earth Observation System, and the U.S.
> Weather Research Program. Supported international programs include UNESCOís
> Intergovernmental Oceanographic Commission, the United Nations Environment
> Programme, the World Climate Research Programme, the World Meteorological
> Organization, and the World Weather Research Programme.
> The new computer setup can simulate using a 3.5 km grid size. Compare the
> Climate simulation output with a 27 km grid:
> Climate simulation output with a 3.5 km grid:
> The actual clouds from the GOES-O satellite:
> Now look at a complex simulation of a cloud around the Aleutian Islands known
> as a von Karman Vortex Street. A vortex street is a train of alternating
> clockwise and anticlockwise eddies. Here's the simulation given the different
> grid sizes again with the smaller size due to the new compute power.
> Finally a picture of what this bad boy looks like:
> Rich Blinne
> Member ASA
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Received on Sun Aug 30 08:59:15 2009
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