Re: [asa] NASA - Climate Simulation Computer Becomes More Powerful

From: Lawrence Johnston <>
Date: Sun Aug 30 2009 - 13:03:02 EDT

It sounds like Los Alamos has come a long way in computing. In
1944-1945, when I was working on the Implosion bomb, we had very good
theorists like Fermi working on the propagation of fission events in a
compressed sphere of Plutonium; But their numerical calculations were
carried on by Richard Feynman, who had a group of about a dozen women
punching the keys on Marchant mechanical calculators. He kept running
around taking the tapes from one woman to the woman handling the next
stage of the calculation.

They made pretty good calculations of the energy output for the Trinity
explosion, but Oppenheimer apparently didn't have much confidence in
their prediction, because he ordered us, who were in a B-29 bomber ready
to fly directly over the explosion at 30,000 feet elevation, he ordered
us to stay 25 miles away from ground zero, which we reluctantly did.

Larry Johnston, ASA member


Lawrence H. Johnston home: 917 E. 8th st.

professor of physics, emeritus Moscow, Id 83843

University of Idaho (208) 882-2765

Fellow of the American Physical Society Website:



Bill Powers wrote:
> 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 I.
> bill

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Received on Sun Aug 30 13:03:19 2009

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