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

From: Bill Powers <>
Date: Sun Aug 30 2009 - 14:31:38 EDT

Yes, that story is legendary at the Lab.

You must have a lot of great stories to tell about those early days.

Another legendary (I don't mean false, but rather often repeated
according to the tradition) story was one about someone talking about
how safe nuclear material was. He was handling two halves of a critical
mass in some sort of demonstration when the two halfs came together. An
intense flash of light followed. As a result, I believe this guy died
and a number of others had shortened lives. I don't remember all the
details. But there are a number of stories like that, things about
screwdrivers getting into places they oughtn't and the like.



On Sun, 30 Aug
2009, Lawrence Johnston wrote:

> 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 14:32:51 2009

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