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

From: Dave Wallace <>
Date: Thu Sep 10 2009 - 11:47:45 EDT

Randy Isaac wrote:
> I do want to comment on this thread before it gets too stale. I'm
> delighted to see several people on this list with expertise in this
> field.
> Regarding Rich's comment about the increased computing capability for
> climate modeling, I like to follow the top 500 list at
> They do a semiannual ranking of the 500 fastest computers in the
> world. I usually incorporate in my talks the chart shown at
> The top
> line is the sum of the performance of those 500 fastest computers.
> This is a good proxy for the trend of compute power generally
> available for compute-intensive applications such as climate modeling.
> Note that this is an incredible compound annual growth rate of about
> 85%. It has been sustained since the rankings began in 1993 and there
> are no signs of it letting up.
> The stories behind the #1 rank data points are also interesting. The
> five points from 2002-2004 are the Earth Simulator from Japan. There
> was a major push during that time for the US to regain the lead. I was
> delighted when the Blue Gene project that I was connected with took
> that lead in 2004 and kept it for 7 rankings. This was a joint project
> between IBM and Lawrence Livermore National Labs (LLNL). Ironically,
> during that time I was the IBM rep for Los Alamos (LANL) which is
> always in rivalry with LLNL. LANL proposed a rather radical joint
> supercomputer project which I strongly opposed. My retirement cleared
> the way for them to revise the proposal and get it going. Sure enough,
> last year they took the #1 prize and have kept it for 3 rankings,
> breaking the petaflops mark in the process. This was code-named
> RoadRunner and was a joint project between IBM and LANL. This system
> is based on the Cell microprocessor which is the core for the Sony
> PlayStation 3. I still wonder who will have the last laugh. I
> continue to suspect that RoadRunner has a much more complex
> programming model than Blue Gene and that BlueGene will soon regain
> the lead. We will see.
> One final point. My estimate is that the computer performance growth
> that is due to hardware (i.e. faster transistors, etc.) is about 20%
> or less. The rest of the 85% is due to architecture and software
> improvements. What is also interesting is the sharp retreat from clock
> frequency to obtain performance. Remember the days when all the
> advertising for computers was about MHz and GHz? All that is gone. In
> fact, the Blue Gene system that took the #1 spot at the end of 2004
> had only about a 750MHz clock. Today the trend in general is to reduce
> the frequency to get speed. Why? Power consumption is the real
> limiter. Power increases by about the third power of frequency. The
> trick to increasing performance is to move to parallel processors.
> Reducing the clock to reduce the power to enable more processors leads
> to faster computers that are more efficient. So slower is faster.
> Randy
What exactly do these numbers represent? Are they the peak number of fp
ops per second if all goes just exactly right eg no cache misses... you
know the drill? Are they an expected peak number of fp ops/sec under
some reasonable assumptions? Lastly does anyone actually measure the
number of fp ops/sec that the application programs actually obtain?

I thought Rich's report that the Intel gaming vector floating point
instructions were being used for climate modeling was interesting.
Years ago when I was looking at the IA32 instructions I wondered if
using these vector instructions might pay off for numerical computation.

Dave W

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Received on Thu Sep 10 11:48:37 2009

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