All FFT's need double precision

Article: PhysX87: Software Deficiency
By: Vincent Diepeveen (, July 19, 2010 3:06 pm
Room: Moderated Discussions
David Kanter ( on 7/19/10 wrote:
>Vincent, you are missing my point.
>John Mann said:
>"Given a 9600GT at 700/1600 core shader has around 4-500GFLOPS of processing power,
>it wouldn't be hard to see it happen."
>A 9600GT has either very very slow DP, or none altogether. My point was that while
>the GPU has a fair bit of FLOP/s, it's not that far off from a CPU.
>If we are talking about double precision, then the difference between GPUs and
>CPUs narrows even further. Which just reinforces my point.

Your point has been taken David.

However our concept of speed differences might be slighty different.

A factor 8 difference in single precision floating point is really a lot. With the slow progress of cpu's past few years, realize at home i run at 4 socket AMD 8356 2.3Ghz @ 16 real cores, as i could build it for under 1000 euro (and yes it has no case and is a noisy thing in my office at 1.5 meters away from where i sit here), whereas on paper there is those great new processors like magny cours and 6 core westmere @ 3.x Ghz, however they're all $$$$.

The 16 core is busy trial factoring prime numbers as we speak. It's final destiny will be a number crunching machine intended for the chessprogram to parameter tune.

Of course as i just compete against big army teams (N*SA) and i'm not paid, i first await until i have some sort of income from wherever.

Until then it's bloody fast in trial factoring at 16 cores. On paper a GPU would be able to do that fast as well and a project is underway trying to get that going (at nvidia), yet they're not very realistic so far comparing factoring times, as the GPU they use and its power usage is more than this entire 16 core box, which still beats it.

There is really very few applications that can use GPU's well. Basically it is applications custom made by a company or by an individual (that's seldom the case) and usually it gets compared with real crappy optimized software for the PC.

For double precision the GPU's so far are total pathetic; if we see the power usage and the amount of gflops it produces double precision effectively that's just a total joke. That can't even closely compete yet with the very well optimized SIMD codes for the intels and amd's x64 cpu's.

So let's not be overly optimistic yet what so far has been achieved in double precision land by gpu's. There is a HANDFUL of organisations that have put total fulltime effort in writing code for gpu's, and THEY have fast single precision code. Also usually those departments don't pay their own powerbill...

So as soon as that you can make use of GPU hardware the difference then is so huge between a GPU and a CPU that it's just not even a contest, it's very similar like comparing a 48 core magny cours box in crunching performance with a Q6600 chippie.

Seemingly BP did not really invest there major league unlike Shell.


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TopicPosted ByDate
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            You are just quoting SINGLE precision flops? OMG what planet do you live? Vincent Diepeveen2010/07/19 09:26 AM
              The prior poster was talking about SP (NT)David Kanter2010/07/19 10:34 AM
                All FFT's need double precisionVincent Diepeveen2010/07/19 01:02 PM
                  All FFT's need double precisionDavid Kanter2010/07/19 01:09 PM
                    All FFT's need double precisionVincent Diepeveen2010/07/19 03:06 PM
                  All FFT's need double precision - notMichael S2010/07/20 12:16 AM
                    All FFT's need double precision - notUngo2010/07/20 11:04 PM
                      All FFT's need double precision - notMichael S2010/07/21 01:35 PM
                      All FFT's need double precision - notEduardoS2010/07/21 01:52 PM
                        All FFT's need double precision - notAnon2010/07/21 04:23 PM
                          All FFT's need double precision - notRicardo B2010/07/26 06:46 AM
                        I'm on a boat!anon2010/07/22 10:42 AM
                        All FFT's need double precision - notVincent Diepeveen2010/07/24 10:39 PM
                          All FFT's need double precision - notslacker2010/07/25 02:27 AM
                            All FFT's need double precision - notRicardo B2010/07/26 06:40 AM
                          All FFT's need double precision - notEduardoS2010/07/25 07:37 AM
                            All FFT's need double precision - notMichael S2010/07/25 09:43 AM
                    All FFT's need double precision - notVincent Diepeveen2010/07/24 10:19 PM
      A bit off baseEduardoS2010/07/08 03:08 PM
        A bit off baseGroo2010/07/08 05:11 PM
          A bit off basejohn mann2010/07/08 05:58 PM
            All right...let's cool it...David Kanter2010/07/08 06:54 PM
    A bit off baseVincent Diepeveen2010/07/19 02:36 PM
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