All FFT's need double precision - not

Article: PhysX87: Software Deficiency
By: Vincent Diepeveen (, July 24, 2010 10:39 pm
Room: Moderated Discussions
EduardoS ( on 7/21/10 wrote:
>Ungo (a@b.c.d.e) on 7/21/10 wrote:
>>24-bit mantissa is usually overkill there, too. It turns out that when you do
>>double blind testing, essentially nobody can tell the difference between 24-bit/192KHz
>>and the same audio sample resampled to 16/44.1. The few who can are young people
>>with truly exceptional high frequency hearing extending a little above 20 KHz.
>>You could provide enough performance for such people with 48 KHz sampling. 96
>>KHz sampling is dumb, and 192K is absurd. 24-bit sample depth is... meh. There's
>>not much need for it, and the ADCs/DACs don't deliver true 24-bit dynamic range anyways.
>Get that data, pass on FFT, separate frequencies, apply distortion and emulate
>an 1969 amplifier, make popular actresses' voices look good and assembly everything to make a hit, is 16/44.1 enough?

Yeah and without Michael knowing some of the most popular multimedia software he runs on his own machine are using the intel math libraries (double precision SSE2+) for all that.

It's a discussion about nothing interesting though, as all this DFT doesn't run in the HPC domain. HPC is all double precision.

And these guys have most hunger for more calculation power.

In case of audio and video what we'd need first is more efficient software for todays processors, for example using SIMD very well and some up to date algorithms instead of brute force calculated stuff :)

All that multimedia is about nothing, as obviously for graphics the GPU has been invented and such simulations seldom get some system time on a supercomputer. It is about software efficiency on PC's, it's not about whether we need an increase in single precision or double precision hardware.

It's about what actually runs in HPC and that's double precision and the hunger after faster double precision is total unlimited. Majority of those calculations have been conversed to FFT or can be using FFT.

Please note Michael doesn't really see the difference between FFT and DFT, but we'll forgive him that.

DFT gets used to recognize objects and patterns usually, and gets used for rough sound conversions, FFT gets used for accurate calculations and is the big system time eater.

Pattern recognition and machine learning is one of my expertises by the way and i don't really see a lot of jobs at the job sites for it. There is a few military applications to it and you speak about software that for example recognizes 100k different facial expressions full automatic (who needs a photo for a passport at a specific angle huh?), yet all that is plug in technology nowadays.

Tells you more about who Michael is, rather than what HPC is doing. HPC is FFT not DFT.


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            You are just quoting SINGLE precision flops? OMG what planet do you live? Vincent Diepeveen2010/07/19 09:26 AM
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                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
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                        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
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          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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