when should one perform fft based filtering?
in [DSP]
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From: Rune Allnor on 28 Jul 2010 11:21 On 28 Jul, 17:11, Jerry Avins <j...(a)ieee.org> wrote: > On 7/27/2010 6:16 PM, robert bristow-johnson wrote: > > > On Jul 27, 4:45 pm, Jerry Avins<j...(a)ieee.org> wrote: > >> On 7/27/2010 10:24 AM, Rune Allnor wrote: > > >> ... > > >>> But the computational algorithms - and thus the computational > >>> workloads - are different. > > >> The algorithms, workloads, and latencies differ, but the results can be > >> bit exact. > > > "bit exact" means that the round-off error would be identical in both > > cases. ... > > I was careful to write "can be". That is, of course, given enough bits > to calculate with. My aim was to challenge Rune's mere approximation. So you dismiss the concept of numerical analysis? The idea that two algorithms for computing the same quantity can, and usually do, differe significantly wrt numerical inaccuracies? Rune
From: Jerry Avins on 28 Jul 2010 11:44 On 7/28/2010 11:21 AM, Rune Allnor wrote: > On 28 Jul, 17:11, Jerry Avins<j...(a)ieee.org> wrote: >> On 7/27/2010 6:16 PM, robert bristow-johnson wrote: >> >>> On Jul 27, 4:45 pm, Jerry Avins<j...(a)ieee.org> wrote: >>>> On 7/27/2010 10:24 AM, Rune Allnor wrote: >> >>>> ... >> >>>>> But the computational algorithms - and thus the computational >>>>> workloads - are different. >> >>>> The algorithms, workloads, and latencies differ, but the results can be >>>> bit exact. >> >>> "bit exact" means that the round-off error would be identical in both >>> cases. ... >> >> I was careful to write "can be". That is, of course, given enough bits >> to calculate with. My aim was to challenge Rune's mere approximation. > > So you dismiss the concept of numerical analysis? The idea that > two algorithms for computing the same quantity can, and usually > do, differe significantly wrt numerical inaccuracies? Of course not. I reject the notion that multiplication in the frequency domain merely approximates convolution in the time domain. If that isn't what you wrote, I misunderstood you. Jerry -- Engineering is the art of making what you want from things you can get. �����������������������������������������������������������������������
From: Steve Pope on 28 Jul 2010 12:37
Jerry Avins <jya(a)ieee.org> wrote: >On 7/28/2010 2:26 AM, Nasser M. Abbasi wrote: >> On 7/27/2010 10:34 PM, Steve Pope wrote: >>> If different frequencies travel at different velocities [..] >> How can a frequency travel at some "velocity"? >Frequencies moving at different speeds is semantic shorthand for energy >at different frequencies moving at different speeds. Thank you, Jerry. Steve |