Hello DSP pros, I'm currently working on an optimized version of FFT for ARM NEON. (FHT, to be exact.) I'm neither a DSP specialist nor mathematician, and it was very hard for me to understand the way FFT works. Now it's about 50% done, and I have my doubt about this : "What's the use of this? What does it bring when my FFT runs 20times faster than some unnamed opensource ones on handhelds?" I really don't see any point int this. Maybe because I know too little about DSP. Could someone enlighten me? It would be really great to be motivated again. Thanks in advance!
[FFT] Why is the performance so important?
Started by ●November 14, 2011
Reply by ●November 14, 20112011-11-14
On Nov 14, 2:22�pm, "Caspian" <matrose@n_o_s_p_a_m.me.com> wrote:> Hello DSP pros, > > I'm currently working on an optimized version of FFT for ARM NEON. (FHT, to > be exact.) > > I'm neither a DSP specialist nor mathematician, and it was very hard for me > to understand the way FFT works. > > Now it's about 50% done, and I have my doubt about this : "What's the use > of this? What does it bring when my FFT runs 20times faster than some > unnamed opensource ones on handhelds?" > > I really don't see any point int this. Maybe because I know too little > about DSP. > > Could someone enlighten me? It would be really great to be motivated > again. > > Thanks in advance!Ask your boss. Performance is a comodity that is paid for, by the need to write specific code for the platform in question, as opposed to using generic libraries or code. One does not accept that extra cost / time / hazzle unless there are good reasons. Your boss is the only person to know the answer to your question. Rune
Reply by ●November 14, 20112011-11-14
Caspian wrote:> Hello DSP pros, > > I'm currently working on an optimized version of FFT for ARM NEON. (FHT, > to be exact.) > > I'm neither a DSP specialist nor mathematician, and it was very hard for > me to understand the way FFT works. > > Now it's about 50% done, and I have my doubt about this : "What's the use > of this? What does it bring when my FFT runs 20times faster than some > unnamed opensource ones on handhelds?"If you don't know why performance is important than it's probably not important. If you do this work because someone asked you to do it than you must ask this person why it pays you to improve performance.> I really don't see any point int this. Maybe because I know too little > about DSP.Better performance could reduce power consumption. bye Andreas -- Andreas H�nnebeck | email: acmh@gmx.de ----- privat ---- | www : http://www.huennebeck-online.de Fax/Anrufbeantworter: 0721/151-284301 GPG-Key: http://www.huennebeck-online.de/public_keys/andreas.asc PGP-Key: http://www.huennebeck-online.de/public_keys/pgp_andreas.asc
Reply by ●November 14, 20112011-11-14
>Caspian wrote: > >> Hello DSP pros, >> >> I'm currently working on an optimized version of FFT for ARM NEON.(FHT,>> to be exact.) >> >> I'm neither a DSP specialist nor mathematician, and it was very hardfor>> me to understand the way FFT works. >> >> Now it's about 50% done, and I have my doubt about this : "What's theuse>> of this? What does it bring when my FFT runs 20times faster than some >> unnamed opensource ones on handhelds?" > >If you don't know why performance is important than it's probably notimportant.>If you do this work because someone asked you to do it than you must askthis>person why it pays you to improve performance. > >> I really don't see any point int this. Maybe because I know too little >> about DSP. > >Better performance could reduce power consumption. > >bye >Andreas >-- >Andreas H�nnebeck | email: acmh@gmx.de >----- privat ---- | www : http://www.huennebeck-online.de >Fax/Anrufbeantworter: 0721/151-284301 >GPG-Key: http://www.huennebeck-online.de/public_keys/andreas.asc >PGP-Key: http://www.huennebeck-online.de/public_keys/pgp_andreas.asc > >Usually I'm the one in the company asking for the last bit of performance. :) I've been working mostly on graphics and image processing where the performance increases were literally visible. But FFT..... I simply know too little about its field of application. Any idea where heavily FFT'ing large blocks would be necessary on handhelds? cya PS : Deutsch kann ich auch, sogar besser als Englisch. Die sind aber beide Fremdsprachen fuer mich. Vielen Dank.
Reply by ●November 14, 20112011-11-14
On 14.11.11 4:23 , Caspian wrote:>> Caspian wrote: >> >>> Hello DSP pros, >>> >>> I'm currently working on an optimized version of FFT for ARM NEON. > (FHT, >>> to be exact.) >>> >>> I'm neither a DSP specialist nor mathematician, and it was very hard > for >>> me to understand the way FFT works. >>> >>> Now it's about 50% done, and I have my doubt about this : "What's the > use >>> of this? What does it bring when my FFT runs 20times faster than some >>> unnamed opensource ones on handhelds?" >> >> If you don't know why performance is important than it's probably not > important. >> If you do this work because someone asked you to do it than you must ask > this >> person why it pays you to improve performance. >> >>> I really don't see any point int this. Maybe because I know too little >>> about DSP. >> >> Better performance could reduce power consumption. >> >> bye >> Andreas >> -- >> Andreas H�nnebeck | email: acmh@gmx.de >> ----- privat ---- | www : http://www.huennebeck-online.de >> Fax/Anrufbeantworter: 0721/151-284301 >> GPG-Key: http://www.huennebeck-online.de/public_keys/andreas.asc >> PGP-Key: http://www.huennebeck-online.de/public_keys/pgp_andreas.asc >> >> > > Usually I'm the one in the company asking for the last bit of performance. > :) > I've been working mostly on graphics and image processing where the > performance increases were literally visible. > > But FFT..... I simply know too little about its field of application. > > Any idea where heavily FFT'ing large blocks would be necessary on > handhelds? > > cya > > > PS : Deutsch kann ich auch, sogar besser als Englisch. Die sind aber beide > Fremdsprachen fuer mich. Vielen Dank.Get a good book, e.g. Richard G. Lyons, Understanding Digital Signal Processing read and understand it, and return with follow-up questions after that. -- Tauno Voipio (Und dasselbe auf Deutsch)
Reply by ●November 14, 20112011-11-14
On Nov 14, 8:22�am, "Caspian" <matrose@n_o_s_p_a_m.me.com> wrote:> Hello DSP pros, > > I'm currently working on an optimized version of FFT for ARM NEON. (FHT, to > be exact.) > > I'm neither a DSP specialist nor mathematician, and it was very hard for me > to understand the way FFT works. > > Now it's about 50% done, and I have my doubt about this : "What's the use > of this? What does it bring when my FFT runs 20times faster than some > unnamed opensource ones on handhelds?" > > I really don't see any point int this. Maybe because I know too little > about DSP. > > Could someone enlighten me? It would be really great to be motivated > again. > > Thanks in advance!If you write an FFT that runs 20 times quicker, you can use a processor 20 times slower = less power, less cost OR you can perform 20 times more funtions, = more accuracy, more features, more stuff to put in your advertising brochure
Reply by ●November 14, 20112011-11-14
On 14 Nov, 15:23, "Caspian" <matrose@n_o_s_p_a_m.me.com> wrote:> PS : Deutsch kann ich auch, sogar besser als Englisch. Die sind aber beide > Fremdsprachen fuer mich. Vielen Dank.Njaaa.... du b�r vel heller tenke p� at engelsk er det mest utbredte spr�ket i det hele tatt. Greit nok at *du* kan skrive tysk (og jeg kan lese det, i alle fall delvis), men de aller fleste her har engelsk enten som sitt morsm�l eller som 1. fremmedspr�k. Hold deg til engelsk. Da n�r du det st�rste publikum - og det st�rste antall potensielle hjelpere. Rune
Reply by ●November 14, 20112011-11-14
On 11/14/2011 6:23 AM, Caspian wrote:> Any idea where heavily FFT'ing large blocks would be necessary on > handhelds?No. It's entirely up to your application. You might do FFTs because you need the *output* to display. You might do them for some other convenience. You might do them on larger blocks to improve convolutional efficiency. etc. In the end, it depends on whether you have enough compute power to get things done in an *acceptable* amount of time. Well, at least that's most often the driving consideration. By "compute power" we could mean time or watts I suppose but usually it's time. So, you could choose to do a "straight" DFT if the software just comes to you for free and the performance is adequate. Only you will know. Or, you could use an FFT if the software just comes to you for free and the performance is adequate .. for the same size it will be better than a straight DFT. etc. Fred
Reply by ●November 15, 20112011-11-15
Rune Allnor wrote:> On 14 Nov, 15:23, "Caspian" <matrose@n_o_s_p_a_m.me.com> wrote: > >> PS : Deutsch kann ich auch, sogar besser als Englisch. Die sind aber >> beide Fremdsprachen fuer mich. Vielen Dank. > > Njaaa.... du b�r vel heller tenke p� at engelsk er > det mest utbredte spr�ket i det hele tatt. Greit nok > at *du* kan skrive tysk (og jeg kan lese det, i alle > fall delvis), men de aller fleste her har engelsk > enten som sitt morsm�l eller som 1. fremmedspr�k. > > Hold deg til engelsk. Da n�r du det st�rste publikum - > og det st�rste antall potensielle hjelpere.Jeg tenker ikke at han har forstatt det ;-) Ha det bra Andreas -- Andreas H�nnebeck | email: acmh@gmx.de ----- privat ---- | www : http://www.huennebeck-online.de Fax/Anrufbeantworter: 0721/151-284301 GPG-Key: http://www.huennebeck-online.de/public_keys/andreas.asc PGP-Key: http://www.huennebeck-online.de/public_keys/pgp_andreas.asc
Reply by ●November 15, 20112011-11-15
Caspian wrote:>[..] >Andreas wrote: >> >>If you don't know why performance is important than it's probably not important. >>If you do this work because someone asked you to do it than you must ask this >>person why it pays you to improve performance. >>[..] >>Better performance could reduce power consumption. > > Usually I'm the one in the company asking for the last bit of performance. :) > I've been working mostly on graphics and image processing where the > performance increases were literally visible. > > But FFT..... I simply know too little about its field of application. > > Any idea where heavily FFT'ing large blocks would be necessary on > handhelds?As I already said above: it could reduce power consumption which means longer battery range on handhelds which will be loved by customers. bye Andreas -- Andreas H�nnebeck | email: acmh@gmx.de ----- privat ---- | www : http://www.huennebeck-online.de Fax/Anrufbeantworter: 0721/151-284301 GPG-Key: http://www.huennebeck-online.de/public_keys/andreas.asc PGP-Key: http://www.huennebeck-online.de/public_keys/pgp_andreas.asc
