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Re: FFT Speeds

From Paul Rubin <no.email@nospam.invalid>
Newsgroups comp.arch.embedded
Subject Re: FFT Speeds
Date 2020-03-31 18:41 -0700
Organization A noiseless patient Spider
Message-ID <87sgho2da0.fsf@nightsong.com> (permalink)
References <ca835548-9fb2-4f5b-bd74-7b7d45fd5c84@googlegroups.com> <9dtlo1ebz00y$.onmgsjic51qw.dlg@40tude.net> <BPRgG.135301$MZ3.6724@fx22.iad>

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Clifford Heath <no.spam@please.net> writes:
> All other things being equal, doubling the length of an FFT adds one
> complex multiply per sample. So performance is O(log2(N))

I think you mean N log N.  Usually we think of complex multiplication as
4 real multiplications plus 2 additions.  I wonder if (on machines with
1 cycle MAC) that makes complex FFT 4x slower than real FFT, or if they
have some interesting optimizations, parallelism, etc.

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Thread

FFT Speeds Rick C <gnuarm.deletethisbit@gmail.com> - 2020-03-30 12:11 -0700
  Re: FFT Speeds David Brown <david.brown@hesbynett.no> - 2020-03-30 21:50 +0200
    Re: FFT Speeds Stef <stef33d@yahooI-N-V-A-L-I-D.com.invalid> - 2020-03-31 09:33 +0200
  Re: FFT Speeds dalai lamah <antonio12358@hotmail.com> - 2020-03-31 16:14 +0200
    Re: FFT Speeds Clifford Heath <no.spam@please.net> - 2020-04-01 12:07 +1100
      Re: FFT Speeds Paul Rubin <no.email@nospam.invalid> - 2020-03-31 18:41 -0700
        Re: FFT Speeds Clifford Heath <no.spam@please.net> - 2020-04-01 13:40 +1100
          Re: FFT Speeds Rick C <gnuarm.deletethisbit@gmail.com> - 2020-03-31 20:53 -0700
            Re: FFT Speeds Clifford Heath <no.spam@please.net> - 2020-04-01 18:45 +1100
            Re: FFT Speeds Clive Arthur <cliveta@nowaytoday.co.uk> - 2020-04-01 17:32 +0100
              Re: FFT Speeds Rick C <gnuarm.deletethisbit@gmail.com> - 2020-04-01 12:20 -0700
                Re: FFT Speeds Clive Arthur <cliveta@nowaytoday.co.uk> - 2020-04-02 09:40 +0100
                Re: FFT Speeds Rick C <gnuarm.deletethisbit@gmail.com> - 2020-04-02 02:00 -0700
                Re: FFT Speeds upsidedown@downunder.com - 2020-04-02 12:50 +0300
              Re: FFT Speeds Richard Damon <Richard@Damon-Family.org> - 2020-04-02 08:02 -0400
                Re: FFT Speeds Rick C <gnuarm.deletethisbit@gmail.com> - 2020-04-02 11:16 -0700
                Re: FFT Speeds Tauno Voipio <tauno.voipio@notused.fi.invalid> - 2020-04-02 21:33 +0300
                Re: FFT Speeds Rick C <gnuarm.deletethisbit@gmail.com> - 2020-04-02 12:39 -0700
                Re: FFT Speeds Paul Rubin <no.email@nospam.invalid> - 2020-04-02 20:33 -0700
                Re: FFT Speeds Rick C <gnuarm.deletethisbit@gmail.com> - 2020-04-02 20:43 -0700
                Re: FFT Speeds upsidedown@downunder.com - 2020-04-03 09:34 +0300
                Re: FFT Speeds Rick C <gnuarm.deletethisbit@gmail.com> - 2020-04-03 01:29 -0700
                Re: FFT Speeds David Brown <david.brown@hesbynett.no> - 2020-04-03 12:23 +0200
                Re: FFT Speeds Clifford Heath <no.spam@please.net> - 2020-04-03 21:48 +1100
                Re: FFT Speeds Rick C <gnuarm.deletethisbit@gmail.com> - 2020-04-03 10:38 -0700
                Re: FFT Speeds Clive Arthur <cliveta@nowaytoday.co.uk> - 2020-04-04 11:50 +0100
                Re: FFT Speeds David Brown <david.brown@hesbynett.no> - 2020-04-03 09:12 +0200
                Re: FFT Speeds Rick C <gnuarm.deletethisbit@gmail.com> - 2020-04-03 01:30 -0700
                Re: FFT Speeds David Brown <david.brown@hesbynett.no> - 2020-04-03 12:39 +0200
          Re: FFT Speeds Paul Rubin <no.email@nospam.invalid> - 2020-04-01 10:43 -0700
            Re: FFT Speeds Clifford Heath <no.spam@please.net> - 2020-04-02 13:26 +1100
      Re: FFT Speeds Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> - 2020-04-01 17:27 -0400

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