Signal Complexity effect on FFT Execution TimeThis is a discussion on Signal Complexity effect on FFT Execution Time within the DSP forums in Other Technologies category; I'm currently using the kiss FFT library in 32-bit fixed point mode in some software. I'm always using the same length FFT e.g. 1024-point. I want to know whether the average execution time of the FFT algorithm is likely to be dependent on the input signal waveform complexity. i.e. would you expect it to run faster for a purely DC signal, versus a complex arbitrary waveform? Thanks in advance.... | ||||||||
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#1
08-26-2008, 07:50 PM
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 Signal Complexity effect on FFT Execution Time I'm currently using the kiss FFT library in 32-bit fixed point mode in some software. I'm always using the same length FFT e.g. 1024-point. I want to know whether the average execution time of the FFT algorithm is likely to be dependent on the input signal waveform complexity. i.e. would you expect it to run faster for a purely DC signal, versus a complex arbitrary waveform? Thanks in advance.  |
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#2
08-26-2008, 09:02 PM
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| Re: Signal Complexity effect on FFT Execution Time Does that mean that the order O( ) off the FFT algorithm is constant, and therefore the execution time depends only the execution speed of the particular mix of number arithmetic on the CPU? |
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#3
08-26-2008, 09:26 PM
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| Re: Signal Complexity effect on FFT Execution Time dim.raft@gmail.com wrote: > I'm currently using the kiss FFT library in 32-bit fixed point mode in > some software. I'm always using the same length FFT e.g. 1024-point. > I want to know whether the average execution time of the FFT algorithm > is likely to be dependent on the input signal waveform complexity. > i.e. would you expect it to run faster for a purely DC signal, versus > a complex arbitrary waveform? How fast it runs depends on how fast the machine executes floating point multiply and add. Some machines can multiply by zero faster than other numbers, others take the same time. -- glen |
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#4
08-27-2008, 01:25 AM
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| Re: Signal Complexity effect on FFT Execution Time On Tue, 26 Aug 2008 18:02:14 -0700 (PDT), dim.raft@gmail.com wrote: >Does that mean that the order O( ) off the FFT algorithm is >constant, and therefore the execution time depends only the execution >speed of the particular mix of number arithmetic on the CPU? The algorithm itself has no data dependence on the computations. So the same number of operations will be performed regardless of the data. Eric Jacobsen Minister of Algorithms Abineau Communications http://www.ericjacobsen.org Blog: http://www.dsprelated.com/blogs-1/hf/Eric_Jacobsen.php |
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#5
08-27-2008, 01:46 AM
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| Re: Signal Complexity effect on FFT Execution Time Thanks Eric. That's exactly the answer I was hoping for. |
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