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CMSIS DSP RFFT - too much cycles

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Author
Knut H
Posted
8-Feb-2019 06:11 GMT
Toolset
ARM
New! CMSIS DSP RFFT - too much cycles

Hi,

I use the CMSIS DSP library to calculate a f32 RFFT with a block size of 1024. For this it takes 262823 cycles. I read in the white-paper that it should take 55538 cycles. Because of the measurement is too slow, i have to speed it up. What could be the reason of the too much cycles?

Thanks

My setup:
Cortex-M4 on a TI-MSP432
TI-Code Composer Studio
wait states = 0
function: arm_rfft_fast_f32()

white-paper: https://community.arm.com/cfs-file/__key/communityserver-blogs-components-weblogfiles/00-00-00-21-42/7563.ARM-white-paper-_2D00_-DSP-capabilities-of-Cortex_2D00_M4-and-Cortex_2D00_M7.pdf

Author
Westonsupermare Pier
Posted
8-Feb-2019 16:53 GMT
Toolset
ARM
New! RE: CMSIS DSP RFFT - too much cycles

Check optimization settings, and that building has FPU enabled.
Review listing file or disassembly of code for FPU instructions and tightness of generated code.

Author
Knut H
Posted
11-Feb-2019 05:47 GMT
Toolset
ARM
New! RE: CMSIS DSP RFFT - too much cycles

Hi,

email the notification ended in my spam folder...

- Yes the building has FPU enabled.
- Optimization settings: At first I used the default setting, then I set it to full speed setup. The difference was marginally.
- Yes, I think that I compare like with like. I calculate a RFFT F32 with block size 1024 on a Cortex-M4 without wait states.

What else could cause be the difference?

Thanks

Author
Andrew Neil
Posted
9-Feb-2019 12:57 GMT
Toolset
ARM
New! RE: the (sic) white-paper

What white paper?

Have you carefully compared all your options and settings to those used in that "white paper"?

Are you sure that your use case is comparable - ie, are you comparing like with like?

Author
Andrew Neil
Posted
9-Feb-2019 12:59 GMT
Toolset
ARM
New! RE: the (sic) white-paper

Oh - that one: http://community.arm.com/cfs-file/__key/communityserver-blogs-components-weblogfiles/00-00-00-21-42/7563.ARM-white-paper-_2D00_-DSP-capabilities-of-Cortex_2D00_M4-and-Cortex_2D00_M7.pdf !

Will this forum ever manage to recognise HTTPS URLs ?!

Author
Knut H
Posted
13-Feb-2019 05:30 GMT
Toolset
ARM
New! RE: the (sic) white-paper

My new reply from the 11th February is between the other replies... maybe it will not be recognized.

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