# time per FFT problem

**URL:** <https://forums.developer.nvidia.com/t/time-per-fft-problem/23410>\
**Category:** CUDA Programming and Performance\
**Created:** [July 8, 2011, 11:28pm UTC](https://forums.developer.nvidia.com/t/time-per-fft-problem/23410 "2011-07-08T23:28:17Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![hding001](https://developer.download.nvidia.com/images/forums/profile-default-devtalk-84.png) [@hding001](https://forums.developer.nvidia.com/u/hding001)\
**Post date:** [July 8, 2011, 11:28pm UTC](https://forums.developer.nvidia.com/t/time-per-fft-problem/23410/1 "2011-07-08T23:28:17Z")

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Hi all,

I need to benchmark the cufft performance. I find that if I do only one 1024FFT, the time is around 70us, but if I loop the FFT for 100 or 1000 times, the average time per FFT is around 10-12 us.

I learnt from others’ benchmarking results: time per FFT should around 1 or less us.  
Can you help to solve my problem if you know them? Thanks a lot.

My GPU is c2050, which is very powerful one.

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<div class="post-metadata">

**Author:** ![hding001](https://developer.download.nvidia.com/images/forums/profile-default-devtalk-84.png) [@hding001](https://forums.developer.nvidia.com/u/hding001)\
**Post date:** [July 11, 2011, 6:44pm UTC](https://forums.developer.nvidia.com/t/time-per-fft-problem/23410/2 "2011-07-11T18:44:39Z")

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> [@](#):
>
> Hi all,
> 
> I need to benchmark the cufft performance. I find that if I do only one 1024FFT, the time is around 70us, but if I loop the FFT for 100 or 1000 times, the average time per FFT is around 10-12 us.
> 
> I learnt from others’ benchmarking results: time per FFT should around 1 or less us.
> 
> Can you help to solve my problem if you know them? Thanks a lot.
> 
> My GPU is c2050, which is very powerful one.

Any prof can help with this? Thanks.

---

<div class="post-metadata">

**Author:** ![hding001](https://developer.download.nvidia.com/images/forums/profile-default-devtalk-84.png) [@hding001](https://forums.developer.nvidia.com/u/hding001)\
**Post date:** [July 11, 2011, 7:08pm UTC](https://forums.developer.nvidia.com/t/time-per-fft-problem/23410/3 "2011-07-11T19:08:48Z")

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> [@](#):
>
> Any prof can help with this? Thanks.

I try the same FFT for twice, I see the first FFT used 70us, but the second one only use 16us.

I understand I need to do large number of FFT to see the performance, my case is sometimes I need to do only 1FFT.

I want to see a good performance if I only need to do 1FFT. Anyone can suggest? Thanks.