# 2D FFT performance on GTX Titan

Hi guys,
i know FFT is a useful performance benchmark, and GPU do it very well expecially with more then 1024 point.
I would like to know processing time for a 2D FFT with 4096x4096 point because i need to use it in a real time application.

Thanks a lot.

I’m using a 3D FFT and I assure you it’s really fast. With almost 2 M elements it takes ~0.7 ms to perform each of these functions:

``````cufftExecR2C()
cufftExecC2R()
``````

So, knowing that FFT is O(n log n), you can estimate how much it will take you. Although, the best way to know it is to run your own benchmark.

Thanks for your reply, of course i will know the exact latency after having tested the benchmark, but at the moment we are still waiting for the Titan from the dealer…

2M = 2 million of elements. In my case, 2 million of floats.
To estimate the processing time in your case, having O(n log n) complexity, you can use my time: 7·10⁻⁴ s

You have a conversion factor: C = 7·10⁻⁴ / (2·10⁶·log(2·10⁶))
so, if I’m not wrong,
~16·10⁶ · C = ~6.4·10⁻³s = ~6.4 ms

As I told you, the best way to know it, is to make your own benchmark and see the results because there could be another factors affecting your performance.