Reg FFT

[RAJENDRA1983]

Sir,

I am using the Intel XEON processor with Quadcore (8 Thread) VPX3-1220 SBC E3 1505L CPU. We are using intel IPP libraries for signal processing. Please confirm how many parallel FFTs and max. FFT length, I can run using parallel threads. Is there any timing analysis??

Please confirm..

Advance thanks

Rajendra

[Gennady_F_Intel]

Rajendra,

The max of IPP FFT length depends on the precisions and real or complex data types, namely:

for double precision complex DFT (64fc) the length upper bound is 67108863 (2^26 - 1).

for single precision complex DFT (32fc) the length upper bound is 134217727 (2^27 - 1).

for double precision complex FFT (64fc) the length upper bound is 2^27.

for double precision complex FFT (32fc) the length upper bound is 2^28.

There are no published perf results, as you may take the IPP Perf system, chose the list of functions you like to test ( e.x. ippsFFTFwd_CToC_32f), and run the perf system on your specific machine with your environment. The output performance results in clock per element would answer your question.

[RAJENDRA1983]

Thank you sir!!

My soubt is as i am using quad core Processor(8 threads) and i am running FFT 64k parallely four separate application threads.  Catch is each FFT consumes two cores of hardware?? In that case i can not run more than two FFTs parallely!! . Hence, requesting you to confirm!!

However as you suggested, i will check with iperf system and comeback to you sir.

Advance thanks 

Rajendra

[Gennady_F_Intel]

  Rajendra,

“running FFT 64k parallely four separate application threads.”

In that case, you may see the thread oversubscription which might lead to performance degradation.The general recommendation to set 1 OpenMP thread call ( ippSetNumThreads(1))

Or explicitly link your application against sequential versions of IPP and didn’t modify your code.

[RAJENDRA1983]

Dear Sir

Thank you!!!

[Gennady_F_Intel]

welcome:). The issue is closing and we will no longer respond to this thread. If you require additional assistance from Intel, please start a new thread. Any further interaction in this thread will be considered community only.