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- BACKGROUND:
- I started coding this because I couldn't find a fixed point FFT that didn't
- use assembly code. I started with floating point numbers so I could get the
- theory straight before working on fixed point issues. In the end, I had a
- little bit of code that could be recompiled easily to do ffts with short, float
- or double (other types should be easy too).
- Once I got my FFT working, I was curious about the speed compared to
- a well respected and highly optimized fft library. I don't want to criticize
- this great library, so let's call it FFT_BRANDX.
- During this process, I learned:
- 1. FFT_BRANDX has more than 100K lines of code. The core of kiss_fft is about 500 lines (cpx 1-d).
- 2. It took me an embarrassingly long time to get FFT_BRANDX working.
- 3. A simple program using FFT_BRANDX is 522KB. A similar program using kiss_fft is 18KB (without optimizing for size).
- 4. FFT_BRANDX is roughly twice as fast as KISS FFT in default mode.
- It is wonderful that free, highly optimized libraries like FFT_BRANDX exist.
- But such libraries carry a huge burden of complexity necessary to extract every
- last bit of performance.
- Sometimes simpler is better, even if it's not better.
-
- -- Mark Borgerding
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