Gilbert Strang, author of the classic textbook Linear Algebra and Its Applications, referred to the Fast Fourier Transform, or FFT, as the most important numerical algorithm in our lifetime.
Wikipedia presents butterfly as "a portion of the computation that combines the results of smaller discrete Fourier transforms (DFTs) into a larger DFT, or vice versa (breaking a larger DFT up into subtransforms). The name "butterfly" comes from the shape of the data-flow diagram in the radix-2 case ..."
The question is: What was the first time that FFT was represented by Butterfly Diagram ? References would be appreciated.
