Can someone explain what a butterfly is in regards to DSP?
Wikipedia has this one covered:


  In the context of fast Fourier transform algorithms, a butterfly is 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, as described below.1 The earliest occurrence in print of the term is thought to be in a 1969 MIT technical report.[2][3] The same structure can also be found in the Viterbi algorithm, used for finding the most likely sequence of hidden states.


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