The Cooley-Tukey algorithm, published by James Cooley and John Tukey in 1965 (though a similar method was devised by Carl Friedrich Gauss around 1805 and unpublished for over a century), reduces the cost of computing a discrete Fourier transform from O(n^2) direct evaluation to O(n log n), one of the most widely used algorithms in computing, underlying digital signal processing, image compression, and large-integer multiplication. Its O(n log n) complexity remains the practical standard nearly 60 years later; whether an asymptotically faster general DFT algorithm is possible remains a formally open question in complexity theory.
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The Cooley-Tukey algorithm, published by James Cooley and John Tukey in 1965 (though a similar method was devised by Carl Friedrich Gauss around 1805 and unpublished for over a century), reduces the cost of computing a discrete Fourier transform from O(n^2) direct evaluation to O(n log n), one of the most widely used algorithms in computing, underlying digital signal processing, image compression, and large-integer multiplication. Its O(n log n) complexity remains the practical standard nearly 60 years later; whether an asymptotically faster general DFT algorithm is possible remains a formally open question in complexity theory.
The Cooley-Tukey fast Fourier transform algorithm computes the discrete Fourier transform of a length-n sequence in O(n log n) arithmetic operations, versus O(n^2) for direct evaluation of the defining sum, remaining the standard general-purpose FFT algorithm complexity in practical use as of 2026, though a matching unconditional lower bound proving no faster general algorithm can exist remains an open theoretical question.
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Limits Registry. LR-FFT-COMPLEXITY. Fastest general-purpose discrete Fourier transform algorithm complexity. 2026.