Fast Walsh–Hadamard transform
（重定向自Fast Walsh transform）
![The fast Walsh–Hadamard transform applied to a vector of length 8](/Images/godic/202501/12/Fast_walsh_hadamard_transform_8.svg4606.png")
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In computational mathematics, the Hadamard ordered fast Walsh–Hadamard transform (FWHTh) is an efficient algorithm to compute the Walsh–Hadamard transform (WHT). A naive implementation of the WHT would have a computational complexity of O(![N^2](/Images/godic/202501/12/6828feb224035a25980fcbdb76126b024606.png")
). The FWHTh requires only ![N \log N](/Images/godic/202501/12/81c6aab9f6afffdae37d04460c5327f64606.png")
additions or subtractions.