程序包 edu.princeton.cs.algs4

类 FFT

  • public class FFT
extends java.lang.Object
    The FFT class provides methods for computing the FFT (Fast-Fourier Transform), inverse FFT, linear convolution, and circular convolution of a complex array.

    It is a bare-bones implementation that runs in n log n time, where n is the length of the complex array. For simplicity, n must be a power of 2. Our goal is to optimize the clarity of the code, rather than performance. It is not the most memory efficient implementation because it uses objects to represents complex numbers and it it re-allocates memory for the subarray, instead of doing in-place or reusing a single temporary array.

    For additional documentation, see Section 9.9 of Algorithms, 4th Edition by Robert Sedgewick and Kevin Wayne.

    • 方法概要

      修饰符和类型 方法 说明
      static Complex[] cconvolve​(Complex[] x, Complex[] y)
      Returns the circular convolution of the two specified complex arrays.
      static Complex[] convolve​(Complex[] x, Complex[] y)
      Returns the linear convolution of the two specified complex arrays.
      static Complex[] fft​(Complex[] x)
      Returns the FFT of the specified complex array.
      static Complex[] ifft​(Complex[] x)
      Returns the inverse FFT of the specified complex array.
      static void main​(java.lang.String[] args)
      Unit tests the FFT class.

      • 从类继承的方法 java.lang.Object

        clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

    • 方法详细资料

      • fft

        public static Complex[] fft​(Complex[] x)
        Returns the FFT of the specified complex array.
        参数:
        x - the complex array
        返回:
        the FFT of the complex array x
        抛出:
        java.lang.IllegalArgumentException - if the length of x is not a power of 2

      • ifft

        public static Complex[] ifft​(Complex[] x)
        Returns the inverse FFT of the specified complex array.
        参数:
        x - the complex array
        返回:
        the inverse FFT of the complex array x
        抛出:
        java.lang.IllegalArgumentException - if the length of x is not a power of 2

      • cconvolve

        public static Complex[] cconvolve​(Complex[] x,
                                  Complex[] y)
        Returns the circular convolution of the two specified complex arrays.
        参数:
        x - one complex array
        y - the other complex array
        返回:
        the circular convolution of x and y
        抛出:
        java.lang.IllegalArgumentException - if the length of x does not equal the length of y or if the length is not a power of 2

      • convolve

        public static Complex[] convolve​(Complex[] x,
                                 Complex[] y)
        Returns the linear convolution of the two specified complex arrays.
        参数:
        x - one complex array
        y - the other complex array
        返回:
        the linear convolution of x and y
        抛出:
        java.lang.IllegalArgumentException - if the length of x does not equal the length of y or if the length is not a power of 2

      • main

        public static void main​(java.lang.String[] args)
        Unit tests the FFT class.
        参数:
        args - the command-line arguments