Package de.gsi.math.spectra.fft

Class FloatFFT_1D

  • public class FloatFFT_1D
extends java.lang.Object
    Computes 1D Discrete Fourier Transform (DFT) of complex and real, single precision data. The size of the data can be an arbitrary number. This is a parallel implementation of split-radix and mixed-radix algorithms optimized for SMP systems.

    This code is derived from General Purpose FFT Package written by Takuya Ooura (http://www.kurims.kyoto-u.ac.jp/~ooura/fft.html) and from JFFTPack written by Baoshe Zhang (http://jfftpack.sourceforge.net/)
    Author:
    Piotr Wendykier (piotr.wendykier@gmail.com)

    • Constructor Summary

      Constructors 
      Constructor Description
      FloatFFT_1D​(int n)
      Creates new instance of FloatFFT_1D.

    • Method Summary

      All Methods Instance Methods Concrete Methods 
      Modifier and Type Method Description
      void complexForward​(float[] a)
      Computes 1D forward DFT of complex data leaving the result in a.
      void complexForward​(float[] a, int offa)
      Computes 1D forward DFT of complex data leaving the result in a.
      void complexInverse​(float[] a, boolean scale)
      Computes 1D inverse DFT of complex data leaving the result in a.
      void complexInverse​(float[] a, int offa, boolean scale)
      Computes 1D inverse DFT of complex data leaving the result in a.
      void realForward​(float[] a)
      Computes 1D forward DFT of real data leaving the result in a .
      void realForward​(float[] a, int offa)
      Computes 1D forward DFT of real data leaving the result in a .
      void realForwardFull​(float[] a)
      Computes 1D forward DFT of real data leaving the result in a .
      void realForwardFull​(float[] a, int offa)
      Computes 1D forward DFT of real data leaving the result in a .
      void realInverse​(float[] a, boolean scale)
      Computes 1D inverse DFT of real data leaving the result in a .
      void realInverse​(float[] a, int offa, boolean scale)
      Computes 1D inverse DFT of real data leaving the result in a .
      protected void realInverse2​(float[] a, int offa, boolean scale)  
      void realInverseFull​(float[] a, boolean scale)
      Computes 1D inverse DFT of real data leaving the result in a .
      void realInverseFull​(float[] a, int offa, boolean scale)
      Computes 1D inverse DFT of real data leaving the result in a .

      • Methods inherited from class java.lang.Object

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

    • Constructor Detail

      • FloatFFT_1D

        public FloatFFT_1D​(int n)
        Creates new instance of FloatFFT_1D.
        Parameters:
        n - size of data

    • Method Detail

      • complexForward

        public void complexForward​(float[] a)
        Computes 1D forward DFT of complex data leaving the result in a. Complex number is stored as two float values in sequence: the real and imaginary part, i.e. the size of the input array must be greater or equal 2*n. The physical layout of the input data has to be as follows:
         a[2*k] = Re[k],
 a[2*k+1] = Im[k], 0<=k<n
        Parameters:
        a - data to transform

      • complexForward

        public void complexForward​(float[] a,
                           int offa)
        Computes 1D forward DFT of complex data leaving the result in a. Complex number is stored as two float values in sequence: the real and imaginary part, i.e. the size of the input array must be greater or equal 2*n. The physical layout of the input data has to be as follows:
         a[offa+2*k] = Re[k],
 a[offa+2*k+1] = Im[k], 0<=k<n
        Parameters:
        a - data to transform
        offa - index of the first element in array a

      • complexInverse

        public void complexInverse​(float[] a,
                           boolean scale)
        Computes 1D inverse DFT of complex data leaving the result in a. Complex number is stored as two float values in sequence: the real and imaginary part, i.e. the size of the input array must be greater or equal 2*n. The physical layout of the input data has to be as follows:
         a[2*k] = Re[k],
 a[2*k+1] = Im[k], 0<=k<n
        Parameters:
        a - data to transform
        scale - if true then scaling is performed

      • complexInverse

        public void complexInverse​(float[] a,
                           int offa,
                           boolean scale)
        Computes 1D inverse DFT of complex data leaving the result in a. Complex number is stored as two float values in sequence: the real and imaginary part, i.e. the size of the input array must be greater or equal 2*n. The physical layout of the input data has to be as follows:
         a[offa+2*k] = Re[k],
 a[offa+2*k+1] = Im[k], 0<=k<n
        Parameters:
        a - data to transform
        offa - index of the first element in array a
        scale - if true then scaling is performed

      • realForward

        public void realForward​(float[] a)
        Computes 1D forward DFT of real data leaving the result in a . The physical layout of the output data is as follows:
        if n is even then 
         a[2*k] = Re[k], 0<=k<n/2
 a[2*k+1] = Im[k], 0<k<n/2
 a[1] = Re[n/2]
        if n is odd then 
         a[2*k] = Re[k], 0<=k<(n+1)/2
 a[2*k+1] = Im[k], 0<k<(n-1)/2
 a[1] = Im[(n-1)/2]
        This method computes only half of the elements of the real transform. The other half satisfies the symmetry condition. If you want the full real forward transform, use realForwardFull. To get back the original data, use realInverse on the output of this method.
        Parameters:
        a - data to transform

      • realForward

        public void realForward​(float[] a,
                        int offa)
        Computes 1D forward DFT of real data leaving the result in a . The physical layout of the output data is as follows:
        if n is even then 
         a[offa+2*k] = Re[k], 0<=k<n/2
 a[offa+2*k+1] = Im[k], 0<k<n/2
 a[offa+1] = Re[n/2]
        if n is odd then 
         a[offa+2*k] = Re[k], 0<=k<(n+1)/2
 a[offa+2*k+1] = Im[k], 0<k<(n-1)/2
 a[offa+1] = Im[(n-1)/2]
        This method computes only half of the elements of the real transform. The other half satisfies the symmetry condition. If you want the full real forward transform, use realForwardFull. To get back the original data, use realInverse on the output of this method.
        Parameters:
        a - data to transform
        offa - index of the first element in array a

      • realForwardFull

        public void realForwardFull​(float[] a)
        Computes 1D forward DFT of real data leaving the result in a . This method computes the full real forward transform, i.e. you will get the same result as from complexForward called with all imaginary parts equal 0. Because the result is stored in a, the size of the input array must greater or equal 2*n, with only the first n elements filled with real data. To get back the original data, use complexInverse on the output of this method.
        Parameters:
        a - data to transform

      • realForwardFull

        public void realForwardFull​(float[] a,
                            int offa)
        Computes 1D forward DFT of real data leaving the result in a . This method computes the full real forward transform, i.e. you will get the same result as from complexForward called with all imaginary part equal 0. Because the result is stored in a, the size of the input array must greater or equal 2*n, with only the first n elements filled with real data. To get back the original data, use complexInverse on the output of this method.
        Parameters:
        a - data to transform
        offa - index of the first element in array a

      • realInverse

        public void realInverse​(float[] a,
                        boolean scale)
        Computes 1D inverse DFT of real data leaving the result in a . The physical layout of the input data has to be as follows:
        if n is even then 
         a[2*k] = Re[k], 0<=k<n/2
 a[2*k+1] = Im[k], 0<k<n/2
 a[1] = Re[n/2]
        if n is odd then 
         a[2*k] = Re[k], 0<=k<(n+1)/2
 a[2*k+1] = Im[k], 0<k<(n-1)/2
 a[1] = Im[(n-1)/2]
        This method computes only half of the elements of the real transform. The other half satisfies the symmetry condition. If you want the full real inverse transform, use realInverseFull.
        Parameters:
        a - data to transform
        scale - if true then scaling is performed

      • realInverse

        public void realInverse​(float[] a,
                        int offa,
                        boolean scale)
        Computes 1D inverse DFT of real data leaving the result in a . The physical layout of the input data has to be as follows:
        if n is even then 
         a[offa+2*k] = Re[k], 0<=k<n/2
 a[offa+2*k+1] = Im[k], 0<k<n/2
 a[offa+1] = Re[n/2]
        if n is odd then 
         a[offa+2*k] = Re[k], 0<=k<(n+1)/2
 a[offa+2*k+1] = Im[k], 0<k<(n-1)/2
 a[offa+1] = Im[(n-1)/2]
        This method computes only half of the elements of the real transform. The other half satisfies the symmetry condition. If you want the full real inverse transform, use realInverseFull.
        Parameters:
        a - data to transform
        offa - index of the first element in array a
        scale - if true then scaling is performed

      • realInverse2

        protected void realInverse2​(float[] a,
                            int offa,
                            boolean scale)

      • realInverseFull

        public void realInverseFull​(float[] a,
                            boolean scale)
        Computes 1D inverse DFT of real data leaving the result in a . This method computes the full real inverse transform, i.e. you will get the same result as from complexInverse called with all imaginary part equal 0. Because the result is stored in a, the size of the input array must greater or equal 2*n, with only the first n elements filled with real data.
        Parameters:
        a - data to transform
        scale - if true then scaling is performed

      • realInverseFull

        public void realInverseFull​(float[] a,
                            int offa,
                            boolean scale)
        Computes 1D inverse DFT of real data leaving the result in a . This method computes the full real inverse transform, i.e. you will get the same result as from complexInverse called with all imaginary part equal 0. Because the result is stored in a, the size of the input array must greater or equal 2*n, with only the first n elements filled with real data.
        Parameters:
        a - data to transform
        offa - index of the first element in array a
        scale - if true then scaling is performed