Crate ndrustfft

ndrustfft: n-dimensional complex-to-complex FFT, real-to-complex FFT and real-to-real DCT

This library is a wrapper for RustFFT, RustDCT and RealFft that enables performing FFTs and DCTs of complex- and real-valued data on n-dimensional arrays (ndarray).

ndrustfft provides Handler structs for FFT’s and DCTs, which must be provided alongside with the arrays to the respective functions (see below) . The Handlers implement a process function, which is a wrapper around Rustfft’s process. Transforms along the outermost axis are in general the fastest, while transforms along other axis’ will temporarily create copies of the input array.

Parallel

The library ships all functions with a parallel version which leverages the parallel iterators of the ndarray crate.

Available transforms

Complex-to-complex

• fft : ndfft, ndfft_par
• ifft: ndifft,ndifft_par

Real-to-complex

• fft_r2c : ndfft_r2c, ndfft_r2c_par,

Complex-to-real

• ifft_r2c: ndifft_r2c,ndifft_r2c_par

Real-to-real

• dct1: nddct1,nddct1_par
• dct2: nddct2,nddct2_par
• dct3: nddct3,nddct3_par
• dct4: nddct4,nddct4_par

Example

2-Dimensional real-to-complex fft along first axis

use ndarray::{Array2, Dim, Ix};
use ndrustfft::{ndfft_r2c, Complex, R2cFftHandler};

let (nx, ny) = (6, 4);
let mut data = Array2::<f64>::zeros((nx, ny));
let mut vhat = Array2::<Complex<f64>>::zeros((nx / 2 + 1, ny));
for (i, v) in data.iter_mut().enumerate() {
    *v = i as f64;
}
let mut fft_handler = R2cFftHandler::<f64>::new(nx);
ndfft_r2c(
    &data.view(),
    &mut vhat.view_mut(),
    &mut fft_handler,
    0,
);

Normalization

RustFFT, RustDCT and RealFft do not normalise, while this library applies normalization as scipy by default. This means, inverse ffts are divided by a factor of data.len(), and dcts are multiplied by two. It is possible to switch from the default normalization to no normalization, or to apply a custom normalization by using the normalization builder.

See: examples/fft_norm

Versions

Changelog

Structs

• Complex
  A complex number in Cartesian form.
• DctHandler
  n-dimensional real-to-real Cosine Transform.
• FftHandler
  n-dimensional complex-to-complex Fourier Transform.
• R2cFftHandler
  n-dimensional real-to-complex Fourier Transform.

Enums

• Normalization
  Normalize spectrum

Traits

• FftNum
  Generic floating point number, implemented for f32 and f64
• Zero
  Defines an additive identity element for Self.

Functions

• nddct1
  Real-to-real Discrete Cosine Transform of type 1 DCT-I (serial).
• nddct1_par
  Real-to-real Discrete Cosine Transform of type 1 DCT-I (parallel).
• nddct2
  Real-to-real Discrete Cosine Transform of type 2 DCT-2 (serial).
• nddct2_par
  Real-to-real Discrete Cosine Transform of type 2 DCT-2 (parallel).
• nddct3
  Real-to-real Discrete Cosine Transform of type 3 DCT-3 (serial).
• nddct3_par
  Real-to-real Discrete Cosine Transform of type 3 DCT-3 (parallel).
• nddct4
  Real-to-real Discrete Cosine Transform of type 4 DCT-4 (serial).
• nddct4_par
  Real-to-real Discrete Cosine Transform of type 4 DCT-4 (parallel).
• ndfft
  Complex-to-complex Fourier Transform (serial).
• ndfft_par
  Complex-to-complex Fourier Transform (parallel).
• ndfft_r2c
  Real-to-complex Fourier Transform (serial).
• ndfft_r2c_par
  Real-to-complex Fourier Transform (parallel).
• ndifft
  Complex-to-complex Inverse Fourier Transform (serial).
• ndifft_par
  Complex-to-complex inverse Fourier Transform (parallel).
• ndifft_r2c
  Complex-to-real inverse Fourier Transform (serial).
• ndifft_r2c_par
  Complex-to-real inverse Fourier Transform (parallel).