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

Features

• parallel: Enables parallel transform using ndarrays + rayon (enabled by default)
• avx: Enables rustfft’s avx feature (enabled by default)
• sse: Enables rustfft’s sse feature (enabled by default)
• neon: Enables rustfft’s neon feature (enabled by default)

Documentation

docs.rs

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

Represents different types of normalization methods.

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).

nddct2

Real-to-real Discrete Cosine Transform of type 2 DCT-2 (serial).

nddct3

Real-to-real Discrete Cosine Transform of type 3 DCT-3 (serial).

nddct4

Real-to-real Discrete Cosine Transform of type 4 DCT-4 (serial).

nddct1_par

Real-to-real Discrete Cosine Transform of type 1 DCT-I (parallel).

nddct2_par

Real-to-real Discrete Cosine Transform of type 2 DCT-2 (parallel).

nddct3_par

Real-to-real Discrete Cosine Transform of type 3 DCT-3 (parallel).

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).