Class to facilitate 1D cross correlation calculations. More...

#include <cpu_tracker.h>

Public Member Functions
	XCor1DBuffer (int xcorw)
	Constructs the buffer and initiates the FFT workers. More...

void	XCorFFTHelper (complex_t prof, complex_t prof_rev, scalar_t *result)
	Calculates a cross correlation much like https://en.wikipedia.org/wiki/Autocorrelation#Efficient_computation. More...

Public Attributes
kissfft< scalar_t >	fft_forward
	Handle to forward FFT kissfft instance. More...

kissfft< scalar_t >	fft_backward
	Handle to backward FFT kissfft instance. More...

int	xcorw
	Width of the cross correlation. More...

Detailed Description

Class to facilitate 1D cross correlation calculations.

Definition at line 9 of file cpu_tracker.h.

Constructor & Destructor Documentation

§ XCor1DBuffer()

XCor1DBuffer::XCor1DBuffer ( int xcorw )

inline

Constructs the buffer and initiates the FFT workers.

Definition at line 12 of file cpu_tracker.h.

12 : fft_forward(xcorw, false), fft_backward(xcorw, true), xcorw(xcorw)

13 {}

XCor1DBuffer::xcorw

int xcorw

Width of the cross correlation.

Definition: cpu_tracker.h:17

XCor1DBuffer::fft_backward

kissfft< scalar_t > fft_backward

Handle to backward FFT kissfft instance.

Definition: cpu_tracker.h:16

XCor1DBuffer::fft_forward

kissfft< scalar_t > fft_forward

Handle to forward FFT kissfft instance.

Definition: cpu_tracker.h:15

Member Function Documentation

§ XCorFFTHelper()

void XCor1DBuffer::XCorFFTHelper	(	complex_t *	prof,
		complex_t *	prof_rev,
		scalar_t *	result
	)

Calculates a cross correlation much like https://en.wikipedia.org/wiki/Autocorrelation#Efficient_computation.

Calculates the FFTs of both the normal and reverse profiles
Multiplies the FFT of the normal profile with the complex conjugate FFT of the reverse profile
Transforms the result back to obtain the cross correlation

Parameters

[in]	prof	The original profile.
[in]	prof_rev	The reversed profile.
[out]	result	Pre-allocated array that will hold the cross correlation.

Definition at line 138 of file cpu_tracker.cpp.

 {
     complex_t* fft_out = (complex_t*)ALLOCA(sizeof(complex_t)*xcorw);
     complex_t* fft_out_rev = (complex_t*)ALLOCA(sizeof(complex_t)*xcorw);
 
     fft_forward.transform(prof, fft_out);
     fft_forward.transform(prof_rev, fft_out_rev);
 
     // Multiply with conjugate of reverse
     for (int x=0;x<xcorw;x++) {
         fft_out[x] *= conjugate(fft_out_rev[x]);
     }
 
     fft_backward.transform(fft_out, fft_out_rev);
 
     for (int x=0;x<xcorw;x++)
         result[x] = fft_out_rev[ (x+xcorw/2) % xcorw ].real();
 }

Member Data Documentation

§ fft_backward

kissfft<scalar_t> XCor1DBuffer::fft_backward

Handle to backward FFT kissfft instance.

Definition at line 16 of file cpu_tracker.h.

§ fft_forward

kissfft<scalar_t> XCor1DBuffer::fft_forward

Handle to forward FFT kissfft instance.

Definition at line 15 of file cpu_tracker.h.

§ xcorw

int XCor1DBuffer::xcorw