Commit a25477a5 authored by Liam Healy's avatar Liam Healy
Browse files

Rewrite test-real-radix2 for clarity

New function realpart-vector makes a real vector with the real part of
the complex vector passed as an argument; was part of
test-real-radix2.  The computations being performed in
test-real-radix2 are now much clearer.
parent af3cb9e6
;; Example FFT: transform a pulse (using the "clean" fft interface)
;; Sumant Oemrawsingh, Sat Oct 31 2009 - 00:24
;; Time-stamp: <2009-11-08 22:39:41EST example.lisp>
;; Time-stamp: <2009-11-09 22:29:03EST example.lisp>
;;; Here is an example program modelled after the example given in Section
;;; 15.3 of the GSL Manual, which computes the FFT of a short pulse. To make
......@@ -58,20 +58,23 @@
(setf (maref vec i) (complex (urand))))
(defun fft-signal-real-noise (element-type size)
"From generated random data, return the data and DFT.
See fft_signal_real_noise in fft/"
(let ((data (make-urand-vector (list 'complex element-type) size)))
(values data (forward-discrete-fourier-transform data))))
(defun realpart-vector (complex-vector)
"The real vector consisting of the real part of the complex vector."
(let ((real-vector
(component-float-type (element-type complex-vector))
:dimensions (dimensions complex-vector))))
(loop for i below (total-size complex-vector) do
(setf (maref real-vector i)
(realpart (maref complex-vector i))))
(defun test-real-radix2 (element-type size)
"Test for FFT; returns the DFT answer and the computed FFT answer.
See test_real_radix2 in fft/"
(multiple-value-bind (complex-vector dft-answer)
(fft-signal-real-noise element-type size) ; results are complex
(let ((real-vector (make-marray element-type :dimensions (list size))))
(loop for i below size do
(setf (maref real-vector i)
(realpart (maref complex-vector i))))
(let ((forward-fft (forward-fourier-transform real-vector)))
(values dft-answer (unpack forward-fft :unpack-type 'complex))))))
(let ((random-vector (make-urand-vector (list 'complex element-type) size)))
(forward-discrete-fourier-transform random-vector)
(forward-fourier-transform (realpart-vector random-vector))
:unpack-type 'complex))))
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