From fa080de7afc95aa1c19a6e6fc0e0708ced2eadc4 Mon Sep 17 00:00:00 2001 From: Joseph Hunkeler Date: Wed, 8 Jul 2015 20:46:52 -0400 Subject: Initial commit --- sys/vops/aiftxx.x | 45 +++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 45 insertions(+) create mode 100644 sys/vops/aiftxx.x (limited to 'sys/vops/aiftxx.x') diff --git a/sys/vops/aiftxx.x b/sys/vops/aiftxx.x new file mode 100644 index 00000000..2871590f --- /dev/null +++ b/sys/vops/aiftxx.x @@ -0,0 +1,45 @@ +# Copyright(c) 1986 Association of Universities for Research in Astronomy Inc. + +# AIFTXX -- Inverse fourier transform (complex transform, complex array). +# The fourier transform of the complex array A of length NPIX pixels is +# computed and the NPIX complex data points are returned in the complex array +# B. The transformation may be performed in place if desired. NPIX must be +# a power of 2. +# +# N.B.: The Fortran 77 standard guarantees that a complex datum is represented +# as two reals, and that the first real in storage order is the real part of +# the complex datum and the second real the imaginary part. We have defined +# A and B to be type COMPLEX arrays in the calling program, but FFT842 expects +# a REAL array containing (real,imag) pairs. The Fortran standard appears to +# guarantee that this will work. + +procedure aiftxx (a, b, npix) + +complex a[ARB] # transform (input) +complex b[ARB] # data (output) +int npix +int ier +pointer sp, xr, xi + +begin + call smark (sp) + call salloc (xr, npix, TY_REAL) + call salloc (xi, npix, TY_REAL) + + # Rearrange the elements of the A array as required by FFT842. + # Convert the array A of complex values into an array of reals + # and an array of imaginaries. + + call aupxr (a, Memr[xr], Memr[xi], npix) + + # Compute the inverse transform. + call fft842 (1, npix, Memr[xr], Memr[xi], ier) + if (ier == 1) + call fatal (1, "afftxx: npix not a power of 2") + + # Repack the real and imaginary arrays to form the complex output + # array. + call apkxr (Memr[xr], Memr[xi], b, npix) + + call sfree (sp) +end -- cgit