fft(3P) Sun Performance Library fft(3P)NAMEfft - Fast Fourier transform subroutines
OVERVIEW
The signal processing software in Sun Performance Library includes a
set of routines based on public domain packages FFTPACK and VFFPACK
that computes the Fast Fourier Transform. These routines are now being
replaced by a new interface (Perflib interface).
MAPPING
Below is a mapping of routines from the FFTPACK interface and the new
Perflib interface. See individual man pages for more detail.
FFTPACK interface Perflib interface
RFFTF (DFFTF) SFFTC (DFFTZ)
RFFTB (DFFTB) CFFTS (ZFFTD)
CFFTF (ZFFTF) CFFTC (ZFFTZ)
EZFFTF (DEZFFTF) SFFTC (DFFTZ)
EZFFTB (DEZFFTB) CFFTS (ZFFTD)
CFFTB (ZFFTB) CFFTC (ZFFTZ)
RFFT2F (DFFT2F) SFFT2C (DFFT2Z)
RFFT2B (DFFT2B) CFFT2S (ZFFT2D)
CFFT2F (ZFFT2F) CFFT2C (ZFFT2Z)
CFFT2B (ZFFT2B) CFFT2C (ZFFT2Z)
RFFT3F (DFFT3F) SFFT3C (DFFT3Z)
RFFT3B (DFFT3B) CFFT3S (ZFFT3D)
CFFT3B (ZFFT3B) CFFT3C (ZFFT3Z)
CFFT3F (ZFFT3F) CFFT3C (ZFFT3Z)
VCFFTF (VZFFTF) CFFTCM (ZFFTZM)
VCFFTB (VZFFTB) CFFTCM (ZFFTZM)
VRFFTF (VDFFTF) SFFTCM (DFFTZM)
VRFFTB (VDFFTB) CFFTSM (ZFFTDM)
RFFTI (DFFTI) SFFTC (DFFTZ), CFFTS (ZFFTD)
CFFTI (ZFFTI) CFFTC (ZFFTZ)
EZFFTI (DEZFFTI) SFFTC (DFFTZ), CFFTS (ZFFTD)
RFFT2I (DFFT2I) SFFTC2 (DFFTZ2), CFFTS2 (ZFFTD2)
RFFT3I (DFFT3I) SFFTC3 (DFFTZ3), CFFTS3 (ZFFTD3)
CFFT2I (ZFFT2I) CFFTC2 (ZFFTZ2)
CFFT3I (ZFFT3I) CFFTC3 (ZFFTZ3)
VCFFTI (VZFFTI) CFFTCM (ZFFTZM)
VRFFTI (VDFFTI) SFFTCM (DFFTZM), CFFTSM (ZFFTDM)
NOTES
Unlike the FFTPACK interface, the Perflib interface does not provide
separate routines for initialization. Computation and initialization
can be selected by an argument in the calling sequence of each routine.
Similar to the FFTPACK routines, the weight and factor tables need to
be initialized once for a particular transform length. Once these
tables are initialized, they can be used repeatedly to compute the for‐
ward and inverse tranforms for different data sets until, of course,
the transform length is changed. The appropriate transform routine is
then called to initialize the tables for the new length.
The Perflib interface gives the user the option of computing the FFT
in-place (input overwritten by transform results) or out-of-place
(input unchanged) in every routine. When an out-of-place transform is
requested, the input and output arrays must not overlap in memory.
In-place transforms require that there be perfect overlay between the
input and output arrays. That is, the arrays must begin at the same
memory location. The routines assume (and therefore do not check) that
these conditions are satisfied. In some cases, the dimension(s) of the
input and output arrays are related to each other. Below is a summary
of requirements of the array dimensions. LDX1 and LDX are leading
dimensions of the input arrays and LDY1 and LDY are leading dimensions
of the output arrays. LDX2 and LDY2 are the second dimensions of the
input and output arrays, respectively. N1 and N2 are the first and
second actual dimensions of the problem.
Routine name in-place out-of-place
SFFTCM, DFFTZM LDX = 2*LDY LDX >= N1
LDY >= N1/2+1 LDY >= N1/2+1
CFFTSM, ZFFTDM LDX >= N1/2+1 LDX >= N1/2+1
LDY = 2*LDX LDY >= N1
CFFTCM, ZFFTZM LDX >= N1 LDX >= N1
LDY = LDX LDY >= N1
SFFTC2, DFFTZ2 LDX = 2*LDY LDX >= N1
LDY >= N1/2+1 LDY >= N1/2+1
CFFTS2, ZFFTD2 LDX >= N1/2+1 LDX >= N1/2+1
LDY = 2*LDX LDY >= 2*LDX; LDY is even
CFFTC2, ZFFTZ2 LDX >= N1 LDX >= N1
LDY = LDX LDY >= N1
CFFTS3, ZFFTD3 LDX1 >= N1/2+1 LDX1 >= N1/2+1
LDX2 >= N2 LDX2 >= N2
LDY1 = 2*LDX1 LDY1 >= 2*LDX1; LDY1 is even
LDY2 = LDX2 LDY2 >= N2
CFFTC3, ZFFTZ3 LDX1 >= N1 LDX1 >= N1
LDX2 >= N2 LDX2 >= N2
LDY1 = LDX1 LDY1 >= N1
LDY2 = LDX2 LDY2 >= N2
SFFTC3, DFFTZ3 LDX1 = 2*LDY1 LDX1 >= N1
LDX2 >= N2 LDX2 >= N2
LDY1 >= N1/2+1 LDY1 >= N1/2+1
LDY2 = LDX2 LDY2 >= N2
In routines that compute transforms between complex and real data type
such as SFFTC2 or CFFTS3 even though the transform length is N1, only
(N1/2+1) complex data points are referenced or computed. These data
points make up the positive-frequency half of the spectrum of the Dis‐
crete Fourier Transform. The remaining N1-(N1/2+1) data points can be
easily derived since they are complex conjugates and therefore are not
stored or referenced.
6 Mar 2009 fft(3P)
