I found a slight inconvenience when using FFTW3 and the PDL::Complex data
types. Subroutines such as fft1 or ifft1 expect PDL's with a first
dimension 2 corresponding to the real and imaginary
parts. PDL::Complex is a type derived from PDL whose first dimension
is 2, but fft1 won't accept it. For example
pdl> use PDL::FFTW3
pdl> $a=sequence(2,10)
pdl> $b=ifft1($a)
works without complain, but
pdl> $a=sequence(2,10)->complex
pdl> $b=ifft1($a)
ifft1 arguments must be of type 'PDL'. Instead I got an arg of
type 'PDL::Complex'. Giving up.
at
/home/mochan/perl5/perlbrew/perls/perl-5.24.0/lib/site_perl/5.24.0/x86_64-linux/PDL/FFTW3.pm
line 617.
PDL::FFTW3::validateArguments(1, "", "i", "ifft1",
PDL::Complex=SCALAR(0x2d9fb10), PDL=SCALAR(0x22ae308)) called at
/home/mochan/perl5/perlbrew/perls/perl-5.24.0/lib/site_perl/5.24.0/x86_64-linux/PDL/FFTW3.pm
line 544
PDL::FFTW3::__fft_internal("ifft1",
PDL::Complex=SCALAR(0x2d9fb10)) called at
/home/mochan/perl5/perlbrew/perls/perl-5.24.0/lib/site_perl/5.24.0/x86_64-linux/PDL/FFTW3.pm
line 910
PDL::FFTW3::ifft1(PDL::Complex=SCALAR(0x2d9fb10))
called at (eval 68) line 4
...
fails, as the routine expected a PDL and got a PDL::Complex.
Nevertheless, a PDL::Complex is a PDL:
pdl> p $a->isa('PDL')
1
For the user the problem may be solved by using the 'real' and
'complex' or 'cplx' routines from PDL::Complex before and after doing
the transforms, but it may lead to errors if the user forgets to
convert back to complex before doing further complex operations on the
Fourier transformed data.
Regards,
Luis
--
o
W. Luis Mochán, | tel:(52)(777)329-1734 /<(*)
Instituto de Ciencias Físicas, UNAM | fax:(52)(777)317-5388 `>/ /\
Apdo. Postal 48-3, 62251 | (*)/\/ \
Cuernavaca, Morelos, México | [email protected] /\_/\__/
GPG: 791EB9EB, C949 3F81 6D9B 1191 9A16 C2DF 5F0A C52B 791E B9EB
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