Major goals of this release:
* Speed: often 20% or more faster than FFTW 2.x, even without SIMD (see below).
* Complete rewrite, to make it easier to add new algorithms and transforms.
* New API, to support more general semantics.
Other enhancements:
* SIMD acceleration on supporting CPUs (SSE, SSE2, 3DNow!, and AltiVec).
(With special thanks to Franz Franchetti for many experimental prototypes
and to Stefan Kral for the vectorizing generator from fftwgel.)
* True in-place 1d transforms of large sizes (as well as compressed
twiddle tables for additional memory/cache savings).
* More arbitrary placement of real & imaginary data, e.g. including
interleaved (as in FFTW 2.x) as well as separate real/imag arrays.
* Efficient prime-size transforms of real data.
* Multidimensional transforms can operate on a subset of a larger matrix,
and/or transform selected dimensions of a multidimensional array.
* By popular demand, simultaneous linking to double precision (fftw),
single precision (fftwf), and long-double precision (fftwl) versions
of FFTW is now supported.
* Cycle counters (on all modern CPUs) are exploited to speed planning.
* Efficient transforms of real even/odd arrays, a.k.a. discrete
cosine/sine transforms (types I-IV). (Currently work via pre/post
processing of real transforms, ala FFTPACK, so are not optimal.)
* DHTs (Discrete Hartley Transforms), again via post-processing
of real transforms (and thus suboptimal, for now).
* Support for linking to just those parts of FFTW that you need,
greatly reducing the size of statically linked programs when
only a limited set of transform sizes/types are required.
* Canonical global wisdom file (/etc/fftw/wisdom) on Unix, along
with a command-line tool (fftw-wisdom) to generate/update it.
* Fortran API can be used with both g77 and non-g77 compilers
simultaneously.
* Multi-threaded version has optional OpenMP support.
* Authors' good looks have greatly improved with age.
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