MAN page from Fedora 5 fftw-3.1.1-1.fc5.i386.rpm
Section: fftw (1)
Updated: February, 2003Index
fftw-wisdom - create wisdom (pre-optimized FFTs)
fftw-wisdomis a utility to generate FFTWwisdomfiles, which contain saved information about how to optimally compute(Fourier) transforms of various sizes. FFTW is a free library tocompute discrete Fourier transforms in one or more dimensions, forarbitrary sizes, and of both real and complex data, among otherrelated operations. More information on FFTW can be found at the FFTWhome page:http://www.fftw.org
Programs using FFTW can be written to load wisdom from an arbitrary file,string, or other source. Moreover, it is likely that many FFTW-usingprograms will load the system wisdom file, which is stored in/etc/fftw/wisdomby default.fftw-wisdomcan be used to create or add to such wisdom files. In its mosttypical usage, the wisdom file can be created to pre-plan a canonicalset of sizes (see below) via:fftw-wisdom -v -c -o wisdom
(this will take many hours, which can be limited by the -toption) and the outputwisdomfile can then be copied (as root) to/etc/fftw/or whatever.
Thefftw-wisdomprogram normally writes the wisdom directly to standard output, but thiscan be changed via the-ooption, as in the example above.
If the system wisdom file/etc/fftw/wisdomalready exists, thenfftw-wisdomreads this existing wisdom (unless the-noption is specified) and outputs both the old wisdom and anynewly created wisdom. In this way, it can be used to add new transformsizes to the existing system wisdom (or other wisdom file, with the -woption).
Although a canonical set of sizes to optimize is specified by the -c
option, the user can also specify zero or more non-canonical transformsizes and types to optimize, via the SIZE
arguments following the option flags. Alternatively, the sizes tooptimize can be read from standard input (whitespace-separated), if aSIZE
argument of "-" is supplied.
Sizes are specified by the syntax:<type><inplace><direction><geometry>
<type> is either 'c' (complex), 'r' (real, r2c/c2r), or'k' (r2r, per-dimension kinds, specified in the geometry, below).
<inplace> is either 'i' (in place) or 'o' (out of place).
<direction> is either 'f' (forward) or 'b' (backward). The<direction> should be omitted for 'k' transforms, where it isspecified via the geometry instead.
<geometry> is the size and dimensionality of the transform,where different dimensions are separated by 'x' (e.g. '16x32' fora two-dimensional 16 by 32 transform). In the case of 'k'transforms, the size of each dimension is followed by a "type" string,which can be one of f/b/h/e00/e01/e10/e11/o00/o01/o10/o11 forR2HC/HC2R/DHT/REDFT00/.../RODFT11, respectively, as defined in theFFTW manual.
For example, 'cif12x13x14' is a three-dimensional 12 by 13 x 14complex DFT operating in-place. 'rob65536' is a one-dimensionalsize-65536 out-of-place complex-to-real (backwards) transformoperating on Hermitian-symmety input. 'ki10hx20e01' is atwo-dimensional 10 by 20 r2r transform where the first dimension is aDHT and the second dimension is an REDFT01 (DCT-III).
- -h, --help
- Display help on the command-line options and usage.
- -V, --version
- Print the version number and copyright information.
- -v, --verbose
- Verbose output. (You can specify this multiple times, or supply a numericargument greater than 1, to increase the verbosity level.) Note that theverbose output will be mixed with the wisdom output (making it impossibleto import), unless you write the wisdom to a file via the -ooption.
- -c, --canonical
- Optimize/pre-plan a canonical set of sizes: all powers of two and tenup to 2^20 (1048576), including both real and complex, forward andbackwards, in-place and out-of-place transforms. Also includes two-and three-dimensional transforms of equal-size dimensions(e.g. 16x16x16).
- -t hours, --time-limit=hours
- Stop after a time ofhours(hours) has elapsed, outputting accumulated wisdom. (The problems are plannedin increasing order of size.) Defaults to 0, indicating no time limit.
- -o file, --output-file=file
- Send wisdom output tofilerather than to standard output (the default).
- -m, --measure; -e, --estimate; -x, --exhaustive
- Normally, fftw-wisdomcreates plans in FFTW_PATIENT mode, but with these options you can insteaduse FFTW_MEASURE, FFTW_ESTIMATE, or FFTW_EXHAUSTIVE modes, respectively,as described in more detail by the FFTW manual.
Note that wisdom is tagged with the planning patience level, and asingle file can mix different levels of wisdom (e.g. you can mostlyuse the patient default, but plan a few sizes that you especially careabout in--exhaustivemode).
- -n, --no-system-wisdom
- Do not import the system wisdom from/etc/fftw/wisdom(which is normally read by default).
- -w file, --wisdom-file=file
- Import wisdom fromfile(in addition to the system wisdom, unless -nis specified). Multiple wisdom files can be read via multiple-woptions. Iffileis "-", then read wisdom from standard input.
Send bug reports to fftwAATTfftw.org.
Written by Steven G. Johnson and Matteo Frigo.
Copyright (c) 2003, 2006 Matteo Frigo
Copyright (c) 2003, 2006 Massachusetts Institute of Technology
- SPECIFYING SIZES
- SEE ALSO
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