fftw-3.3.8

#### Beyond Linux® From Scratch - Version 2019-02-27

### Chapter 9. General Libraries

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# fftw-3.3.8

## Introduction to fftw

FFTW is a C subroutine library for computing the discrete Fourier transform (DFT) in one or more dimensions, of arbitrary input size, and of both real and complex data (as well as of even/odd data, i.e. the discrete cosine/sine transforms or DCT/DST).

This package is known to build and work properly using an LFS-8.4 platform.

### Package Information

- Download (HTTP): http://www.fftw.org/fftw-3.3.8.tar.gz

- Download (FTP): ftp://ftp.fftw.org/pub/fftw/fftw-3.3.8.tar.gz

- Download MD5 sum: 8aac833c943d8e90d51b697b27d4384d

- Download size: 3.9 MB

- Estimated disk space required: 57 MB (add 1 MB for tests)

- Estimated build time: 1.6 SBU (using parallelism=4; add 1.9 SBU for tests)

User Notes: http://wiki.linuxfromscratch.org/blfs/wiki/fftw

## Installation of fftw

### Note

We build fftw three times for different libraries in different numerical precisions: the default double precision floating point, the older 32-bit (single precision) version named float which sacrifices precision for speed, and the long double which offers increased precision at the cost of slower execution.

The first build is for double precision arithmetic. Install fftw by running the following commands:

    ./configure --prefix=/usr    \
                --enable-shared  \
                --enable-threads \
                --enable-sse2    \
                --enable-avx     &&
    make

To test the results, issue: make check. On 32-bit systems, the tests can take substantially longer than they would on 64-bit machines.

Now, as the `root` user:

    make install

Now build single precision:

    make clean &&

    ./configure --prefix=/usr    \
                --enable-shared  \
                --enable-threads \
                --enable-sse2    \
                --enable-avx     \
                --enable-float   &&
    make

As the `root` user:

    make install

Finally, build long double precision:

    make clean &&

    ./configure --prefix=/usr    \
                --enable-shared  \
                --enable-threads \
                --enable-long-double &&
    make

As the `root` user:

    make install

## Command Explanations

`--enable-shared`: Use shared libs instead of static libs.

`--enable-threads`: This enables `libfftw3_threads.so` to be compiled. It is used by e.g. the gimp plugin from G'MIC.

`--enable-float`: This enables building the library that uses single precision floating point arithmetic. It is faster but less precise than the default double precision library. The library will be called `libfftw3f.so` needed by PulseAudio-12.2.

`--enable-long-double`: This enables building the library that uses higher precision long-double floating point arithmetic. The library will be called `libfftw3l.so`.

## Contents

Installed Programs: fftw-wisdom and fftw-wisdom-to-conf
Installed Libraries: libfftw3.so, libfftw3_threads.so, libfftw3f.so, libfftw3f_threads.so, libfftw3l.so and libfftw3l_threads.so
Installed Directories: None

### Short Descriptions

fftw-wisdom | is a utility to generate FFTW wisdom files, which contain saved information about how to optimally compute (Fourier) transforms of various sizes.
fftw-wisdom-to-conf | is a utility to generate C configuration routines from FFTW wisdom files, where the latter contain saved information about how to optimally compute (Fourier) transforms of various sizes.
`libfftw3.so` | is the Fast Fourier Transform library
`libfftw3_threads.so` | is the threaded Fast Fourier Transform library
`libfftw3f.so` | is the single-precision Fast Fourier Transform library, described as 'float' for historic reasons
`libfftw3f_threads.so` | is the threaded single-precision Fast Fourier Transform library
`libfftw3l.so` | is the long double Fast Fourier Transform library
`libfftw3l_threads.so` | is the threaded long double Fast Fourier Transform library

Last updated on 2019-02-20 17:07:01 -0600

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