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1 @node Installation and Customization, Acknowledgments, Upgrading from FFTW version 2, Top
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2 @chapter Installation and Customization
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3 @cindex installation
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4
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5 This chapter describes the installation and customization of FFTW, the
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6 latest version of which may be downloaded from
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7 @uref{http://www.fftw.org, the FFTW home page}.
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8
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9 In principle, FFTW should work on any system with an ANSI C compiler
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10 (@code{gcc} is fine). However, planner time is drastically reduced if
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11 FFTW can exploit a hardware cycle counter; FFTW comes with cycle-counter
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12 support for all modern general-purpose CPUs, but you may need to add a
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13 couple of lines of code if your compiler is not yet supported
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14 (@pxref{Cycle Counters}). (On Unix, there will be a warning at the end
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15 of the @code{configure} output if no cycle counter is found.)
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16 @cindex cycle counter
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17 @cindex compiler
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18 @cindex portability
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19
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20
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21 Installation of FFTW is simplest if you have a Unix or a GNU system,
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22 such as GNU/Linux, and we describe this case in the first section below,
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23 including the use of special configuration options to e.g. install
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24 different precisions or exploit optimizations for particular
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25 architectures (e.g. SIMD). Compilation on non-Unix systems is a more
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26 manual process, but we outline the procedure in the second section. It
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27 is also likely that pre-compiled binaries will be available for popular
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28 systems.
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29
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30 Finally, we describe how you can customize FFTW for particular needs by
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31 generating @emph{codelets} for fast transforms of sizes not supported
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32 efficiently by the standard FFTW distribution.
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33 @cindex codelet
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34
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35 @menu
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36 * Installation on Unix::
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37 * Installation on non-Unix systems::
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38 * Cycle Counters::
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39 * Generating your own code::
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40 @end menu
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41
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42 @c ------------------------------------------------------------
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43
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44 @node Installation on Unix, Installation on non-Unix systems, Installation and Customization, Installation and Customization
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45 @section Installation on Unix
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46
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47 FFTW comes with a @code{configure} program in the GNU style.
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48 Installation can be as simple as:
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49 @fpindex configure
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50
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51 @example
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52 ./configure
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53 make
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54 make install
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55 @end example
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56
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57 This will build the uniprocessor complex and real transform libraries
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58 along with the test programs. (We recommend that you use GNU
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59 @code{make} if it is available; on some systems it is called
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60 @code{gmake}.) The ``@code{make install}'' command installs the fftw
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61 and rfftw libraries in standard places, and typically requires root
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62 privileges (unless you specify a different install directory with the
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63 @code{--prefix} flag to @code{configure}). You can also type
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64 ``@code{make check}'' to put the FFTW test programs through their paces.
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65 If you have problems during configuration or compilation, you may want
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66 to run ``@code{make distclean}'' before trying again; this ensures that
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67 you don't have any stale files left over from previous compilation
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68 attempts.
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69
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70 The @code{configure} script chooses the @code{gcc} compiler by default,
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71 if it is available; you can select some other compiler with:
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72 @example
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73 ./configure CC="@r{@i{<the name of your C compiler>}}"
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74 @end example
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75
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76 The @code{configure} script knows good @code{CFLAGS} (C compiler flags)
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77 @cindex compiler flags
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78 for a few systems. If your system is not known, the @code{configure}
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79 script will print out a warning. In this case, you should re-configure
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80 FFTW with the command
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81 @example
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82 ./configure CFLAGS="@r{@i{<write your CFLAGS here>}}"
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83 @end example
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84 and then compile as usual. If you do find an optimal set of
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85 @code{CFLAGS} for your system, please let us know what they are (along
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86 with the output of @code{config.guess}) so that we can include them in
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87 future releases.
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88
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89 @code{configure} supports all the standard flags defined by the GNU
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90 Coding Standards; see the @code{INSTALL} file in FFTW or
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91 @uref{http://www.gnu.org/prep/standards/html_node/index.html, the GNU web page}.
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92 Note especially @code{--help} to list all flags and
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93 @code{--enable-shared} to create shared, rather than static, libraries.
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94 @code{configure} also accepts a few FFTW-specific flags, particularly:
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95
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96 @itemize @bullet
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97
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98 @item
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99 @cindex precision
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100 @code{--enable-float}: Produces a single-precision version of FFTW
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101 (@code{float}) instead of the default double-precision (@code{double}).
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102 @xref{Precision}.
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103
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104 @item
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105 @cindex precision
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106 @code{--enable-long-double}: Produces a long-double precision version of
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107 FFTW (@code{long double}) instead of the default double-precision
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108 (@code{double}). The @code{configure} script will halt with an error
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109 message if @code{long double} is the same size as @code{double} on your
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110 machine/compiler. @xref{Precision}.
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111
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112 @item
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113 @cindex precision
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114 @code{--enable-quad-precision}: Produces a quadruple-precision version
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115 of FFTW using the nonstandard @code{__float128} type provided by
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116 @code{gcc} 4.6 or later on x86, x86-64, and Itanium architectures,
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117 instead of the default double-precision (@code{double}). The
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118 @code{configure} script will halt with an error message if the
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119 compiler is not @code{gcc} version 4.6 or later or if @code{gcc}'s
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120 @code{libquadmath} library is not installed. @xref{Precision}.
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121
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122 @item
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123 @cindex threads
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124 @code{--enable-threads}: Enables compilation and installation of the
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125 FFTW threads library (@pxref{Multi-threaded FFTW}), which provides a
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126 simple interface to parallel transforms for SMP systems. By default,
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127 the threads routines are not compiled.
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128
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129 @item
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130 @code{--enable-openmp}: Like @code{--enable-threads}, but using OpenMP
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131 compiler directives in order to induce parallelism rather than
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132 spawning its own threads directly, and installing an @samp{fftw3_omp} library
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133 rather than an @samp{fftw3_threads} library (@pxref{Multi-threaded
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134 FFTW}). You can use both @code{--enable-openmp} and @code{--enable-threads}
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135 since they compile/install libraries with different names. By default,
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136 the OpenMP routines are not compiled.
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137
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138 @item
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139 @code{--with-combined-threads}: By default, if @code{--enable-threads}
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140 is used, the threads support is compiled into a separate library that
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141 must be linked in addition to the main FFTW library. This is so that
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142 users of the serial library do not need to link the system threads
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143 libraries. If @code{--with-combined-threads} is specified, however,
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144 then no separate threads library is created, and threads are included
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145 in the main FFTW library. This is mainly useful under Windows, where
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146 no system threads library is required and inter-library dependencies
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147 are problematic.
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148
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149 @item
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150 @cindex MPI
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151 @code{--enable-mpi}: Enables compilation and installation of the FFTW
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152 MPI library (@pxref{Distributed-memory FFTW with MPI}), which provides
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153 parallel transforms for distributed-memory systems with MPI. (By
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154 default, the MPI routines are not compiled.) @xref{FFTW MPI
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155 Installation}.
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156
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157 @item
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158 @cindex Fortran-callable wrappers
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159 @code{--disable-fortran}: Disables inclusion of legacy-Fortran
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160 wrapper routines (@pxref{Calling FFTW from Legacy Fortran}) in the standard
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161 FFTW libraries. These wrapper routines increase the library size by
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162 only a negligible amount, so they are included by default as long as
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163 the @code{configure} script finds a Fortran compiler on your system.
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164 (To specify a particular Fortran compiler @i{foo}, pass
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165 @code{F77=}@i{foo} to @code{configure}.)
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166
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167 @item
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168 @code{--with-g77-wrappers}: By default, when Fortran wrappers are
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169 included, the wrappers employ the linking conventions of the Fortran
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170 compiler detected by the @code{configure} script. If this compiler is
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171 GNU @code{g77}, however, then @emph{two} versions of the wrappers are
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172 included: one with @code{g77}'s idiosyncratic convention of appending
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173 two underscores to identifiers, and one with the more common
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174 convention of appending only a single underscore. This way, the same
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175 FFTW library will work with both @code{g77} and other Fortran
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176 compilers, such as GNU @code{gfortran}. However, the converse is not
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177 true: if you configure with a different compiler, then the
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178 @code{g77}-compatible wrappers are not included. By specifying
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179 @code{--with-g77-wrappers}, the @code{g77}-compatible wrappers are
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180 included in addition to wrappers for whatever Fortran compiler
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181 @code{configure} finds.
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182 @fpindex g77
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183
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184 @item
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185 @code{--with-slow-timer}: Disables the use of hardware cycle counters,
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186 and falls back on @code{gettimeofday} or @code{clock}. This greatly
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187 worsens performance, and should generally not be used (unless you don't
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188 have a cycle counter but still really want an optimized plan regardless
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189 of the time). @xref{Cycle Counters}.
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190
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191 @item
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192 @code{--enable-sse} (single precision),
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193 @code{--enable-sse2} (single, double),
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194 @code{--enable-avx} (single, double),
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195 @code{--enable-avx2} (single, double),
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196 @code{--enable-avx512} (single, double),
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197 @code{--enable-avx-128-fma},
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198 @code{--enable-kcvi} (single),
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199 @code{--enable-altivec} (single),
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200 @code{--enable-vsx} (single, double),
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201 @code{--enable-neon} (single, double on aarch64),
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202 @code{--enable-generic-simd128},
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203 and
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204 @code{--enable-generic-simd256}:
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205
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206 Enable various SIMD instruction sets. You need compiler that supports
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207 the given SIMD extensions, but FFTW will try to detect at runtime
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208 whether the CPU supports these extensions. That is, you can compile
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209 with@code{--enable-avx} and the code will still run on a CPU without AVX
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210 support.
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211
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212 @itemize @minus
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213 @item
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214 These options require a compiler supporting SIMD extensions, and
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215 compiler support is always a bit flaky: see the FFTW FAQ for a list of
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216 compiler versions that have problems compiling FFTW.
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217 @item
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218 Because of the large variety of ARM processors and ABIs, FFTW
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219 does not attempt to guess the correct @code{gcc} flags for generating
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220 NEON code. In general, you will have to provide them on the command line.
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221 This command line is known to have worked at least once:
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222 @example
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223 ./configure --with-slow-timer --host=arm-linux-gnueabi \
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224 --enable-single --enable-neon \
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225 "CC=arm-linux-gnueabi-gcc -march=armv7-a -mfloat-abi=softfp"
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226 @end example
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227 @end itemize
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228
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229 @end itemize
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230
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231 @cindex compiler
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232 To force @code{configure} to use a particular C compiler @i{foo}
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233 (instead of the default, usually @code{gcc}), pass @code{CC=}@i{foo} to the
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234 @code{configure} script; you may also need to set the flags via the variable
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235 @code{CFLAGS} as described above.
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236 @cindex compiler flags
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237
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238 @c ------------------------------------------------------------
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239 @node Installation on non-Unix systems, Cycle Counters, Installation on Unix, Installation and Customization
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240 @section Installation on non-Unix systems
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241
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242 It should be relatively straightforward to compile FFTW even on non-Unix
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243 systems lacking the niceties of a @code{configure} script. Basically,
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244 you need to edit the @code{config.h} header (copy it from
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245 @code{config.h.in}) to @code{#define} the various options and compiler
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246 characteristics, and then compile all the @samp{.c} files in the
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247 relevant directories.
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248
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249 The @code{config.h} header contains about 100 options to set, each one
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250 initially an @code{#undef}, each documented with a comment, and most of
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251 them fairly obvious. For most of the options, you should simply
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252 @code{#define} them to @code{1} if they are applicable, although a few
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253 options require a particular value (e.g. @code{SIZEOF_LONG_LONG} should
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254 be defined to the size of the @code{long long} type, in bytes, or zero
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255 if it is not supported). We will likely post some sample
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256 @code{config.h} files for various operating systems and compilers for
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257 you to use (at least as a starting point). Please let us know if you
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258 have to hand-create a configuration file (and/or a pre-compiled binary)
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259 that you want to share.
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260
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261 To create the FFTW library, you will then need to compile all of the
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262 @samp{.c} files in the @code{kernel}, @code{dft}, @code{dft/scalar},
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263 @code{dft/scalar/codelets}, @code{rdft}, @code{rdft/scalar},
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264 @code{rdft/scalar/r2cf}, @code{rdft/scalar/r2cb},
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265 @code{rdft/scalar/r2r}, @code{reodft}, and @code{api} directories.
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266 If you are compiling with SIMD support (e.g. you defined
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267 @code{HAVE_SSE2} in @code{config.h}), then you also need to compile
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268 the @code{.c} files in the @code{simd-support},
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269 @code{@{dft,rdft@}/simd}, @code{@{dft,rdft@}/simd/*} directories.
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270
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271 Once these files are all compiled, link them into a library, or a shared
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272 library, or directly into your program.
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273
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274 To compile the FFTW test program, additionally compile the code in the
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275 @code{libbench2/} directory, and link it into a library. Then compile
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276 the code in the @code{tests/} directory and link it to the
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277 @code{libbench2} and FFTW libraries. To compile the @code{fftw-wisdom}
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278 (command-line) tool (@pxref{Wisdom Utilities}), compile
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279 @code{tools/fftw-wisdom.c} and link it to the @code{libbench2} and FFTW
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280 libraries
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281
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282 @c ------------------------------------------------------------
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283 @node Cycle Counters, Generating your own code, Installation on non-Unix systems, Installation and Customization
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284 @section Cycle Counters
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285 @cindex cycle counter
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286
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287 FFTW's planner actually executes and times different possible FFT
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288 algorithms in order to pick the fastest plan for a given @math{n}. In
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289 order to do this in as short a time as possible, however, the timer must
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290 have a very high resolution, and to accomplish this we employ the
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291 hardware @dfn{cycle counters} that are available on most CPUs.
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292 Currently, FFTW supports the cycle counters on x86, PowerPC/POWER, Alpha,
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293 UltraSPARC (SPARC v9), IA64, PA-RISC, and MIPS processors.
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294
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295 @cindex compiler
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296 Access to the cycle counters, unfortunately, is a compiler and/or
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297 operating-system dependent task, often requiring inline assembly
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298 language, and it may be that your compiler is not supported. If you are
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299 @emph{not} supported, FFTW will by default fall back on its estimator
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300 (effectively using @code{FFTW_ESTIMATE} for all plans).
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301 @ctindex FFTW_ESTIMATE
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302
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303 You can add support by editing the file @code{kernel/cycle.h}; normally,
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304 this will involve adapting one of the examples already present in order
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305 to use the inline-assembler syntax for your C compiler, and will only
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306 require a couple of lines of code. Anyone adding support for a new
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307 system to @code{cycle.h} is encouraged to email us at @email{fftw@@fftw.org}.
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308
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309 If a cycle counter is not available on your system (e.g. some embedded
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310 processor), and you don't want to use estimated plans, as a last resort
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311 you can use the @code{--with-slow-timer} option to @code{configure} (on
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312 Unix) or @code{#define WITH_SLOW_TIMER} in @code{config.h} (elsewhere).
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313 This will use the much lower-resolution @code{gettimeofday} function, or even
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314 @code{clock} if the former is unavailable, and planning will be
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315 extremely slow.
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316
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317 @c ------------------------------------------------------------
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318 @node Generating your own code, , Cycle Counters, Installation and Customization
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319 @section Generating your own code
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320 @cindex code generator
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321
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322 The directory @code{genfft} contains the programs that were used to
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323 generate FFTW's ``codelets,'' which are hard-coded transforms of small
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324 sizes.
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325 @cindex codelet
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326 We do not expect casual users to employ the generator, which is a rather
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327 sophisticated program that generates directed acyclic graphs of FFT
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328 algorithms and performs algebraic simplifications on them. It was
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329 written in Objective Caml, a dialect of ML, which is available at
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330 @uref{http://caml.inria.fr/ocaml/index.en.html}.
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331 @cindex Caml
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332
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333
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334 If you have Objective Caml installed (along with recent versions of
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335 GNU @code{autoconf}, @code{automake}, and @code{libtool}), then you
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336 can change the set of codelets that are generated or play with the
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337 generation options. The set of generated codelets is specified by the
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338 @code{@{dft,rdft@}/@{codelets,simd@}/*/Makefile.am} files. For example, you can add
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339 efficient REDFT codelets of small sizes by modifying
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340 @code{rdft/codelets/r2r/Makefile.am}.
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341 @cindex REDFT
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342 After you modify any @code{Makefile.am} files, you can type @code{sh
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343 bootstrap.sh} in the top-level directory followed by @code{make} to
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344 re-generate the files.
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345
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346 We do not provide more details about the code-generation process, since
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347 we do not expect that most users will need to generate their own code.
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348 However, feel free to contact us at @email{fftw@@fftw.org} if
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349 you are interested in the subject.
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350
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351 @cindex monadic programming
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352 You might find it interesting to learn Caml and/or some modern
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353 programming techniques that we used in the generator (including monadic
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354 programming), especially if you heard the rumor that Java and
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355 object-oriented programming are the latest advancement in the field.
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356 The internal operation of the codelet generator is described in the
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357 paper, ``A Fast Fourier Transform Compiler,'' by M. Frigo, which is
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358 available from the @uref{http://www.fftw.org,FFTW home page} and also
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359 appeared in the @cite{Proceedings of the 1999 ACM SIGPLAN Conference on
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360 Programming Language Design and Implementation (PLDI)}.
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361
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