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<head><title>
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FFTW FAQ - Section 2
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</title>
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<link rev="made" href="mailto:fftw@theory.lcs.mit.edu">
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<link rel="Contents" href="index.html">
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<link rel="Start" href="index.html">
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<link rel="Next" href="section3.html"><link rel="Previous" href="section1.html"><link rel="Bookmark" title="FFTW FAQ" href="index.html">
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</head><body text="#000000" bgcolor="#FFFFFF"><h1>
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FFTW FAQ - Section 2 <br>
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Installing FFTW
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</h1>
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<ul>
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<li><a href="#systems" rel=subdocument>Q2.1. Which systems does FFTW run on?</a>
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<li><a href="#runOnDOS" rel=subdocument>Q2.2. Does FFTW run on DOS/Windows?</a>
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<li><a href="#compilerCrashes" rel=subdocument>Q2.3. My compiler crashes when compiling FFTW.</a>
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<li><a href="#solarisSucks" rel=subdocument>Q2.4. FFTW does not compile on Solaris, complaining about
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<code>const</code>.</a>
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<li><a href="#languages" rel=subdocument>Q2.5. Which language is FFTW written in?</a>
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<li><a href="#fortran" rel=subdocument>Q2.6. Can I call FFTW from FORTRAN?</a>
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<li><a href="#cplusplus" rel=subdocument>Q2.7. Can I call FFTW from C++?</a>
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<li><a href="#whynotfortran" rel=subdocument>Q2.8. Why isn't FFTW written in FORTRAN/C++?</a>
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<li><a href="#singleprec" rel=subdocument>Q2.9. How do I compile FFTW to run in single precision?</a>
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</ul><hr>
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<h2><A name="systems">
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Question 2.1.  Which systems does FFTW run
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on?
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</A></h2>
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FFTW is written in ANSI C, and should work on any system with
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a decent C compiler.  (See also <A href="#runOnDOS">Q2.2 `Does FFTW run on DOS/Windows?'</A> and  <A href="#compilerCrashes">Q2.3 `My compiler crashes when compiling FFTW.'</A>.)
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<h2><A name="runOnDOS">
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Question 2.2.  Does FFTW run on DOS/Windows?
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</A></h2>
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It should.  FFTW was not developed on DOS or Windows, but the source
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code is straight ANSI C.  Some users have reported using FFTW on
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DOS/Windows using various compilers.  See also the
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<A href="http://theory.lcs.mit.edu/~fftw/install/install-Windows.html">FFTW Windows installation notes</A> and <A href="#compilerCrashes">Q2.3 `My compiler crashes when compiling FFTW.'</A>
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<h2><A name="compilerCrashes">
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Question 2.3.  My compiler crashes when compiling
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FFTW.
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</A></h2>
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Complain fiercely to the vendor of the compiler.
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<p>
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FFTW is a heavily-optimized piece of software that is likely to push
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compilers to their limits.  We had no problems with, for example,
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<code>gcc 2.7.2</code>, Sun's <code>SC4.0</code>, IBM's <code>XLC</code>, Metrowerks' compilers for the Macintosh, and SGI's compilers for IRIX
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6.2.  Users have also reported successful compilations of FFTW using
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Borland's C/C++ compilers on Windows.  
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<p>
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Visual C++ 4.0 crashes when compiling FFTW 1.2 with all optimizations
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turned on.  Visual C++ 5.0 reportedly produces incorrect code for the
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real transforms in FFTW 2.x when the option &quot;Maximize speed&quot;
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is set.  We are told that Service Pack 3 fixes the bug.
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<p>
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Various problems have also been observed with SGI's MIPSpro compilers,
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versions 7.2.0 and 7.2.1 (you may have to lower the optimization level
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for some files to get them to compile).  The test program in earlier
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versions of FFTW had problems with the <code>-xO5</code> option in Sun's <code>SC4.0</code> C compiler.  
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<h2><A name="solarisSucks">
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Question 2.4.  FFTW does not compile on Solaris, complaining about
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<code>const</code>.
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</A></h2>
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We know that at least on Solaris 2.5.x with Sun's compilers 4.2 you
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might get error messages from <code>make</code> such as
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<p>
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<code>&quot;./fftw.h&quot;, line 88: warning: const is a keyword in ANSI
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C</code>
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<p>
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This is the case when the <code>configure</code> script reports that <code>const</code> does not work:
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<p>
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<code>checking for working const... (cached) no</code>
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<p>
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You should be aware that Solaris comes with two compilers, namely,
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<code>/opt/SUNWspro/SC4.2/bin/cc</code> and <code>/usr/ucb/cc</code>.  The latter compiler is non-ANSI.  Indeed, it is a perverse shell script
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that calls the real compiler in non-ANSI mode.  In order
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to compile FFTW, change your path so that the right
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<code>cc</code> is used.  
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<p>
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To know whether your compiler is the right one,  type
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<code>cc -V</code>.  If the compiler prints ``<code>ucbcc</code>'', as in  
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<p>
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<code>ucbcc: WorkShop Compilers 4.2 30 Oct 1996 C
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4.2</code>
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<p>
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then the compiler is wrong.  The right message is something like
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<p>
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<code>cc: WorkShop Compilers 4.2 30 Oct 1996 C
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4.2</code>
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<h2><A name="languages">
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Question 2.5.  Which language is FFTW written
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in?
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</A></h2>
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FFTW is written in ANSI C.  Most of the code, however, was
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automatically generated by a program called
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<code>genfft</code>, written in the Objective Caml dialect of ML.  You do not need to know ML or to
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have an Objective Caml compiler in order to use FFTW.
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<p>
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<code>genfft</code> is provided with the FFTW sources, which means that
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you can play with the code generator if you want.  In this case, you
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need a working Objective Caml system.  Objective Caml is available
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from <code>ftp.inria.fr</code> in the directory <A href="ftp://ftp.inria.fr/lang/caml-light"><code>/lang/caml-light</code></A>.  
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<h2><A name="fortran">
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Question 2.6.  Can I call FFTW from FORTRAN?
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</A></h2>
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Yes, but not directly.  The main problem is that Fortran cannot pass
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parameters by value.  However, FFTW can be called indirectly from
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Fortran through the use of special C &quot;wrapper&quot; routines.
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Appropriate wrapper code, documented in the FFTW manual, is included with FFTW
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(versions 1.3 and higher).  
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<h2><A name="cplusplus">
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Question 2.7.  Can I call FFTW from C++?
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</A></h2>
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Most definitely.  FFTW should compile and run under any C++ compiler.
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<h2><A name="whynotfortran">
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Question 2.8.  Why isn't FFTW written in
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FORTRAN/C++?
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</A></h2>
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Because we don't like those languages, and neither approaches the
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portability of C.  
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<h2><A name="singleprec">
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Question 2.9.  How do I compile FFTW to run in single
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precision?
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</A></h2>
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On a Unix system: <code>configure --enable-float</code>.  On a non-Unix system: edit <code>fftw/fftw.h</code> to <code>#define</code> the symbol <code>FFTW_ENABLE_FLOAT</code>.  In both cases, you must then recompile
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FFTW.  <hr>
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Next: <a href="section3.html" rel=precedes>Using FFTW</a>.<br>
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Back: <a href="section1.html" rev=precedes>Introduction and General Information</a>.<br>
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<a href="index.html" rev=subdocument>Return to contents</a>.<p>
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<address>
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<A href="http://theory.lcs.mit.edu/~fftw/">Matteo Frigo and Steven G. Johnson</A> / <A href="mailto:fftw@theory.lcs.mit.edu">fftw@theory.lcs.mit.edu</A>
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- 18 May 1999
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</address><br>
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Extracted from FFTW Frequently Asked Questions with Answers,
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Copyright &copy; 1999 Massachusetts Institute of Technology.
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