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Current fftw source
author Chris Cannam
date Tue, 18 Oct 2016 13:40:26 +0100
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1 <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 3.2//EN">
2 <html>
3 <head><title>
4 FFTW Frequently Asked Questions with Answers
5 </title>
6 <link rev="made" href="mailto:fftw@fftw.org">
7 <link rel="Contents" href="index.html">
8 <link rel="Start" href="index.html">
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10 content="Frequently asked questions and answers (FAQ) for FFTW.">
11 <link rel="Bookmark" title="FFTW FAQ" href="index.html">
12 <LINK rel="Bookmark" title="FFTW Home Page"
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14 <LINK rel="Bookmark" title="FFTW Manual"
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16 </head><body text="#000000" bgcolor="#FFFFFF"><h1>
17 FFTW Frequently Asked Questions with Answers
18 </h1>
19 This is the list of Frequently Asked Questions about FFTW, a
20 collection of fast C routines for computing the Discrete Fourier
21 Transform in one or more dimensions.
22 <h1>
23 Index
24 </h1>
25
26 <ul>
27 <li><b><font size="+2"><a href="section1.html" rel=subdocument>Section 1. Introduction and General Information</a></font></b>
28 <li><a href="section1.html#whatisfftw" rel=subdocument>Q1.1. What is FFTW?</a>
29 <li><a href="section1.html#whereisfftw" rel=subdocument>Q1.2. How do I obtain FFTW?</a>
30 <li><a href="section1.html#isfftwfree" rel=subdocument>Q1.3. Is FFTW free software?</a>
31 <li><a href="section1.html#nonfree" rel=subdocument>Q1.4. What is this about non-free licenses?</a>
32 <li><a href="section1.html#west" rel=subdocument>Q1.5. In the West? I thought MIT was in the East?</a>
33 <br><br><li><b><font size="+2"><a href="section2.html" rel=subdocument>Section 2. Installing FFTW</a></font></b>
34 <li><a href="section2.html#systems" rel=subdocument>Q2.1. Which systems does FFTW run on?</a>
35 <li><a href="section2.html#runOnWindows" rel=subdocument>Q2.2. Does FFTW run on Windows?</a>
36 <li><a href="section2.html#compilerCrashes" rel=subdocument>Q2.3. My compiler has trouble with FFTW.</a>
37 <li><a href="section2.html#solarisSucks" rel=subdocument>Q2.4. FFTW does not compile on Solaris, complaining about
38 <code>const</code>.</a>
39 <li><a href="section2.html#3dnow" rel=subdocument>Q2.5. What's the difference between <code>--enable-3dnow</code> and <code>--enable-k7</code>?</a>
40 <li><a href="section2.html#fma" rel=subdocument>Q2.6. What's the difference between the fma and the non-fma
41 versions?</a>
42 <li><a href="section2.html#languages" rel=subdocument>Q2.7. Which language is FFTW written in?</a>
43 <li><a href="section2.html#fortran" rel=subdocument>Q2.8. Can I call FFTW from Fortran?</a>
44 <li><a href="section2.html#cplusplus" rel=subdocument>Q2.9. Can I call FFTW from C++?</a>
45 <li><a href="section2.html#whynotfortran" rel=subdocument>Q2.10. Why isn't FFTW written in Fortran/C++?</a>
46 <li><a href="section2.html#singleprec" rel=subdocument>Q2.11. How do I compile FFTW to run in single precision?</a>
47 <li><a href="section2.html#64bitk7" rel=subdocument>Q2.12. --enable-k7 does not work on x86-64</a>
48 <br><br><li><b><font size="+2"><a href="section3.html" rel=subdocument>Section 3. Using FFTW</a></font></b>
49 <li><a href="section3.html#fftw2to3" rel=subdocument>Q3.1. Why not support the FFTW 2 interface in FFTW
50 3?</a>
51 <li><a href="section3.html#planperarray" rel=subdocument>Q3.2. Why do FFTW 3 plans encapsulate the input/output arrays and not just
52 the algorithm?</a>
53 <li><a href="section3.html#slow" rel=subdocument>Q3.3. FFTW seems really slow.</a>
54 <li><a href="section3.html#slows" rel=subdocument>Q3.4. FFTW slows down after repeated calls.</a>
55 <li><a href="section3.html#segfault" rel=subdocument>Q3.5. An FFTW routine is crashing when I call it.</a>
56 <li><a href="section3.html#fortran64" rel=subdocument>Q3.6. My Fortran program crashes when calling FFTW.</a>
57 <li><a href="section3.html#conventions" rel=subdocument>Q3.7. FFTW gives results different from my old
58 FFT.</a>
59 <li><a href="section3.html#nondeterministic" rel=subdocument>Q3.8. FFTW gives different results between runs</a>
60 <li><a href="section3.html#savePlans" rel=subdocument>Q3.9. Can I save FFTW's plans?</a>
61 <li><a href="section3.html#whyscaled" rel=subdocument>Q3.10. Why does your inverse transform return a scaled
62 result?</a>
63 <li><a href="section3.html#centerorigin" rel=subdocument>Q3.11. How can I make FFTW put the origin (zero frequency) at the center of
64 its output?</a>
65 <li><a href="section3.html#imageaudio" rel=subdocument>Q3.12. How do I FFT an image/audio file in <i>foobar</i> format?</a>
66 <li><a href="section3.html#linkfails" rel=subdocument>Q3.13. My program does not link (on Unix).</a>
67 <li><a href="section3.html#linkheader" rel=subdocument>Q3.14. I included your header, but linking still
68 fails.</a>
69 <li><a href="section3.html#nostack" rel=subdocument>Q3.15. My program crashes, complaining about stack
70 space.</a>
71 <li><a href="section3.html#leaks" rel=subdocument>Q3.16. FFTW seems to have a memory leak.</a>
72 <li><a href="section3.html#allzero" rel=subdocument>Q3.17. The output of FFTW's transform is all zeros.</a>
73 <li><a href="section3.html#vbetalia" rel=subdocument>Q3.18. How do I call FFTW from the Microsoft language du
74 jour?</a>
75 <li><a href="section3.html#pruned" rel=subdocument>Q3.19. Can I compute only a subset of the DFT outputs?</a>
76 <li><a href="section3.html#transpose" rel=subdocument>Q3.20. Can I use FFTW's routines for in-place and out-of-place matrix
77 transposition?</a>
78 <br><br><li><b><font size="+2"><a href="section4.html" rel=subdocument>Section 4. Internals of FFTW</a></font></b>
79 <li><a href="section4.html#howworks" rel=subdocument>Q4.1. How does FFTW work?</a>
80 <li><a href="section4.html#whyfast" rel=subdocument>Q4.2. Why is FFTW so fast?</a>
81 <br><br><li><b><font size="+2"><a href="section5.html" rel=subdocument>Section 5. Known bugs</a></font></b>
82 <li><a href="section5.html#rfftwndbug" rel=subdocument>Q5.1. FFTW 1.1 crashes in rfftwnd on Linux.</a>
83 <li><a href="section5.html#fftwmpibug" rel=subdocument>Q5.2. The MPI transforms in FFTW 1.2 give incorrect results/leak
84 memory.</a>
85 <li><a href="section5.html#testsingbug" rel=subdocument>Q5.3. The test programs in FFTW 1.2.1 fail when I change FFTW to use single
86 precision.</a>
87 <li><a href="section5.html#teststoobig" rel=subdocument>Q5.4. The test program in FFTW 1.2.1 fails for n &gt;
88 46340.</a>
89 <li><a href="section5.html#linuxthreads" rel=subdocument>Q5.5. The threaded code fails on Linux Redhat 5.0</a>
90 <li><a href="section5.html#bigrfftwnd" rel=subdocument>Q5.6. FFTW 2.0's rfftwnd fails for rank &gt; 1 transforms with a final
91 dimension &gt;= 65536.</a>
92 <li><a href="section5.html#primebug" rel=subdocument>Q5.7. FFTW 2.0's complex transforms give the wrong results with prime
93 factors 17 to 97.</a>
94 <li><a href="section5.html#mpichbug" rel=subdocument>Q5.8. FFTW 2.1.1's MPI test programs crash with
95 MPICH.</a>
96 <li><a href="section5.html#aixthreadbug" rel=subdocument>Q5.9. FFTW 2.1.2's multi-threaded transforms don't work on
97 AIX.</a>
98 <li><a href="section5.html#bigprimebug" rel=subdocument>Q5.10. FFTW 2.1.2's complex transforms give incorrect results for large prime
99 sizes.</a>
100 <li><a href="section5.html#solaristhreadbug" rel=subdocument>Q5.11. FFTW 2.1.3's multi-threaded transforms don't give any speedup on
101 Solaris.</a>
102 <li><a href="section5.html#aixflags" rel=subdocument>Q5.12. FFTW 2.1.3 crashes on AIX.</a>
103 </ul><hr>
104 <address>
105 <A href="http://www.fftw.org">Matteo Frigo and Steven G. Johnson</A> / <A href="mailto:fftw@fftw.org">fftw@fftw.org</A>
106 - 30 July 2016
107 </address><br>
108 Extracted from FFTW Frequently Asked Questions with Answers,
109 Copyright &copy; 2016 Matteo Frigo and Massachusetts Institute of Technology.
110 </body></html>