cannam@127: cannam@127: cannam@127: cannam@127: FFTW Frequently Asked Questions with Answers cannam@127: cannam@127: cannam@127: cannam@127: cannam@127: cannam@127: cannam@127: cannam@127: cannam@127:

cannam@127: FFTW Frequently Asked Questions with Answers cannam@127:

cannam@127: This is the list of Frequently Asked Questions about FFTW, a cannam@127: collection of fast C routines for computing the Discrete Fourier cannam@127: Transform in one or more dimensions. cannam@127:

cannam@127: Index cannam@127:

cannam@127: cannam@127:

Section 1. Introduction and General Information cannam@127:
Q1.1. What is FFTW? cannam@127:
Q1.2. How do I obtain FFTW? cannam@127:
Q1.3. Is FFTW free software? cannam@127:
Q1.4. What is this about non-free licenses? cannam@127:
Q1.5. In the West? I thought MIT was in the East? cannam@127:
Section 2. Installing FFTW cannam@127:
Q2.1. Which systems does FFTW run on? cannam@127:
Q2.2. Does FFTW run on Windows? cannam@127:
Q2.3. My compiler has trouble with FFTW. cannam@127:
Q2.4. FFTW does not compile on Solaris, complaining about cannam@127: const. cannam@127:
Q2.5. What's the difference between --enable-3dnow and --enable-k7? cannam@127:
Q2.6. What's the difference between the fma and the non-fma cannam@127: versions? cannam@127:
Q2.7. Which language is FFTW written in? cannam@127:
Q2.8. Can I call FFTW from Fortran? cannam@127:
Q2.9. Can I call FFTW from C++? cannam@127:
Q2.10. Why isn't FFTW written in Fortran/C++? cannam@127:
Q2.11. How do I compile FFTW to run in single precision? cannam@127:
Q2.12. --enable-k7 does not work on x86-64 cannam@127:
Section 3. Using FFTW cannam@127:
Q3.1. Why not support the FFTW 2 interface in FFTW cannam@127: 3? cannam@127:
Q3.2. Why do FFTW 3 plans encapsulate the input/output arrays and not just cannam@127: the algorithm? cannam@127:
Q3.3. FFTW seems really slow. cannam@127:
Q3.4. FFTW slows down after repeated calls. cannam@127:
Q3.5. An FFTW routine is crashing when I call it. cannam@127:
Q3.6. My Fortran program crashes when calling FFTW. cannam@127:
Q3.7. FFTW gives results different from my old cannam@127: FFT. cannam@127:
Q3.8. FFTW gives different results between runs cannam@127:
Q3.9. Can I save FFTW's plans? cannam@127:
Q3.10. Why does your inverse transform return a scaled cannam@127: result? cannam@127:
Q3.11. How can I make FFTW put the origin (zero frequency) at the center of cannam@127: its output? cannam@127:
Q3.12. How do I FFT an image/audio file in foobar format? cannam@127:
Q3.13. My program does not link (on Unix). cannam@127:
Q3.14. I included your header, but linking still cannam@127: fails. cannam@127:
Q3.15. My program crashes, complaining about stack cannam@127: space. cannam@127:
Q3.16. FFTW seems to have a memory leak. cannam@127:
Q3.17. The output of FFTW's transform is all zeros. cannam@127:
Q3.18. How do I call FFTW from the Microsoft language du cannam@127: jour? cannam@127:
Q3.19. Can I compute only a subset of the DFT outputs? cannam@127:
Q3.20. Can I use FFTW's routines for in-place and out-of-place matrix cannam@127: transposition? cannam@127:
Section 4. Internals of FFTW cannam@127:
Q4.1. How does FFTW work? cannam@127:
Q4.2. Why is FFTW so fast? cannam@127:
Section 5. Known bugs cannam@127:
Q5.1. FFTW 1.1 crashes in rfftwnd on Linux. cannam@127:
Q5.2. The MPI transforms in FFTW 1.2 give incorrect results/leak cannam@127: memory. cannam@127:
Q5.3. The test programs in FFTW 1.2.1 fail when I change FFTW to use single cannam@127: precision. cannam@127:
Q5.4. The test program in FFTW 1.2.1 fails for n > cannam@127: 46340. cannam@127:
Q5.5. The threaded code fails on Linux Redhat 5.0 cannam@127:
Q5.6. FFTW 2.0's rfftwnd fails for rank > 1 transforms with a final cannam@127: dimension >= 65536. cannam@127:
Q5.7. FFTW 2.0's complex transforms give the wrong results with prime cannam@127: factors 17 to 97. cannam@127:
Q5.8. FFTW 2.1.1's MPI test programs crash with cannam@127: MPICH. cannam@127:
Q5.9. FFTW 2.1.2's multi-threaded transforms don't work on cannam@127: AIX. cannam@127:
Q5.10. FFTW 2.1.2's complex transforms give incorrect results for large prime cannam@127: sizes. cannam@127:
Q5.11. FFTW 2.1.3's multi-threaded transforms don't give any speedup on cannam@127: Solaris. cannam@127:
Q5.12. FFTW 2.1.3 crashes on AIX. cannam@127:

cannam@127:

cannam@127: Matteo Frigo and Steven G. Johnson / fftw@fftw.org cannam@127: - 30 July 2016 cannam@127: