Chris@42: Chris@42: Chris@42: Chris@42: FFTW Frequently Asked Questions with Answers Chris@42: Chris@42: Chris@42: Chris@42: Chris@42: Chris@42: Chris@42: Chris@42: Chris@42:

Chris@42: FFTW Frequently Asked Questions with Answers Chris@42:

Chris@42: This is the list of Frequently Asked Questions about FFTW, a Chris@42: collection of fast C routines for computing the Discrete Fourier Chris@42: Transform in one or more dimensions. Chris@42:

Chris@42: Index Chris@42:

Chris@42: Chris@42:

Section 1. Introduction and General Information Chris@42:
Q1.1. What is FFTW? Chris@42:
Q1.2. How do I obtain FFTW? Chris@42:
Q1.3. Is FFTW free software? Chris@42:
Q1.4. What is this about non-free licenses? Chris@42:
Q1.5. In the West? I thought MIT was in the East? Chris@42:
Section 2. Installing FFTW Chris@42:
Q2.1. Which systems does FFTW run on? Chris@42:
Q2.2. Does FFTW run on Windows? Chris@42:
Q2.3. My compiler has trouble with FFTW. Chris@42:
Q2.4. FFTW does not compile on Solaris, complaining about Chris@42: const. Chris@42:
Q2.5. What's the difference between --enable-3dnow and --enable-k7? Chris@42:
Q2.6. What's the difference between the fma and the non-fma Chris@42: versions? Chris@42:
Q2.7. Which language is FFTW written in? Chris@42:
Q2.8. Can I call FFTW from Fortran? Chris@42:
Q2.9. Can I call FFTW from C++? Chris@42:
Q2.10. Why isn't FFTW written in Fortran/C++? Chris@42:
Q2.11. How do I compile FFTW to run in single precision? Chris@42:
Q2.12. --enable-k7 does not work on x86-64 Chris@42:
Section 3. Using FFTW Chris@42:
Q3.1. Why not support the FFTW 2 interface in FFTW Chris@42: 3? Chris@42:
Q3.2. Why do FFTW 3 plans encapsulate the input/output arrays and not just Chris@42: the algorithm? Chris@42:
Q3.3. FFTW seems really slow. Chris@42:
Q3.4. FFTW slows down after repeated calls. Chris@42:
Q3.5. An FFTW routine is crashing when I call it. Chris@42:
Q3.6. My Fortran program crashes when calling FFTW. Chris@42:
Q3.7. FFTW gives results different from my old Chris@42: FFT. Chris@42:
Q3.8. FFTW gives different results between runs Chris@42:
Q3.9. Can I save FFTW's plans? Chris@42:
Q3.10. Why does your inverse transform return a scaled Chris@42: result? Chris@42:
Q3.11. How can I make FFTW put the origin (zero frequency) at the center of Chris@42: its output? Chris@42:
Q3.12. How do I FFT an image/audio file in foobar format? Chris@42:
Q3.13. My program does not link (on Unix). Chris@42:
Q3.14. I included your header, but linking still Chris@42: fails. Chris@42:
Q3.15. My program crashes, complaining about stack Chris@42: space. Chris@42:
Q3.16. FFTW seems to have a memory leak. Chris@42:
Q3.17. The output of FFTW's transform is all zeros. Chris@42:
Q3.18. How do I call FFTW from the Microsoft language du Chris@42: jour? Chris@42:
Q3.19. Can I compute only a subset of the DFT outputs? Chris@42:
Q3.20. Can I use FFTW's routines for in-place and out-of-place matrix Chris@42: transposition? Chris@42:
Section 4. Internals of FFTW Chris@42:
Q4.1. How does FFTW work? Chris@42:
Q4.2. Why is FFTW so fast? Chris@42:
Section 5. Known bugs Chris@42:
Q5.1. FFTW 1.1 crashes in rfftwnd on Linux. Chris@42:
Q5.2. The MPI transforms in FFTW 1.2 give incorrect results/leak Chris@42: memory. Chris@42:
Q5.3. The test programs in FFTW 1.2.1 fail when I change FFTW to use single Chris@42: precision. Chris@42:
Q5.4. The test program in FFTW 1.2.1 fails for n > Chris@42: 46340. Chris@42:
Q5.5. The threaded code fails on Linux Redhat 5.0 Chris@42:
Q5.6. FFTW 2.0's rfftwnd fails for rank > 1 transforms with a final Chris@42: dimension >= 65536. Chris@42:
Q5.7. FFTW 2.0's complex transforms give the wrong results with prime Chris@42: factors 17 to 97. Chris@42:
Q5.8. FFTW 2.1.1's MPI test programs crash with Chris@42: MPICH. Chris@42:
Q5.9. FFTW 2.1.2's multi-threaded transforms don't work on Chris@42: AIX. Chris@42:
Q5.10. FFTW 2.1.2's complex transforms give incorrect results for large prime Chris@42: sizes. Chris@42:
Q5.11. FFTW 2.1.3's multi-threaded transforms don't give any speedup on Chris@42: Solaris. Chris@42:
Q5.12. FFTW 2.1.3 crashes on AIX. Chris@42:

Chris@42:

Chris@42: Matteo Frigo and Steven G. Johnson / fftw@fftw.org Chris@42: - 30 July 2016 Chris@42: