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FFTW Frequently Asked Questions with Answers

Index

• Section 1. Introduction and General Information
• Q1.1. What is FFTW?
• Q1.2. How do I obtain FFTW?
• Q1.3. Is FFTW free software?
• Q1.4. What is this about non-free licenses?
  
  
• Section 2. Installing FFTW
• Q2.1. Which systems does FFTW run on?
• Q2.2. Does FFTW run on DOS/Windows?
• Q2.3. My compiler has trouble with FFTW.
• Q2.4. FFTW does not compile on Solaris, complaining about const.
• Q2.5. Which language is FFTW written in?
• Q2.6. Can I call FFTW from FORTRAN?
• Q2.7. Can I call FFTW from C++?
• Q2.8. Why isn't FFTW written in FORTRAN/C++?
• Q2.9. How do I compile FFTW to run in single precision?
  
  
• Section 3. Using FFTW
• Q3.1. FFTW seems really slow.
• Q3.2. FFTW gives results different from my old FFT.
• Q3.3. Can I save FFTW's plans?
• Q3.4. Why does your inverse transform return a scaled result?
• Q3.5. How can I make FFTW put the origin (zero frequency) at the center of its output?
• Q3.6. How do I FFT an image/audio file in foobar format?
• Q3.7. My program does not link (on Unix).
  
  
• Section 4. Internals of FFTW
• Q4.1. How does FFTW work?
• Q4.2. Why is FFTW so fast?
• Q4.3. What is this wisdom thing?
• Q4.4. Why do you use wisdom? I just wanted to save a plan.
  
  
• Section 5. Known bugs
• Q5.1. FFTW 1.1 crashes in rfftwnd on Linux.
• Q5.2. The MPI transforms in FFTW 1.2 give incorrect results/leak memory.
• Q5.3. The test programs in FFTW 1.2.1 fail when I change FFTW to use single precision.
• Q5.4. The test program in FFTW 1.2.1 fails for n > 46340.
• Q5.5. The threaded code fails on Linux Redhat 5.0
• Q5.6. FFTW 2.0's rfftwnd fails for rank > 1 transforms with a final dimension >= 65536.
• Q5.7. FFTW 2.0's complex transforms give the wrong results with prime factors 17 to 97.
• Q5.8. FFTW 2.1.1's MPI test programs crash with MPICH.
• Q5.9. FFTW 2.1.2's multi-threaded transforms don't work on AIX.
• Q5.10. FFTW 2.1.2's complex transforms give incorrect results for large prime sizes.