FFTW FAQ - Section 5
Known bugs


Question 5.1. FFTW 1.1 crashes in rfftwnd on Linux.

This bug was fixed in FFTW 1.2. There was a bug in rfftwnd causing an incorrect amount of memory to be allocated. The bug showed up in Linux with libc-5.3.12 (and nowhere else that we know of).

Question 5.2. The MPI transforms in FFTW 1.2 give incorrect results/leak memory.

These bugs were corrected in FFTW 1.2.1. The MPI transforms (really, just the transpose routines) in FFTW 1.2 had bugs that could cause errors in some situations.

Question 5.3. The test programs in FFTW 1.2.1 fail when I change FFTW to use single precision.

This bug was fixed in FFTW 1.3. (Older versions of FFTW did work in single precision, but the test programs didn't--the error tolerances in the tests were set for double precision.)

Question 5.4. The test program in FFTW 1.2.1 fails for n > 46340.

This bug was fixed in FFTW 1.3. FFTW 1.2.1 produced the right answer, but the test program was wrong. For large n, n*n in the naive transform that we used for comparison overflows 32 bit integer precision, breaking the test.

Question 5.5. The threaded code fails on Linux Redhat 5.0

We had problems with glibc-2.0.5. The code should work with glibc-2.0.7.

Question 5.6. FFTW 2.0's rfftwnd fails for rank > 1 transforms with a final dimension >= 65536.

This bug was fixed in FFTW 2.0.1. (There was a 32-bit integer overflow due to a poorly-parenthesized expression.)

Question 5.7. FFTW 2.0's complex transforms give the wrong results with prime factors 17 to 97.

There was a bug in the complex transforms that could cause incorrect results under rare circumstances for lengths with intermediate-size prime factors (17-97). This bug was fixed in FFTW 2.1.1.
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Matteo Frigo and Steven G. Johnson / fftw@theory.lcs.mit.edu - 30 March 1999

Extracted from FFTW Frequently Asked Questions with Answers, Copyright © 1999 Massachusetts Institute of Technology.