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FFTW FAQ - Section 5
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FFTW FAQ - Section 5
<br>
Known bugs
</h1>
<ul>
<li><a href="#rfftwndbug" rel=subdocument>Q5.1. FFTW 1.1 crashes in rfftwnd on Linux.
</a>
<li><a href="#fftwmpibug" rel=subdocument>Q5.2. The MPI transforms in FFTW 1.2 give incorrect results/leak
memory.
</a>
<li><a href="#testsingbug" rel=subdocument>Q5.3. The test programs in FFTW 1.2.1 fail when I change FFTW to use single
precision.
</a>
<li><a href="#teststoobig" rel=subdocument>Q5.4. The test program in FFTW 1.2.1 fails for n
>
46340.
</a>
<li><a href="#linuxthreads" rel=subdocument>Q5.5. The threaded code fails on Linux Redhat 5.0
</a>
<li><a href="#bigrfftwnd" rel=subdocument>Q5.6. FFTW 2.0's rfftwnd fails for rank
> 1 transforms with a final
dimension
>= 65536.
</a>
<li><a href="#primebug" rel=subdocument>Q5.7. FFTW 2.0's complex transforms give the wrong results with prime
factors 17 to 97.
</a>
<li><a href="#mpichbug" rel=subdocument>Q5.8. FFTW 2.1.1's MPI test programs crash with
MPICH.
</a>
</ul><hr>
<h2><A name="rfftwndbug">
Question 5.1. FFTW 1.1 crashes in rfftwnd on
Linux.
</A></h2>
This bug was fixed in FFTW 1.2. There was a bug in
<code>rfftwnd
</code> 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).
<h2><A name="fftwmpibug">
Question 5.2. The MPI transforms in FFTW 1.2 give incorrect
results/leak memory.
</A></h2>
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.
<h2><A name="testsingbug">
Question 5.3. The test programs in FFTW 1.2.1 fail when I change FFTW
to use single precision.
</A></h2>
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.)
<h2><A name="teststoobig">
Question 5.4. The test program in FFTW 1.2.1 fails for n
>
46340.
</A></h2>
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.
<h2><A name="linuxthreads">
Question 5.5. The threaded code fails on Linux Redhat
5.0
</A></h2>
We had problems with glibc-2.0.5. The code should work with
glibc-2.0.7.
<h2><A name="bigrfftwnd">
Question 5.6. FFTW 2.0's rfftwnd fails for rank
> 1 transforms
with a final dimension
>= 65536.
</A></h2>
This bug was fixed in FFTW 2.0.1. (There was a 32-bit integer
overflow due to a poorly-parenthesized expression.)
<h2><A name="primebug">
Question 5.7. FFTW 2.0's complex transforms give the wrong results
with prime factors 17 to 97.
</A></h2>
There was a bug in the complex transforms that could cause incorrect
results under (hopefully rare) circumstances for lengths with
intermediate-size prime factors (17-97). This bug was fixed in FFTW
2.1.1.
<h2><A name="mpichbug">
Question 5.8. FFTW 2.1.1's MPI test programs crash with
MPICH.
</A></h2>
This was fixed in FFTW 2.1.2. The 2.1/2.1.1 MPI test programs crashed
when using the MPICH implementation of MPI with the
<code>ch_p4
</code> device (TCP/IP); the transforms themselves worked fine. (The source
of the bug was some strange constraints that MPICH imposes on access
to the program argument list.)
<hr>
Back:
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</a>.
<br>
<a href="index.html" rev=subdocument>Return to contents
</a>.
<p>
<address>
<A href="http://theory.lcs.mit.edu/~fftw/">Matteo Frigo and Steven G. Johnson
</A> /
<A href="mailto:fftw@theory.lcs.mit.edu">fftw@theory.lcs.mit.edu
</A>
- 18 May 1999
</address><br>
Extracted from FFTW Frequently Asked Questions with Answers,
Copyright
© 1999 Massachusetts Institute of Technology.
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