FPGA Central

Dear FFTW users,

we are pleased to announce the availability of FFTW 3.1.3, which
you can download from the web page:

http://fftw.org/download.html

This release fixes a bug that causes incorrect results to be computed
in programs that use both REDFT11 (a.k.a. DCT-IV) and RODFT11
(a.k.a. DST-IV) at the same time. Because of the potential for
incorrect results, users of FFTW 3.1.2 are encouraged to upgrade to
3.1.3, or alternatively apply the following one-line patch to FFTW
3.1.2:

--- kernel/twiddle.c.old 2008-10-03 10:50:57.791097391 -0400
+++ kernel/twiddle.c 2008-10-03 10:51:11.875771979 -0400
@@ -50,7 +50,7 @@

switch (p->op) {
case TW_NEXT:
- return 1;
+ return (p->v == q->v); /* p->i is ignored */

case TW_FULL:
case TW_HALF:

Alpha releases of FFTW 3.2 are not affected by this bug.

We apologize for the inconvenience. Please report any problems to
[email protected].

Cordially,
Matteo Frigo
Steven G. Johnson

Changes since FFTW 3.1.2:

* Bug fix: FFTW computes incorrect results when the user plans both
REDFT11 and RODFT11 transforms of certain sizes. The bug is caused
by incorrect sharing of twiddle-factor tables between the two
transforms, and only occurs when both are used. Thanks to Paul
A. Valiant for the bug report.