 OpenMP) must concern
themselves with the <dfn>thread safety</dfn> of the libraries they
use&mdash;that is, whether it is safe to call routines in parallel from
multiple threads.  FFTW can be used in such an environment, but some
care must be taken because the planner routines share data
(e.g. wisdom and trigonometric tables) between calls and plans.

   <p>The upshot is that the only thread-safe (re-entrant) routine in FFTW is
<code>fftw_execute</code> (and the new-array variants thereof).  All other routi