(if it still exists).
</p>
<p>The planner returns <code>NULL</code> if the plan cannot be created.  A
non-<code>NULL</code> plan is always returned by the basic interface unless
you are using a customized FFTW configuration supporting a restricted
set of transforms, or for size-1 <code>FFTW_REDFT00</code> kinds (which are
not defined).
<span id="index-FFTW_005fREDFT00-1"></span>
</p>
<span id="Arguments-2"></span><h4 class="subsubheading">Arguments</h4>
<ul>
<li> <code>rank</code> is the dimensionality of t