 continues, and FFTW&rsquo;s planning routines in general form a
&ldquo;partial order,&rdquo; sequences of
<a name="index-partial-order"></a>
interfaces with strictly increasing generality but correspondingly
greater complexity.
</p>
<p><code>fftw_plan_dft</code> is the most general complex-DFT routine that we
describe in this tutorial, but there are also the advanced and guru interfaces,
<a name="index-advanced-interface-1"></a>
<a name="index-guru-interface-1"></a>
which allow one to efficiently combine m