s that planned for
a particular array and stride, but the plan could still be used for
other arrays and strides.)  That is, much of the information that was
formerly specified at execution time is now specified at planning time.
</p>
<p>Like FFTW 2&rsquo;s specific planner routines, the FFTW 3 planner overwrites
the input/output arrays unless you use <code>FFTW_ESTIMATE</code>.
</p>
<p>FFTW 2 had separate data types <code>fftw_plan</code>, <code>fftwnd_plan</code>,
<code>rfftw_plan</code>, and <code>rfftwnd