before the planner is called by
<code>fftw_plan_with_nthreads</code>.  The threads initialization routine used
to be called <code>fftw_threads_init</code> and would return zero on success;
the new routine is called <code>fftw_init_threads</code> and returns zero on
failure.  See <a href="Multi_002dthreaded-FFTW.html#Multi_002dthreaded-FFTW">Multi-threaded FFTW</a>.
</p>
<p>There is no separate threads header file in FFTW 3; all the function
prototypes are in <code>&lt;fftw3.h&gt;</code>.  However, you still