me="index-out_002dof_002dplace"></a>

</li><li> <a name="index-FFTW_005fPRESERVE_005fINPUT-1"></a>
<code>FFTW_PRESERVE_INPUT</code> specifies that an out-of-place transform must
<em>not change its input</em> array.  This is ordinarily the
<em>default</em>, except for c2r and hc2r (i.e. complex-to-real)
transforms for which <code>FFTW_DESTROY_INPUT</code> is the default.  In the
latter cases, passing <code>FFTW_PRESERVE_INPUT</code> will attempt to use
algorithms that do not destroy the input, at the expense