s="special">,</span> <span class="identifier">n</span><span class="special">,</span> <span class="identifier">p</span><span class="special">);</span>
<span class="keyword">double</span> <span class="identifier">dvdt</span> <span class="special">=</span> <span class="identifier">lanczos</span><span class="special">(</span><span class="identifier">v</span><span class="special">,</span> <span class="identifier">i</span><span class="special">);</span>
</pre>
<p>
      If <span class="emphasis"><em>p=2n</em></sp