floor(kernel_-&gt;CutOffRadius() * inv_grid_spacing_);</div><div class="line"><a name="l00073"></a><span class="lineno">   73</span>&#160;        };</div><div class="line"><a name="l00074"></a><span class="lineno">   74</span>&#160;        <span class="keywordtype">int</span> operator()(<span class="keywordtype">size_t</span> particle_index)<span class="keyword"> const </span>{ <span class="keywordflow">return</span> search_depth_; };</div><div class="line"><a name="l00075"></a><span class="lineno">   75</s