">REAL</span><span class="p">(</span><span class="n">rp</span><span class="p">),</span> <span class="k">DIMENSION</span><span class="p">(:,:),</span> <span class="k">ALLOCATABLE</span><span class="p">,</span> <span class="k">INTENT</span><span class="p">(</span><span class="n">IN</span><span class="p">)</span>      <span class="kd">::</span> <span class="n">Y</span>
  <span class="c">!! Particles&#39; position in cylindrical coordinates,</span>
  <span class="c">!! Y(1,:) = \(R\), Y(2,:) = \(\phi\), and Y(3