an> <span class="mi">1</span>  <span class="c1"># half dimension</span>

                <span class="n">p</span> <span class="o">=</span> <span class="n">hdim</span>
                <span class="c1"># x11 = np.copy(mat[0:hdim, 0:hdim], &#39;C&#39;)</span>
                <span class="c1"># x12 = np.copy(mat[0:hdim, hdim:dim], &#39;C&#39;)</span>
                <span class="c1"># x21 = np.copy(mat[hdim:dim, 0:hdim], &#39;C&#39;)</span>
                <span class="c1"># x22 = np.copy(mat[hdim:dim, hdim:dim