x-Vector Product<a class="anchor-link" href="#Step-2:-Matrix-Vector-Product">&#182;</a></h2><p>Compare the following three ways of computing <code>A*u</code></p>
<ul>
<li><p>Generate a big sparse matrix using the tensor product of 1-D tri-diagonal finite difference matrix and compute <code>A*u</code> using this matrix</p>
</li>
<li><p>Code matrix-free version of <code>A*u</code></p>
</li>
<li><p>Use the 1-D matrix and tensor product structure to compute <code>A*u</code></p>
</li>
</ul>
<p>Use them to verify