h the geometric multigrid linear solver and profile the run
    <pre>
     mpiexec -n 4 ./ex19 -da_refine 5 -log_view -pc_type mg     <a href="https://www.mcs.anl.gov/petsc/petsc-current/src/snes/tutorials/output/ex19_tut_7.out">[Expected output]</a>
    </pre>
    Compare the runtime for SNESSolve to the 1 processor case with multigrid. What is the speedup?
    Why is the speedup for multigrid lower than the speedup for the default solver?
  </li>
</ul>
</div>

<div id="example4">
<h2>Example 4: Linear Sto