Scalable multi-level deflation preconditioning for the highly indefinite Helmholtz equation

</p><p class="MsoNormal">Recent research efforts aimed at iteratively solving the Helmholtz equation have focused on incorporating deflation techniques for accelerating the convergence of Krylov subspace methods. In this work, we extend the two-level deflation method in [6] to a multilevel deflation method. By using higher-order deflation...