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<p class="MsoNormal">Hello PETSc users,<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">I am fairly inexperienced with PETSc as of now and am new to the mailing list! Thanks for running this channel.<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">I seek basic help regarding running AMG routines (BoomerAMG/ML/GAMG). I am trying to compare the performance of solving a Poisson problem using a AMG Preconditioned GMRES iterative solve vs using AMG as the solver. I use PETSc options using
the options database keys as of now, and it is connected to a flow solver (Nektar++) I use for my research.<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">I currently run the AMG Preconditioned GMRES iterative solve by setting
<span style="font-family:"Courier New"">-ksp_type gmres</span> and then specifying the preconditioner I want using, for e.g, -<span style="font-family:"Courier New"">pc_type hypre -pc_hypre_type boomeramg</span>. If I want to use the AMG routine, I am currently
setting <span style="font-family:"Courier New"">-ksp_type preonly</span> and the same
<span style="font-family:"Courier New"">-pc_type</span>. However, I am not sure if this is correct way to go about it due to two reasons: a) my solution using AMG as a solver with these options has a larger error than AMG Preconditioned GMRES (which could
still be acceptable), and b) I could not find any clear documentation regarding how to use AMG directly as a solver. I saw some hints in the examples here
<a href="https://petsc.org/main/tutorials/handson/">https://petsc.org/main/tutorials/handson/#</a>, but it hasn’t helped me.
<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Any hints on how to use AMG directly as a solver?<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Best<o:p></o:p></p>
<p class="MsoNormal">Parv<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
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