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<p>Dear users,</p>
<p>I have been using petsc's KSP for over 20 years and I am
considering using DMPLEX to replace my own data structure in a
mixed FEM/FVM CFD code.</p>
<p>To do so, I am trying to understand DMPLEX by writing a 1D code
that solves u_t = u_xx using PSEUDOTS.</p>
<p>In order to prescribe Dirichlet BCs at the endpoints of the 1D
box, I use PetscSectionSetConstraintDof when building the
PetscSection.<br>
</p>
<p>
<blockquote type="cite">A global vector is missing both the shared
dofs which are not owned by this process, as well as <em>constrained</em>
dofs. These constraints represent essential (Dirichlet)
boundary conditions. They are dofs that have a given fixed
value, so they are present in local vectors for assembly
purposes, but absent
from global vectors since they are never solved for during
algebraic solves.</blockquote>
</p>
<p>My global Vec has indeed two entries less than the local one.</p>
<p>When initializing the solution or evaluating the rhs function I
transfer data from the global to local representation, do the
calculation, then transfer back.</p>
<p>I am doing something wrong, though, which shows up in the
attached log file.</p>
<p>My simple code is also attached.</p>
<p>Thank you for your advice.</p>
<p>Aldo<br>
</p>
<pre class="moz-signature" cols="72">--
Dr. Aldo Bonfiglioli
Associate professor of Fluid Machines
Scuola di Ingegneria
Universita' della Basilicata
V.le dell'Ateneo lucano, 10 85100 Potenza ITALY
tel:+39.0971.205203 fax:+39.0971.205215
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