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<p class="MsoNormal">Hi,</p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">I am trying to solve the below parabolic system for a constant time interval dt</p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">(M + dt * K) x = M * x^(old)</p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Where,</p>
<p class="MsoNormal">M – Mass matrix</p>
<p class="MsoNormal">K – Stiffness matrix </p>
<p class="MsoNormal">A = M + dt * K (remains constant)</p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">I apply the boundary condition using MatZeroRowsColumns. For homogenous boundary conditions, I notice that the A matrix remains unmodified from one-time step to the next.</p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">For the non-homogenous boundary condition, I supply ‘x’ with the prescribed boundary value and pass it to MatZeroRowsColumns as follows</p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="p1"><span class="s1">MatZeroRowsColumnsIS</span>(<span class="s2">A</span>,
<span class="s2">is</span>, <span class="s3">1</span>, <span class="s2">x,</span>
<span class="s2">b</span>);</p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">After the linear solve, I find that A is modified. So I have to reassemble A again for every time step. Is it MatZeroRowsColumns or the solve itself that modifies A and why?</p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Kind regards,</p>
<p class="MsoNormal">Karthik.</p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
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