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<p class="MsoNormal"><span style="font-size:12.0pt;font-family:"Times New Roman",serif">For problems with constraints on the states, I would recommend trying the event functionality, TSEvent, that allows detection and location of discrete events, such as one
that you have in your problem.<o:p></o:p></span></p>
<p class="MsoNormal"><a href="https://www.mcs.anl.gov/petsc/petsc-current/docs/manualpages/TS/TSSetEventHandler.html">https://www.mcs.anl.gov/petsc/petsc-current/docs/manualpages/TS/TSSetEventHandler.html</a>.
<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">An example using TSEvent functionality: <a href="https://www.mcs.anl.gov/petsc/petsc-current/src/ts/examples/tutorials/ex40.c.html">https://www.mcs.anl.gov/petsc/petsc-current/src/ts/examples/tutorials/ex40.c.html</a><o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">A brief intro to TSEvent can be found <a href="https://www.mcs.anl.gov/petsc/petsc-20/conference/Abhyankar_S.pdf">
here</a>.<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">Thanks,<o:p></o:p></p>
<p class="MsoNormal">Shri <o:p></o:p></p>
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<p class="MsoNormal"><span style="font-size:12.0pt;font-family:"Times New Roman",serif"><o:p> </o:p></span></p>
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<p class="MsoNormal" style="margin-left:.5in"><b><span style="font-size:12.0pt;color:black">From:
</span></b><span style="font-size:12.0pt;color:black">petsc-users <petsc-users-bounces@mcs.anl.gov> on behalf of "Huck, Moritz via petsc-users" <petsc-users@mcs.anl.gov><br>
<b>Reply-To: </b>"Huck, Moritz" <Moritz.Huck@rwth-aachen.de><br>
<b>Date: </b>Monday, August 5, 2019 at 5:18 AM<br>
<b>To: </b>"petsc-users@mcs.anl.gov" <petsc-users@mcs.anl.gov><br>
<b>Subject: </b>[petsc-users] Problem with TS and SNES VI<o:p></o:p></span></p>
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<p class="MsoNormal" style="margin-left:.5in"><o:p> </o:p></p>
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<p class="MsoNormal" style="margin-left:.5in">Hi,<o:p></o:p></p>
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<p class="MsoNormal" style="margin-left:.5in">I am trying to solve a DAE with the ARKIMEX solver, which works mostly fine.<o:p></o:p></p>
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<p class="MsoNormal" style="margin-left:.5in">The problem arises when some states go to unphysical values. I try to constrain my states with SNESVISetVariableBounds (through the petsc4py interface).<o:p></o:p></p>
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<p class="MsoNormal" style="margin-left:.5in">But TS seems not respect this e.g. I have a state with is usually between 1 and 1e3 for which I set a lower bound of 1, but the state goes t0 -0.8 at some points.<o:p></o:p></p>
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<p class="MsoNormal" style="margin-left:.5in">Are there some tolerances I have to set for VI or something like this?<o:p></o:p></p>
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<p class="MsoNormal" style="margin-left:.5in"><o:p> </o:p></p>
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<p class="MsoNormal" style="margin-left:.5in">Best Regards,<o:p></o:p></p>
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<p class="MsoNormal" style="margin-left:.5in">Moritz<o:p></o:p></p>
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<p class="MsoNormal" style="margin-left:.5in"><o:p> </o:p></p>
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