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Hi Barry,</div>
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I hope you are doing well.</div>
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Attached are the output. To give a little more context, this is a "new" way of running the code where multiple instances are created and communicate together every few time steps (like coupling the code with itself in memory). Here there are 3 instances that
each have a separate TS object, plus one "main" instance that doesn't solve anything but compute rates to exchange between the other instances.</div>
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Cheers,</div>
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Sophie</div>
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<div id="divRplyFwdMsg" dir="ltr"><font face="Calibri, sans-serif" style="font-size:11pt" color="#000000"><b>From:</b> Barry Smith <bsmith@petsc.dev><br>
<b>Sent:</b> Monday, December 9, 2024 15:12<br>
<b>To:</b> Blondel, Sophie <sblondel@utk.edu><br>
<b>Cc:</b> petsc-users@mcs.anl.gov <petsc-users@mcs.anl.gov>; xolotl-psi-development@lists.sourceforge.net <xolotl-psi-development@lists.sourceforge.net><br>
<b>Subject:</b> Re: [petsc-users] "-ts_exact_final_time matchstep" leads to DIVERGED_STEP_REJECTED</font>
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<div>On Dec 9, 2024, at 2:56 PM, Blondel, Sophie via petsc-users <petsc-users@mcs.anl.gov> wrote:</div>
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Hi,</div>
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I am trying to understand a strange behavior I'm encountering: when running my application with "-ts_exact_final_time stepover" everything goes well, but when I switch to "matchstep" I get DIVERGED_STEP_REJECTED before the first time step is finished.
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<div> This is in the very first time-step in TSSolve? </div>
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<div> Please run with -ts_monitor and send all the output (best for a short time interval and do it twice once with <span style="font-family:Calibri,Helvetica,sans-serif; font-size:12pt">-ts_exact_final_time stepover and once with exact.</span></div>
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<div><span style="font-family:Calibri,Helvetica,sans-serif; font-size:12pt"> Barry</span></div>
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I tried increasing the maximum number of rejections and it just takes longer to diverge, and if I set the value to "unlimited" it is basically an infinite loop.</div>
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Is there a way to check why is the step rejected? Could the "matchstep" option change tolerances somewhere that would cause that behavior?</div>
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Let me know if I should provide more information.</div>
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Best,</div>
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Sophie Blondel</div>
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