<div dir="ltr"><div dir="ltr">On Tue, Jul 12, 2022 at 7:39 AM Pierre Jolivet <<a href="mailto:pierre@joliv.et">pierre@joliv.et</a>> wrote:<br></div><div class="gmail_quote"><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex"><div style="overflow-wrap: break-word;"><br><div><br><blockquote type="cite"><div>On 12 Jul 2022, at 2:32 PM, Matthew Knepley <<a href="mailto:knepley@gmail.com" target="_blank">knepley@gmail.com</a>> wrote:</div><br><div><div dir="ltr"><div dir="ltr">On Mon, Jul 11, 2022 at 1:17 PM Pierre Jolivet <<a href="mailto:pierre@joliv.et" target="_blank">pierre@joliv.et</a>> wrote:<br></div><div class="gmail_quote"><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex">Hello,<br>
Could anyone help me understand what is going on in the following example, please?<br>
I have a VecNest.<br>
I either: a) initialize all values to 0.0, then set a specific part of the vector to nonzero or b) initialize a part of the vector to 0.0 and set the other part to nonzero.<br>
I don’t see why a) and b) produce different results.<br>
<br>
$ ./ex1111 -pc_type fieldsplit -ksp_monitor_true_residual -ksp_converged_reason -fieldsplit_pc_type jacobi -ksp_pc_side right -ksp_view_final_residual -nest_subvec true <br>
0 KSP unpreconditioned resid norm 8.375635517980e-01 true resid norm 8.375635517980e-01 ||r(i)||/||b|| 1.000000000000e+00<br>
1 KSP unpreconditioned resid norm 4.748816884247e-01 true resid norm 4.748816884247e-01 ||r(i)||/||b|| 5.669798875623e-01<br>
2 KSP unpreconditioned resid norm 4.713006778679e-01 true resid norm 4.713006778679e-01 ||r(i)||/||b|| 5.627043784990e-01<br>
3 KSP unpreconditioned resid norm 7.092979927129e-02 true resid norm 7.092979927129e-02 ||r(i)||/||b|| 8.468587144106e-02<br>
4 KSP unpreconditioned resid norm 1.457836310255e-02 true resid norm 1.457836310255e-02 ||r(i)||/||b|| 1.740567992870e-02<br>
5 KSP unpreconditioned resid norm 1.625040500524e-14 true resid norm 1.633468028779e-14 ||r(i)||/||b|| 1.950261595401e-14<br>
Linear solve converged due to CONVERGED_RTOL iterations 5<br>
KSP final norm of residual 1.63347e-14<br>
$ ./ex1111 -pc_type fieldsplit -ksp_monitor_true_residual -ksp_converged_reason -fieldsplit_pc_type jacobi -ksp_pc_side right -ksp_view_final_residual -nest_subvec false<br>
0 KSP unpreconditioned resid norm 0.000000000000e+00 true resid norm 8.375635517980e-01 ||r(i)||/||b|| inf<br>
Linear solve converged due to CONVERGED_ATOL iterations 0<br>
KSP final norm of residual 0.837564<br></blockquote><div><br></div><div>I find if I assemble the vector, I get the same answers. Will try to figure out what assembly is doing.</div></div></div></div></blockquote><div><br></div><div>It’s probably reseting all these values <a href="https://petsc.org/main/src/vec/vec/interface/rvector.c.html#line511" target="_blank">https://petsc.org/main/src/vec/vec/interface/rvector.c.html#line511</a>, which I believe are being used in VecNorm() inside VecNormalize().</div><div>I guess any call to VecNestSubVec() should invalidate those as well, otherwise we get wrong cached norms.</div><div>I will give this a go.</div></div></div></blockquote><div><br></div><div>I believe the bug is the following:</div><div><br></div><div> You change values in a subvector, which does StateIncrease on the subvector, but not StateIncrease on the nest vector, so it has its cached norm</div><div><br></div><div>I am not sure what to do about this, since how can the parent know you pulled out the subvector? Will think.</div><div><br></div><div> Matt</div><div> </div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex"><div style="overflow-wrap: break-word;"><div><div>Thanks,</div><div>Pierre</div><br><blockquote type="cite"><div><div dir="ltr"><div class="gmail_quote"><div> Thanks,</div><div><br></div><div> Matt</div><div> </div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex">
Thanks,<br>
Pierre<br>
<br>
</blockquote></div><br clear="all"><div><br></div>-- <br><div dir="ltr"><div dir="ltr"><div><div dir="ltr"><div><div dir="ltr"><div>What most experimenters take for granted before they begin their experiments is infinitely more interesting than any results to which their experiments lead.<br>-- Norbert Wiener</div><div><br></div><div><a href="http://www.cse.buffalo.edu/~knepley/" target="_blank">https://www.cse.buffalo.edu/~knepley/</a><br></div></div></div></div></div></div></div></div>
</div></blockquote></div><br></div></blockquote></div><br clear="all"><div><br></div>-- <br><div dir="ltr" class="gmail_signature"><div dir="ltr"><div><div dir="ltr"><div><div dir="ltr"><div>What most experimenters take for granted before they begin their experiments is infinitely more interesting than any results to which their experiments lead.<br>-- Norbert Wiener</div><div><br></div><div><a href="http://www.cse.buffalo.edu/~knepley/" target="_blank">https://www.cse.buffalo.edu/~knepley/</a><br></div></div></div></div></div></div></div></div>