Thank you Bruno for your suggestion. I tried in regular mode and it doesn't seem to improve the accuracy. The results are approximately the same as I was getting using the shift-invert method.
One thing that I didn't understand is that I used the scipy function "eigs" in python <https://github.com/scipy/scipy/tree/master/scipy/sparse/linalg/eigen/arpack> which essentially uses ARPACK, and it still it doesn't match with that. Does it have to do something with the way the ARPACK code is written in dealii? Can you let me know how to use Anasazi, I don't see anything related to this in the documentation of deaii? I am planning to now try this eigensolver for my problem and would want to see how much it improves the results. Thanks! Animesh On Wednesday, December 16, 2020 at 3:26:57 AM UTC+5:30 bruno.t...@gmail.com wrote: > Animesh, > > You need to download the patch to the deal.II directory. If you cloned > deal.II, you can simply use git apply > 0001-Enable-ARPACK-in-regular-mode.patch. If you didn't use git to get > deal.II, I think patch -i 0001-Enable-ARPACK-in-regular-mode.patch > should work. I have also noted that Arpack was not very accurate. I am > not sure why because according to the documentation, many other > packages are successfully using Arpack. At the end, we gave up on > Arpack and switched to lobpcg from anasazi. The results were more > accurate and more stable. > > Best, > > Bruno > > Le mar. 15 déc. 2020 à 07:52, Animesh Rastogi IIT Gandhinagar > <animesh...@alumni.iitgn.ac.in> a écrit : > > > > Hi Bruno, > > > > I would like to use this patch to compute the smallest eigenvalues in my > case. Could you please let me know how should I update my source code in > the arpack.h header file to accommodate these changes in the patch. I > understand that I would need to reinstall dealii after updating the source > code, which I am fine with. > > > > When I am using the shift-inverse mode, I am not getting the results > similar to what I would get using the eigenvalue solver in MATLAB or Python > for the same matrix. There is a difference of about 15 to 20 in the > eigenvalues (even when comparing it with the ARPACK solver in Python). This > is the reason that I would want to try calculating the eigenvalues using > the patch you created in regular mode. > > > > Thanks! > > > > Animesh > > On Sunday, November 8, 2020 at 6:00:58 PM UTC+5:30 Animesh Rastogi IIT > Gandhinagar wrote: > >> > >> Thank you Bruno, I was able to change the source code accordingly. I > reinstalled dealii and it worked fine! > >> > >> Thanks again! > >> > >> Animesh > >> > >> On Friday, November 6, 2020 at 3:55:29 AM UTC+5:30 bruno.t...@gmail.com > wrote: > >>> > >>> Animesh, > >>> > >>> On Thursday, November 5, 2020 at 1:11:33 PM UTC-5 > animesh...@alumni.iitgn.ac.in wrote: > >>>> > >>>> However, I have no way of passing it as a parameter to the solver > function. I was planning to edit the header file arpack.h accordingly which > is inside the /usr/local/include/deal.II/lac to have that functionality. I > was actually thinking of passing the flag "rvec" as an argument to the > function solve. I was wondering if I change the permission of the file to > write mode, edit it and save it, would I be able to run my code inside the > examples folder. Or do I need to take care of something else while and > after editing that headerfile? > >>> > >>> You should change the source code and reinstall deal.II. I would do > what you propose only if you cannot compile deal.II on that machine. It > might work in this particular case but I really advise you against it. > >>> > >>> Best, > >>> > >>> Bruno > >>> > > > > -- > > The deal.II project is located at http://www.dealii.org/ > > For mailing list/forum options, see > https://groups.google.com/d/forum/dealii?hl=en > > --- > > You received this message because you are subscribed to a topic in the > Google Groups "deal.II User Group" group. > > To unsubscribe from this topic, visit > https://groups.google.com/d/topic/dealii/2hA57ZghGqs/unsubscribe. > > To unsubscribe from this group and all its topics, send an email to > dealii+un...@googlegroups.com. > > To view this discussion on the web visit > https://groups.google.com/d/msgid/dealii/81e7a0d4-4ab9-4323-8beb-aa7897feb4c2n%40googlegroups.com > . > -- The deal.II project is located at http://www.dealii.org/ For mailing list/forum options, see https://groups.google.com/d/forum/dealii?hl=en --- You received this message because you are subscribed to the Google Groups "deal.II User Group" group. To unsubscribe from this group and stop receiving emails from it, send an email to dealii+unsubscr...@googlegroups.com. To view this discussion on the web visit https://groups.google.com/d/msgid/dealii/aa324ad1-b51d-4940-a34d-68680074b4b4n%40googlegroups.com.
