[petsc-users] Need to update matrix in every loop

Jed Brown jed at jedbrown.org
Fri Aug 14 11:10:02 CDT 2015

Please always use "reply-all" so that your messages go to the list.
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answer faster that way too.

sheng liu <ustc.liu at gmail.com> writes:

> Thank you! I have a small question: What does the "degree of freedom" mean
> in the DMDA object? If I have a spin-1/2 system, and I discrete the system,
> does that mean I have DOF=2?

DOF is the number of PetscScalar values at each grid point.

> 2015-08-12 23:46 GMT+08:00 Jed Brown <jed at jedbrown.org>:
>> sheng liu <ustc.liu at gmail.com> writes:
>> > Thank you very much! I have another question. If I need all the
>> eigenvalues
>> > of the sparse matrix, which solver should I use? Thanks!
>> That's O(n^3) with n=1e6.  Better find a way to not need all the
>> eigenvalues or to make the system smaller.
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