Thank you for the example, it is indeed useful!
In my application, an additional complication is that the stiffness
matrix "K" is also singular. So when I run my code with the suggested
runtime flags, I persistently get a zero pivot error for the LU
calculation (for the st_pc probably). I'm not sure what factorization or
solver I should use in this case.
TLDR: I have K.v=lam*M.v where BOTH K and M are singular. The nullspace
of M is a subset of the nullspace of K.
Thank you,
Nidish
On 8/16/20 1:50 AM, Jose E. Roman wrote:
Nothing special is required for solving a GHEP with singular M, except for
setting the problem type as GHEP, see
https://slepc.upv.es/documentation/current/src/eps/tutorials/ex13.c.html
Jose
El 16 ago 2020, a las 1:09, Nidish <n...@rice.edu> escribió:
Hello,
I'm presently working with a large finite element model with several RBE3 constraints
with "virtual" 6DOF nodes in the model.
I have about ~36000 3DOF nodes making up my model and about ~10 RBE3 virtual
nodes (which have zero intrinsic mass and stiffness). I've extracted the
matrices from Abaqus.
The way these constraints are implemented is by introducing static linear
constraints (populating the stiffness matrix) and padding the mass matrix with
zero rows and columns in the rows corresponding to the virtual nodes. So this
leaves me with an eigenproblem of the form,
K.v = lam*M.v
where M is singular but the eigenproblem is well defined. Abaqus seems to solve
this perfectly well, but after exporting the matrices, I'm struggling to get
slepc to solve this. The manual talks about deflation, etc., but I couldn't
really understand too much.
Is there any example code for such a case with a singular matrix where these
procedures are carried out? Or could you provide references/guidances for
approaching the problem?
Thank you,
Nidish
--
Nidish
