[petsc-users] Applying Multi-Point-Constraints with SNES

[Hongrui Yu]

Hello PETSc users,

 

In our Finite Element application we would like to apply
Multi-Point-Constraints to some vertices. In these Multi-Point-Constraints
we force certain DoF in the following nodes to be the same as those in
controlling nodes. We use DMPlex to store our mesh. I'm wondering what would
be a good way to implement this together with SNES? Or is there an example
that does similar thing?

 

Currently both right-hand-side and solution vectors in out application are
created using DMCreateGlobalVec(). And we tried (unsuccessfully) to modify
solution within FormRHS or FormJacobian routines but the solution vector
seems to be read-only (for good reason). Is there a way to tell SNES about
these constraints? Or perhaps one can somehow create a vector with only a
subset of the DoFs (the actual "unknowns")?

 

Thank you in advance for any help or advice!

 

Hongrui

 

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