Dear All,
First, I'd like to thank you guys for Libmesh, great job!
Encouraged by the examples, I started to write and run (successfully!) some
codes for linear elasticity (both static and dynamic cases). Now I'm trying to
solve a nonlinear problem using Newton-Raphson iterations. The Hessian
is explicit so I just need to build at each iteration a certain matrix A and
rhs
F depending on the solution from the previous iteration. The idea is: given
u_old, solve v such that
<A(u_old) v, w> = <F(u_old), w> for all w
and then the new solution is u_new = u_old + v.
The first iteration runs ok, but the second iteration stops during the call
to solve(), throwing the message:
[0]PETSC ERROR: Caught signal number 11 SEGV: Segmentation Violation, probably
memory access out of range
Debugging with gdb, I only get that the error is produced during the execution
of "libMesh::PetscLinearSolver<double>::solve( ..."
I'm using the LinearImplicitSystem class to solve the problem. I think that may
be,
something is zero or null after the first iteration, hence we would need to
"clear"
or "reinit" the system class.
In this example I did not use clear, reinit nor close (the last for matrices
and vectors)...
because from the examples it is not very clear for me the way to use it.
So, I would really appreciate if someone could explain why, how and when
we should use the "clear", "reinit" and "close" member functions (and
eventually others, if necessary) in order to properly rebuild the matrix and
the rhs.
Thanks.
Joaquin.
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