[petsc-users] problem with initial value

[Dominik Szczerba]

I am doing a transient computation, solving one linear problem per timestep,
so naturally I want to exploit 'x' from the previous time step to be the
initial value for the next solve (KSPSetInitialGuessNonzero).
For the longest time, however, I was getting wrong results, unless I was
resetting 'x' each time step (to some constant value, pure zero caused bcgs
to break down).
After hours of debugging I was unable to find any errors in my coefficients,
I experimentally found out, however, that changing the solver from bcgs to
gmres or fgmres removes the problem: I no longer need to clear the solution
vector.
Now I am a bit worried, if this is still some time bomb in my code or is a
known phenomenon. Thanks for any hints.

Regards, Dominik
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