Wrong absolute residual computed for istl backend in parallel
Summary
When running simulation using the ISTL backend in parallel, the automatic computed absolute residual |b - A*x|
is wrong. It is computed with the local parts of the matrix and vectors only.
Possible fix:
- Either do not compute this residual in parallel, but only show the reduction of the
InverseOperatorResult
- Or, make a proper computation of the residual using parallel matrix-vector product and inner products.