Merge branch 'feature/jacobian-apply-in-onestep-grid-operator' into 'master'

ref:pdelab/dune-pdelab This adds the jacobian apply method to the one step
grid operator.

See merge request [pdelab/dune-pdelab!444]

  [pdelab/dune-pdelab!444]: gitlab.dune-project.org/pdelab/dune-pdelab/merge_requests/444

Merge branch 'feature/vtkwriter-lifetime-issues' into 'master'

ref:pdelab/dune-pdelab This commit introduces an additional signature for
addSolutionToVTKWriter that takes grid function space and data vector as
shared pointers. This is necessary because of the delayed nature of VTK
export: Data sets are registered in a first step and written in a second step.
Currently PDELab implicitly requires both steps to happen in the same scope,
as otherwise the registered function objects can be destroyed before written
into a file. The additional signature allows to pass shared pointer objects
that the VTK functions take ownership of. Internally, this required the
BlockVector of the ISTL vector backend to store the grid function space as a
shared pointer.

See merge request [pdelab/dune-pdelab!434]

  [pdelab/dune-pdelab!434]: gitlab.dune-project.org/pdelab/dune-pdelab/merge_requests/434

Merge branch 'feature/construct-composite-gridfunction-from-shared-ptr' into 'master'

See merge request [pdelab/dune-pdelab!443]

  [pdelab/dune-pdelab!443]: Nonepdelab/dune-pdelab/merge_requests/443

Note: The solution might be unvalid, if you have a linear problem it never gets
set!

Merge branch 'feature/jacobian-apply-cleanup' into 'master'

ref:pdelab/dune-pdelab This merge request cleans up the existing jacobian
apply engines. We remove the NonlinearJacobianApply engine and instead make
sure that the JacobianApply engine can handle the linear and the non-linear
case. This is done by introducing a flag isLinear to the local operators
through <dune/pdelab/localoperator/flags.hh>. The JacobianApply uses this flag
to decide which methods need to be called.

On the GridOperator side we have two methods called jacobian_apply that take a
different number of arguments for the linear and non-linear case. The method
nonlinear_jacobian_apply still exists but is deprecated. If you use the wrong
method you will get an error.

Changes for users: If you have a non-linear residual and want to use the
nonlinear_jacobian_apply method you need to set the isLinear flag in your
local operator.

This merge request is based on inspired by the work of @smuething and @marian
in the EXADune project, checked out on commit
70c0f644dee360259b36cb17888e6baf90da5056.

See merge request [pdelab/dune-pdelab!439]

  [pdelab/dune-pdelab!439]: gitlab.dune-project.org/pdelab/dune-pdelab/merge_requests/439

Merge branch 'feature/keep-old-newton-backward-compatible' into 'master'

ref:pdelab/dune-pdelab This way it should be completely backward compatible
(to the time before the new Newton was introduced)

See merge request [pdelab/dune-pdelab!445]

  [pdelab/dune-pdelab!445]: gitlab.dune-project.org/pdelab/dune-pdelab/merge_requests/445

This way it should be completely backward compatible (to the time before the
new Newton was introduced)

Merge branch 'feature/vtkwriter-lifetime-issues' of ssh://gitlab.dune-project.org:22022/pdelab/dune-pdelab into feature/vtkwriter-lifetime-issues

Note: For some reason the Jacobian method does not work. This is most likely an
artifact that comes from the fact that this test never assembles
anything. For real problems everything seems to work fine.

Merge branch 'feature/grid-function-probe-initialization' into 'master'

ref:pdelab/dune-pdelab There is a setter for the function anyway, so it is
natural to be able to construct the probe object without a function.

See merge request [pdelab/dune-pdelab!438]

  [pdelab/dune-pdelab!438]: gitlab.dune-project.org/pdelab/dune-pdelab/merge_requests/438

This bug originates from a C&P bug. It never worked, but nobody notices.

Merge branch 'cleanup/internal-renaming-in-engine' into 'master'

ref:pdelab/dune-pdelab Before really starting [!439] it would make sense to
rename some things in the engines. The proposal is as follows:

-   The engines have methods and members corresponding to data vectors.
    Current naming is like this:

  -------------------------- ----------------------------
  residual                   Residual, Solution
  jacobian                   Jacobian, Solution
  jacobian_apply             Residual, Solution
  nonlinear_jacobian_apply   Residual, Solution, Update
  -------------------------- ----------------------------

-   The proposal is to change those names to:

  -------------------------- --------------------------
  residual                   Residual, Solution
  jacobian                   Jacobian, Solution
  jacobian_apply             Result, Update
  nonlinear_jacobian_apply   Result, Update, Solution
  -------------------------- --------------------------

The changes would be: Solution-\>Update in the linear case of jacobian_apply
and Solution-\>Update, Update-\>Solution in the nonlinear case of
jacobian_apply. For me it would also be fine to always call the result
'Result' and not 'Residual' or 'Jacobian'.

-   Why renaming?

Residual form:

    r(u,v)=a(u,v)-b

Residual vector:

    (R(z))_i = r(\sum_j(z)_j\phi_j, \phi_i)

Jacobian:

    \nabla R(z)

Jacobian Apply:

    \nabla R(z) w

If you look at the jacobian and the jacobian_apply the names of the objects
should be different since they have different mathematical meaning. If it
stays as it is, it is really confusing in the nonlinear case since the
Solution at the moment corresponds to w and the update to z and this doesn't
make any sense at all.

After renaming the name update actually makes sense. If you think about a
Newton solver or a linear solver in residual formulation you actually evaluate
the jacobian for a given solution and try to solve for an update. So calling z
Solution and w update seems reasonable.

See merge request [pdelab/dune-pdelab!440]

  [!439]: gitlab.dune-project.org/NoneNone/merge_requests/439
  [pdelab/dune-pdelab!440]: gitlab.dune-project.org/pdelab/dune-pdelab/merge_requests/440

Merge branch 'feature/newton-improve-documentation' into 'master'

See merge request [pdelab/dune-pdelab!441]

  [pdelab/dune-pdelab!441]: Nonepdelab/dune-pdelab/merge_requests/441