Merge branch 'feature/implement-scalarmatrixview' into 'master'

ref:core/dune-istl This is based on [dune-common!656] which introduces
Impl::asMatrix() using this we can avoid many Hybrid::ifElse constructions
which increase complexity of the implementation and error messages.
Furthermore we can drop toMatrix() which fixed [#63].

This is a clone of [!288]. Is was created in order to tell the CI to use the
corresponding branch in dune-common using a matching branch name.

See merge request [!289]

  [dune-common!656]: gitlab.dune-project.org/Nonedune-common/merge_requests/656
  [#63]: gitlab.dune-project.org/NoneNone/issues/63
  [!288]: gitlab.dune-project.org/NoneNone/merge_requests/288
  [!289]: gitlab.dune-project.org/core/dune-istl/merge_requests/289


Closes #63

Replace many `Hybrid::ifElse(IsNumber<...` constructions by
using `Impl::asMatrix()`. In some cases the (now only) implementation
of the matrix branch was additionally cleaned up using range-based
for.

Using `Impl::asMatrix()` we can replace many special case
implementations based on `Hybrid::ifElse(IsNumber...` which
simplifies code and error messages and avoids some code duplication.

This invokes undefined behaviour and was now replaced by asMatrix()
in dune-common.

The fundamental difference is, that `toMatrix()` leads to undefined
behaviour, because it dereference a pointer obtained from a
`reinterpret_cast` violating strict aliasing rules. In contrast
`asMatrix()` returns a wrapper modelling a proxy-matrix which
is safe to use.

Merge branch 'feature/simplify-scalar-entries' into 'master'

ref:core/dune-istl Using the new Impl::asVector() from dune-common we can get
rid of

-   several Hybrid::isElse() constructions used to implement special cases for
    isNumber,
-   undefined behaviour invoked by toVector() due to the latter violating
    strict aliasing rules.

This also removed the dangerous toVector() methods. This is only a partial
solution to [#63]. We also need to do the same for toMatrix() which requires
an analogue Impl::asMatrix() function and a ScalarMatrixView wrapper class.

See merge request [!287]

  [#63]: gitlab.dune-project.org/NoneNone/issues/63
  [!287]: gitlab.dune-project.org/core/dune-istl/merge_requests/287

Carsten Gräser authored 5 years ago and Oliver Sander committed 5 years ago

Using the wrapper generated by `asVector()` we can get rid of `toVector()`.
The important difference is, that `toVector()` invokes undefined behaviour
by dereferencing the result of an aliasing `reinterpret_cast`. However,
there's no noteable properties of the new implementation:
* You can't use `asVector()` directly in calls to `mv()` and friends,
  because the latter is not robust wrt. to proxy references.
* When creating copies of values, you can't replace
  `auto rhs = v[i];` by `auto rhs = Impl::asVector(v[i])`
  because proxy references don't use deep copy on purpose.
  Instead we have to use the two step
  `auto rhsValue = v[i]; auto&& rhs = Impl::asVector(rhsValue);`

Carsten Gräser authored 5 years ago and Oliver Sander committed 5 years ago

Using `Impl::asVector()` we can get rid of several `Hybrid::ifElse()`
constructions used to implement the special case of scalar entries
(i.e. `IsNumber==true`).

Merge branch 'fix_matrixredistribute_for_scalar_valued_matrices' into 'master'

ref:core/dune-istl This MR adapts matrixredistribute.hh for matrices with
scalar block_type like BCRSMatrix<double> and adapts the
matrixredistributetest.

See merge request [!278]

  [!278]: gitlab.dune-project.org/core/dune-istl/merge_requests/278

Merge branch 'improve-matrix-testing' into 'master'

See merge request [!282]

  [!282]: Nonecore/dune-istl/merge_requests/282

in order to get a `static constexpr` result, the method must be called via the type and not via `this`.

And test it.

In preparation of testing more matrix types

... and use it in bcrsmatrixtest.cc

Currently we are only testing whether these methods are implemented
and can be compiled.

Found by porting the unit test to the general vectortest.hh framework.

Rather than testing them manually.

This is possible now because we have IsNumber in dune-common.

This uncovers a bug in the method axpy, which is also fixed
in this patch.

... and use it to test the BCRSMatrix class.

Currently, the new test only tests the vector space operations
required of a dune-istl matrix.  More is to come in subsequent
patches.

Merge branch 'bugfix/silence-useless-warnings' into 'master'

See merge request [!281]

  [!281]: Nonecore/dune-istl/merge_requests/281

Merge branch 'feature/fix-novlpschwarz' into 'master'

See merge request [!280]

  [!280]: Nonecore/dune-istl/merge_requests/280

Merge branch 'feature/use-latexmk' into 'master'

See merge request [!275]

  [!275]: Nonecore/dune-istl/merge_requests/275

It caused problems with latexmk