Christian Engwer authored 5 years ago and Timo Koch committed 5 years ago

* update MatrixAdapter, OverlappingSchwarzOperator and NonoverlappingSchwarzOperator
* store matrix as `shared_ptr`
* update construction traits accordingly

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.

Carsten Gräser authored 6 years ago and Oliver Sander committed 6 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 6 years ago and Oliver Sander committed 6 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`).

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.

if on the initial AMG pre was called, it is currently it not necessary to
call pre on a copy of that AMG. This is a feature that is not required
by the Preconditioner interface and thus it nothing anybody can rely on.
We now don't copy the temporary data anymore.

Hierarchy and MatrixHierarchy now have separate headers to improve
readability.