Instead of calling the BCCSInitializer, we directly parse the matrix into
an UMFPACK compatible form. This allows us to use almost every blocked
matrix structure, such as MultiTypeBlockedMatrix. Moreover, the 'setMatrix'
method is extended by a second bitVector argument to handle exclusion of
indices. The old 'setSubMatrix' method is kept. The new interface is
inspired by the neighbored 'Cholmod' class.

The additional routines on the vector data are linear in time and have no
measurable influence on the run time of UMFPACK.

So far doxygen did not process this file since
`HAVE_SUITESPARSE_CHOLMOD` was missing.
This also adds the missing editor hints.

CHOLMOD supports this, it just wasn't exposed in the interface.
It is needed for large problems.

Using `std::uint_least32_t` instead of `std::size_t` halves the required memory
and thus also improves performance.
Notice that `std::uint32_t` is optional and `std::uint_fast32_t` is intended to be
fast in terms of computations and may have 64 bits. Here we're interested in reducing
memory and thus bandwith. Hence `std::uint_least32_t`, which is the smallest sufficient
type is most appropriate.

This replaces the `std::set` used to store the column indices for each
rows by a `std::vector` based implementation. The `std::vector` is
kept sorted when inserting such that we can avoid duplicates. This
can improve assembly time of matrices significantly (if `MatrixIndexSet` is used).

In the worst case (insertion in reverse) this may lead to O(n^2) complexity
when inserting n entries in a row compared to O(n log(n)) for `std::set`.
However, the sorted `std::vector` implementation still wins for relatively
large n. To avoid the worst case complexity when using very dense rows,
the implementation is switched to `std::set` if the size exceeds the threshold
value `maxVectorSize`. The default `maxVectorSize=2048` was selected based
on benchmark results.

The CMAKE_GUARD for multiple guarding variables requires a
porper boolean statement.

Robert K authored 2 years ago and Andreas Dedner committed 2 years ago

use using and SizeType to size_type to adhere to istl conventions

Notice that this also fixes an incorrect `MultiTypeBlockMatrix::field_type`
in a special setting: If you have a nested matrix
`MultiTypeBlockMatrix< MultiTypeBlockVector<MultiTypeBlockMatrix<...>>>`,
the outer `MultiTypeBlockMatrix::field_type` forwards to the `MultiTypeBlockVector::field_type`
which forwards to the inner `FieldTraits<MultiTypeBlockMatrix>::field_type`.

And fix all spelling errors that codespell currently finds.

... because we also specialize `std::tuple_element` and
it derives from `std::tuple` after all.

Corner case that sometimes happens and produced a segmentation fault.

Unused variable warning indicated this oversight

See https://reuse.software/ for a description.

Nested sparse matrices were not allowed to have empty rows/cols. By choosing the minimum offset of other blocks, we get an educated guess for these cases.

Before this commit, the pattern was deallocated with the wrong size that created a huge memory leak.

The current behavior (allocating each row separately ) is rather
surprising and unnecessary as the matrix market file stores the
number of nonzeros anyway. Hence we now pass this number to
BCRSMatrix::SetSize to get the most efficient behavior