This is to avoid dynamic memory allocations in the compute() methods of
ComplexEigenSolver, EigenSolver, and SelfAdjointEigenSolver where possible.
As a result, Tridiagonalization::decomposeInPlace() is no longer used.
Biggest remaining issue is the allocation in HouseholderSequence::evalTo().
According to people on #llvm, this is indeed not allowed by c++ standard:
[01:33] <coppro> what good would mutable do on a reference?
[01:33] <dgregor> orzel: gcc is wrong to allow "mutable" on references
[01:33] <coppro> just remove mutable; it won't damage the code at all
[01:34] <dgregor> "The mutable specifier can be applied only to names of
class data members (9.2) and cannot be applied to
[01:34] <dgregor> names declared const or static, and cannot be applied to
reference members."
[01:34] <coppro> constness is not passed from an object to the referents of
its members anyways
(error was appearing when building tests with alignmnet disabled)
What is this stuff still doing in MatrixBase.h? Shouldn't it move to DenseBase.h? How are Array blocks compiling?
Rationale: coeffRef() methods should only exist when we have DirectAccess. So a natural thing to do would have been to use enable_if, but since there are many methods it made more sense to do the "enable_if" for the whole group by introducing a new class. And that also that the benefit of not changing method prototypes.
I didn't even put it in Eigen2Support because it requires several other modules. But if you want we can always create a new module, Eigen2Support_LeastSquares...
* Now completely generic so all standard integer types (like char...) are supported.
** add unit test for that (integer_types).
* NumTraits does no longer inherit numeric_limits
* All math functions are now templated
* Better guard (static asserts) against using certain math functions on integer types.
* reduce scope of declarations
* use that low = 0 and high = size-1
* rename some variables
* rename hqr2_step2() to computeEigenvectors()
* exploit that ei_isMuchSmallerThan takes absolute value of arguments
