Build instructions for LAPACK vs Eigen are either wrong or confusing

[Paul Wilson]

For some time there has been an option to build with LAPACK/BLAS, but it appears to:

1. only be used in Matrix3.hpp and,
2. be skipped if Eigen3 is available on the system

Since some build configurations (HYPRE) require Eigen3, it seems like it has to be possible to build with both Eigen3 and LAPACK. This suggests that LAPACK should dominate Eigen3 in Matrix3.hpp rather than the other way around.

Can you confirm the desired behavior?

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[Vijay M]

Actually HYPRE should not require Eigen3. It does require LAPACK - since it is a required dependency for Hypre package.

Yes, we can make LAPACK have a higher priority than Eigen3 in Matrix3.hpp.

[Paul Wilson]

From HypreParMatrix.hpp:

#ifdef MOAB_HAVE_EIGEN
#include <Eigen/Core>
#include <Eigen/Sparse>
#else
#error Configure with Eigen3 enabled
#endif

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[Vijay M]

I will take a look at this soon. The parallel linear algebra code paths need some refactoring.

[Paul Wilson]

I think my concerns were addressed in PR#438. I am sure there is more that could be done, but I think it is now clearer.

[Vijay M]

Concerns have been addressed already