[petsc-dev] Handling ESSL + Lapack and PESSL

[Jed Brown]

I was just chatting with Aron and two issues came up.  First, he is
successfully linking PESSL, but configure currently has

  raise RuntimeError('Cannot use PESSL instead of ESSL!')

(apparently this was patched to let it through).  Why this guard, it
prevents user code from calling PESSL.


Additionally, he has built PETSc with both Lapack and ESSL (linking
Lapack first so those symbols resolve to the standard interface).  This
is a problem since PETSc dispatches on PETSC_HAVE_ESSL to determine the
interface of LAPACKgeev (even though it is getting the standard Lapack
one in the scenario above), I think it should test which version of this
function it has and dispatch on PETSC_HAVE_ESSL_GEEV.

Jed