[petsc-users] Shell matrices and complex NHEP SVD problems

[Miguel Fosas]

Hi everyone,

I have a question concerning the usage of shell matrices with SLEPc
and the SVD solvers. When I compute the largest singular values from a
complex non-hermitian matrix A with SLEPc, the solver asks the user to
provide MATOP_MULT and MATOP_MULT_TRANSPOSE operations for A.

As I have observed in the documentation of SLEPc, both the cyclic and
cross solvers require matrix-vector product  of A* v, with A* the
complex conjugate of A. After having taken a look at the source code,
it is not clear to me how the complex case is handled.

The question is: for the complex case, does the implementation of
MatMultTranspose have to compute A* v or A^T v? Is there a reason why
it is not implemented using MatMultHermitianTranspose?

Thanks in advance,

Miguel.