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

[Matthew Knepley]

On Sat, Jul 14, 2012 at 6:30 PM, Miguel Fosas <miguel.fosas at gmail.com>wrote:

> 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?
>

I believe it is done this way because we originally did not distinguish
(they were not there in 2009). It
should probably be updated.

    Matt


> Thanks in advance,
>
> Miguel.
>



-- 
What most experimenters take for granted before they begin their
experiments is infinitely more interesting than any results to which their
experiments lead.
-- Norbert Wiener
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