[petsc-users] Trivial parallelizing in SLEPc

[Hong]

Anders:

> Dear PETSc Users,
>
> I want to find the smallest eigenpairs of a hermitian operator, A,
> implemented as a matrix-less operator.
>

Do you mean matrix-free operator?
There are slepc examples  using shell matrix:
slepc/src/eps/examples/tutorials
grep -i shell *.c
ex3.c
ex9.c
ex10.c
...
Take a look at these examples.

>
> When computing y = Ax, I need the entire vector x, and I calculate the
> entire vector y, therefore I want to avoid the ownership of x and y to be
> spread over different processes.
>

Do you mean you want  x and y owned by a single process, not distributed?
Suggest doing sequential computation first, then move to parallel execution.

>
> To what extend can this problem be parallelized in SLEPc. For instance can
> I use a block Krylov or block JD algorithm where different processes
> compute different matrix vector multiplications. If I provide the correct
> operations when constructing my MatShell, can I expect the FEAST algorithm
> to compute each contour point on a different process?
>

Slepc developer might answer this question.

Hong
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