.. _ShellMatrix_Petsc:

#############
Petsc wrapper
#############

The following objects are only available if ``PetscDefined`` is set which is the case if :ref:`Petsc<Petsc_setup>` is included.

The `Petsc MATSHELL <https://petsc.org/release/manualpages/Mat/MATSHELL/>`_ is created by the :ref:`Operator class<Operator>` by calling :ref:`create_PetscShellMatrix()<Operator_Functions_Frontends_create_PetscShellMatrix>`.
It contains a pointer to an instance of the the :ref:`ShellMatrix class<ShellMatrix>` which works with the vector structure, `Vec <https://petsc.org/main/manualpages/Vec/>`_, of :ref:`Petsc<Petsc_setup>`.

The **matrix-free** multiplcation is a wrapper of the low-level function :ref:`MATMUL_basic(...)<ShellMatrix_MATMUL_MAMTUL_basic>`:

.. _ShellMatrix_Petsc_MATMUL_PETSC:

.. doxygenfunction:: danceq::internal::MATMUL_PETSC
    :no-link:

The function :ref:`MATDESTROY_PETSC()<ShellMatrix_Petsc_MATMUL_DESTROY>` destroys the shell by deleting the pointer to the :ref:`ShellMatrix class<ShellMatrix>`:

.. _ShellMatrix_Petsc_MATMUL_DESTROY:

.. doxygenfunction:: danceq::internal::MATDESTROY_PETSC
    :no-link: