Incomplete Cholesky preconditionner
===================================

To start experimenting with the preconditionned conjugate gradient
(PCG) solver, we provide a readily usable preconditioner based on the
incomplete Cholesky factorization. The storage scheme is comparable
`InvCooMatrix` class: to setup a preconditioner for a matrix :math:`A`,
an incomplete Cholesky factorization is computed and
stored, for later used as a coarse approximation of :math:`A^{-1}`.

For object of type `CholeskyPrec`, only the matrix vector product is
available which, however, is already sufficient for serving as a valid
preconditioner in a PCG algorithm.

Like for the `InvCooMatrix` class, the implementation of this
class relies on the `Eigen3 library`_.

.. _Eigen3 library: https://eigen.tuxfamily.org/index.php?title=Main_Page

.. doxygenclass:: CholeskyPrec
   :members: