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* Users can now supply their own bilinear form (or scalar product) for the computation of the shape gradient, which is then used instead of the linear elasticity formulation. This is documented at `<https://cashocs.readthedocs.io/en/stable/user/demos/shape_optimization/demo_custom_scalar_product>`_.
* Added a curvature regularization term for shape optimization, which can be enabled via the config files, similarly to already implemented regularizations. This is documented at `<https://cashocs.readthedocs.io/en/stable/user/demos/shape_optimization/demo_regularization>`_.
* cashocs can now scale individual terms of the cost functional if this is desired. This allows for a more granular handling of problems with cost functionals consisting of multiple terms. This also extends to the regularizations for shape optimization, see `<https://cashocs.readthedocs.io/en/stable/user/demos/shape_optimization/demo_regularization>`_. This feature is documented at `<https://cashocs.readthedocs.io/en/stable/user/demos/shape_optimization/demo_scaling>`_.
* cashocs now uses the logging module to issue messages for the user. The level of verbosity can be controlled via :py:func:`cashocs.set_log_level`.
* New configuration file parameters:
* Section Regularization:
* :ini:`factor_curvature` can be used to specify the weight for the curvature regularization term.
* :ini:`use_relative_weights` is a boolean which specifies, whether the weights should be used as scaling factor in front of the regularization terms (if this is `False`), or whether they should be used to scale the regularization terms so that they have the prescribed value on the initial iteration (if this is `True`).