Blurb::
Hessians are needed and will be obtained from a mix of numerical,
analytic, and "quasi" sources
Description::
The ``mixed_hessians`` specification means that some Hessian
information is available directly from the simulation (analytic)
whereas the rest will have to be estimated by finite differences
(numerical) or approximated by secant updating. As for
mixed gradients, this specification allows the user to make use of as
much analytic information as is available and then
estimate/approximate the rest.

The ``id_analytic_hessians`` list
specifies by number the functions which have analytic Hessians, and
the ``id_numerical_hessians`` and ``id_quasi_hessians`` lists specify by
number the functions which must use numerical Hessians and
secant Hessian updates, respectively. Each function identifier,
from 1 through the total number of functions, must appear once and
only once within the union of the ``id_analytic_hessians``,
``id_numerical_hessians``, and ``id_quasi_hessians`` lists.

The
``fd_hessian_step_size`` and ``bfgs``, ``damped`` ``bfgs``, or ``sr1``
secant update selections are as described previously in
:dakkw:`responses` and pertain to those functions
listed by the ``id_numerical_hessians`` and ``id_quasi_hessians``
lists.
Topics::

Examples::

Theory::

Faq::

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