Blurb::
Identify metadata by label for capturing online cost estimates
Description::
Metadata can be used for a variety of response annotation
purposes, including the online recovery of simulation cost (using facilities
either implemented in a user's analysis driver or codified in an embedded
test driver).  This information can then be used by certain algorithms that
allocate resources based on relative cost, e.g. multifidelity UQ methods.

Cost estimates may be provided a priori, e.g. using ``solution_level_cost``,
in cases where they can be assumed fixed for each model form and/or
resolution.  In cases such as model tuning over a set of hyper-parameters,
costs will generally be a function of these hyper-parameters and need to
be captured online during initialization of the algorithm (e.g. during
evaluation of the pilot sample).

*Default Behavior*
No recovery of cost estimates from the response metadata.

*Usage Tips*
It is common to employ total CPU time, aggregated across all computing
cores involved in a (parallel) simulation instance.  Wall time, even when
the number of cores is fixed, can be subject to additional variability
due to system load.
Topics::

Examples::

.. code-block::

    model,
     id_model = 'TUNABLE_LF'
     simulation
       cost_recovery_metadata = 'core_time'
    
    responses,
     response_functions = 1
     descriptors = 'Q'
     no_gradients
     no_hessians
     metadata 'core_time'


Theory::

Faq::

See_Also::
