.. _method-multifidelity_sampling-numerical_solve-model_reordering-auto_reorder:

""""""""""""
auto_reorder
""""""""""""


Address any model misordering in MFMC numerical solutions by reordering on the fly.



.. toctree::
   :hidden:
   :maxdepth: 1



**Specification**

- *Alias:* None

- *Arguments:* None


**Description**


The ordering of the model hierarchy is continuously redefined as needed
to allow for proper evaluation of MFMC estimator variance expressions.
The specified model order in the ensemble surrogate model specification
is only used as the starting point for the algorithm.

On-the-fly model reordering can result in lower estimator variance,
but it can affect solution robustness (due to discontinuous gradients)
and complicate comparisons with published MFMC implementations.  The
use of global-local numerical solver selections can mitigate the first
concern to a degree.




**Examples**



.. code-block::

    method,
	multifidelity_sampling
	numerical_solve override
	  global_local
	  model_reordering auto_reorder   # default approach
	solution_mode online_pilot
	pilot_samples = 50 seed = 8674132
	max_function_evaluations = 500