.. _method-surrogate_based_local-trust_region-contraction_factor:

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contraction_factor
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Amount by which step length is rescaled


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**Specification**

- *Alias:* None

- *Arguments:* REAL

- *Default:* 0.25


**Description**


For pattern search methods, ``contraction_factor`` specifies the amount
by which step length is rescaled after unsuccesful iterates, must be
strictly between 0 and 1.

For methods that can expand the step length, the expansion is 1/ ``contraction_factor``


