1Blurb:: 2Specification group for trust region model management 3Description:: 4The \c trust_region optional group specification can be used to 5specify the initial size of the trust region (using \c initial_size) 6relative to the total variable bounds, the minimum size of the trust 7region (using \c minimum_size), the contraction factor for the trust 8region size (using \c contraction_factor) used when the surrogate 9model is performing poorly, and the expansion factor for the trust 10region size (using \c expansion_factor) used when the the surrogate 11model is performing well. Two additional commands are the trust region 12size contraction threshold (using \c contract_threshold) and the trust 13region size expansion threshold (using \c expand_threshold). These two 14commands are related to what is called the trust region ratio, which 15is the actual decrease in the truth model divided by the predicted 16decrease in the truth model in the current trust region. The command 17\c contract_threshold sets the minimum acceptable value for the trust 18region ratio, i.e., values below this threshold cause the trust region 19to shrink for the next surrogate_based_local iteration. The command \c 20expand_threshold determines the trust region value above which the 21trust region will expand for the next surrogate_based_local iteration. 22 23Each of these specifications are \c REAL scalars, with the exception of 24\c initial_size, which is a \c REALLIST. 25 26Topics:: 27Examples:: 28Theory:: 29Faq:: 30See_Also:: 31