1Blurb:: 2Trust region expansion factor 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 14two commands are related to what is called the trust region ratio, 15which is the actual decrease in the truth model divided by the 16predicted decrease in the truth model in the current trust region. The 17command \c contract_threshold sets the minimum acceptable value for 18the trust region ratio, i.e., values below this threshold cause the 19trust region to shrink for the next SBL iteration. The command \c 20expand_threshold determines the trust region value above which the 21trust region will expand for the next SBL iteration. 22 23Topics:: 24Examples:: 25Theory:: 26Faq:: 27See_Also:: 28