/usr/include/dlib/optimization/ is in libdlib-dev 18.18-1.
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/usr/include/dlib/optimization/find_max_factor_graph_nmplp.h
/usr/include/dlib/optimization/find_max_factor_graph_nmplp_abstract.h
/usr/include/dlib/optimization/find_max_factor_graph_viterbi.h
/usr/include/dlib/optimization/find_max_factor_graph_viterbi_abstract.h
/usr/include/dlib/optimization/find_max_parse_cky.h
/usr/include/dlib/optimization/find_max_parse_cky_abstract.h
/usr/include/dlib/optimization/max_cost_assignment.h
/usr/include/dlib/optimization/max_cost_assignment_abstract.h
/usr/include/dlib/optimization/max_sum_submatrix.h
/usr/include/dlib/optimization/max_sum_submatrix_abstract.h
/usr/include/dlib/optimization/optimization.h
/usr/include/dlib/optimization/optimization_abstract.h
/usr/include/dlib/optimization/optimization_bobyqa.h
/usr/include/dlib/optimization/optimization_bobyqa_abstract.h
/usr/include/dlib/optimization/optimization_least_squares.h
/usr/include/dlib/optimization/optimization_least_squares_abstract.h
/usr/include/dlib/optimization/optimization_line_search.h
/usr/include/dlib/optimization/optimization_line_search_abstract.h
/usr/include/dlib/optimization/optimization_oca.h
/usr/include/dlib/optimization/optimization_oca_abstract.h
/usr/include/dlib/optimization/optimization_search_strategies.h
/usr/include/dlib/optimization/optimization_search_strategies_abstract.h
/usr/include/dlib/optimization/optimization_solve_qp2_using_smo.h
/usr/include/dlib/optimization/optimization_solve_qp2_using_smo_abstract.h
/usr/include/dlib/optimization/optimization_solve_qp3_using_smo.h
/usr/include/dlib/optimization/optimization_solve_qp3_using_smo_abstract.h
/usr/include/dlib/optimization/optimization_solve_qp_using_smo.h
/usr/include/dlib/optimization/optimization_solve_qp_using_smo_abstract.h
/usr/include/dlib/optimization/optimization_stop_strategies.h
/usr/include/dlib/optimization/optimization_stop_strategies_abstract.h
/usr/include/dlib/optimization/optimization_trust_region.h
/usr/include/dlib/optimization/optimization_trust_region_abstract.h