# gf_cont_struct¶

Synopsis

S = gf_cont_struct(model md, string dataname_parameter[,string dataname_init, string dataname_final, string dataname_current], scalar sc_fac[, ...])


Description :

General constructor for cont_struct objects.

This object serves for storing parameters and data used in numerical continuation of solution branches of models (for more details about continuation see the GetFEM user documentation).

Command list :

S = gf_cont_struct(model md, string dataname_parameter[,string dataname_init, string dataname_final, string dataname_current], scalar sc_fac[, ...])

The variable <literal>dataname_parameter</literal> should parametrise the model given by <literal>md</literal>. If the parameterization is done via a vector datum, <literal>dataname_init</literal> and <literal>dataname_final</literal> should store two given values of this datum determining the parameterization, and <literal>dataname_current</literal> serves for actual values of this datum. <literal>sc_fac</literal> is a scale factor involved in the weighted norm used in the continuation.

• ‘lsolver’, string SOLVER_NAME
name of the solver to be used for the incorporated linear systems (the default value is ‘auto’, which lets getfem choose itself); possible values are ‘superlu’, ‘mumps’ (if supported), ‘cg/ildlt’, ‘gmres/ilu’ and ‘gmres/ilut’;
• ‘h_init’, scalar HIN
initial step size (the default value is 1e-2);
• ‘h_max’, scalar HMAX
maximum step size (the default value is 1e-1);
• ‘h_min’, scalar HMIN
minimum step size (the default value is 1e-5);
• ‘h_inc’, scalar HINC
factor for enlarging the step size (the default value is 1.3);
• ‘h_dec’, scalar HDEC
factor for diminishing the step size (the default value is 0.5);
• ‘max_iter’, int MIT
maximum number of iterations allowed in the correction (the default value is 10);
• ‘thr_iter’, int TIT
threshold number of iterations of the correction for enlarging the step size (the default value is 4);
• ‘max_res’, scalar RES
target residual value of a new point on the solution curve (the default value is 1e-6);
• ‘max_diff’, scalar DIFF
determines a convergence criterion for two consecutive points (the default value is 1e-6);
• ‘min_cos’, scalar MCOS
minimal value of the cosine of the angle between tangents to the solution curve at an old point and a new one (the default value is 0.9);
• ‘max_res_solve’, scalar RES_SOLVE
target residual value for the linear systems to be solved (the default value is 1e-8);
• ‘singularities’, int SING
activates tools for detection and treatment of singular points (1 for limit points, 2 for bifurcation points and points requiring special branching techniques);
• ‘non-smooth’
determines that some special methods for non-smooth problems can be used;
• ‘delta_max’, scalar DMAX
maximum size of division for evaluating the test function on the convex combination of two augmented Jacobians that belong to different smooth pieces (the default value is 0.005);
• ‘delta_min’, scalar DMIN
minimum size of division for evaluating the test function on the convex combination (the default value is 0.00012);
• ‘thr_var’, scalar TVAR
threshold variation for refining the division (the default value is 0.02);
• ‘nb_dir’, int NDIR
total number of the linear combinations of one couple of reference vectors when searching for new tangent predictions during location of new one-sided branches (the default value is 40);
• ‘nb_span’, int NSPAN
total number of the couples of the reference vectors forming the linear combinations (the default value is 1);
• ‘noisy’ or ‘very_noisy’
determines how detailed information has to be displayed during the continuation process (residual values etc.).