daeoptions

Description

Sets a variable %DAEOPTIONS that is used in function dae to set solver options, only for dassl, dasrt ("root") and daskr ("root2") solvers.

This daeoptions function interactively displays a window which sets various options of the dae solver.

The dae function checks if this variable exists and in this case it uses it. For using default values you should clear this variable. Note that daeoptions does not create this variable. To create it you must execute the command line displayed by daeoptions.

The variable %DAEOPTIONS is a list with the following elements:

list(tstop,imode,band,maxstep,stepin,nonneg,isest)

The default value is:

list([],0,[],[],[],0,0)

The meaning of the elements is described below.

solver

if it is 0, dae will use the dassl/dasrt solver, and if it is 1, dae will use daskr.

tstop

a real scalar or an empty matrix, gives the maximum time for which g is allowed to be evaluated. An empty matrix means "no limits" imposed for time.

imode

if it is 0, dae returns only the user specified time point values, and if it is 1, dae returns its intermediate computed values.

band

a two components vector which give the definition [ml,mu] of band matrix computed by jac;

r(i - j + ml + mu + 1,j) = dg(i)/dy(j)+cj*dg(i)/dydot(j). If jac returns a full matrix set band=[]

maxstep

a scalar or an empty matrix, the maximum step size, empty matrix means "no limitation".

stepin

a scalar or an empty matrix, the minimum step size, empty matrix means "not specified".

nonneg

a scalar, must be set to 0 if the solution is known to be non negative . In the other case it must be set to 1.

isest

a scalar, must be set to 0 if the given initial condition is compatible: g(t0,x0,xdot0)=0. If xdot0 is just an estimation, then set to 1 if you are using dassl, or set to [+-1, ..., +-1], with: 1 if y(i) is a differential variable and -1 if y(i) is an algebraic variable (if its derivatives do not appear explicitly in the function g(t, y, ydot)).

method

a scalar, direct / Krylov method. Set to 1 and provide a routine psol in dae() if you want the solver to use Krylov iterations, else (daskr's direct method) set to 0.

Kry_params

a vector, treat as dummy argument if you have set method=0. Otherwise, set to [] or to [maxl kmp nrmax epli], where: - maxl = maximum number of iterations in the GMRes algorithm (default min(5, neq)), - kmp = number of vectors on which orthogonalization is done in the GMRes algorithm (default maxl), - nrmax = maximum number of restarts of the GMRes algorithm per nonlinear iteration (default 5), - epli = convergence test constant in GMRes algorithm (default 0.05).

init

a scalar, treat as dummy argument if you have set isest=0. Set to 1 if the solver should stop right after computation of the initial conditions, else set to 0.

precond

a scalar, preconditioner computation and LU-factorization routine for psol. Treat as dummy argument if method=0. Set to 1 and provide a pjac routine in dae if the external psol should use a specific routine, else set to 0.

control

a vector, treat as dummy argument if you have set isest=0if you wish to control errors locally on all the variables then set to []. Otherwise, set to [+-1, ..., +-1], 1 if y(i) is a differential variable and -1 if y(i) is an algebraic variable (if its derivatives do not appear explicitly in the function g(t, y, ydot)).

heuristic

a vector, heuristic parameters. Treat as dummy argument if isest=0. Otherwise, set to [] or to [mxnit mxnj mxnh lsoff stptol epinit], where: - mxnit = maximum number of Newton iterations per Jacobian or preconditioner evaluation (default 5 if info(8)=0, 15 otherwise), - mxnj = maximum number of Jacobian or preconditioner evaluations (default 6 if info(8)=0, 2 otherwise), - mxnh = maximum number of values of the artificial stepsize parameter h to be tried if info(7) ≠ [] (default 5), - lsoff = flag to turn off the linesearch algorithm (lsoff = 0 means linesearch is on, lsoff = 1 means it is turned off) (default 0), - stptol = minimum scaled step in linesearch algorithm (default (unit roundoff)^(2/3)), - epinit = swing factor in the Newton iteration convergence test (default 0.01).

verbosity

a scalar, verbosity. Set to 1 for minimal extra printing, 2 for full printing, else set to 0.

See also

• dae — Differential algebraic equations solver