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C++ API

: daspk_options ()
: val = daspk_options (opt)
: daspk_options (opt, val)

Query or set options for the function daspk.

When called with no arguments, the names of all available options and their current values are displayed.

Given one argument, return the value of the option opt.

When called with two arguments, daspk_options sets the option opt to value val.

Options include

"absolute tolerance"

Absolute tolerance. May be either vector or scalar. If a vector, it must match the dimension of the state vector, and the relative tolerance must also be a vector of the same length.

"relative tolerance"

Relative tolerance. May be either vector or scalar. If a vector, it must match the dimension of the state vector, and the absolute tolerance must also be a vector of the same length.

The local error test applied at each integration step is 

 abs (local error in x(i))
      <= rtol(i) * abs (Y(i)) + atol(i)
"compute consistent initial condition"

Denoting the differential variables in the state vector by ‘Y_d’ and the algebraic variables by ‘Y_a’, ddaspk can solve one of two initialization problems:

  1. Given Y_d, calculate Y_a and Y’_d
  2. Given Y’, calculate Y.

In either case, initial values for the given components are input, and initial guesses for the unknown components must also be provided as input. Set this option to 1 to solve the first problem, or 2 to solve the second (the default is 0, so you must provide a set of initial conditions that are consistent).

If this option is set to a nonzero value, you must also set the "algebraic variables" option to declare which variables in the problem are algebraic.

"use initial condition heuristics"

Set to a nonzero value to use the initial condition heuristics options described below.

"initial condition heuristics"

A vector of the following parameters that can be used to control the initial condition calculation.

MXNIT

Maximum number of Newton iterations (default is 5).

MXNJ

Maximum number of Jacobian evaluations (default is 6).

MXNH

Maximum number of values of the artificial stepsize parameter to be tried if the "compute consistent initial condition" option has been set to 1 (default is 5).

Note that the maximum total number of Newton iterations allowed is MXNIT*MXNJ*MXNH if the "compute consistent initial condition" option has been set to 1 and MXNIT*MXNJ if it is set to 2.

LSOFF

Set to a nonzero value to disable the linesearch algorithm (default is 0).

STPTOL

Minimum scaled step in linesearch algorithm (default is eps^(2/3)).

EPINIT

Swing factor in the Newton iteration convergence test. The test is applied to the residual vector, premultiplied by the approximate Jacobian. For convergence, the weighted RMS norm of this vector (scaled by the error weights) must be less than EPINIT*EPCON, where EPCON = 0.33 is the analogous test constant used in the time steps. The default is EPINIT = 0.01.

"print initial condition info"

Set this option to a nonzero value to display detailed information about the initial condition calculation (default is 0).

"exclude algebraic variables from error test"

Set to a nonzero value to exclude algebraic variables from the error test. You must also set the "algebraic variables" option to declare which variables in the problem are algebraic (default is 0).

"algebraic variables"

A vector of the same length as the state vector. A nonzero element indicates that the corresponding element of the state vector is an algebraic variable (i.e., its derivative does not appear explicitly in the equation set).

This option is required by the "compute consistent initial condition" and "exclude algebraic variables from error test" options.

"enforce inequality constraints"

Set to one of the following values to enforce the inequality constraints specified by the "inequality constraint types" option (default is 0).

  1. To have constraint checking only in the initial condition calculation.
  2. To enforce constraint checking during the integration.
  3. To enforce both options 1 and 2.
"inequality constraint types"

A vector of the same length as the state specifying the type of inequality constraint. Each element of the vector corresponds to an element of the state and should be assigned one of the following codes

-2

Less than zero.

-1

Less than or equal to zero.

0

Not constrained.

1

Greater than or equal to zero.

2

Greater than zero.

This option only has an effect if the "enforce inequality constraints" option is nonzero.

"initial step size"

Differential-algebraic problems may occasionally suffer from severe scaling difficulties on the first step. If you know a great deal about the scaling of your problem, you can help to alleviate this problem by specifying an initial stepsize (default is computed automatically).

"maximum order"

Restrict the maximum order of the solution method. This option must be between 1 and 5, inclusive (default is 5).

"maximum step size"

Setting the maximum stepsize will avoid passing over very large regions (default is not specified).

Package: octave