naginterfaces.library.ode.dae_​dassl_​setup

naginterfaces.library.ode.dae_dassl_setup(neq, maxord, jceval, hmax, h0, itol)

dae_dassl_setup is a setup function which must be called prior to the integrator dae_dassl_gen(), if the DASSL implementation of Backward Differentiation Formulae (BDF) is to be used.

For full information please refer to the NAG Library document for d02mw

https://support.nag.com/numeric/nl/nagdoc_30.3/flhtml/d02/d02mwf.html

Parameters

neqint

The number of differential-algebraic equations to be solved.

maxordint

The maximum order to be used for the BDF method. Orders up to 5th order are available; setting $maxord>5$ means that the maximum order used will be $5$.

jcevalstr, length 1

Specifies the technique to be used to compute the Jacobian.

$jceval=\text{'N'}$

The Jacobian is to be evaluated numerically by the integrator.

$jceval=\text{'A'}$

You must supply a function to evaluate the Jacobian on a call to the integrator.

Only the first character of the actual paramater $jceval$ is passed to dae_dassl_setup; hence it is permissible for the actual argument to be more descriptive, e.g., ‘Numerical’ or ‘Analytical’, on a call to dae_dassl_setup.

hmaxfloat

The maximum absolute step size to be allowed. Set $hmax=0.0$ if this option is not required.

h0float

The step size to be attempted on the first step. Set $h0=0.0$ if the initial step size is calculated internally.

itolint

A value to indicate the form of the local error test.

$itol=0$

$\text{rtol}$ and $\text{atol}$ are single element vectors.

$itol=1$

$\text{rtol}$ and $\text{atol}$ are vectors. This should be chosen if you want to apply different tolerances to each equation in the system.

See dae_dassl_gen().

Note: the tolerances must either both be single element vectors or both be vectors of length $neq$.

Returns

commdict, communication object

Communication structure.

Raises

NagValueError

(errno $1$)

On entry, $neq=⟨value⟩$.

Constraint: $neq\ge 1$.

(errno $2$)

On entry, $maxord=⟨value⟩$.

Constraint: $maxord\ge 1$.

(errno $3$)

On entry, $jceval$ has an illegal value: $jceval=⟨value⟩$.

Constraint: $jceval=\text{'N'}$ or $\text{'A'}$.

(errno $4$)

On entry, $hmax=⟨value⟩$.

Constraint: $hmax\ge 0.0$.

(errno $6$)

On entry, $itol=⟨value⟩$.

Constraint: $itol=0$ or $1$.

Notes

This integrator setup function must be called before the first call to the integrator dae_dassl_gen(). This setup function dae_dassl_setup permits you to define options for the DASSL integrator, such as: whether the Jacobian is to be provided or is to be approximated numerically by the integrator; the initial and maximum step-sizes for the integration; whether relative and absolute tolerances are system wide or per system equation; and the maximum order of BDF method permitted.