NAG Library Routine Document

D02NZF

1  Purpose

2  Specification

3  Description

4  References

5  Parameters

1:     NEQMAX – INTEGERInput

On entry: the value used for the parameter NEQMAX when calling the integrator.

Constraint: $\mathbf{NEQMAX}\ge 1$.

2:     TCRIT – REAL (KIND=nag_wp)Input

On entry: a point beyond which integration must not be attempted. The use of TCRIT is described under the parameter ITASK in the specification for the integrator (e.g., see D02NBF). A value, $0.0$ say, must be specified even if ITASK subsequently specifies that TCRIT will not be used.

3:     H – REAL (KIND=nag_wp)Input

On entry: the next step size to be attempted. Set $\mathbf{H}=0.0$ if the current value of H is not to be changed.

4:     HMIN – REAL (KIND=nag_wp)Input

On entry: the minimum absolute step size to be allowed. Set $\mathbf{HMIN}=0.0$ if this option is not required. Set $\mathbf{HMIN}<0.0$ if the current value of HMIN is not to be changed.

5:     HMAX – REAL (KIND=nag_wp)Input

On entry: the maximum absolute step size to be allowed. Set $\mathbf{HMAX}=0.0$ if this option is not required. Set $\mathbf{HMAX}<0.0$ if the current value of HMAX is not to be changed.

6:     MAXSTP – INTEGERInput

On entry: the maximum number of steps to be attempted during one call to the integrator after which it will return with $\mathbf{IFAIL}=\mathbf{2}$ (see D02NCF). Set $\mathbf{MAXSTP}=0$ if this option is not required. Set $\mathbf{MAXSTP}<0$ if the current value of MAXSTP is not to be changed.

7:     MXHNIL – INTEGERInput

On entry: the maximum number of warnings printed (if $\mathbf{ITRACE}\ge 0$, e.g., see D02NBF) per problem when $t+h=t$ on a step ($h=\text{ current step size}$). If $\mathbf{MXHNIL}\le 0$, a default value of $10$ is assumed.

8:     RWORK($50+4\times \mathbf{NEQMAX}$) – REAL (KIND=nag_wp) arrayCommunication Array

This must be the same workspace array as the array RWORK supplied to the integrator. It is used to pass information from the integrator to D02NZF and therefore its contents must not be changed before calling D02NZF.

9:     IFAIL – INTEGERInput/Output

On entry: IFAIL must be set to $0$, $-1\text{ or }1$. If you are unfamiliar with this parameter you should refer to Section 3.3 in the Essential Introduction for details.

For environments where it might be inappropriate to halt program execution when an error is detected, the value $-1\text{ or }1$ is recommended. If the output of error messages is undesirable, then the value $1$ is recommended. Otherwise, if you are not familiar with this parameter, the recommended value is $0$. When the value $-\mathbf{1}\text{ or }\mathbf{1}$ is used it is essential to test the value of IFAIL on exit.

On exit: $\mathbf{IFAIL}=\mathbf{0}$ unless the routine detects an error or a warning has been flagged (see Section 6).

6  Error Indicators and Warnings

$\mathbf{IFAIL}=1$

$\mathbf{NEQMAX}<1$.

7  Accuracy

8  Further Comments

9  Example