NAG FL Interface
d02lyf (ivp_​2nd_​rkn_​diag)

1 Purpose

2 Specification

3 Description

4 References

5 Arguments

1: $\mathbf{neq}$ – Integer Input

On entry: the number of second-order ordinary differential equations solved by d02laf. It must be the same as the argument neq supplied to d02laf and d02lxf.

2: $\mathbf{hnext}$ – Real (Kind=nag_wp) Output

On exit: the next step size which d02laf, if called, would attempt.

3: $\mathbf{hused}$ – Real (Kind=nag_wp) Output

On exit: the last successful step size used by d02laf.

4: $\mathbf{hstart}$ – Real (Kind=nag_wp) Output

On exit: the initial step size used on the current integration problem by d02laf.

5: $\mathbf{nsucc}$ – Integer Output

On exit: the number of steps attempted by d02laf that have been successful since the start of the current problem.

6: $\mathbf{nfail}$ – Integer Output

On exit: the number of steps attempted by d02laf that have failed since the start of the current problem.

7: $\mathbf{natt}$ – Integer Output

On exit: the number of steps attempted before the initial step was successful. Over a large number of problems the cost of an attempted step of this type is approximately half that of a normal attempted step.

8: $\mathbf{thres}\left(\mathbf{neq}\right)$ – Real (Kind=nag_wp) array Output

On exit: the $i$th solution threshold value used in the error control strategy. (See d02lxf.)

9: $\mathbf{thresp}\left(\mathbf{neq}\right)$ – Real (Kind=nag_wp) array Output

On exit: the $i$th derivative threshold value used in the error control strategy. (See d02lxf.)

10: $\mathbf{rwork}\left(\mathbf{lrwork}\right)$ – Real (Kind=nag_wp) array Communication Array

On entry: this must be the same argument rwork as supplied to d02laf. It is used to pass information from d02laf to d02lyf and, therefore, the contents of this array must not be changed before calling d02lyf.

11: $\mathbf{lrwork}$ – Integer Input

On entry: the dimension of the array rwork as declared in the (sub)program from which d02lyf is called.

This must be the same argument lrwork as supplied to d02lxf.

12: $\mathbf{ifail}$ – Integer Input/Output

On entry: ifail must be set to $0$, $\mathrm{-1}$ or $1$ to set behaviour on detection of an error; these values have no effect when no error is detected.

A value of $0$ causes the printing of an error message and program execution will be halted; otherwise program execution continues. A value of $\mathrm{-1}$ means that an error message is printed while a value of $1$ means that it is not.

If halting is not appropriate, the value $\mathrm{-1}$ or $1$ is recommended. If message printing is undesirable, then the value $1$ is recommended. Otherwise, the value $0$ is recommended. When the value $-\mathbf{1}$ 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

$\mathbf{ifail}=1$

On entry, $\mathbf{lrwork}=⟨\mathit{\text{value}}⟩$, but in a previous call to the setup routine $\mathbf{lrwork}=⟨\mathit{\text{value}}⟩$.

On entry, $\mathbf{neq}=⟨\mathit{\text{value}}⟩$, but in the previous call to the setup routine $\mathbf{neq}=⟨\mathit{\text{value}}⟩$.

The integrator routine d02laf has not been called.

$\mathbf{ifail}=-99$

An unexpected error has been triggered by this routine. Please contact NAG.

See Section 7 in the Introduction to the NAG Library FL Interface for further information.

$\mathbf{ifail}=-399$

Your licence key may have expired or may not have been installed correctly.

See Section 8 in the Introduction to the NAG Library FL Interface for further information.

$\mathbf{ifail}=-999$

Dynamic memory allocation failed.

See Section 9 in the Introduction to the NAG Library FL Interface for further information.

7 Accuracy

8 Parallelism and Performance

9 Further Comments

10 Example