NAG FL Interface
d02qzf (ivp_​adams_​interp)

1 Purpose

2 Specification

3 Description

4 References

5 Arguments

1: $\mathbf{neqf}$ – Integer Input

On entry: the number of first-order ordinary differential equations being solved by the integration routine. It must contain the same value as the argument neqf in a prior call to the setup routine d02qwf.

2: $\mathbf{twant}$ – Real (Kind=nag_wp) Input

On entry: the point at which components of the solution and derivative are to be evaluated. twant should not normally be an extrapolation point, that is twant should satisfy

• $\mathit{told}\le \mathbf{twant}\le \mathrm{T}$,

or if integration is proceeding in the negative direction

• $\mathit{told}\ge \mathbf{twant}\ge \mathrm{T}$,

where $\mathit{told}$ is the previous integration point and is, to within rounding, tcurr – hlast (see d02qxf). Extrapolation is permitted but not recommended and $\mathbf{ifail}=\mathbf{2}$ is returned whenever extrapolation is attempted.

3: $\mathbf{nwant}$ – Integer Input

On entry: the number of components of the solution and derivative whose values at twant are required. The first nwant components are evaluated.

Constraint: $1\le \mathbf{nwant}\le \mathbf{neqf}$.

4: $\mathbf{ywant}\left(\mathbf{nwant}\right)$ – Real (Kind=nag_wp) array Output

On exit: the calculated value of the $\mathit{i}$th component of the solution at twant, for $\mathit{i}=1,2,\dots ,\mathbf{nwant}$.

5: $\mathbf{ypwant}\left(\mathbf{nwant}\right)$ – Real (Kind=nag_wp) array Output

On exit: the calculated value of the $\mathit{i}$th component of the derivative at twant, for $\mathit{i}=1,2,\dots ,\mathbf{nwant}$.

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

On entry: this must be the same argument rwork as supplied to d02qwf and to d02qff or d02qgf. It is used to pass information from these routines to d02qzf. Therefore its contents must not be changed before a call to d02qzf.

7: $\mathbf{lrwork}$ – Integer Input

On entry: the dimension of the array rwork as declared in the (sub)program from which d02qzf is called.

This must be the same argument lrwork as supplied to d02qwf.

8: $\mathbf{iwork}\left(\mathbf{liwork}\right)$ – Integer array Communication Array

On entry: this must be the same argument iwork as supplied to d02qwf and to d02qff or d02qgf. It is used to pass information from these routines to d02qzf. Therefore its contents must not be changed before a call to d02qzf.

9: $\mathbf{liwork}$ – Integer Input

On entry: the dimension of the array iwork as declared in the (sub)program from which d02qzf is called.

This must be the same argument liwork as supplied to d02qwf.

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

On entry: ifail must be set to $0$, $-1$ 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 $-1$ means that an error message is printed while a value of $1$ means that it is not.

If halting is not appropriate, the value $-1$ 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

$\mathbf{ifail}=1$

Neither of the appropriate two integrator routines has been called.

No successful steps had been taken, so interpolation is impossible at $\mathbf{twant}=〈\mathit{\text{value}}〉$.

On entry, $\mathbf{liwork}=〈\mathit{\text{value}}〉$ and $\mathbf{liwork}=〈\mathit{\text{value}}〉$ in d02qwf.
Constraint: $\mathbf{liwork}=\mathbf{liwork}$ in d02qwf.

On entry, $\mathbf{lrwork}=〈\mathit{\text{value}}〉$ and $\mathbf{lrwork}=〈\mathit{\text{value}}〉$ in d02qwf.
Constraint: $\mathbf{lrwork}=\mathbf{lrwork}$ in d02qwf.

On entry, $\mathbf{neqf}=〈\mathit{\text{value}}〉$ and $\mathbf{neqf}=〈\mathit{\text{value}}〉$ in d02qwf.
Constraint: $\mathbf{neqf}=\mathbf{neqf}$ in d02qwf.

On entry, $\mathbf{nwant}=〈\mathit{\text{value}}〉$.
Constraint: $\mathbf{nwant}\ge 1$.

On entry, $\mathbf{nwant}=〈\mathit{\text{value}}〉$ and $\mathbf{neqf}=〈\mathit{\text{value}}〉$.
Constraint: $\mathbf{nwant}\le \mathbf{neqf}$.

$\mathbf{ifail}=2$

Extrapolation performed at $\mathbf{twant}=〈\mathit{\text{value}}〉$.

$\mathbf{ifail}=-99$

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

10.1 Program Text

10.2 Program Data

10.3 Program Results