NAG FL Interface
m01zaf (permute_​invert)

1 Purpose

2 Specification

3 Description

4 References

5 Arguments

1: $\mathbf{iperm}\left(\mathbf{m2}\right)$ – Integer array Input/Output

On entry: elements m1 to m2 of iperm must contain a permutation of the integers m1 to m2.

On exit: these elements contain the inverse permutation of the integers m1 to m2.

2: $\mathbf{m1}$ – Integer Input

3: $\mathbf{m2}$ – Integer Input

On entry: m1 and m2 must specify the range of elements used in the array iperm and the range of values in the permutation, as specified under iperm.

Constraint: $0<\mathbf{m1}\le \mathbf{m2}$.

4: $\mathbf{ifail}$ – 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

$\mathbf{ifail}=1$

On entry, $\mathbf{m1}=〈\mathit{\text{value}}〉$.
Constraint: $\mathbf{m1}\ge 1$.

On entry, $\mathbf{m1}=〈\mathit{\text{value}}〉$ and $\mathbf{m2}=〈\mathit{\text{value}}〉$.
Constraint: $\mathbf{m1}\le \mathbf{m2}$.

On entry, $\mathbf{m2}=〈\mathit{\text{value}}〉$.
Constraint: $\mathbf{m2}\ge 1$.

$\mathbf{ifail}=2$

$\mathbf{iperm}\left(\mathbf{m1}:\mathbf{m2}\right)$ does not contain a permutation of the integers m1 to m2. $\mathbf{iperm}\left(I\right)$ contains an out-of-range value: $I=〈\mathit{\text{value}}〉$, $\mathbf{iperm}\left(I\right)=〈\mathit{\text{value}}〉$.

Elements m1 to m2 of iperm do not contain a permutation of the integers m1 to m2; on exit these elements are usually corrupted. To check the validity of a permutation without the risk of corrupting it, use m01zbf.

$\mathbf{ifail}=3$

$\mathbf{iperm}\left(\mathbf{m1}:\mathbf{m2}\right)$ does not contain a permutation of the integers m1 to m2. iperm contains a repeated value: $〈\mathit{\text{value}}〉$.

Elements m1 to m2 of iperm do not contain a permutation of the integers m1 to m2; on exit these elements are usually corrupted. To check the validity of a permutation without the risk of corrupting it, use m01zbf.

$\mathbf{ifail}=-99$

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