NAG FL Interface
m01zbf (permute_​check)

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1 Purpose

m01zbf checks the validity of a permutation.

2 Specification

Fortran Interface
Subroutine m01zbf ( iperm, m1, m2, ifail)
Integer, Intent (In) :: m1, m2
Integer, Intent (Inout) :: iperm(m2), ifail
C Header Interface
#include <nag.h>
void  m01zbf_ (Integer iperm[], const Integer *m1, const Integer *m2, Integer *ifail)
The routine may be called by the names m01zbf or nagf_sort_permute_check.

3 Description

m01zbf can be used to check the validity of user-supplied ranks or indices, without the ranks or indices being corrupted.

4 References

None.

5 Arguments

1: iperm(m2) Integer array Input/Output
On entry: elements m1 to m2 of iperm must be set to values which are supposed to be a permutation of the integers m1 to m2. If they are a valid permutation, the routine exits with ifail=0.
On exit: used as internal workpsace prior to being restored and hence is unchanged.
2: m1 Integer Input
3: m2 Integer Input
On entry: the range of elements used in the array iperm and the range of values in the permutation, as specified under iperm.
Constraint: 0<m1m2.
4: 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 -1 or 1 is used it is essential to test the value of ifail on exit.
On exit: ifail=0 unless the routine detects an error or a warning has been flagged (see Section 6).

6 Error Indicators and Warnings

If on entry ifail=0 or −1, explanatory error messages are output on the current error message unit (as defined by x04aaf).
Errors or warnings detected by the routine:
ifail=1
On entry, m1=value.
Constraint: m11.
On entry, m1=value and m2=value.
Constraint: m1m2.
On entry, m2=value.
Constraint: m21.
ifail=2
iperm(m1:m2) does not contain a permutation of the integers m1 to m2. iperm(I) contains an out-of-range value: I=value, iperm(I)=value.
Elements m1 to m2 of iperm do not contain a permutation of the integers m1 to m2.
ifail=3
iperm(m1:m2) does not contain a permutation of the integers m1 to m2. iperm contains a repeated value: value.
Elements m1 to m2 of iperm do not contain a permutation of the integers m1 to m2.
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.
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.
ifail=-999
Dynamic memory allocation failed.
See Section 9 in the Introduction to the NAG Library FL Interface for further information.

7 Accuracy

Not applicable.

8 Parallelism and Performance

m01zbf is not threaded in any implementation.

9 Further Comments

None.

10 Example

This example reads in a vector of real numbers, and a vector of ranks; it calls m01zbf to check the validity of the ranks before calling m01eaf to rearrange the real numbers into the specified order.

10.1 Program Text

Program Text (m01zbfe.f90)

10.2 Program Data

Program Data (m01zbfe.d)

10.3 Program Results

Program Results (m01zbfe.r)