NAG Library Routine Document

m01dzf (arbitrary_rank)

1

Purpose

2

Specification

3

Description

4

References

5

Arguments

1:     $\mathbf{compar}$ – Logical Function, supplied by the user.External Procedure

compar must specify the relative ordering of any two data items; it must return .TRUE. if item i must come strictly after item j in the rank ordering.

The specification of compar is:

Fortran Interface

Function compar ( i, j) Logical :: compar Integer, Intent (In) :: i, j

C Header Interface

#include <nagmk26.h> Nag_Boolean  compar (const Integer *i, const Integer *j)

1:     $\mathbf{i}$ – IntegerInput

2:     $\mathbf{j}$ – IntegerInput

On entry: i and j identify the data items to be compared.

compar must either be a module subprogram USEd by, or declared as EXTERNAL in, the (sub)program from which m01dzf is called. Arguments denoted as Input must not be changed by this procedure.

2:     $\mathbf{m1}$ – IntegerInput

3:     $\mathbf{m2}$ – IntegerInput

On entry: m1 and m2 must specify the range of data items to be ranked, and the range of ranks to be assigned. Specifically, m01dzf ranks the data items identified by integers in the range m1 to m2, and assigns ranks in the range m1 to m2 which are stored in elements m1 to m2 of irank.

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

4:     $\mathbf{irank}\left(\mathbf{m2}\right)$ – Integer arrayOutput

On exit: elements m1 to m2 of irank contain the ranks of the data items m1 to m2. Note that the ranks are in the range m1 to m2: thus, if item $i$ is first in the rank ordering, $\mathbf{irank}\left(i\right)$ contains m1.

5:     $\mathbf{ifail}$ – IntegerInput/Output

On entry: ifail must be set to $0$, $-1\text{ or }1$. If you are unfamiliar with this argument you should refer to Section 3.4 in How to Use the NAG Library and its Documentation 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 argument, 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

$\mathbf{ifail}=1$

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: $\mathbf{m2}\ge 1$.

$\mathbf{ifail}=-99$

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

See Section 3.9 in How to Use the NAG Library and its Documentation for further information.

$\mathbf{ifail}=-399$

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

See Section 3.8 in How to Use the NAG Library and its Documentation for further information.

$\mathbf{ifail}=-999$

Dynamic memory allocation failed.

See Section 3.7 in How to Use the NAG Library and its Documentation for further information.

7

Accuracy

8

Parallelism and Performance

9

Further Comments

10

Example

10.1

Program Text

Program Text (m01dzfe.f90)

10.2

Program Data

Program Data (m01dzfe.d)

10.3

Program Results

Program Results (m01dzfe.r)