NAG Library Routine Document

m01caf (realvec_sort)

1

Purpose

2

Specification

3

Description

4

References

5

Arguments

1:     $\mathbf{rv}\left(\mathbf{m2}\right)$ – Real (Kind=nag_wp) arrayInput/Output

On entry: elements m1 to m2 of rv must contain real values to be sorted.

On exit: these values are rearranged into sorted order.

2:     $\mathbf{m1}$ – IntegerInput

On entry: the index of the first element of rv to be sorted.

Constraint: $\mathbf{m1}>0$.

3:     $\mathbf{m2}$ – IntegerInput

On entry: the index of the last element of rv to be sorted.

Constraint: $\mathbf{m2}\ge \mathbf{m1}$.

4:     $\mathbf{order}$ – Character(1)Input

On entry: if $\mathbf{order}=\text{'A'}$, the values will be sorted into ascending (i.e., nondecreasing) order.

If $\mathbf{order}=\text{'D'}$, into descending order.

Constraint: $\mathbf{order}=\text{'A'}$ or $\text{'D'}$.

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

$\mathbf{ifail}=2$

On entry, order has an illegal value: $\mathbf{order}=〈\mathit{\text{value}}〉$.

$\mathbf{ifail}=-99$

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 (m01cafe.f90)

10.2

Program Data

Program Data (m01cafe.d)

10.3

Program Results

Program Results (m01cafe.r)