NAG FL Interfacem01ebf (intvec_​rank_​rearrange)

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1Purpose

m01ebf rearranges a vector of integer numbers into the order specified by a vector of ranks.

2Specification

Fortran Interface
 Subroutine m01ebf ( iv, m1, m2,
 Integer, Intent (In) :: m1, m2 Integer, Intent (Inout) :: iv(m2), irank(m2), ifail
#include <nag.h>
 void m01ebf_ (Integer iv[], const Integer *m1, const Integer *m2, Integer irank[], Integer *ifail)
The routine may be called by the names m01ebf or nagf_sort_intvec_rank_rearrange.

3Description

m01ebf is designed to be used typically in conjunction with the ranking routines m01daf, m01dbf, m01dcf, m01def, m01dff, m01djf, m01dkf and m01dzf. After one of those routines has been called to determine a vector of ranks, m01ebf can be called to rearrange a vector of integer numbers into the rank order. If the vector of ranks has been generated in some other way, then m01zbf should be called to check its validity before m01ebf is called.

None.

5Arguments

1: $\mathbf{iv}\left({\mathbf{m2}}\right)$Integer array Input/Output
On entry: elements ${\mathbf{m1}}$ to ${\mathbf{m2}}$ of iv must contain integer values to be rearranged.
On exit: these values are rearranged into rank order. For example, if ${\mathbf{irank}}\left(i\right)={\mathbf{m1}}$, then the initial value of ${\mathbf{iv}}\left(i\right)$ is moved to ${\mathbf{iv}}\left({\mathbf{m1}}\right)$.
2: $\mathbf{m1}$Integer Input
3: $\mathbf{m2}$Integer Input
On entry: m1 and m2 specify the range of the ranks supplied in irank and the elements of iv to be rearranged.
Constraint: $0<{\mathbf{m1}}\le {\mathbf{m2}}$.
4: $\mathbf{irank}\left({\mathbf{m2}}\right)$Integer array Input/Output
On entry: elements ${\mathbf{m1}}$ to ${\mathbf{m2}}$ of irank must contain a permutation of the integers m1 to m2, which are interpreted as a vector of ranks.
On exit: used as internal workspace prior to being restored and hence is unchanged.
5: $\mathbf{ifail}$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).

6Error Indicators and Warnings

If on entry ${\mathbf{ifail}}=0$ or $-1$, explanatory error messages are output on the current error message unit (as defined by x04aaf).
Errors or warnings detected by the routine:
${\mathbf{ifail}}=1$
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: ${\mathbf{m2}}\ge 1$.
${\mathbf{ifail}}=2$
${\mathbf{irank}}\left({\mathbf{m1}}:{\mathbf{m2}}\right)$ does not contain a permutation of the integers m1 to m2. ${\mathbf{irank}}\left(I\right)$ contains an out-of-range value: $I=⟨\mathit{\text{value}}⟩$, ${\mathbf{irank}}\left(I\right)=⟨\mathit{\text{value}}⟩$.
Elements m1 to m2 of irank do not contain a permutation of the integers m1 to m2. On exit, the contents of iv may be corrupted. To check the validity of irank without the risk of corrupting iv, use m01zbf.
${\mathbf{ifail}}=3$
${\mathbf{irank}}\left({\mathbf{m1}}:{\mathbf{m2}}\right)$ does not contain a permutation of the integers m1 to m2. irank contains a repeated value: $⟨\mathit{\text{value}}⟩$.
Elements m1 to m2 of irank do not contain a permutation of the integers m1 to m2. On exit, the contents of iv may be corrupted. To check the validity of irank without the risk of corrupting iv, 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.

Not applicable.

8Parallelism and Performance

Background information to multithreading can be found in the Multithreading documentation.
m01ebf is not threaded in any implementation.

The average time taken by the routine is approximately proportional to $n$, where $n={\mathbf{m2}}-{\mathbf{m1}}+1$.

10Example

This example reads a matrix of integers and rearranges its rows so that the elements of the $k$th column are in ascending order. To do this, the program first calls m01dbf to rank the elements of the $k$th column, and then calls m01ebf to rearrange each column into the order specified by the ranks. The value of $k$ is read from the datafile.

10.1Program Text

Program Text (m01ebfe.f90)

10.2Program Data

Program Data (m01ebfe.d)

10.3Program Results

Program Results (m01ebfe.r)