NAG Library Function Document

nag_reorder_vector (m01esc)

+− Contents

1 Purpose

2 Specification

3 Description

4 References

5 Arguments

6 Error Indicators and Warnings

7 Accuracy

8 Parallelism and Performance

9 Further Comments

+− 10 Example

10.1 Program Text

10.2 Program Data

10.3 Program Results

1 Purpose

nag_reorder_vector (m01esc) rearranges a vector of arbitrary type data objects into the order specified by a vector of indices.

2 Specification

#include <nag.h>

#include <nagm01.h>

void	nag_reorder_vector (Pointer vec, size_t n, size_t size, ptrdiff_t stride, size_t indices[], NagError *fail)

3 Description

nag_reorder_vector (m01esc) uses a variant of list merging as described by Knuth (1973). The function rearranges a set of

n

data objects of arbitrary type, which are stored in an array at intervals of length stride, into the order specified by an array of indices.

4 References

Knuth D E (1973) The Art of Computer Programming (Volume 3) (2nd Edition) Addison–Wesley

5 Arguments

1: vec[ $n$ ] – Pointer Input/Output: On entry: the array of objects to be rearranged.

On exit: the objects rearranged according to array indices.
2: n – size_tInput: On entry: the number, $n$ , of objects to be rearranged.
Constraint: $n \geq 0$ .
3: size – size_tInput: On entry: the size of each object to be rearranged.
Constraint: $size \geq 1$ .
4: stride – ptrdiff_tInput: On entry: the increment between data items in vec to be rearranged.
Note: if stride is positive, vec should point at the first data object; otherwise vec should point at the last data object.

Constraint: $|stride| \geq size$ .
5: indices[n] – size_tInput: On entry: the indices specifying the order in which the elements of vector are to be rearranged.
6: fail – NagError *Input/Output: The NAG error argument (see Section 3.6 in the Essential Introduction).

6 Error Indicators and Warnings

NE_2_INT_ARG_LT: On entry, $|stride| = ⟨value⟩$ while $size = ⟨value⟩$ . These arguments must satisfy $|stride| \geq size$ .
NE_ALLOC_FAIL: Dynamic memory allocation failed.
NE_BAD_RANK: Invalid indices vector.
NE_INT_ARG_GT: On entry, $|stride|$ must not be greater than $⟨value⟩$ : $|stride| = ⟨value⟩$ .
On entry, $n = ⟨value⟩$ .
Constraint: $n \leq ⟨value⟩$ .
On entry, $size = ⟨value⟩$ .
Constraint: $size \leq ⟨value⟩$ .
These arguments are limited to an implementation-dependent size which is printed in the error message.
NE_INT_ARG_LT: On entry, $n = ⟨value⟩$ .
Constraint: $n \geq 0$ .
On entry, $size = ⟨value⟩$ .
Constraint: $size \geq 1$ .

7 Accuracy

Not applicable.

8 Parallelism and Performance

Not applicable.

9 Further Comments

The average time taken by the function is approximately proportional to n.

10 Example

The example program.

NAG Library Function Documentnag_reorder_vector (m01esc)