NAG CL Interface
m01csc (quicksort)

1 Purpose

2 Specification

3 Description

4 References

5 Arguments

1: $\mathbf{vec}\left[\mathbf{n}\right]$ – Pointer  Input/Output

On entry: the array of objects to be sorted.

On exit: the objects rearranged into sorted order.

2: $\mathbf{n}$ – size_t Input

On entry: the number, $n$, of objects to be sorted.

Constraint: $0\le \mathbf{n}\le \mathrm{MAX\_LENGTH}$, where $\mathrm{MAX\_LENGTH}$ is an implementation-dependent value for the maximum size of an array.

3: $\mathbf{size}$ – size_t Input

On entry: the size of each object to be sorted.

Constraint: $1\le \mathbf{size}\le p$, where $p$ is an implementation-dependent value for the maximum size_t size on the system, divided by n if n is positive.

4: $\mathbf{stride}$ – ptrdiff_t Input

On entry: the increment between data items in vec to be sorted.

Note: if stride is positive, vec should point at the first data object; otherwise vec should point at the last data object.

Constraint: $\mathbf{size}\le \left|\mathbf{stride}\right|\le p$, where $p$ is an implementation-dependent value for the maximum size_t size on the system, divided by n if n is positive.

5: $\mathbf{compare}$ – function, supplied by the user External Function

m01csc compares two data objects. If its arguments are pointers to a structure, this function must allow for the offset of the data field in the structure (if it is not the first).

The function must return:

$-1$	if the first data field is less than the second,
$\phantom{-}0$	if the first data field is equal to the second,
$\phantom{-}1$	if the first data field is greater than the second.

The specification of compare is:

copy

Integer  compare (const Nag_Pointer a, const Nag_Pointer b)

1: $\mathbf{a}$ – const Nag_Pointer  Input

On entry: the first data field.

2: $\mathbf{b}$ – const Nag_Pointer  Input

On entry: the second data field.

6: $\mathbf{order}$ – Nag_SortOrder Input

On entry: specifies whether the array is to be sorted into ascending or descending order.

Constraint: $\mathbf{order}=\mathrm{Nag\_Ascending}$ or $\mathrm{Nag\_Descending}$.

7: $\mathbf{fail}$ – NagError * Input/Output

The NAG error argument (see Section 7 in the Introduction to the NAG Library CL Interface).

6 Error Indicators and Warnings

NE_2_INT_ARG_LT

On entry, $\left|\mathbf{stride}\right|=⟨\mathit{\text{value}}⟩$ while $\mathbf{size}=⟨\mathit{\text{value}}⟩$. These arguments must satisfy $\left|\mathbf{stride}\right|\ge \mathbf{size}$.

NE_ALLOC_FAIL

Dynamic memory allocation failed.

NE_BAD_PARAM

On entry, argument order had an illegal value.

NE_INT_ARG_GT

On entry, $\left|\mathbf{stride}\right|=⟨\mathit{\text{value}}⟩$.
Constraint: $\left|\mathbf{stride}\right|\le ⟨\mathit{\text{value}}⟩$, an implementation-dependent size that is printed in the error message.

On entry, $\mathbf{n}=⟨\mathit{\text{value}}⟩$.
Constraint: $\mathbf{n}\le ⟨\mathit{\text{value}}⟩$, an implementation-dependent size that is printed in the error message.

On entry, $\mathbf{size}=⟨\mathit{\text{value}}⟩$.
Constraint: $\mathbf{size}\le ⟨\mathit{\text{value}}⟩$, an implementation-dependent size that is printed in the error message.

NE_INT_ARG_LT

On entry, $\mathbf{n}=⟨\mathit{\text{value}}⟩$.
Constraint: $\mathbf{n}\ge 0$.

On entry, $\mathbf{size}=⟨\mathit{\text{value}}⟩$.
Constraint: $\mathbf{size}\ge 1$.

7 Accuracy

8 Parallelism and Performance

9 Further Comments

10 Example

10.1 Program Text

10.2 Program Data

10.3 Program Results