NAG Library Routine Document

x03abf  (complex_prec)

1

Purpose

2

Specification

3

Description

4

References

5

Arguments

1:     $\mathbf{a}\left(\mathbf{isizea}\right)$ – Complex (Kind=nag_wp) arrayInput

On entry: the elements of the first vector.

The $i$th vector element is stored in the array element $\mathbf{a}\left(\left(i-1\right)\times \mathbf{istepa}+1\right)$. In your subroutine from which x03abf is called, a can be part of a multidimensional array and the actual argument must be the array element containing the first vector element.

2:     $\mathbf{isizea}$ – IntegerInput

On entry: the dimension of the array a as declared in the (sub)program from which x03abf is called.

The upper bound for isizea is found by multiplying together the dimensions of a as declared in your subroutine from which x03abf is called, subtracting the starting position and adding $1$.

Constraint: $\mathbf{isizea}\ge \left(\mathbf{n}-1\right)\times \mathbf{istepa}+1$.

3:     $\mathbf{b}\left(\mathbf{isizeb}\right)$ – Complex (Kind=nag_wp) arrayInput

On entry: the elements of the second vector.

The $i$th vector element is stored in the array element $\mathbf{b}\left(\left(i-1\right)\times \mathbf{istepb}+1\right)$. In your subroutine from which x03abf is called, b can be part of a multidimensional array and the actual argument must be the array element containing the first vector element.

4:     $\mathbf{isizeb}$ – IntegerInput

On entry: the dimension of the array b as declared in the (sub)program from which x03abf is called.

The upper bound for isizeb is found by multiplying together the dimensions of b as declared in your subroutine from which x03abf is called, subtracting the starting position and adding $1$.

Constraint: $\mathbf{isizeb}\ge \left(\mathbf{n}-1\right)\times \mathbf{istepb}+1$.

5:     $\mathbf{n}$ – IntegerInput

On entry: $n$, the number of elements in the scalar product.

6:     $\mathbf{istepa}$ – IntegerInput

On entry: the step length between elements of the first vector in array a.

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

7:     $\mathbf{istepb}$ – IntegerInput

On entry: the step length between elements of the second vector in array b.

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

8:     $\mathbf{cx}$ – Complex (Kind=nag_wp)Input

On entry: the initial value $c$.

9:     $\mathbf{dx}$ – Complex (Kind=nag_wp)Output

On exit: the result $d$.

10:   $\mathbf{sw}$ – LogicalInput

On entry: the precision to be used in the calculation.

$\mathbf{sw}=\mathrm{.TRUE.}$

additional precision.

$\mathbf{sw}=\mathrm{.FALSE.}$

basic precision.

11:   $\mathbf{ifail}$ – 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,	$\mathbf{istepa}\le 0$,
or	$\mathbf{istepb}\le 0$.

$\mathbf{ifail}=2$

On entry,	$\mathbf{isizea}<\left(\mathbf{n}-1\right)\times \mathbf{istepa}+1$,
or	$\mathbf{isizeb}<\left(\mathbf{n}-1\right)\times \mathbf{istepb}+1$.

$\mathbf{ifail}=-99$

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 (x03abfe.f90)

10.2

Program Data

Program Data (x03abfe.d)

10.3

Program Results

Program Results (x03abfe.r)