NAG Library Routine Document

c06baf (accelerate)

1

Purpose

2

Specification

3

Description

4

References

5

Arguments

1:     $\mathbf{seqn}$ – Real (Kind=nag_wp)Input

On entry: the next term of the sequence to be considered.

2:     $\mathbf{ncall}$ – IntegerInput/Output

On entry: on the first call ncall must be set to $0$. Thereafter ncall must not be changed between calls.

On exit: the number of terms in the sequence that have been considered.

3:     $\mathbf{result}$ – Real (Kind=nag_wp)Output

On exit: the estimate of the limit of the sequence. For the first two calls, $\mathbf{result}=\mathbf{seqn}$.

4:     $\mathbf{abserr}$ – Real (Kind=nag_wp)Output

On exit: an estimate of the absolute error in result. For the first three calls, abserr is set to a large machine-dependent constant.

5:     $\mathbf{work}\left(\mathbf{lwork}\right)$ – Real (Kind=nag_wp) arrayCommunication Array

Used as workspace, but must not be changed between calls.

6:     $\mathbf{lwork}$ – IntegerInput

On entry: the dimension of the array work as declared in the (sub)program from which c06baf is called.

Suggested value: $\text{(maximum number of terms in the sequence)}+6$. See Section 9.2.

Constraint: $\mathbf{lwork}\ge 7$.

7:     $\mathbf{ifail}$ – 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, $\mathbf{ncall}=〈\mathit{\text{value}}〉$.
Constraint: $\mathbf{ncall}\ge 0$.

$\mathbf{ifail}=2$

On entry, $\mathbf{lwork}=〈\mathit{\text{value}}〉$.
Constraint: $\mathbf{lwork}\ge 7$.

$\mathbf{ifail}=-99$

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

9.1

Timing

9.2

Choice of lwork

9.3

Convergence

10

Example

10.1

Program Text

Program Text (c06bafe.f90)

10.2

Program Data

10.3

Program Results

Program Results (c06bafe.r)