NAG FL Interface
e02rbf (pade_​eval)

1 Purpose

2 Specification

3 Description

4 References

5 Arguments

1: $\mathbf{a}\left(\mathbf{ia}\right)$ – Real (Kind=nag_wp) array Input

On entry: $\mathbf{a}\left(\mathit{j}+1\right)$, for $\mathit{j}=1,2,\dots ,l+1$, must contain the value of the coefficient $a_{\mathit{j}}$ in the numerator of the rational function.

2: $\mathbf{ia}$ – Integer Input

On entry: the value of $l+1$, where $l$ is the degree of the numerator.

Constraint: $\mathbf{ia}\ge 1$.

3: $\mathbf{b}\left(\mathbf{ib}\right)$ – Real (Kind=nag_wp) array Input

On entry: $\mathbf{b}\left(\mathit{k}+1\right)$, for $\mathit{k}=1,2,\dots ,m+1$, must contain the value of the coefficient $b_k$ in the denominator of the rational function.

Constraint: if $\mathbf{ib}=1$, $\mathbf{b}\left(1\right)\ne 0.0$.

4: $\mathbf{ib}$ – Integer Input

On entry: the value of $m+1$, where $m$ is the degree of the denominator.

Constraint: $\mathbf{ib}\ge 1$.

5: $\mathbf{x}$ – Real (Kind=nag_wp) Input

On entry: the point $x$ at which the rational function is to be evaluated.

6: $\mathbf{ans}$ – Real (Kind=nag_wp) Output

On exit: the result of evaluating the rational function at the given point $x$.

7: $\mathbf{ifail}$ – 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).

6 Error Indicators and Warnings

$\mathbf{ifail}=1$

Evaluation at or near a pole.

$\mathbf{ifail}=2$

On entry, $\mathbf{ia}=〈\mathit{\text{value}}〉$.
Constraint: $\mathbf{ia}\ge 1$.

On entry, $\mathbf{ib}=〈\mathit{\text{value}}〉$.
Constraint: $\mathbf{ib}\ge 1$.

The first ib entries in b are zero: $\mathbf{ib}=〈\mathit{\text{value}}〉$.

$\mathbf{ifail}=-99$

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.

7 Accuracy

8 Parallelism and Performance

9 Further Comments

10 Example

10.1 Program Text

10.2 Program Data

10.3 Program Results