NAG Library Routine Document

E04WLF

1  Purpose

2  Specification

3  Description

CALL E04WLF ('LU Factor Tolerance', FACTOL, IW, RW, IFAIL)

4  References

5  Parameters

1:     STRING – CHARACTER(*)Input

On entry: a single valid keyword of a real optional parameter (as described in Section 11 in E04WDF).

2:     RVALUE – REAL (KIND=nag_wp)Output

On exit: the real value associated with the keyword in STRING.

3:     IW($*$) – INTEGER arrayCommunication Array

Note: the dimension of the array IW must be at least $\mathbf{LENIW}$ (see E04WCF).

4:     RW($*$) – REAL (KIND=nag_wp) arrayCommunication Array

Note: the dimension of the array RW must be at least $\mathbf{LENRW}$ (see E04WCF).

5:     IFAIL – INTEGERInput/Output

On entry: IFAIL must be set to $0$, $-1\text{ or }1$. If you are unfamiliar with this parameter you should refer to Section 3.3 in the Essential Introduction 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 parameter, 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

$\mathbf{IFAIL}=1$

The initialization routine E04WCF has not been called.

$\mathbf{IFAIL}=2$

The supplied option is invalid. Check that the keywords are neither ambiguous nor misspelt.

7  Accuracy

8  Further Comments

9  Example