**keywords:**

`CHECK-ALL-DERIVATIVES`

`CHECK-DERIVATIVES`

`CHECK-ELEMENT-DERIVATIVES`

`CHECK-GROUP-DERIVATIVES`

`IGNORE-DERIVATIVE-WARNINGS`

`IGNORE-ELEMENT-DERIVATIVE-WARNINGS`

`IGNORE-GROUP-DERIVATIVE-WARNINGS`

The derivatives of the nonlinear element and group functions specified
in the SEIF and SGIF files may be checked to reduce the
likelihood that programming
errors have been made. Numerical estimates of the derivatives are
compared with their exact representations and warning messages issued
if any of the derivatives appear to be inaccurate. The derivatives of
each of the nonlinear elements
and groups used are checked if the
`CHECK-ALL-DERIVATIVES` keyword is specified.
To save effort when many of the elements or groups are of the same type,
the derivatives of a single example of each different type of nonlinear
element and group supplied are checked if the
`CHECK-DERIVATIVES` keyword is specified.
The nonlinear element values
are checked if `CHECK-ELEMENT-DERIVATIVES` is specified while the
`CHECK-GROUP-DERIVATIVES` keyword ensures that the group function
derivatives are checked. The default
is that no derivative checking
is performed but it is recommended that newly specified problems are
always checked for accuracy.

It is sometimes possible that a derivative is reported to be
inaccurate when in fact it has been coded correctly - this is a
consequence of truncation errors in the numerical tests performed.
*LANCELOT* will not allow the optimization to proceed if a derivative
error is detected unless the user specifically requests it using one
of the `IGNORE-DERIVATIVE-WARNINGS`,
`IGNORE-ELEMENT-DERIVATIVE-WARNINGS`
or `IGNORE-GROUP-DERIVATIVE-WARNINGS` keywords. All warnings are
ignored when the first of these keywords is present while only element
and group warnings, respectively, are overridden with the
latter two keywords.