**Parent Command**

all third-level commands in block` > PARAMETER`

**Subcommand**`
- `

**Description**

This command defines the maximum allowable step size, limiting the change in the
corresponding parameter per iTOUGH2 iteration. Large steps are usually proposed for a
parameter if

(i) the initial guess is far away from the best estimate;

(ii) the parameter has a low sensitivity, or

(iii) the parameter is highly correlated to more sensitive parameters.

If the system state is a strongly non-linear function of the parameter, even a moderate step size may
make the inversion unstable. Parameter *max_step* should be chosen large enough, so
that the proposed step size |deltpa(p')| is reduced to |delta(pmax)| only during the first few
iterations. The figure below illustrates that limiting the step size also changes the direction of
the step taken in the parameter space. A global step size limitation can also be specified (see command `>>> STEP),`**p**).

**Example**`
> PARAMETER
>> POROSITY
>>> MATERIAL: SANDY
>>>> standard DEVIATION: 0.10
>>>> max. STEP size : 0.05
<<<<
<<<
<<
`

**See Also**`
>>> STEP |
>>>> DEVIATION (p) |
>>>> RANGE`

Page updated: July 29, 1997