Manual Page for Command >>> STEP

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Syntax
>>> STEP (UNSCALED): max_step

Parent Command
>> CONVERGENCE

 

Subcommand
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Description
This command defines the maximum allowable size of the scaled (f_i = σ_pi, default; f_i = p_i; keyword CURRENT) or unscaled (f_i = 1, keyword UNSCALED) update vector Δp per iTOUGH2 iteration. The step length of the scaled parameter update vector is defined as follows:

This is a global step size limitation as opposed to the one specified for each individual parameter (see command >>>> STEP). Limiting the global step size may make the inversion more stable. Parameter max_step should be chosen large enough, so that the size of the proposed step size |Δp| is reduced to |Δp_max)| only during the first few iterations. The figure below illustrates that limiting the step size maintains the direction of the step taken in the parameter space.

Example
> COMPUTATION
>> CONVERGENCE
>>> number of ITERATIONS : 10 (may need more iterations!)
>>> limit scaled STEP size to: 1.0 [dimensionless]
<<<
<<

 

See Also
>>>> STEP (p)

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