Command >>> GRID SEARCH
Manual Page for Command >>> GRID SEARCH
Syntax
>>> GRID SEARCH (UNSORTED) (: ninval1 (ninval2 (ninval3)) / FILE:
filename)
or
>>> OBJECTIVE (UNSORTED) (: ninval1 (ninval2 (ninval3)) / FILE:
filename)
Parent Command
>> OPTION
Subcommand

Description
This command evaluates the objective function for a number of specific parameter sets.
A arbitrarily long list of parameter sets can be provided on file filename,
each row consisting of one parameter set, whereby inactive and tied parameters are to be omitted.
Alternatively, parameter sets are generated internally on a regular grid,
mapping out the entire parameter space.
In this case, lower and upper bounds must be defined for each
parameter using command >>>> RANGE in block > PARAMETER. This range is then
subdivided into ninteri intervals by inserting ninvali+1 equally spaced
points, generating parameter sets on a regular grid in the ndimensional
parameter space. The objective function is evaluated at each grid point.
Evaluating the objective function throughout the entire parameter space is
referred to as grid searching.
The parameter set, the value of the objective function, and the contribution
of each observation type to the objective function is printed to the iTOUGH2
output file. The global minimum is likely to be in the vicinity of the
parameter set with the lowest objective function. Furthermore, the
information listed in the output file can be used to visually represent and
study the topology of the objective function. For example, oneliner can generate
a contour plot of the objective function for n=2 which may reveal the
presence local minima.
If only one output variable is defined in block > OBSERVATION and no data
are provided, this option can also be used in combination with command
>>> L1ESTIMATOR to examine the sensitivity of the output variable over an
extensive parameter range.
Keyword UNSORTED can be used in PVM applications to improve efficiency.
The output list must then be sorted in a postprocessing step.
Example
> COMPUTATION
>> OPTION
>>> GRID SEARCH! subdivide 2Dparameter space into: 20 10 intervals
<<<
<<
See Also
>>> ANNEAL 
>>> LEVENBERGMARQUARDT 
>>> GAUSSNEWTON 
>>> TORNADO
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Page updated: September 30, 1998