Download Getting Started with PEST

model input files using the input template files. Then the model (batch file) is called. If
the model runs successfully, the model will generate a set of output files. The modelgenerated outputs in the model output files, which will be compared against the
corresponding observations, are then read by PEST through using model output
instruction file. At this stage, the objective function and Jacobian matrix are calculated,
based on which the PEST will make its decision for next iteration until one of its stopping
criteria is met. The stop criteria are specified in PEST control file as you may suspect.
PEST Control File
Input Template
File
Model Input
(input files)
PEST
Optimization
Algorithm
Model (model
batch file)
Output
Instruction File
Model Output
(output files)
Figure 1. Schematic diagram of PEST optimization process
1.1 Model batch file
Model batch file is simple. It can be as short as one line – the model DOS command. But
if the model output files are not text format files; or you plan to use TSPROC as your
model post-processor, the model batch file will get slightly longer, like in Example 1.
The purpose of each command in Example 1 is briefly explained as follows. The first line
of Example 1 (@echo off) is to tell the computer system not to display the commands
while executing them. The second line (del basins.rch > nul) is to delete the
SWAT output file basins.rch that has been generated by previous modeling run. If it
had not been deleted, even though the following SWAT run is not successful, PEST
would still have read model outputs from the existing basins.rch file, which
obviously should be avoided. The suffix of the second line (> nul) is to suppress the
deleting command to be displayed in screen so that the messages issued by system
commands (or model) will not interfered with the messages issued by PEST. The third
line is a SWAT model command line. The fourth line is a short Fortran program I coded
to convert partial information contained in the SWAT basins.rch file to a Site
Sample File (SSF), a file format that the TSPROC can read. The information of what
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