User's guide of Proceessing Modflow 5.0

150 Processing Modflow
- NPHINORED is the first termination criterion. A value of 3 is often suitable. If PEST
has failed to lower the objective function over NPHINORED successive iterations, the
program stops.
- RELPARSTP and NRELPAR represent the second termination criterion. If the
< Options:
magnitude of the maximum relative parameter change between optimization iterations
is less than RELPARSTP over NRELPAR successive iterations, the program stops. The
relative parameter change between optimization iterations for any parameter is calculated
using equation 3.55. For many cases, a value of 0.01 for RELPARSTP and a value of 3
for NRELPAR is adequate.
When the optimization process is complete, one of the termination criteria having been met
(or perhaps another termination criterion such as zero objective function or zero objective
function gradient, for which no user-supplied settings are required), PEST writes some
information concerning the optimized parameter set to its run record file PESTCTL.REC.
This file is saved in the data directory of your model. It tabulates the optimal values and the
95% confidence intervals pertaining to all adjustable parameters. It also tabulates the
model-calculated values based on these parameters, together with the residuals, i.e., the
differences between measured and model-calculated values. If you wish, PEST will write
the parameter covariance matrix, the parameter correlation coefficient matrix and the
matrix of normalised eigenvectors of the covariance matrix to the run record file
PESTCTL.REC.
If the option Save data for a possible restart is checked, PEST will dump the contents
of many of its data arrays to a binary file at the beginning of each optimization iteration; this
allows PEST to be restarted later if execution is prematurely terminated. If subsequent PEST
execution is initiated using the "/r" command line switch (see the PEST manual for details),
it will recommence execution at the beginning of the iteration during which it was
interrupted.
If the option Include decimal point even if redundant is not checked, PEST will omit
the decimal point from parameter values on model input files if the decimal point is
redundant, thus making room for the use of one extra significant figure. If this option is
checked, PEST will ensure that the decimal point is always present.
3.6.5 PEST (Inverse Modeling)