A Monte Carlo search of parameter space.
montecarlo [nloop] [iseed]
The MONTECARLO method randomly samples the parameter space bounded by the
lower and upper limits of each thawed parameter.
At each chosen point, the fit statistic is evaluated.
The advantage of MONTECARLO is that it can provide a good sampling of
parameter space. This is good for situations where the best-fit
parameter values are not easily guessed a priori, and where there is a
high probability that false minima would be found if
one-shot techniques such as POWELL are used instead.
Its disadvantages are that it can be slow (if many points are selected),
and that because of the
random, discrete nature of the search, the global
fit-statistic minimum can easily be missed.
(The latter disadvantage may be
alleviated by combining a Monte Carlo search with Powell minimization;
see MONTE-POWELL.)
If the number of thawed parameters is larger than 3, one should increase
the value of nloop from its default value. Otherwise the sampling
may be too sparse to estimate the global fit-statistic minimum well.
nloop |
integer |
500 |
1 |
1.6777e+7 |
iseed |
integer |
14391 |
-1.e+20 |
1.e+20 |
Parameter=nloop (integer default=500 min=1 max=1.6777e+7)
Number of parameter space samples.
Parameter=iseed (integer default=14391 min=-1.e+20 max=1.e+20)
Seed for random number generator.
- sherpa
-
get_method_expr,
grid,
grid-powell,
levenberg-marquardt,
method,
monte-lm,
monte-powell,
powell,
sigma-rejection,
simplex,
simul-ann-1,
simul-ann-2,
simul-pow-1,
simul-pow-2,
usermethod
|