Add recommended options for users to supply custom parameter bounds to the SA process.

[tobeycarman]

Currently in SA_setup_and_run.py the parameter sampling bounds are set only from the config file and are even around the initial value. The example sampling range is set to +/- 90% of initial value.

Users would like two things:

1. better support for expanded ranges - this might exist already by simply setting the values in the percent_diffs array to something greater than 1.0.

2. support for sampling bounds to be uneven with respect to the initial value (for example lower bound -5% of initial value, upper bound +600% of initial value).

This is not handled not by the SA_setup_and_run.py script, however a user could manually do it by writing their own wrapper (custom copy of SA_setup_and_run.py) or interactively in a python session, something like this:

import drivers.Sensitivity 

driver = drivers.Sensitivity.Sensitivity.fromfilename(config_file_name)

At this point the sample matrix is setup according to the params and percent diffs in the config file. For example:

driver.params[0]
{'name': 'nmax',
 'bounds': [0.4099999999999997, 7.789999999999999],
 'initial': 4.1,
 'cmtnum': 6,
 'pftnum': 0}

And

driver.sample_matrix['nmax_pft0']
0    5.596648
1    1.566672
2    6.899297
3    2.804200
4    4.634849
Name: nmax_pft0, dtype: float64

If want custom bounds, you can supply them and then re-generate the sample matrix:

driver.params[0]['bounds']=[-2000, 1000]
driver.sample_matrix = drivers.Sensitivity.generate_lhc( len(driver.sample_matrix), driver.params )

driver.sample_matrix['nmax_pft0']
Out[18]: 
0    -467.464092
1   -1996.862232
2     856.594456
3    -178.813187
4    -952.559730
Name: nmax_pft0, dtype: float64

It would be nice to better support this with settings in the .yaml config file so users do not need to write their own script.

[tobeycarman]

Addressed this in sha: 912c0ee .
Opted to expose this in the config file. More details in the sample configs.