"""
This file is part of CLIMADA.
Copyright (C) 2017 ETH Zurich, CLIMADA contributors listed in AUTHORS.
CLIMADA is free software: you can redistribute it and/or modify it under the
terms of the GNU General Public License as published by the Free
Software Foundation, version 3.
CLIMADA is distributed in the hope that it will be useful, but WITHOUT ANY
WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A
PARTICULAR PURPOSE. See the GNU General Public License for more details.
You should have received a copy of the GNU General Public License along
with CLIMADA. If not, see <https://www.gnu.org/licenses/>.
---
Define Calc (uncertainty calculate) class.
"""
import logging
import copy
import itertools
import datetime as dt
import pandas as pd
import numpy as np
from climada.util.value_representation import sig_dig as u_sig_dig
from climada.engine.unsequa import UncOutput
LOGGER = logging.getLogger(__name__)
[docs]
class Calc():
"""
Base class for uncertainty quantification
Contains the generic sampling and sensitivity methods. For computing
the uncertainty distribution for specific CLIMADA outputs see
the subclass CalcImpact and CalcCostBenefit.
Attributes
----------
_input_var_names : tuple(str)
Names of the required uncertainty variables.
_metric_names : tuple(str)
Names of the output metrics.
Notes
-----
Parallelization logics: for computation of the uncertainty users may
specify a number N of processes on which to perform the computations in
parallel. Since the computation for each individual sample of the
input parameters is independent of one another, we implemented a simple
distribution on the processes.
1. The samples are divided in N equal sub-sample chunks
2. Each chunk of samples is sent as one to a node for processing
Hence, this is equivalent to the user running the computation N times,
once for each sub-sample.
Note that for each process, all the input variables must be copied once,
and hence each parallel process requires roughly the same amount of memory
as if a single process would be used.
This approach differs from the usual parallelization strategy (where individual
samples are distributed), because each sample requires the entire input data.
With this method, copying data between processes is reduced to a minimum.
Parallelization is currently not available for the sensitivity computation,
as this requires all samples simoultenaously in the current implementation
of the SaLib library.
"""
_input_var_names = ()
"""Names of the required uncertainty variables"""
_metric_names = ()
"""Names of the output metrics"""
[docs]
def __init__(self):
"""
Empty constructor to be overwritten by subclasses
"""
[docs]
def check_distr(self):
"""
Log warning if input parameters repeated among input variables
Returns
-------
True.
"""
distr_dict = dict()
for input_var in self.input_vars:
for input_param_name, input_param_func in input_var.distr_dict.items():
if input_param_name in distr_dict:
func = distr_dict[input_param_name]
x = np.linspace(func.ppf(0.01), func.ppf(0.99), 100)
if not np.all(func.cdf(x) == input_param_func.cdf(x)):
raise ValueError(
f"The input parameter {input_param_name}"
" is shared among two input variables with"
" different distributions."
)
LOGGER.warning(
"\n\nThe input parameter %s is shared "
"among at least 2 input variables. Their uncertainty is "
"thus computed with the same samples for this "
"input paramter.\n\n", input_param_name
)
distr_dict[input_param_name] = input_param_func
return True
@property
def input_vars(self):
"""
Uncertainty variables
Returns
-------
tuple(UncVar)
All uncertainty variables associated with the calculation
"""
return tuple(getattr(self, var) for var in self._input_var_names)
@property
def distr_dict(self):
"""
Dictionary of the input variable distribution
Probabilitiy density distribution of all the parameters of all the
uncertainty variables listed in self.InputVars
Returns
-------
distr_dict : dict( sp.stats objects )
Dictionary of all probability density distributions.
"""
distr_dict = dict()
for input_var in self.input_vars:
distr_dict.update(input_var.distr_dict)
return distr_dict
[docs]
def est_comp_time(self, n_samples, time_one_run, processes=None):
"""
Estimate the computation time
Parameters
----------
n_samples : int/float
The total number of samples
time_one_run : int/float
Estimated computation time for one parameter set in seconds
pool : pathos.pool, optional
pool that would be used for parallel computation.
The default is None.
Returns
-------
Estimated computation time in secs.
"""
time_one_run = u_sig_dig(time_one_run, n_sig_dig=3)
if time_one_run > 5:
LOGGER.warning("Computation time for one set of parameters is "
"%.2fs. This is rather long."
"Potential reasons: InputVars are loading data, centroids have "
"been assigned to exp before defining input_var, ..."
"\n If computation cannot be reduced, consider using"
" a surrogate model https://www.uqlab.com/", time_one_run)
total_time = n_samples * time_one_run / processes
LOGGER.info("\n\nEstimated computaion time: %s\n",
dt.timedelta(seconds=total_time))
return total_time
[docs]
def make_sample(self, N, sampling_method='saltelli',
sampling_kwargs = None):
"""
Make samples of the input variables
For all input parameters, sample from their respective
distributions using the chosen sampling_method from SALib.
https://salib.readthedocs.io/en/latest/api.html
This sets the attributes
unc_output.samples_df,
unc_output.sampling_method,
unc_output.sampling_kwargs.
Parameters
----------
N : int
Number of samples as used in the sampling method from SALib
sampling_method : str, optional
The sampling method as defined in SALib. Possible choices:
'saltelli', 'fast_sampler', 'latin', 'morris', 'dgsm', 'ff'
https://salib.readthedocs.io/en/latest/api.html
The default is 'saltelli'.
sampling_kwargs : kwargs, optional
Optional keyword arguments passed on to the SALib sampling_method.
The default is None.
Returns
-------
unc_output : climada.engine.uncertainty.unc_output.UncOutput()
Uncertainty data object with the samples
See Also
--------
SALib.sample: sampling methods from SALib SALib.sample
https://salib.readthedocs.io/en/latest/api.html
"""
if sampling_kwargs is None:
sampling_kwargs = {}
param_labels = list(self.distr_dict.keys())
problem_sa = {
'num_vars' : len(param_labels),
'names' : param_labels,
'bounds' : [[0, 1]]*len(param_labels)
}
uniform_base_sample = self._make_uniform_base_sample(N, problem_sa,
sampling_method,
sampling_kwargs)
df_samples = pd.DataFrame(uniform_base_sample, columns=param_labels)
for param in list(df_samples):
df_samples[param] = df_samples[param].apply(
self.distr_dict[param].ppf
)
sampling_kwargs = {
key: str(val)
for key, val in sampling_kwargs.items()
}
df_samples.attrs['sampling_method'] = sampling_method
df_samples.attrs['sampling_kwargs'] = tuple(sampling_kwargs.items())
unc_output = UncOutput(df_samples)
LOGGER.info("Effective number of made samples: %d", unc_output.n_samples)
return unc_output
def _make_uniform_base_sample(self, N, problem_sa, sampling_method,
sampling_kwargs):
"""
Make a uniform distributed [0,1] sample for the defined
uncertainty parameters (self.param_labels) with the chosen
method from SALib (self.sampling_method)
https://salib.readthedocs.io/en/latest/api.html
Parameters
----------
N: int
Number of samples as defined for the SALib sample method.
Note that the effective number of created samples might be
larger (c.f. SALib)
problem_sa: dict()
Description of input variables. Is used as argument for the
SALib sampling method.
sampling_method: string
The sampling method as defined in SALib. Possible choices:
'saltelli', 'fast_sampler', 'latin', 'morris', 'dgsm', 'ff'
https://salib.readthedocs.io/en/latest/api.html
sampling_kwargs: dict()
Optional keyword arguments passed on to the SALib sampling method.
Returns
-------
sample_uniform : np.matrix
Returns a NumPy matrix containing the sampled uncertainty
parameters using the defined sampling method
"""
if sampling_kwargs is None:
sampling_kwargs = {}
#Import the named submodule from the SALib sample module
#From the workings of __import__ the use of 'from_list' is necessary
#c.f. https://stackoverflow.com/questions/2724260/why-does-pythons-import-require-fromlist
import importlib # pylint: disable=import-outside-toplevel
salib_sampling_method = importlib.import_module(f'SALib.sample.{sampling_method}')
sample_uniform = salib_sampling_method.sample(
problem = problem_sa, N = N, **sampling_kwargs)
return sample_uniform
[docs]
def sensitivity(self, unc_output, sensitivity_method = 'sobol',
sensitivity_kwargs = None):
"""
Compute the sensitivity indices using SALib.
Prior to doing the sensitivity analysis, one must compute the
uncertainty (distribution) of the output values
(with self.uncertainty()) for all the samples
(rows of self.samples_df).
According to Wikipedia, sensitivity analysis is “the study of how the
uncertainty in the output of a mathematical model or system (numerical
or otherwise) can be apportioned to different sources of uncertainty
in its inputs.” The sensitivity of each input is often represented by
a numeric value, called the sensitivity index. Sensitivity indices
come in several forms.
This sets the attributes:
sens_output.sensistivity_method
sens_output.sensitivity_kwargs
sens_output.xxx_sens_df for each metric unc_output.xxx_unc_df
Parameters
----------
unc_output : climada.engine.unsequa.UncOutput
Uncertainty data object in which to store the sensitivity indices
sensitivity_method : str, optional
sensitivity analysis method from SALib.analyse
Possible choices:
'fast', 'rbd_fact', 'morris', 'sobol', 'delta', 'ff'
The default is 'sobol'.
Note that in Salib, sampling methods and sensitivity analysis
methods should be used in specific pairs.
https://salib.readthedocs.io/en/latest/api.html
sensitivity_kwargs: dict, optional
Keyword arguments of the chosen SALib analyse method.
The default is to use SALib's default arguments.
Returns
-------
sens_output : climada.engine.unsequa.UncOutput
Uncertainty data object with all the sensitivity indices,
and all the uncertainty data copied over from unc_output.
"""
if sensitivity_kwargs is None:
sensitivity_kwargs = {}
#Check compatibility of sampling and sensitivity methods
unc_output.check_salib(sensitivity_method)
#Import the named submodule from the SALib analyse module
#From the workings of __import__ the use of 'from_list' is necessary
#c.f. https://stackoverflow.com/questions/2724260/why-does-pythons-import-require-fromlist
method = getattr(
__import__('SALib.analyze',
fromlist=[sensitivity_method]
),
sensitivity_method
)
sens_output = copy.deepcopy(unc_output)
#Certaint Salib method required model input (X) and output (Y), others
#need only ouput (Y)
salib_kwargs = method.analyze.__code__.co_varnames # obtain all kwargs of the salib method
X = unc_output.samples_df.to_numpy() if 'X' in salib_kwargs else None
for metric_name in self._metric_names:
unc_df = unc_output.get_unc_df(metric_name)
sens_df = _calc_sens_df(method, unc_output.problem_sa, sensitivity_kwargs,
unc_output.param_labels, X, unc_df)
sens_output.set_sens_df(metric_name, sens_df)
sensitivity_kwargs = {
key: str(val)
for key, val in sensitivity_kwargs.items()}
sens_output.sensitivity_method = sensitivity_method
sens_output.sensitivity_kwargs = tuple(sensitivity_kwargs.items())
return sens_output
def _multiprocess_chunksize(samples_df, processes):
"""Divides the samples into chunks for multiprocesses computing
The goal is to send to each processing node an equal number
of samples to process. This make the parallel processing anologous
to running the uncertainty assessment independently on each nodes
for a subset of the samples, instead of distributing individual samples
on the nodes dynamically. Hence, all the heavy input variables
are copied/sent once to each node only.
Parameters
----------
samples_df : pd.DataFrame
samples dataframe
processes : int
number of processes
Returns
-------
int
the number of samples in each chunk
"""
return np.ceil(
samples_df.shape[0] / processes
).astype(int)
def _transpose_chunked_data(metrics):
"""Transposes the output metrics lists from one list per
chunk of samples to one list per output metric
[ [x1, [y1, z1]], [x2, [y2, z2]] ] ->
[ [x1, x2], [[y1, z1], [y2, z2]] ]
Parameters
----------
metrics : list
list of list as returned by the uncertainty mapings
Returns
-------
list
list of climada output uncertainty
See Also
--------
calc_impact._map_impact_calc
map for impact uncertainty
calc_cost_benefits._map_costben_calc
map for cost benefit uncertainty
"""
return [
list(itertools.chain.from_iterable(x))
for x in zip(*metrics)
]
def _sample_parallel_iterator(samples, chunksize, **kwargs):
"""
Make iterator over chunks of samples
with repeated kwargs for each chunk.
Parameters
----------
samples : pd.DataFrame
Dataframe of samples
**kwargs : arguments to repeat
Arguments to repeat for parallel computations
Returns
-------
iterator
suitable for methods _map_impact_calc and _map_costben_calc
"""
def _chunker(df, size):
"""
Divide the dataframe into chunks of size number of lines
"""
for pos in range(0, len(df), size):
yield df.iloc[pos:pos + size]
return zip(
_chunker(samples, chunksize),
*(itertools.repeat(item) for item in kwargs.values())
)
def _calc_sens_df(method, problem_sa, sensitivity_kwargs, param_labels, X, unc_df):
"""Compute the sensitifity indices
Parameters
----------
method : str
SALib sensitivity method name
problem_sa :dict
dictionnary for sensitivty method for SALib
sensitivity_kwargs : kwargs
passed on to SALib.method.analyse
param_labels : list(str)
list of name of uncertainty input parameters
X : numpy.ndarray
array of input parameter samples
unc_df : DataFrame
Dataframe containing the uncertainty values
Returns
-------
DataFrame
Values of the sensitivity indices
"""
sens_first_order_dict = {}
sens_second_order_dict = {}
for (submetric_name, metric_unc) in unc_df.items():
Y = metric_unc.to_numpy()
if X is not None:
sens_indices = method.analyze(problem_sa, X, Y,
**sensitivity_kwargs)
else:
sens_indices = method.analyze(problem_sa, Y,
**sensitivity_kwargs)
sens_first_order = np.array([
np.array(si_val_array)
for si, si_val_array in sens_indices.items()
if (np.array(si_val_array).ndim == 1 and si!='names') # dirty trick due to Salib incoherent output
]).ravel()
sens_first_order_dict[submetric_name] = sens_first_order
sens_second_order = np.array([
np.array(si_val_array)
for si_val_array in sens_indices.values()
if np.array(si_val_array).ndim == 2
]).ravel()
sens_second_order_dict[submetric_name] = sens_second_order
sens_first_order_df = pd.DataFrame(sens_first_order_dict, dtype=np.number)
if not sens_first_order_df.empty:
si_names_first_order, param_names_first_order = _si_param_first(param_labels, sens_indices)
sens_first_order_df.insert(0, 'si', si_names_first_order)
sens_first_order_df.insert(1, 'param', param_names_first_order)
sens_first_order_df.insert(2, 'param2', None)
sens_second_order_df = pd.DataFrame(sens_second_order_dict)
if not sens_second_order_df.empty:
si_names_second_order, param_names_second_order, param_names_second_order_2 = \
_si_param_second(param_labels, sens_indices)
sens_second_order_df.insert(0, 'si', si_names_second_order,)
sens_second_order_df.insert(1, 'param', param_names_second_order)
sens_second_order_df.insert(2, 'param2', param_names_second_order_2)
sens_df = pd.concat(
[sens_first_order_df, sens_second_order_df]
).reset_index(drop=True)
return sens_df
def _si_param_first(param_labels, sens_indices):
"""Extract the first order sensivity indices from SALib ouput
Parameters
----------
param_labels : list(str)
name of the unceratinty input parameters
sens_indices : dict
sensitivity indidices dictionnary as produced by SALib
Returns
-------
si_names_first_order, param_names_first_order: list, list
Names of the sensivity indices of first order for all input parameters
and Parameter names for each sentivity index
"""
n_params = len(param_labels)
si_name_first_order_list = [
key
for key, array in sens_indices.items()
if (np.array(array).ndim == 1 and key!='names') # dirty trick due to Salib incoherent output
]
si_names_first_order = [
si
for si in si_name_first_order_list
for _ in range(n_params)
]
param_names_first_order = param_labels * len(si_name_first_order_list)
return si_names_first_order, param_names_first_order
def _si_param_second(param_labels, sens_indices):
"""Extract second order sensitivity indices
Parameters
----------
param_labels : list(str)
name of the unceratinty input parameters
sens_indices : dict
sensitivity indidices dictionnary as produced by SALib
Returns
-------
si_names_second_order, param_names_second_order, param_names_second_order_2: list, list, list
Names of the sensivity indices of second order for all input parameters
and Pairs of parameter names for each 2nd order sentivity index
"""
n_params = len(param_labels)
si_name_second_order_list = [
key
for key, array in sens_indices.items()
if np.array(array).ndim == 2
]
si_names_second_order = [
si
for si in si_name_second_order_list
for _ in range(n_params**2)
]
param_names_second_order_2 = param_labels \
* len(si_name_second_order_list) * n_params
param_names_second_order = [
param
for param in param_labels
for _ in range(n_params)
] * len(si_name_second_order_list)
return si_names_second_order, param_names_second_order, param_names_second_order_2
