# import dependencies
from pyomo.environ import ConcreteModel, Set, Var, Objective, minimize, Constraint, log
from pyomo.core.expr.numvalue import NumericValue
import numpy as np
import pandas as pd
from ..constant import CET_ADDI, CET_MULT, FUN_PROD, FUN_COST, RTS_CRS, RTS_VRS, OPT_DEFAULT, OPT_LOCAL
from .tools import optimize_model
[docs]
class CNLSZG1:
"""initial Group-VC-added CNLSZ (CNLSZ+G) model
"""
[docs]
def __init__(self, y, x, z, cutactive, cet=CET_ADDI, fun=FUN_PROD, rts=RTS_VRS):
"""CNLSZ+G model
Args:
y (float): output variable.
x (float): input variables.
z (float, optional): Contextual variable(s). Defaults to None.
cutactive (float): active concavity constraint.
cet (String, optional): CET_ADDI (additive composite error term) or CET_MULT (multiplicative composite error term). Defaults to CET_ADDI.
fun (String, optional): FUN_PROD (production frontier) or FUN_COST (cost frontier). Defaults to FUN_PROD.
rts (String, optional): RTS_VRS (variable returns to scale) or RTS_CRS (constant returns to scale). Defaults to RTS_VRS.
"""
# TODO(error/warning handling): Check the configuration of the model exist
self.x, self.y, self.z, self.cet, self.fun, self.rts = x, y, z, cet, fun, rts
self.cutactive = cutactive
# Initialize the CNLS model
self.__model__ = ConcreteModel()
# Initialize the sets
self.__model__.I = Set(initialize=range(len(self.y)))
self.__model__.J = Set(initialize=range(len(self.x[0])))
self.__model__.K = Set(initialize=range(len(self.z[0])))
# Initialize the variables
self.__model__.alpha = Var(self.__model__.I, doc='alpha')
self.__model__.beta = Var(self.__model__.I,
self.__model__.J,
bounds=(0.0, None),
doc='beta')
self.__model__.lamda = Var(self.__model__.K, doc='Zvalue')
self.__model__.epsilon = Var(self.__model__.I, doc='residual')
self.__model__.frontier = Var(self.__model__.I,
bounds=(0.0, None),
doc='estimated frontier')
# Setup the objective function and constraints
self.__model__.objective = Objective(rule=self.__objective_rule(),
sense=minimize,
doc='objective function')
self.__model__.regression_rule = Constraint(self.__model__.I,
rule=self.__regression_rule(),
doc='regression equation')
if self.cet == CET_MULT:
self.__model__.log_rule = Constraint(self.__model__.I,
rule=self.__log_rule(),
doc='log-transformed regression equation')
self.__model__.afriat_rule = Constraint(self.__model__.I,
rule=self.__afriat_rule(),
doc='elementary Afriat approach')
self.__model__.sweet_rule = Constraint(self.__model__.I,
self.__model__.I,
rule=self.__sweet_rule(),
doc='sweet spot approach')
# Optimize model
self.optimization_status, self.problem_status = 0, 0
[docs]
def optimize(self, email=OPT_LOCAL, solver=OPT_DEFAULT):
"""Optimize the function by requested method
Args:
email (string): The email address for remote optimization. It will optimize locally if OPT_LOCAL is given.
solver (string): The solver chosen for optimization. It will optimize with default solver if OPT_DEFAULT is given.
"""
# TODO(error/warning handling): Check problem status after optimization
self.problem_status, self.optimization_status = optimize_model(
self.__model__, email, self.cet, solver)
def __objective_rule(self):
"""Return the proper objective function"""
def objective_rule(model):
return sum(model.epsilon[i] ** 2 for i in model.I)
return objective_rule
def __regression_rule(self):
"""Return the proper regression constraint"""
if self.cet == CET_ADDI:
if self.rts == RTS_VRS:
def regression_rule(model, i):
return self.y[i] == model.alpha[i] \
+ sum(model.beta[i, j] * self.x[i][j] for j in model.J) \
+ sum(model.lamda[k] * self.z[i][k]
for k in model.K) + model.epsilon[i]
return regression_rule
elif self.rts == RTS_CRS:
def regression_rule(model, i):
return self.y[i] == sum(model.beta[i, j] * self.x[i][j] for j in model.J) \
+ sum(model.lamda[k] * self.z[i][k]
for k in model.K) + model.epsilon[i]
return regression_rule
elif self.cet == CET_MULT:
def regression_rule(model, i):
return log(self.y[i]) == log(model.frontier[i] + 1) + sum(model.lamda[k] * self.z[i][k] for k in model.K) + model.epsilon[i]
return regression_rule
raise ValueError("Undefined model parameters.")
def __log_rule(self):
"""Return the proper log constraint"""
if self.cet == CET_MULT:
if self.rts == RTS_VRS:
def log_rule(model, i):
return model.frontier[i] == model.alpha[i] + sum(
model.beta[i, j] * self.x[i][j] for j in model.J) - 1
return log_rule
elif self.rts == RTS_CRS:
def log_rule(model, i):
return model.frontier[i] == sum(
model.beta[i, j] * self.x[i][j] for j in model.J) - 1
return log_rule
raise ValueError("Undefined model parameters.")
def __afriat_rule(self):
"""Return the proper elementary Afriat approach constraint"""
if self.fun == FUN_PROD:
__operator = NumericValue.__le__
elif self.fun == FUN_COST:
__operator = NumericValue.__ge__
if self.cet == CET_ADDI:
if self.rts == RTS_VRS:
def afriat_rule(model, i):
return __operator(
model.alpha[i] + sum(model.beta[i, j] * self.x[i][j]
for j in model.J),
model.alpha[self.__model__.I.nextw(i)] +
sum(model.beta[self.__model__.I.nextw(i), j] * self.x[i][j]
for j in model.J))
return afriat_rule
elif self.rts == RTS_CRS:
def afriat_rule(model, i):
return __operator(
sum(model.beta[i, j] * self.x[i][j]
for j in model.J),
sum(model.beta[self.__model__.I.nextw(i), j] * self.x[i][j]
for j in model.J))
return afriat_rule
elif self.cet == CET_MULT:
if self.rts == RTS_VRS:
def afriat_rule(model, i):
return __operator(
model.alpha[i] + sum(model.beta[i, j] * self.x[i][j]
for j in model.J),
model.alpha[self.__model__.I.nextw(i)] +
sum(model.beta[self.__model__.I.nextw(i), j] * self.x[i][j]
for j in model.J))
return afriat_rule
elif self.rts == RTS_CRS:
def afriat_rule(model, i):
return __operator(
sum(model.beta[i, j] * self.x[i][j] for j in model.J),
sum(model.beta[self.__model__.I.nextw(i), j] * self.x[i][j] for j in model.J))
return afriat_rule
raise ValueError("Undefined model parameters.")
def __sweet_rule(self, ):
"""Return the proper sweet spot approach constraint"""
if self.fun == FUN_PROD:
__operator = NumericValue.__le__
elif self.fun == FUN_COST:
__operator = NumericValue.__ge__
if self.cet == CET_ADDI:
if self.rts == RTS_VRS:
def sweet_rule(model, i, h):
if self.cutactive[i][h]:
if i == h:
return Constraint.Skip
return __operator(model.alpha[i] + sum(model.beta[i, j] * self.x[i][j]
for j in model.J),
model.alpha[h] + sum(model.beta[h, j] * self.x[i][j]
for j in model.J))
return Constraint.Skip
return sweet_rule
elif self.rts == RTS_CRS:
def sweet_rule(model, i, h):
if self.cutactive[i][h]:
if i == h:
return Constraint.Skip
return __operator(sum(model.beta[i, j] * self.x[i][j]
for j in model.J),
sum(model.beta[h, j] * self.x[i][j]
for j in model.J))
return Constraint.Skip
return sweet_rule
elif self.cet == CET_MULT:
if self.rts == RTS_VRS:
def sweet_rule(model, i, h):
if self.cutactive[i][h]:
if i == h:
return Constraint.Skip
return __operator(model.alpha[i] + sum(model.beta[i, j] * self.x[i][j]
for j in model.J),
model.alpha[h] + sum(model.beta[h, j] * self.x[i][j]
for j in model.J))
return Constraint.Skip
return sweet_rule
elif self.rts == RTS_CRS:
def sweet_rule(model, i, h):
if self.cutactive[i][h]:
if i == h:
return Constraint.Skip
return __operator(sum(model.beta[i, j] * self.x[i][j] for j in model.J),
sum(model.beta[h, j] * self.x[i][j] for j in model.J))
return Constraint.Skip
return sweet_rule
raise ValueError("Undefined model parameters.")
[docs]
def get_alpha(self):
"""Return alpha value by array"""
if self.optimization_status == 0:
self.optimize()
alpha = list(self.__model__.alpha[:].value)
return np.asarray(alpha)
[docs]
def get_beta(self):
"""Return beta value by array"""
if self.optimization_status == 0:
self.optimize()
beta = np.asarray([i + tuple([j]) for i, j in zip(list(self.__model__.beta),
list(self.__model__.beta[:, :].value))])
beta = pd.DataFrame(beta, columns=['Name', 'Key', 'Value'])
beta = beta.pivot(index='Name', columns='Key', values='Value')
return beta.to_numpy()