def add_parameter(self, expression):
"""
Adds a parameter to the problem from a string expression
Parameters:
expression: string, variable name expression in python code with a value
Example:
problem.add_parameter('A = 5')
problem.add_parameter('p[i,j] = 0.20 if j==0 else 0.30 for i in range(24) for j in range(5)')
"""
# parse the rest of the expression
(name, indexvalue, value) = parse.variable(expression)
if value == []:
raise ValueError("Parameters are required to have a value. {}".format(expression))
# add the parameter
if len(indexvalue) == 0:
setattr(self.model, name, pm.Param(default=value, mutable=True))
else:
setattr(self.model, name, pm.Param(indexvalue, default=lambda model, *args: value[args], mutable=True))
self.parameters[name] = getattr(self.model, name)
def add_variable(self, expression):
"""
Adds a variable to the problem from a string expression
Parameters:
expression: string, variable name expression in python code with optional default value
Example:
problem = jsonipopt.Problem()
problem.add_variable('Reals x[j] for j in range(25)')
problem.add_variable('Reals p[i,j] = 0.20 if j==0 else 0.30 for i in range(24) for j in range(5)')
"""
# get the domain of the variable
splitexpression = expression.split(" ")
domainexpr = splitexpression[0]
if domainexpr in self.validDomainExpressions:
domain = eval("pm." + domainexpr)
else:
raise ValueError(
"The domain {} is not a valid domain. Valid domains are:\n{}".format(
domainexpr, self.validDomainExpressions
)
)
restexpression = " ".join(splitexpression[1:])
# parse the rest of the expression
(name, indexvalue, initial) = parse.variable(restexpression)
# add the variable
if len(indexvalue) == 0:
if initial == []:
setattr(self.model, name, pm.Var(domain=domain))
else:
setattr(self.model, name, pm.Var(domain=domain, initialize=initial))
else:
if initial == []:
setattr(self.model, name, pm.Var(indexvalue, domain=domain))
else:
setattr(
self.model, name, pm.Var(indexvalue, domain=domain, initialize=lambda model, *args: initial[args])
)
self.variables[name] = getattr(self.model, name)
