Source code for pybamm.expression_tree.parameter

#
# Parameter classes
#
import numbers
import sys

import numpy as np
import sympy

import pybamm


class Parameter(pybamm.Symbol):
    """
    A node in the expression tree representing a parameter.

    This node will be replaced by a :class:`pybamm.Scalar` node

    Parameters
    ----------

    name : str
        name of the node
    """

    def __init__(self, name):
        super().__init__(name)

    def create_copy(self):
        """See :meth:`pybamm.Symbol.new_copy()`."""
        return Parameter(self.name)

    def _evaluate_for_shape(self):
        """
        Returns the scalar 'NaN' to represent the shape of a parameter.
        See :meth:`pybamm.Symbol.evaluate_for_shape()`
        """
        return np.nan

    def is_constant(self):
        """See :meth:`pybamm.Symbol.is_constant()`."""
        # Parameter is not constant since it can become an InputParameter
        return False

    def to_equation(self):
        """Convert the node and its subtree into a SymPy equation."""
        if self.print_name is not None:
            return sympy.Symbol(self.print_name)
        else:
            return sympy.Symbol(self.name)


class FunctionParameter(pybamm.Symbol):
    """
    A node in the expression tree representing a function parameter.

    This node will be replaced by a :class:`pybamm.Function` node if a callable function
    is passed to the parameter values, and otherwise (in some rarer cases, such as
    constant current) a :class:`pybamm.Scalar` node.

    Parameters
    ----------

    name : str
        name of the node
    inputs : dict
        A dictionary with string keys and :class:`pybamm.Symbol` values representing
        the function inputs. The string keys should provide a reasonable description
        of what the input to the function is
        (e.g. "Electrolyte concentration [mol.m-3]")
    diff_variable : :class:`pybamm.Symbol`, optional
        if diff_variable is specified, the FunctionParameter node will be replaced by a
        :class:`pybamm.Function` and then differentiated with respect to diff_variable.
        Default is None.
    print_name : str, optional
        The name to show when printing. Default is 'calculate', in which case the name
        is calculated using sys._getframe().
    """

    def __init__(
        self,
        name,
        inputs,
        diff_variable=None,
        print_name="calculate",
    ):
        # assign diff variable
        self.diff_variable = diff_variable
        children_list = list(inputs.values())

        # Turn numbers into scalars
        for idx, child in enumerate(children_list):
            if isinstance(child, numbers.Number):
                children_list[idx] = pybamm.Scalar(child)

        domains = self.get_children_domains(children_list)
        super().__init__(name, children=children_list, domains=domains)

        self.input_names = list(inputs.keys())

        # Use the inspect module to find the function's "short name" from the
        # Parameters module that called it
        if print_name != "calculate":
            self.print_name = print_name
        else:
            frame = sys._getframe().f_back
            print_name = frame.f_code.co_name
            if print_name.startswith("_"):
                self.print_name = None
            else:
                try:
                    parent_param = frame.f_locals["self"]
                except KeyError:
                    parent_param = None
                if hasattr(parent_param, "domain") and parent_param.domain is not None:
                    # add "_n" or "_s" or "_p" if this comes from a Parameter class with
                    # a domain
                    d = parent_param.domain[0]
                    print_name += f"_{d}"
                self.print_name = print_name

    @property
    def input_names(self):
        return self._input_names

    def print_input_names(self):
        if self._input_names:
            for inp in self._input_names:
                print(inp)

    @input_names.setter
    def input_names(self, inp=None):
        if inp:
            if inp.__class__ is list:
                for i in inp:
                    if i.__class__ is not str:
                        raise TypeError(
                            "Inputs must be a provided as"
                            + "a dictionary of the form:"
                            + "{{str: :class:`pybamm.Symbol`}}"
                        )
            else:
                raise TypeError(
                    "Inputs must be a provided as"
                    + " a dictionary of the form:"
                    + "{{str: :class:`pybamm.Symbol`}}"
                )

        self._input_names = inp

    def set_id(self):
        """See :meth:`pybamm.Symbol.set_id`"""
        self._id = hash(
            (self.__class__, self.name, self.diff_variable)
            + tuple([child.id for child in self.children])
            + tuple(self.domain)
        )

    def diff(self, variable):
        """See :meth:`pybamm.Symbol.diff()`."""
        # return a new FunctionParameter, that knows it will need to be differentiated
        # when the parameters are set
        children_list = self.orphans
        input_names = self._input_names

        input_dict = {input_names[i]: children_list[i] for i in range(len(input_names))}

        return FunctionParameter(
            self.name,
            input_dict,
            diff_variable=variable,
            print_name=self.print_name + "'",
        )

    def create_copy(self):
        """See :meth:`pybamm.Symbol.new_copy()`."""
        out = self._function_parameter_new_copy(
            self._input_names, self.orphans, print_name=self.print_name
        )
        return out

    def _function_parameter_new_copy(
        self, input_names, children, print_name="calculate"
    ):
        """
        Returns a new copy of the function parameter.

        Inputs
        ------
        input_names : : list
            A list of str of the names of the children/function inputs
        children : : list
            A list of the children of the function

        Returns
        -------
        :class:`pybamm.FunctionParameter`
            A new copy of the function parameter
        """

        input_dict = {input_names[i]: children[i] for i in range(len(input_names))}

        return FunctionParameter(
            self.name,
            input_dict,
            diff_variable=self.diff_variable,
            print_name=print_name,
        )

    def _evaluate_for_shape(self):
        """
        Returns the sum of the evaluated children
        See :meth:`pybamm.Symbol.evaluate_for_shape()`
        """
        # add 1e-16 to avoid division by zero
        return sum(child.evaluate_for_shape() for child in self.children) + 1e-16

    def to_equation(self):
        """Convert the node and its subtree into a SymPy equation."""
        if self.print_name is not None:
            return sympy.Symbol(self.print_name)
        else:
            return sympy.Symbol(self.name)