utils.py 文件源码

def eval_expression(expr, values=None):
    """
    Evaluate a symbolic expression and returns a numerical array.
    :param expr: A symbolic expression to evaluate, in the form of a N_terms * N_Vars matrix
    :param values: None, or a dictionary of variable:value pairs, to substitute in the symbolic expression.
    :return: An evaled expression, in the form of an N_terms array.
    """
    n_coeffs = expr.shape[0]
    evaled_expr = np.zeros(n_coeffs)
    for (i, term) in enumerate(expr):
        if values:
            evaled_term = np.array([values.get(elem, 0) if isinstance(elem, str) else elem for elem in term])
        else:
            evaled_term = np.array(
                [0 if isinstance(elem, str) else elem for elem in term])  # All variables at 0
        evaled_expr[i] = np.product(evaled_term.astype(float))  # Gradient is the product of values
    return evaled_expr