PyRates.pyrates.backend

pyrates.backend module

PyRates backend module including the following sub-modules:

• parser

  Used to parse string-based equations into symbolic backend representations.

• computegraph

  Used to realize hierarchical structure between mathematical equations.

• backend_wrapper

  Interface to the backends available in PyRates.

exception pyrates.backend.PyRatesException

Bases: Exception

exception pyrates.backend.PyRatesWarning

Bases: Warning

• PyRates.pyrates.backend.base
  • pyrates.backend.base module
  • pyrates.backend.base.base_backend module
  • pyrates.backend.base.base_funcs module
• PyRates.pyrates.backend.fortran
  • pyrates.backend.fortran module
  • pyrates.backend.fortran.fortran_backend module
  • pyrates.backend.fortran.fortran_funcs module
• PyRates.pyrates.backend.julia
  • pyrates.backend.julia module
  • pyrates.backend.julia.julia_backend module
  • pyrates.backend.julia.julia_funcs module
• PyRates.pyrates.backend.tensorflow
  • pyrates.backend.tensorflow module
  • pyrates.backend.tensorflow.tensorflow_backend module
  • pyrates.backend.tensorflow.tensorflow_funcs module
• PyRates.pyrates.backend.torch
  • pyrates.backend.torch module
  • pyrates.backend.torch.torch_backend module
  • pyrates.backend.torch.torch_funcs module

pyrates.backend.computegraph module

This module provides the backend class that should be used to set up any backend in pyrates.

class pyrates.backend.computegraph.ComputeGraph(backend: str, **kwargs)

Bases: networkx.classes.multidigraph.MultiDiGraph

Creates a compute graph where nodes are all constants and variables of the network and edges are the mathematical operations linking those variables/constants together to form equations.

add_op(inputs: Union[list, tuple], label: str, expr: sympy.core.expr.Expr, func: Callable, **kwargs)

add_var(label: str, value: Any, vtype: str, **kwargs)

add_var_update(var: str, update: str, differential_equation: bool = False)

clear() → None

Deletes build directory and removes all compute graph nodes

compile()

eval_graph()

eval_node(n)

eval_nodes(nodes: Iterable[T_co])

eval_subgraph(n)

get_op(op: str, **kwargs) → dict

get_var(var: str, from_backend: bool = False)

remove_subgraph(n)

run(func: Callable, func_args: tuple, T: float, dt: float, dts: Optional[float] = None, outputs: Optional[dict] = None, **kwargs)

state_vars

to_func(func_name: str, to_file: bool = True, dt_adapt: bool = True, **kwargs)

class pyrates.backend.computegraph.ComputeNode(name: str, symbol: Union[sympy.core.symbol.Symbol, sympy.core.expr.Expr, sympy.core.function.Function], dtype: Optional[str] = None, shape: Optional[tuple] = None, def_shape: Optional[tuple] = None)

Bases: object

Base class for adding variables to the compute graph. Creates a numpy array with additional attributes for variable identification/retrieval from graph. Should be used as parent class for custom variable classes.

Parameters:

• name – Full name of the variable in the original NetworkGraph (including the node and operator it belongs to).
• dtype – Data-type of the variable. For valid data-types, check the documentation of the backend in use.
• shape – Shape of the variable.

dtype

is_complex

is_constant

is_float

name

reshape(shape: tuple, **kwargs)

set_value(v: Union[float, numpy.ndarray])

shape

squeeze(axis=None)

symbol

value

Returns current value of BaseVar.

class pyrates.backend.computegraph.ComputeOp(name: str, symbol: Union[sympy.core.symbol.Symbol, sympy.core.expr.Expr, sympy.core.function.Function], func: Callable, expr: sympy.core.expr.Expr, dtype: Optional[str] = None, shape: Optional[str] = None)

Bases: pyrates.backend.computegraph.ComputeNode

Class for ComputeGraph nodes that represent mathematical operations.

dtype

expr

func

is_constant

name

shape

symbol

class pyrates.backend.computegraph.ComputeVar(name: str, symbol: Union[sympy.core.symbol.Symbol, sympy.core.expr.Expr, sympy.core.function.Function], vtype: str, dtype: Optional[str] = None, shape: Optional[str] = None, value: Union[list, numpy.ndarray, None] = None, def_shape: Optional[tuple] = None)

Bases: pyrates.backend.computegraph.ComputeNode

Class for variables and vector-valued constants in the ComputeGraph.

dtype

is_constant

name

shape

symbol

vtype

pyrates.backend.parser module

This module provides parser classes and functions to parse string-based equations into symbolic representations of operations.

class pyrates.backend.parser.Algebra(**kwargs)

Bases: object

class pyrates.backend.parser.ExpressionParser(expr_str: str, args: dict, cg: pyrates.backend.computegraph.ComputeGraph, def_shape: Optional[tuple] = None, parsing_method: str = 'sympy')

Bases: object

Class for parsing mathematical expressions from a string format into a symbolic representation of the mathematical operation expressed by it.

Parameters:

• expr_str – Mathematical expression in string format.
• args – Dictionary containing all variables and functions needed to evaluate the expression.
• cg – ComputeGraph instance in which to parse all variables and operations. See pyrates.backend.computegraph.ComputeGraph for a full documentation of its methods and attributes.
• parsing_method – Name of the parsing method to use. Valid options: sympy for a sympy-based parser, pyrates for the pyrates-internal, pyparsing-based parser.

lhs

Boolean, indicates whether expression is left-hand side or right-hand side of an equation

rhs

PyRatesOp for the evaluation of the right-hand side of the equation

vars

Dictionary containing the variables of an expression

expr_str

String representation of the mathematical expression

expr_stack

List representation of the syntax tree of the (parsed) mathematical expression.

parse_func

Function that will be used to deduce an operation stack/tree from a given expression.

cg

Passed ComputeGraph instance into which the expression will be parsed.

parse_expr() → dict

Parses string-based mathematical expression/equation.

Returns:Variables of the parsed equation. Return type:dict

pyrates.backend.parser.extract_var(var: str) → tuple

pyrates.backend.parser.get_unique_label(label: str, labels: list) → str

pyrates.backend.parser.is_diff_eq(eq: str) → bool

Checks whether eq is a differential equation or not.

Parameters:eq – Equation string. Returns:True, if eq is a differential equation. Return type:bool

pyrates.backend.parser.parse_equations(equations: list, equation_args: dict, cg: pyrates.backend.computegraph.ComputeGraph, def_shape: tuple, **kwargs) → dict

Parses a system (list) of equations into the backend. Transforms differential equations into the appropriate set of right-hand side evaluations that can be solved later on.

Parameters:

• equations – Collection of equations that describe the dynamics of the nodes and edges.
• equation_args – Key-value pairs of arguments needed for parsing the equations.
• cg – ComputeGraph instance that all equations will be parsed into.
• def_shape – Default shape of variables that are scalar. Can either be (1,) or ().
• kwargs – Additional keyword arguments to be passed to the backend methods.

Returns:

The updated equations args (in-place manipulation of all variables in equation_args happens during equation parsing).

Return type:

dict

pyrates.backend.parser.replace(eq: str, term: str, replacement: str, rhs_only: Optional[bool] = False, lhs_only: Optional[bool] = False) → str

Replaces a term in an equation with a replacement term (save replacement).

Parameters:

• eq – Equation that includes the term.
• term – Term that should be replaced.
• replacement – Replacement for all occurences of term.
• rhs_only – If True, replacements will only be performed in right-hand side of the equation.
• lhs_only – IF True, replacements will only be performed in left-hand side of the equation.

Returns:

The updated equation.

Return type:

str

pyrates.backend.parser.replace_in_expr(expr: sympy.core.expr.Expr, replacements: dict)

pyrates.backend.parser.split_equation(expr: str) → tuple

Splits an equation string into a left-hand side, right-and side and an assign type.

Parameters:expr – Equation string. Should contain a left-hand side and a right-hand side, separated by some form of assign symbol. Returns:left-hand side string, right-hand side string, assign operation string. Return type:tuple

pyrates.backend.parser.var_in_expression(var: str, expr: str) → bool