pywr.nodes.BreakLink

class pywr.nodes.BreakLink(*args, **kwargs)

Compound node used to reduce the number of routes in a model

Parameters:

modelpywr.model.Model
namestring
min_flowfloat or pywr.parameters.Parameter
max_flowfloat or pywr.parameters.Parameter
costfloat or pywr.parameters.Parameter

Notes

In a model with form (3, 1, 3), i.e. 3 (A,B,C) inputs connected to 3 outputs (D,E,F) via a bottleneck (X), there are 3*3 routes = 9 routes.

A -->\ /--> D
B --> X --> E
C -->/ \--> F

If X is a storage, there are only 6 routes: A->X_o, B->X_o, C->X_o and X_i->D_o, X_i->E_o, X_i->F_o.

The BreakLink node is a compound node composed of a Storage with zero volume and a Link. It can be used in place of a normal Link, but with the benefit that it reduces the number of routes in the model (in the situation described above). The resulting LP is easier to solve.

__init__(model, name, **kwargs)

Initialise a new Node object

Parameters:

modelModel: The model the node belongs to
namestring: A unique name for the node

Methods

`__init__`(model, name, **kwargs)	Initialise a new Node object
`after`(self, Timestep ts)
`before`(self, Timestep ts)	Called at the beginning of the timestep
`check`()	Check the node is valid
`commit`(self, int scenario_index, double value)	Called once for each route the node is a member of
`commit_all`(self, double[)	Called once for each route the node is a member of
`connect`(node[, from_slot, to_slot])	Create an edge from this Node to another Node
`disconnect`([node, slot_name, all_slots])	Remove a connection from this Node to another Node
`finalise_load`()	Finish loading a node by converting parameter name references to instance references.
`finish`(self)
`get_all_cost`(self, double[)
`get_all_max_flow`(self, double[)
`get_all_min_flow`(self, double[)
`get_constant_max_flow`(self)	Returns max_flow value if it is a constant parameter or fixed value otherwise returns NaN.
`get_constant_min_flow`(self)	Returns min_flow value if it is a constant parameter or fixed value otherwise returns NaN.
`get_conversion_factor`(self)	Get the conversion factor
`get_cost`(self, ScenarioIndex scenario_index)	Get the cost per unit flow at a given timestep
`get_fixed_max_flow`(self)	Returns max_flow value if it is fixed value otherwise returns NaN.
`get_fixed_min_flow`(self)	Returns min_flow value if it is a fixed value otherwise returns NaN.
`get_max_flow`(self, ScenarioIndex scenario_index)	Get the maximum flow at a given timestep
`get_min_flow`(self, ScenarioIndex scenario_index)	Get the minimum flow at a given timestep
`iter_slots`([slot_name, is_connector])	Returns the object(s) wich should be connected to given slot_name
`pre_load`(model, data)	Create a node instance from data.
`reset`(self)	Called at the beginning of a run
`setup`(self, model)	Called before the first run of the model

Attributes

`allow_isolated`
`comment`	comment: basestring
`component_attrs`
`components`	Generator that returns all of the Components attached to the Node
`conversion_factor`	The conversion between inflow and outflow for the node
`cost`	The cost per unit flow via the node
`domain`
`flow`	Total flow via this node in the current timestep
`fully_qualified_name`
`has_constant_flows`	Returns true if both min_flow and max_flow are literal constants or "constant" Parameters.
`has_fixed_cost`	Returns true if cost is not a Parameter.
`has_fixed_flows`	Returns true if both min_flow and max_flow are not Parameters.
`max_flow`	The maximum flow constraint on the node
`min_flow`	The minimum flow constraint on the node
`model`	The recorder for the node, e.g. a NumpyArrayRecorder.
`name`	Name of the node.
`parent`	The parent Node/Storage of this object.
`prev_flow`	Total flow via this node in the previous timestep
`recorders`	Returns a list of pywr.recorders.Recorder objects attached to this node.
`virtual`	virtual: 'bool'