Entities¶
Constr
¶
Graph
¶
The graph class.
Graphs are created by adding them to a model using the the addGraph method.
idx
property
readonly
¶
The unique id of the graph in the model.
m
property
readonly
¶
The number of edges.
n
property
readonly
¶
The number of vertices.
sink
property
readonly
¶
The sink vertex of the graph.
source
property
readonly
¶
The source vertex of the graph.
vars
property
readonly
¶
The edge variables associated to the graph
LinEqua
¶
Class to represent linear equations.
Equations are primarily used as temporary objects when adding linear expressions to models. It should not be necessary to use them by themselves.
The equation consists of an LinExpr and a ConstrSense such that
expr = 2 * x + 3 * y + 6
equa = LinEqua(expr, 'L') # 2 * x + 3 * y <= 6
equa = expr <= 0 # 2 * x + 3 * y <= 6
The LinEqua derives from LinExpr and can be manipulated in the same fashion.
__init__(self, expr, sense='E', rhs=0)
special
¶
Initialize linear equation
Parameters:
Name | Type | Description | Default |
---|---|---|---|
expr |
Union[flowty.entities.LinExpr, LinEqua] |
An expression or copy from another equation |
required |
sense |
str |
The constraints sense as either Equal, LessOrEqual, or GreaterOrEqual. |
'E' |
LinExpr
¶
Class to represent linear expressions.
Expressions are operator overloaded so it is possible to do
expr = 2 * x - y + 4
expr += 3 * z
expr *= 2
expr += otherExpr
coefs: List[float]
property
readonly
¶
A list of the coefficients.
constant: float
property
readonly
¶
The constant term.
vars: List[Var]
property
readonly
¶
A list of the variables.
__init__(self, coefs=[], vars=[], constant=0.0)
special
¶
Initialize linear expression
Parameters:
Name | Type | Description | Default |
---|---|---|---|
coefs |
List[float] |
List of coefficients. |
[] |
vars |
List[Var] |
List of variables. |
[] |
constant |
float |
A constant term |
0.0 |
Exceptions:
Type | Description |
---|---|
ValueError |
If |
addConstant(self, constant)
¶
Adds a constant to the linear expression.
Parameters:
Name | Type | Description | Default |
---|---|---|---|
constant |
float |
The constant to add. |
required |
addExpr(self, expr)
¶
Adds another expression to the linear expression.
Parameters:
Name | Type | Description | Default |
---|---|---|---|
expr |
LinExpr |
The expression to add. |
required |
addTerm(self, coef, var)
¶
Adds a term to the linear expression.
Parameters:
Name | Type | Description | Default |
---|---|---|---|
coef |
float |
The coefficients. |
required |
var |
Var |
The variable. |
required |
Var
¶
The variable class.
Variables are created by adding variables to a model using the either the addVar method to create a single variable or the addGraph method to add a graph with corresponding edge variables stored in the Graph.vars property.
For an edge variable this class offers the possibility to query for source and target vertices or the edge in the graph.
edge: Tuple[int, int]
property
readonly
¶
The edge of a edge variable.
Exceptions:
Type | Description |
---|---|
ValueError |
If the variable is not associated with a graph. |
idx: int
property
readonly
¶
The unique id of the variable in the model.
lb: float
property
readonly
¶
The lower bound.
name: str
property
readonly
¶
The variable name.
obj: float
property
readonly
¶
The objective coefficient.
source: int
property
readonly
¶
The source vertex of a edge variable.
Exceptions:
Type | Description |
---|---|
ValueError |
If the variable is not associated with a graph. |
target: int
property
readonly
¶
The target vertex of a edge variable.
Exceptions:
Type | Description |
---|---|
ValueError |
If the variable is not associated with a graph. |
ub: float
property
readonly
¶
The upper bound.
x: float
property
readonly
¶
The value in the current solution