3.2.13.3. flow/LinExp.hpp¶
Linear expressions and constraints can be implicitly created from variable specifiers and operators, meaning one rarely need to instantiate them explicitly. However creating the zero-expression might sometimes be useful (e.g., in a sum expression) and can be done simply with the expression flow::LinExp().
A variable specifier is a representation of either a single variable or a sum of variables. The addition, multiplication and division operators are overloaded for variable specifiers and linear expressions such that expressions can be written in the natural manner.
The operators <=, == and >= are overloaded on linear expressions to make the creation of
linear constraints easier. However, one argument to the operator must be a linear expression while
the other argument must be a number.
3.2.13.3.1. Variable Specifiers¶
The main variables in a flow model are associated with either vertices or hyperedges in the underlying derivation graph. A variable specifier represents either a set of variables or a single variable, Each specifier has an associated ID that must be registered by a flow model module at the time when the specifier is added to the model. See also Hyperflow Model for an overview of the specifiers.
3.2.13.3.2. Class flow::VarSumVertex¶
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class flow::VarSumVertex¶
Represents the sum of all variables indicated by the given id. Can be indexed to retrieve a specifier for a single variable in the set.
3.2.13.3.2.1. Synopsis¶
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explicit VarSumVertex(std::string id)
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friend std::ostream &operator<<(std::ostream &s, const VarSumVertex &v)
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friend bool operator==(const VarSumVertex &a, const VarSumVertex &b)
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VarVertex operator[](dg::DG::Vertex v) const
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VarVertexGraph operator[](std::shared_ptr<graph::Graph> g) const
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std::string id
3.2.13.3.2.2. Details¶
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explicit VarSumVertex(std::string id)¶
Construct a variable specifier for a sum of variables associated with vertices in the underlying derivation graph.
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friend std::ostream &operator<<(std::ostream &s, const VarSumVertex &v)¶
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friend bool operator==(const VarSumVertex &a, const VarSumVertex &b)¶
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VarVertex operator[](dg::DG::Vertex v) const¶
Select the variable associated with the given derivation graph vertex. When the resulting specifier is given to a flow model the vertex must be from the underlying derivation graph.
- Returns
a variable specifier for a single variable in the set represented by this object.
- Throws
LogicError if !v.
Select the variable associated with the derivation graph vertex which represents the given graph. When the resulting specifier is given to a flow model such a vertex must then exist in the underlying derivation graph.
- Returns
a variable specifier for a single variable in the set represented by this object.
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std::string id¶
The ID for this specifier.
3.2.13.3.3. Class flow::VarVertex¶
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class flow::VarVertex¶
Represents a variable associated with a single vertex in a derivation graph.
3.2.13.3.3.1. Synopsis¶
3.2.13.3.4. Class flow::VarVertexGraph¶
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class flow::VarVertexGraph¶
Represents a variable associated with a single vertex in a derivation graph. This is done implicitly by a graph, and when this specifier is later given to a flow model a vertex with the graph associated must exist in the underlying derivation graph.
3.2.13.3.4.1. Synopsis¶
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explicit VarVertexGraph(std::string id, std::shared_ptr<graph::Graph> g)
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friend std::ostream &operator<<(std::ostream &s, const VarVertexGraph &v)
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friend bool operator==(const VarVertexGraph &a, const VarVertexGraph &b)
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std::string id
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std::shared_ptr<graph::Graph> g
3.2.13.3.4.2. Details¶
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friend std::ostream &operator<<(std::ostream &s, const VarVertexGraph &v)¶
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friend bool operator==(const VarVertexGraph &a, const VarVertexGraph &b)¶
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std::string id¶
3.2.13.3.5. Class flow::VarSumEdge¶
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class flow::VarSumEdge¶
Represents the sum of all variables indicated by the given id. Can be indexed to retrieve a specifier for a single variable in the set.
3.2.13.3.5.1. Synopsis¶
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explicit VarSumEdge(std::string id)
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friend std::ostream &operator<<(std::ostream &s, const VarSumEdge &v)
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friend bool operator==(const VarSumEdge &a, const VarSumEdge &b)
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VarEdge operator[](dg::DG::HyperEdge e) const
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std::string id
3.2.13.3.5.2. Details¶
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explicit VarSumEdge(std::string id)¶
Construct a variable specifier for a sum of variables associated with hyperedges in the underlying derivation graph.
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friend std::ostream &operator<<(std::ostream &s, const VarSumEdge &v)¶
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friend bool operator==(const VarSumEdge &a, const VarSumEdge &b)¶
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VarEdge operator[](dg::DG::HyperEdge e) const¶
Select the variable associated with the given derivation graph hyperedge. When the resulting specifier is given to a flow model its underlying derivation graph must be the same as the derivation graph the given hyperedge belongs to.
- Returns
a variable specifier for a single variable in the set represented by this object.
- Throws
LogicErrorif !e.
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std::string id¶
3.2.13.3.6. Class flow::VarEdge¶
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class flow::VarEdge¶
Represents a variable associated with a single hyperedge in a derivation graph. When this specifier is later given to a flow model its underlying derivation graph must be the same as the derivation graph the hyperedge in this object belongs to.
3.2.13.3.6.1. Synopsis¶
3.2.13.3.7. Class flow::VarSumCustom¶
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class flow::VarSumCustom¶
Represents the sum of all variables indicated by the given id. Can be indexed to retrieve a specifier for a single variable in the set.
3.2.13.3.7.1. Synopsis¶
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explicit VarSumCustom(std::string id)
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friend std::ostream &operator<<(std::ostream &s, const VarSumCustom &v)
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friend bool operator==(const VarSumCustom &a, const VarSumCustom &b)
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VarCustom operator[](std::string name) const
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std::string id
3.2.13.3.7.2. Details¶
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explicit VarSumCustom(std::string id)¶
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friend std::ostream &operator<<(std::ostream &s, const VarSumCustom &v)¶
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friend bool operator==(const VarSumCustom &a, const VarSumCustom &b)¶
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VarCustom operator[](std::string name) const¶
Select the variable associated with the given name. When the resulting specifier is given to a flow model that variable must have been created in the specification in some way.
- Returns
a variable specifier for a single variable in the set represented by this object.
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std::string id¶
3.2.13.3.8. Class flow::VarCustom¶
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class flow::VarCustom¶
Represents a custom variable.
3.2.13.3.8.1. Synopsis¶
3.2.13.3.9. Class flow::Var¶
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class flow::Var¶
Represents any of the variable specifier types, and can be implicitly converted to from any of them.
3.2.13.3.9.1. Synopsis¶
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using VarImpl = std::variant<VarSumVertex, VarVertex, VarVertexGraph, VarSumEdge, VarEdge, VarSumCustom, VarCustom>
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template<typename T>
Var(T v) -
template<typename Visitor>
decltype(auto) applyVisitor(Visitor &&visitor) -
template<typename Visitor>
decltype(auto) applyVisitor(Visitor &&visitor) const -
template<typename T>
const T *get() const -
friend std::ostream &operator<<(std::ostream &s, const Var &v)
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friend bool operator==(const Var &a, const Var &b)
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private VarImpl v
3.2.13.3.9.2. Details¶
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using VarImpl = std::variant<VarSumVertex, VarVertex, VarVertexGraph, VarSumEdge, VarEdge, VarSumCustom, VarCustom>¶
3.2.13.3.10. Class flow::LinExp¶
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class flow::LinExp¶
Represents a linear expression over variable specifiers.
3.2.13.3.10.1. Synopsis¶
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using IntElement = std::pair<long int, Var>
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using FloatElement = std::pair<double, Var>
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LinExp() = default
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template<typename T>
LinExp(T v) -
friend std::ostream &operator<<(std::ostream &s, const LinExp &exp)
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const std::vector<IntElement> &getIntElements() const
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const std::vector<FloatElement> &getFloatElements() const
3.2.13.3.10.2. Details¶
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LinExp() = default¶
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const std::vector<IntElement> &getIntElements() const¶
- Returns
all elements of the linear expression that have integer coefficients.
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const std::vector<FloatElement> &getFloatElements() const¶
- Returns
all elements of the linear expression that have floating point coefficients.