2.2.11.3. 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.
2.2.11.3.1. 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.
2.2.11.3.2. Class flow::VarSumVertex¶
-
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.
2.2.11.3.2.1. Synopsis¶
struct MOD_DECL VarSumVertex {
explicit VarSumVertex(std::string id);
MOD_DECL friend std::ostream &operator<<(std::ostream &s, const VarSumVertex &v);
MOD_DECL friend bool operator==(const VarSumVertex &a, const VarSumVertex &b) {
return a.id == b.id;
}
VarVertex operator[](dg::DG::Vertex v) const;
VarVertexGraph operator[](std::shared_ptr<graph::Graph> g) const;
public:
std::string id;
};
2.2.11.3.2.2. Details¶
-
explicit
VarSumVertex(std::string id)¶ Construct a variable specifier for a sum of variables associated with vertices in the underlying derivation graph.
-
friend std::ostream &
operator<<(std::ostream &s, const VarSumVertex &v)¶
-
friend bool
operator==(const VarSumVertex &a, const VarSumVertex &b)¶
-
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
LogicErrorif!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.
-
std::string
id¶ The ID for this specifier.
2.2.11.3.3. Class flow::VarVertex¶
-
class
flow::VarVertex¶ Represents a variable associated with a single vertex in a derivation graph.
2.2.11.3.3.1. Synopsis¶
struct MOD_DECL VarVertex {
explicit VarVertex(std::string id, dg::DG::Vertex v);
MOD_DECL friend std::ostream &operator<<(std::ostream &s, const VarVertex &v);
MOD_DECL friend bool operator==(const VarVertex &a, const VarVertex &b) {
return a.id == b.id && a.v == b.v;
}
public:
std::string id;
dg::DG::Vertex v;
};
2.2.11.3.4. Class flow::VarVertexGraph¶
-
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.
2.2.11.3.4.1. Synopsis¶
struct MOD_DECL VarVertexGraph {
explicit VarVertexGraph(std::string id, std::shared_ptr<graph::Graph> g);
MOD_DECL friend std::ostream &operator<<(std::ostream &s, const VarVertexGraph &v);
MOD_DECL friend bool operator==(const VarVertexGraph &a, const VarVertexGraph &b) {
return a.id == b.id && a.g == b.g;
}
public:
std::string id;
std::shared_ptr<graph::Graph> g;
};
2.2.11.3.4.2. Details¶
-
friend std::ostream &
operator<<(std::ostream &s, const VarVertexGraph &v)¶
-
friend bool
operator==(const VarVertexGraph &a, const VarVertexGraph &b)¶
-
std::string
id¶
2.2.11.3.5. Class flow::VarSumEdge¶
-
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.
2.2.11.3.5.1. Synopsis¶
struct MOD_DECL VarSumEdge {
explicit VarSumEdge(std::string id);
public:
MOD_DECL friend std::ostream &operator<<(std::ostream &s, const VarSumEdge &v);
MOD_DECL friend bool operator==(const VarSumEdge &a, const VarSumEdge &b) {
return a.id == b.id;
}
VarEdge operator[](dg::DG::HyperEdge e) const;
public:
std::string id;
};
2.2.11.3.5.2. Details¶
-
explicit
VarSumEdge(std::string id)¶ Construct a variable specifier for a sum of variables associated with hyperedges in the underlying derivation graph.
-
friend std::ostream &
operator<<(std::ostream &s, const VarSumEdge &v)¶
-
friend bool
operator==(const VarSumEdge &a, const VarSumEdge &b)¶
-
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.
-
std::string
id¶
2.2.11.3.6. Class flow::VarEdge¶
-
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.
2.2.11.3.6.1. Synopsis¶
struct MOD_DECL VarEdge {
explicit VarEdge(std::string id, dg::DG::HyperEdge e);
MOD_DECL friend std::ostream &operator<<(std::ostream &s, const VarEdge &v);
MOD_DECL friend bool operator==(const VarEdge &a, const VarEdge &b) {
return a.id == b.id && a.edge == b.edge;
}
public:
std::string id;
dg::DG::HyperEdge edge;
};
2.2.11.3.7. Class flow::VarSumCustom¶
-
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.
2.2.11.3.7.1. Synopsis¶
struct MOD_DECL VarSumCustom {
explicit VarSumCustom(std::string id);
MOD_DECL friend std::ostream &operator<<(std::ostream &s, const VarSumCustom &v);
MOD_DECL friend bool operator==(const VarSumCustom &a, const VarSumCustom &b) {
return a.id == b.id;
}
VarCustom operator[](std::string name) const;
public:
std::string id;
};
2.2.11.3.7.2. Details¶
-
explicit
VarSumCustom(std::string id)¶
-
friend std::ostream &
operator<<(std::ostream &s, const VarSumCustom &v)¶
-
friend bool
operator==(const VarSumCustom &a, const VarSumCustom &b)¶
-
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.
-
std::string
id¶
2.2.11.3.8. Class flow::VarCustom¶
-
class
flow::VarCustom¶ Represents a custom variable.
2.2.11.3.8.1. Synopsis¶
struct MOD_DECL VarCustom {
explicit VarCustom(std::string id, std::string name);
MOD_DECL friend std::ostream &operator<<(std::ostream &s, const VarCustom &v);
MOD_DECL friend bool operator==(const VarCustom &a, const VarCustom &b) {
return a.id == b.id && a.name == b.name;
}
public:
std::string id;
std::string name;
};
2.2.11.3.9. Class flow::Var¶
-
class
flow::Var¶ Represents any of the variable specifier types, and can be implicitly converted to from any of them.
2.2.11.3.9.1. Synopsis¶
struct MOD_DECL Var {
using VarImpl = boost::variant<VarSumVertex, VarVertex, VarVertexGraph, VarSumEdge, VarEdge, VarSumCustom, VarCustom>;
public:
template<typename T, typename = typename std::enable_if<std::is_convertible<T, VarImpl>::value>::type>
Var(T v) : v(std::move(v)) {}
template<typename Visitor>
typename Visitor::result_type applyVisitor(Visitor visitor) {
return boost::apply_visitor(visitor, v);
}
template<typename Visitor>
typename Visitor::result_type applyVisitor(Visitor visitor) const {
return boost::apply_visitor(visitor, v);
}
template<typename T>
const T *get() const {
return get<T>(&v);
}
MOD_DECL friend std::ostream &operator<<(std::ostream &s, const Var &v);
MOD_DECL friend bool operator==(const Var &a, const Var &b) {
return a.v == b.v;
}
private:
VarImpl v;
};
2.2.11.3.9.2. Details¶
-
using
VarImpl= boost::variant<VarSumVertex, VarVertex, VarVertexGraph, VarSumEdge, VarEdge, VarSumCustom, VarCustom>¶
2.2.11.3.10. Class flow::LinExp¶
-
class
flow::LinExp¶ Represents a linear expression over variable specifiers.
2.2.11.3.10.1. Synopsis¶
struct MOD_DECL LinExp {
using IntElement = std::pair<long int, Var>;
using FloatElement = std::pair<double, Var>;
public:
LinExp() = default;
LinExp(Var v);
template<typename T, typename = typename std::enable_if<std::is_convertible<T, Var>::value>::type>
LinExp(T v) : LinExp(Var(std::move(v))) {}
MOD_DECL friend std::ostream &operator<<(std::ostream &s, const LinExp &exp);
const std::vector<IntElement> &getIntElements() const;
const std::vector<FloatElement> &getFloatElements() const;
LinExp &operator+=(const LinExp &e);
LinExp &operator-=(const LinExp &e);
LinExp &operator*=(int c);
LinExp &operator*=(double c);
private:
std::vector<IntElement> intElements;
std::vector<FloatElement> floatElements;
};
2.2.11.3.10.2. Details¶
-
LinExp() = default¶
-
const std::vector<IntElement> &
getIntElements() const¶ - Returns
all elements of the linear expression that have integer coefficients.
-
const std::vector<FloatElement> &
getFloatElements() const¶ - Returns
all elements of the linear expression that have floating point coefficients.
2.2.11.3.11. Class flow::LinConstraint¶
2.2.11.3.11.1. Synopsis¶
struct MOD_DECL LinConstraint {
enum class Relation {
Leq, Eq, Geq
};
public:
explicit LinConstraint(LinExp exp, Relation relation, double bound);
MOD_DECL friend std::ostream &operator<<(std::ostream &s, const LinConstraint &c);
public:
LinExp exp;
Relation relation;
double bound;
};