8.3.6. MdoExprLinear¶

class mindoptpy.MdoExprLinear¶

Bases: mindoptpy.MdoExpr

This object implements the data structure to hold a linear constraint expression object, which consists of a set of coefficient-variable pairs.

Typical steps to input a linear constraint expression are:

Create a set of empty variable objects by calling mindoptpy.MdoModel.add_var().

Create an empty linear expression object, mindoptpy.MdoExprLinear().

Input linear expression using overloaded operators such as +, or member function mindoptpy.MdoExprLinear.add_terms().

Note

This is a temporary object with a short lifespan in general.
In general, overloaded operators such as + are less efficient and thus shall be avoided in a loop. Note taht the most efficient way to build an expression object is to call mindoptpy.MdoExprLinear.add_terms().

Examples

MdoVar x1 = model.add_var()
MdoVar x3 = model.add_var()
expr1 = 1 * x1
expr1 = expr1 + x2
MdoVar x3 = model.add_var()
expr2 = expr1 + x3

Methods

`add_constant()`	This function adds a constant term to the expression object.
`add_term()`	This function adds a nonzero term.
`add_terms()`	This function adds a set of nonzero terms.
`clear()`	This function removes all nonzero elements from the expression object.
`get_coeff()`	This function returns the value of a nonzero element from the expression object, given a variable index.
`get_constant()`	This function returns the constant term in the expression object.
`get_size()`	This function returns the number of nonzero elements stored in the expression object.
`get_terms()`	This function returns the nonzero elements stored in the column object.
`get_var()`	This function returns the variable object from the expression object, given a variable object.
`remove_term()`	This function removes a nonzero element from the expression object, given a variable index.
`remove_var()`	This function removes a nonzero element from the expression object, given a variable object.
`set_constant()`	This function changes the constant term in the expression object.
`get_dual_value()`	This function returns the dual variable associated with this constraint.

add_constant(constant: float)¶

This function adds a constant term to the expression object.

Parameters: constant (float) – A constant term that will be added.

add_term(var: mindoptpy.MdoVar, coeff: float)¶

This function adds a nonzero term. A nonzero term is a pair of variable and coefficient.

Parameters

var (MdoVar) – A variable object associated with the nonzero term.
coeff (float) – A coefficient of the nonzero term.

add_terms(vars: Union[list, mindoptpy.MdoVar], coeffs: Union[list, float])¶

This function adds a set of nonzero terms. A nonzero term is a pair of variable and coefficient.

Parameters

conss (array-like or single variable object) – An array that holds the variable objects, or a single variable object.
coeffs (array-like or a single coefficient) – An array that holds the coefficients of the nonzero terms, or a single coefficient.

clear()¶: This function removes all nonzero elements from the expression object.

get_coeff(pos: int)¶

This function returns the value of a nonzero element from the expression object, given a variable index.

Parameters: pos (int) – The term that is currently stored at position pos.
Returns: The value of the nonzero coefficient.
Return type: float

get_constant()¶

This function returns the constant term in the expression object.

Returns: A constant term in the expression object.
Return type: float

get_terms()¶

This function returns the nonzero elements stored in the column object.

Returns: Return the nonzero elements stored in the column object.
Return type: array-like

get_var(pos: int)¶

This function returns the variable object from the expression object, given a variable index.

Parameters: pos (int) – The term that is currently stored at position pos.
Returns: A variable object.
Return type: MdoVar

remove_term(pos: int)¶

This function removes a nonzero element from the expression object, given a variable index.

Parameters: pos (int) – A nonzero element stored at position pos.

remove_var(var: mindoptpy.MdoVar)¶

This function removes a nonzero element from the expression object, given a variable object.

Parameters: var (MdoVar) – A variable object whose coefficient will be removed.
Returns: Return true if the specified coefficient is in the expression and has been removed.
Return type: bint

set_constant(constant: float)¶

This function changes the constant term in the expression object.

Parameters: constant (float) – A new constant term.

get_dual_value()¶

This function returns the dual variable associated with this constraint.

Returns: The dual variable associated with this constraint.
Return type: float