8.3.1. MdoCol¶

class mindoptpy.MdoCol¶

Bases: object

This object implements the data structure to hold a column object, which consists of a set of constraint and coefficient pairs.

Typical steps to to input a column into the optimization model are:

Create an empty column object, mindoptpy.MdoCol().

Input nonzero elements by calling mindoptpy.MdoCol.add_terms().

A nonzero element can be queried by calling mindoptpy.MdoCol.get_coeff() to access the associated constraint and coefficient.

Note

This is a temporary object with a short lifespan in general.

Examples

from mindoptpy import *

# Create an empty model.
model = MdoModel()
MDO_INFINITY = MdoModel.get_infinity()

# Add variables.
x1 = model.add_var(0, MDO_INFINITY, 1, None, "x1", False)
x2 = model.add_var(0, MDO_INFINITY, 1, None, "x2", False)
x3 = model.add_var(0, 3, 1, None, "x2", False)

# Set/get column object
col1 = MdoCol()
col1.add_term(x2, 1)
col1.add_terms([x3], [2])
col1.get_terms()
col1.get_coeff(0)
col1.get_coeff(1)
col1.get_size()

# Remove
col1.remove_cons((col1.get_cons(1)))
col1.remove_term(0)
col1.clear()
col1.get_size()

Methods

`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 column object.
`get_coeff()`	This function returns the value of a nonzero element from the column object.
`get_cons()`	This function returns the constraint object from the column object.
`get_size()`	This function returns the number of nonzero elements stored in the column object.
`get_terms()`	This function returns the nonzero elements stored in the column object.
`remove_cons()`	This function removes a nonzero element from the column object, given a constraint object.
`remove_term()`	This function removes a nonzero element from the column object, given a constraint index.

add_term(cons: mindoptpy.MdoCons, coeff: float)¶

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

Parameters

cons (MdoCons) – A constraint object associated with the nonzero term.
coeff (float) – A coefficient of the nonzero term.

add_terms(conss: Union[list, mindoptpy.MdoCons], coeffs: Union[list, float])¶

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

Parameters

conss (array-like or single constraint object) – An array that holds the constraint objects, or a single constraint 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 column object.

get_coeff(pos: int)¶

This function returns the value of a nonzero element from the column object.

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

get_cons(pos: int)¶

This function returns the constraint object from the column object.

Parameters: pos (int) – The term that is currently stored at position pos.
Returns: The corresponding constraint object of the nonzero coefficient.
Return type: MdoCons

get_size()¶

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

Returns: The numner of nonzero elements stored in the column object.
Return type: int

get_terms()¶

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

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

remove_cons(cons: mindoptpy.MdoCons)¶

This function removes a nonzero element from the column object, given a constraint object.

Parameters: cons (MdoCons) – A constraint object whose nonzero coefficient will be removed.
Returns: Return true if the specified coefficient is in the column and has been removed.
Return type: bint

remove_term(pos: int)¶

This function removes a nonzero element from the column object, given a constraint index.

Parameters: pos (int) – The term that is currently stored at position pos.