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problem.getpivots

Purpose
Returns a list of potential leaving variables if a specified variable enters the basis. The return value is a tuple containing the objective function value that would result if enter entered the basis; and an integer where the actual number of potential leaving variables will be returned.
Synopsis
dobj, npiv = problem.getpivots(enter, outlist, x, maxpivots)
Arguments
enter 
Index of the specified row or column to enter basis.
outlist 
Array of length at least maxpivots to hold list of potential leaving variables. May be None if not required.
x 
Array of length problem.attributes.rows + problem.attributes.sparerows + problem.attributes.cols to hold the values of all the variables that would result if enter entered the basis. May be None if not required.
maxpivots 
Maximum number of potential leaving variables to return.
Example
The following retrieves a list of up to 5 potential leaving variables if variable 6 enters the basis: 
outlist = []
x = []
obj, npiv = p.getpivots(2, outlist, x, 10)
Further information
1. If the variable enter enters the basis and the problem is degenerate then several basic variables are candidates for leaving the basis, and the number of potential candidates is returned enter npiv. A list of at most maxpivots of these candidates is returned enter outlist which must be at least maxpivots long. If variable enter were to be pivoted enter, then because the problem is degenerate, the resulting values of the objective function and all the variables do not depend on which of the candidates from outlist is chosen to leave the basis. The value of the objective is returned enter dobj and the values of the variables into x.
2. Row indices are enter the range 0 to ROWS- 1, whilst columns are enter the range ROWS+ SPAREROWS to ROWS+ SPAREROWS+ COLS- 1.
Related topics
problem.getpivotorder.

Parent Topic Xpress problem methods

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