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XPRSgetpivots

Purpose
Returns a list of potential leaving variables if a specified variable enters the basis.
Topic areas
Simplex, LP
Synopsis
int XPRS_CC XPRSgetpivots(XPRSprob prob, int enter, int outlist[], double x[], double *p_objval, int *p_npivots, int maxpivots);
Arguments
prob 
The current problem.
enter 
Index of the specified row or column to enter basis.
outlist 
Integer array of length at least maxpivots to hold list of potential leaving variables. May be NULL if not required.
x 
Double array of length ROWS + SPAREROWS + COLS to hold the values of all the variables that would result if enter entered the basis. May be NULL if not required.
p_objval 
Pointer to a double where the objective function value that would result if enter entered the basis will be returned.
p_npivots 
Pointer to an integer where the actual number of potential leaving variables will be returned.
maxpivots 
Maximum number of potential leaving variables to return.
Error value
425 
Indicates enter is invalid (out of range or already basic).
Example
The following retrieves a list of up to 5 potential leaving variables if variable 6 enters the basis: 
int npivots, outlist[5];
double objective;
...
XPRSgetpivots(prob,6,outlist,NULL,&objective,&npivots,5);
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 p_npivots. 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 in p_objval and the values of the variables into x.
2. Row indices are in the range 0 to ROWS- 1, whilst columns are in the range ROWS+ SPAREROWS to ROWS+ SPAREROWS+ COLS- 1.
Related topics
XPRSgetpivotorder, XPRSpivot.

Parent Topic Console and Library Functions

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