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XPRSgetpivots

Purpose

Returns a list of potential leaving variables if a specified variable enters the basis.

Synopsis

               int XPRS_CC XPRSgetpivots(XPRSprob prob, int in, int outlist[], double x[], double *dobj, int *npiv, int 
               maxpiv);
               

Arguments

prob	The current problem.
in	Index of the specified row or column to enter basis.
outlist	Integer array of length at least maxpiv 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 in entered the basis. May be NULL if not required.
dobj	Pointer to a double where the objective function value that would result if in entered the basis will be returned.
npiv	Pointer to an integer where the actual number of potential leaving variables will be returned.
maxpiv	Maximum number of potential leaving variables to return.

Error value

425	Indicates in 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 npiv, outlist[5];
double dobj;
...
XPRSgetpivots(prob,6,outlist,NULL,&dobj,&npiv,5);

Further information

1. If the variable in 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 in npiv. A list of at most maxpiv of these candidates is returned in outlist which must be at least maxpiv long. If variable in were to be pivoted in, 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 dobj 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.