Returns the indices of the variables that make up the current basis matrix.
A non-zero return value indicates that a problem occurred while extracting the basis. Refer to the Error Code table for a list of possible return values. Details on the error can be obtained by calling GRBgeterrormsg.
model: The model. Note that the model must have a current optimal basis, as computed by GRBoptimize.
bhead: The constraint matrix columns that make up the current basis. The result contains one entry per constraint in . If bhead[i]=j, then column i in the basis matrix is column j from the constraint matrix . Note that the basis may contain slack or artificial variables. If bhead[i] is greater than or equal to cols (the number of columns in ), then the corresponding basis column is the artificial or slack variable from row bhead[i]-cols.