If I changed column/row status, I didn't must to delete column/row?
Cedric[FR] wrote: > > > I understand the column status. > For row, if I understood well, the row is active if Ax=b > for the problem Ax<=b with x auxiliary variables. So, structural variables > = 0 > > my algorithm is: > > ->solve problem > ->delete columns and rows > ->add columns > ->resolve problem > > But, if I delete column or rows, I must to have a basis solution to > resolve my problem. > So I must resolve my problem after fix the column status > > my algorithm become: > ->solve problem > ->change status > ->resolve problem > ->delete columns and rows > ->add columns > ->resolve problem > > > Andrew Makhorin wrote: >> >>> Yes, I delete Rows and Cols >> >> If the current basis is valid (whether optimal or not) and if you >> delete active rows (i.e. the rows for which glp_get_row_stat returns >> GLP_NL, GLP_NU, GLP_NF, or GLP_NS) and/or basic columns (i.e. the >> columns for which glp_get_col_stat returns GLP_BS), the basis becomes >> invalid. To keep it valid you either have not to delete such rows or >> columns or have to change the statuses of remaining rows and columns >> appropriately. >> >>> For Row, must I use glp_set_row_stat(lp , i , GLP_NL)? >> >>> For Column, must I use glp_set_col_stat(lp , i , GLP_NL)? >> >> Do you understand what is the row/column status? >> >>> How can I fix my column at 0? >> >> glp_set_col_bnds(lp, j, GLP_FX, 0.0, 0.0); >> >>> must I resolve my problem before to add column or row? >> >>> Or >> >>> must I only start again the routine lpx_std_basis(lp)? >> >> lpx_std_basis makes all auxiliary variables basic and all structural >> variables non-basic, i.e. using it you lose all the current basis >> information. >> >> >> >> >> >> _______________________________________________ >> Help-glpk mailing list >> [email protected] >> http://lists.gnu.org/mailman/listinfo/help-glpk >> >> > > -- View this message in context: http://www.nabble.com/Problem-%3A-basis-tf3882882.html#a11022932 Sent from the Gnu - GLPK - Help mailing list archive at Nabble.com. _______________________________________________ Help-glpk mailing list [email protected] http://lists.gnu.org/mailman/listinfo/help-glpk
