/* glpapi05.c (LP basis constructing routines) */

 /***********************************************************************

 *  This code is part of GLPK (GNU Linear Programming Kit).

 *

 *  Copyright (C) 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008,

 *  2009, 2010 Andrew Makhorin, Department for Applied Informatics,

 *  Moscow Aviation Institute, Moscow, Russia. All rights reserved.

 *  E-mail: <mao@gnu.org>.

 *

 *  GLPK is free software: you can redistribute it and/or modify it

 *  under the terms of the GNU General Public License as published by

 *  the Free Software Foundation, either version 3 of the License, or

 *  (at your option) any later version.

 *

 *  GLPK is distributed in the hope that it will be useful, but WITHOUT

 *  ANY WARRANTY; without even the implied warranty of MERCHANTABILITY

 *  or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public

 *  License for more details.

 *

 *  You should have received a copy of the GNU General Public License

 *  along with GLPK. If not, see <http://www.gnu.org/licenses/>.

 ***********************************************************************/

 #include "glpapi.h"

 /***********************************************************************

 *  NAME

 *

 *  glp_set_row_stat - set (change) row status

 *

 *  SYNOPSIS

 *

 *  void glp_set_row_stat(glp_prob *lp, int i, int stat);

 *

 *  DESCRIPTION

 *

 *  The routine glp_set_row_stat sets (changes) status of the auxiliary

 *  variable associated with i-th row.

 *

 *  The new status of the auxiliary variable should be specified by the

 *  parameter stat as follows:

 *

 *  GLP_BS - basic variable;

 *  GLP_NL - non-basic variable;

 *  GLP_NU - non-basic variable on its upper bound; if the variable is

 *           not double-bounded, this means the same as GLP_NL (only in

 *           case of this routine);

 *  GLP_NF - the same as GLP_NL (only in case of this routine);

 *  GLP_NS - the same as GLP_NL (only in case of this routine). */

 void glp_set_row_stat(glp_prob *lp, int i, int stat)

 {     GLPROW *row;

       if (!(1 <= i && i <= lp->m))

          xerror("glp_set_row_stat: i = %d; row number out of range\n",

             i);

       if (!(stat == GLP_BS || stat == GLP_NL || stat == GLP_NU ||

             stat == GLP_NF || stat == GLP_NS))

          xerror("glp_set_row_stat: i = %d; stat = %d; invalid status\n",

             i, stat);

       row = lp->row[i];

       if (stat != GLP_BS)

       {  switch (row->type)

          {  case GLP_FR: stat = GLP_NF; break;

             case GLP_LO: stat = GLP_NL; break;

             case GLP_UP: stat = GLP_NU; break;

             case GLP_DB: if (stat != GLP_NU) stat = GLP_NL; break;

             case GLP_FX: stat = GLP_NS; break;

             default: xassert(row != row);

          }

       }

       if (row->stat == GLP_BS && stat != GLP_BS ||

           row->stat != GLP_BS && stat == GLP_BS)

       {  /* invalidate the basis factorization */

          lp->valid = 0;

       }

       row->stat = stat;

       return;

 }

 /***********************************************************************

 *  NAME

 *

 *  glp_set_col_stat - set (change) column status

 *

 *  SYNOPSIS

 *

 *  void glp_set_col_stat(glp_prob *lp, int j, int stat);

 *

 *  DESCRIPTION

 *

 *  The routine glp_set_col_stat sets (changes) status of the structural

 *  variable associated with j-th column.

 *

 *  The new status of the structural variable should be specified by the

 *  parameter stat as follows:

 *

 *  GLP_BS - basic variable;

 *  GLP_NL - non-basic variable;

 *  GLP_NU - non-basic variable on its upper bound; if the variable is

 *           not double-bounded, this means the same as GLP_NL (only in

 *           case of this routine);

 *  GLP_NF - the same as GLP_NL (only in case of this routine);

 *  GLP_NS - the same as GLP_NL (only in case of this routine). */

 void glp_set_col_stat(glp_prob *lp, int j, int stat)

 {     GLPCOL *col;

       if (!(1 <= j && j <= lp->n))

          xerror("glp_set_col_stat: j = %d; column number out of range\n"

             , j);

       if (!(stat == GLP_BS || stat == GLP_NL || stat == GLP_NU ||

             stat == GLP_NF || stat == GLP_NS))

          xerror("glp_set_col_stat: j = %d; stat = %d; invalid status\n",

             j, stat);

       col = lp->col[j];

       if (stat != GLP_BS)

       {  switch (col->type)

          {  case GLP_FR: stat = GLP_NF; break;

             case GLP_LO: stat = GLP_NL; break;

             case GLP_UP: stat = GLP_NU; break;

             case GLP_DB: if (stat != GLP_NU) stat = GLP_NL; break;

             case GLP_FX: stat = GLP_NS; break;

             default: xassert(col != col);

          }

       }

       if (col->stat == GLP_BS && stat != GLP_BS ||

           col->stat != GLP_BS && stat == GLP_BS)

       {  /* invalidate the basis factorization */

          lp->valid = 0;

       }

       col->stat = stat;

       return;

 }

 /***********************************************************************

 *  NAME

 *

 *  glp_std_basis - construct standard initial LP basis

 *

 *  SYNOPSIS

 *

 *  void glp_std_basis(glp_prob *lp);

 *

 *  DESCRIPTION

 *

 *  The routine glp_std_basis builds the "standard" (trivial) initial

 *  basis for the specified problem object.

 *

 *  In the "standard" basis all auxiliary variables are basic, and all

 *  structural variables are non-basic. */

 void glp_std_basis(glp_prob *lp)

 {     int i, j;

       /* make all auxiliary variables basic */

       for (i = 1; i <= lp->m; i++)

          glp_set_row_stat(lp, i, GLP_BS);

       /* make all structural variables non-basic */

       for (j = 1; j <= lp->n; j++)

       {  GLPCOL *col = lp->col[j];

          if (col->type == GLP_DB && fabs(col->lb) > fabs(col->ub))

             glp_set_col_stat(lp, j, GLP_NU);

          else

             glp_set_col_stat(lp, j, GLP_NL);

       }

       return;

 }

 /* eof */