/* 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 */