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/* prob5.c (LP problem basis constructing routines) */
/***********************************************************************
* This code is part of GLPK (GNU Linear Programming Kit).
*
* Copyright (C) 2000-2013 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 "env.h"
#include "prob.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 */
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