diff -r d59bea55db9b -r c445c931472f src/glpapi05.c
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/glpapi05.c	Mon Dec 06 13:09:21 2010 +0100
@@ -0,0 +1,168 @@
+/* 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 */