[1] | 1 | /* glpapi05.c (LP basis constructing routines) */ |
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| 2 | |
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| 3 | /*********************************************************************** |
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| 4 | * This code is part of GLPK (GNU Linear Programming Kit). |
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| 5 | * |
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| 6 | * Copyright (C) 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008, |
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| 7 | * 2009, 2010 Andrew Makhorin, Department for Applied Informatics, |
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| 8 | * Moscow Aviation Institute, Moscow, Russia. All rights reserved. |
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| 9 | * E-mail: <mao@gnu.org>. |
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| 10 | * |
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| 11 | * GLPK is free software: you can redistribute it and/or modify it |
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| 12 | * under the terms of the GNU General Public License as published by |
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| 13 | * the Free Software Foundation, either version 3 of the License, or |
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| 14 | * (at your option) any later version. |
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| 15 | * |
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| 16 | * GLPK is distributed in the hope that it will be useful, but WITHOUT |
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| 17 | * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY |
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| 18 | * or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public |
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| 19 | * License for more details. |
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| 20 | * |
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| 21 | * You should have received a copy of the GNU General Public License |
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| 22 | * along with GLPK. If not, see <http://www.gnu.org/licenses/>. |
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| 23 | ***********************************************************************/ |
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| 24 | |
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| 25 | #include "glpapi.h" |
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| 26 | |
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| 27 | /*********************************************************************** |
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| 28 | * NAME |
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| 29 | * |
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| 30 | * glp_set_row_stat - set (change) row status |
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| 31 | * |
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| 32 | * SYNOPSIS |
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| 33 | * |
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| 34 | * void glp_set_row_stat(glp_prob *lp, int i, int stat); |
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| 35 | * |
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| 36 | * DESCRIPTION |
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| 37 | * |
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| 38 | * The routine glp_set_row_stat sets (changes) status of the auxiliary |
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| 39 | * variable associated with i-th row. |
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| 40 | * |
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| 41 | * The new status of the auxiliary variable should be specified by the |
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| 42 | * parameter stat as follows: |
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| 43 | * |
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| 44 | * GLP_BS - basic variable; |
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| 45 | * GLP_NL - non-basic variable; |
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| 46 | * GLP_NU - non-basic variable on its upper bound; if the variable is |
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| 47 | * not double-bounded, this means the same as GLP_NL (only in |
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| 48 | * case of this routine); |
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| 49 | * GLP_NF - the same as GLP_NL (only in case of this routine); |
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| 50 | * GLP_NS - the same as GLP_NL (only in case of this routine). */ |
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| 51 | |
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| 52 | void glp_set_row_stat(glp_prob *lp, int i, int stat) |
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| 53 | { GLPROW *row; |
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| 54 | if (!(1 <= i && i <= lp->m)) |
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| 55 | xerror("glp_set_row_stat: i = %d; row number out of range\n", |
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| 56 | i); |
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| 57 | if (!(stat == GLP_BS || stat == GLP_NL || stat == GLP_NU || |
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| 58 | stat == GLP_NF || stat == GLP_NS)) |
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| 59 | xerror("glp_set_row_stat: i = %d; stat = %d; invalid status\n", |
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| 60 | i, stat); |
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| 61 | row = lp->row[i]; |
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| 62 | if (stat != GLP_BS) |
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| 63 | { switch (row->type) |
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| 64 | { case GLP_FR: stat = GLP_NF; break; |
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| 65 | case GLP_LO: stat = GLP_NL; break; |
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| 66 | case GLP_UP: stat = GLP_NU; break; |
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| 67 | case GLP_DB: if (stat != GLP_NU) stat = GLP_NL; break; |
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| 68 | case GLP_FX: stat = GLP_NS; break; |
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| 69 | default: xassert(row != row); |
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| 70 | } |
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| 71 | } |
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| 72 | if (row->stat == GLP_BS && stat != GLP_BS || |
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| 73 | row->stat != GLP_BS && stat == GLP_BS) |
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| 74 | { /* invalidate the basis factorization */ |
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| 75 | lp->valid = 0; |
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| 76 | } |
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| 77 | row->stat = stat; |
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| 78 | return; |
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| 79 | } |
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| 80 | |
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| 81 | /*********************************************************************** |
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| 82 | * NAME |
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| 83 | * |
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| 84 | * glp_set_col_stat - set (change) column status |
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| 85 | * |
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| 86 | * SYNOPSIS |
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| 87 | * |
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| 88 | * void glp_set_col_stat(glp_prob *lp, int j, int stat); |
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| 89 | * |
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| 90 | * DESCRIPTION |
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| 91 | * |
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| 92 | * The routine glp_set_col_stat sets (changes) status of the structural |
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| 93 | * variable associated with j-th column. |
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| 94 | * |
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| 95 | * The new status of the structural variable should be specified by the |
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| 96 | * parameter stat as follows: |
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| 97 | * |
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| 98 | * GLP_BS - basic variable; |
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| 99 | * GLP_NL - non-basic variable; |
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| 100 | * GLP_NU - non-basic variable on its upper bound; if the variable is |
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| 101 | * not double-bounded, this means the same as GLP_NL (only in |
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| 102 | * case of this routine); |
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| 103 | * GLP_NF - the same as GLP_NL (only in case of this routine); |
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| 104 | * GLP_NS - the same as GLP_NL (only in case of this routine). */ |
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| 105 | |
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| 106 | void glp_set_col_stat(glp_prob *lp, int j, int stat) |
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| 107 | { GLPCOL *col; |
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| 108 | if (!(1 <= j && j <= lp->n)) |
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| 109 | xerror("glp_set_col_stat: j = %d; column number out of range\n" |
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| 110 | , j); |
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| 111 | if (!(stat == GLP_BS || stat == GLP_NL || stat == GLP_NU || |
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| 112 | stat == GLP_NF || stat == GLP_NS)) |
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| 113 | xerror("glp_set_col_stat: j = %d; stat = %d; invalid status\n", |
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| 114 | j, stat); |
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| 115 | col = lp->col[j]; |
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| 116 | if (stat != GLP_BS) |
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| 117 | { switch (col->type) |
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| 118 | { case GLP_FR: stat = GLP_NF; break; |
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| 119 | case GLP_LO: stat = GLP_NL; break; |
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| 120 | case GLP_UP: stat = GLP_NU; break; |
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| 121 | case GLP_DB: if (stat != GLP_NU) stat = GLP_NL; break; |
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| 122 | case GLP_FX: stat = GLP_NS; break; |
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| 123 | default: xassert(col != col); |
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| 124 | } |
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| 125 | } |
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| 126 | if (col->stat == GLP_BS && stat != GLP_BS || |
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| 127 | col->stat != GLP_BS && stat == GLP_BS) |
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| 128 | { /* invalidate the basis factorization */ |
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| 129 | lp->valid = 0; |
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| 130 | } |
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| 131 | col->stat = stat; |
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| 132 | return; |
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| 133 | } |
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| 134 | |
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| 135 | /*********************************************************************** |
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| 136 | * NAME |
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| 137 | * |
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| 138 | * glp_std_basis - construct standard initial LP basis |
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| 139 | * |
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| 140 | * SYNOPSIS |
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| 141 | * |
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| 142 | * void glp_std_basis(glp_prob *lp); |
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| 143 | * |
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| 144 | * DESCRIPTION |
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| 145 | * |
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| 146 | * The routine glp_std_basis builds the "standard" (trivial) initial |
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| 147 | * basis for the specified problem object. |
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| 148 | * |
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| 149 | * In the "standard" basis all auxiliary variables are basic, and all |
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| 150 | * structural variables are non-basic. */ |
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| 151 | |
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| 152 | void glp_std_basis(glp_prob *lp) |
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| 153 | { int i, j; |
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| 154 | /* make all auxiliary variables basic */ |
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| 155 | for (i = 1; i <= lp->m; i++) |
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| 156 | glp_set_row_stat(lp, i, GLP_BS); |
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| 157 | /* make all structural variables non-basic */ |
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| 158 | for (j = 1; j <= lp->n; j++) |
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| 159 | { GLPCOL *col = lp->col[j]; |
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| 160 | if (col->type == GLP_DB && fabs(col->lb) > fabs(col->ub)) |
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| 161 | glp_set_col_stat(lp, j, GLP_NU); |
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| 162 | else |
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| 163 | glp_set_col_stat(lp, j, GLP_NL); |
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| 164 | } |
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| 165 | return; |
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| 166 | } |
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| 167 | |
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| 168 | /* eof */ |
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