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Diffstat (limited to 'glpk-5.0/src/api/advbas.c')
| -rw-r--r-- | glpk-5.0/src/api/advbas.c | 153 |
1 files changed, 153 insertions, 0 deletions
diff --git a/glpk-5.0/src/api/advbas.c b/glpk-5.0/src/api/advbas.c new file mode 100644 index 0000000..1aa76d0 --- /dev/null +++ b/glpk-5.0/src/api/advbas.c @@ -0,0 +1,153 @@ +/* advbas.c (construct advanced initial LP basis) */ + +/*********************************************************************** +* This code is part of GLPK (GNU Linear Programming Kit). +* Copyright (C) 2008-2016 Free Software Foundation, Inc. +* Written by Andrew Makhorin <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" +#include "triang.h" + +/*********************************************************************** +* NAME +* +* glp_adv_basis - construct advanced initial LP basis +* +* SYNOPSIS +* +* void glp_adv_basis(glp_prob *P, int flags); +* +* DESCRIPTION +* +* The routine glp_adv_basis constructs an advanced initial LP basis +* for the specified problem object. +* +* The parameter flag is reserved for use in the future and should be +* specified as zero. +* +* NOTE +* +* The routine glp_adv_basis should be called after the constraint +* matrix has been scaled (if scaling is used). */ + +static int mat(void *info, int k, int ind[], double val[]) +{ glp_prob *P = info; + int m = P->m; + int n = P->n; + GLPROW **row = P->row; + GLPCOL **col = P->col; + GLPAIJ *aij; + int i, j, len; + if (k > 0) + { /* retrieve scaled row of constraint matrix */ + i = +k; + xassert(1 <= i && i <= m); + len = 0; + if (row[i]->type == GLP_FX) + { for (aij = row[i]->ptr; aij != NULL; aij = aij->r_next) + { j = aij->col->j; + if (col[j]->type != GLP_FX) + { len++; + ind[len] = j; + val[len] = aij->row->rii * aij->val * aij->col->sjj; + } + } + } + } + else + { /* retrieve scaled column of constraint matrix */ + j = -k; + xassert(1 <= j && j <= n); + len = 0; + if (col[j]->type != GLP_FX) + { for (aij = col[j]->ptr; aij != NULL; aij = aij->c_next) + { i = aij->row->i; + if (row[i]->type == GLP_FX) + { len++; + ind[len] = i; + val[len] = aij->row->rii * aij->val * aij->col->sjj; + } + } + } + } + return len; +} + +void glp_adv_basis(glp_prob *P, int flags) +{ int i, j, k, m, n, min_mn, size, *rn, *cn; + char *flag; + if (flags != 0) + xerror("glp_adv_basis: flags = %d; invalid flags\n", flags); + m = P->m; /* number of rows */ + n = P->n; /* number of columns */ + if (m == 0 || n == 0) + { /* trivial case */ + glp_std_basis(P); + goto done; + } + xprintf("Constructing initial basis...\n"); + /* allocate working arrays */ + min_mn = (m < n ? m : n); + rn = talloc(1+min_mn, int); + cn = talloc(1+min_mn, int); + flag = talloc(1+m, char); + /* make the basis empty */ + for (i = 1; i <= m; i++) + { flag[i] = 0; + glp_set_row_stat(P, i, GLP_NS); + } + for (j = 1; j <= n; j++) + glp_set_col_stat(P, j, GLP_NS); + /* find maximal triangular part of the constraint matrix; + to prevent including non-fixed rows and fixed columns in the + triangular part, such rows and columns are temporarily made + empty by the routine mat */ +#if 1 /* FIXME: tolerance */ + size = triang(m, n, mat, P, 0.001, rn, cn); +#endif + xassert(0 <= size && size <= min_mn); + /* include in the basis non-fixed structural variables, whose + columns constitute the triangular part */ + for (k = 1; k <= size; k++) + { i = rn[k]; + xassert(1 <= i && i <= m); + flag[i] = 1; + j = cn[k]; + xassert(1 <= j && j <= n); + glp_set_col_stat(P, j, GLP_BS); + } + /* include in the basis appropriate auxiliary variables, whose + unity columns preserve triangular form of the basis matrix */ + for (i = 1; i <= m; i++) + { if (flag[i] == 0) + { glp_set_row_stat(P, i, GLP_BS); + if (P->row[i]->type != GLP_FX) + size++; + } + } + /* size of triangular part = (number of rows) - (number of basic + fixed auxiliary variables) */ + xprintf("Size of triangular part is %d\n", size); + /* deallocate working arrays */ + tfree(rn); + tfree(cn); + tfree(flag); +done: return; +} + +/* eof */ |